FI20245284A1

FI20245284A1 - Method and system for calibration

Info

Publication number: FI20245284A1
Application number: FI20245284A
Authority: FI
Inventors: Risto Hyypiö
Original assignee: Timegate Instr Oy
Priority date: 2024-03-08
Filing date: 2024-03-08
Publication date: 2025-09-09

Abstract

Disclosed is method for calibration. The method comprises receiving reference light (206) emitted by reference light source (204), at spectrograph (216), wherein reference light is dispersed by spectrograph, and directed from spectrograph towards detector unit (224, 300); measuring at least one first peak value (400) corresponding to dispersed reference light using predetermined part (226, 304) of detector unit; emitting laser light (210) from laser source towards a sample (212), wherein the sample interacts with the laser light for emitting light (214); receiving emitted light from the sample, at spectrograph, wherein emitted light is dispersed by spectrograph, and directed upon dispersion from spectrograph towards detector unit; measuring at least one second peak value (402) corresponding to dispersed emitted light using another predetermined part (228, 308) of detector unit, based on calibration of detector unit by adjusting wavelength axis of detector unit based on measured at least one first peak value.

Description

METHOD AND SYSTEM FOR CALIBRATION

TECHNICAL FIELD

The present disclosure relates to methods for calibration. Moreover, the present disclosure relates to systems for calibrations.

BACKGROUND

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. However, a problem encountered in

Raman spectroscopy involves the interference of fluorescence. This challenge arises due to the fact that the same illumination employed to excite Raman scattering often triggers intense fluorescence emissions from a diverse array of samples. Consequently, the fluorescence emission tends to overshadow weaker Raman scattering signals, leading to partial or complete masking. Also, the calibration of the Raman spectrometer is required to obtain accurate measurements. Several methods have been developed to reduce the fluorescence problem and to calibrate a Raman + 20 spectrometer in Raman detection.

N

& & Time-gated Raman spectrometers have been built based on optical gates, = time-resolved photomultiplier tubes, streak cameras, time-resolved = intensified charge coupled devices, and time-resolved single-photon : avalanche diodes fabricated in complementary Metal-Oxide- & 25 Semiconductor (CMOS) technology to minimise the fluorescence. The

N time-gated spectrometers typically utilize pulsed illumination that is

N synchronized with the time-resolved detector. In a time-gated Raman measurement, the detector collects photons only during the illumination pulses to collect most of the Raman scattering while simultaneously excluding a major part of the fluorescence. However, said approaches require precise synchronization and calibration to perform accurately.

Moreover, aligning the spectrometer using calibration standards with known Raman scattering peaks is done. However, this process is time- consuming, requires access to accurate calibration standards and is vulnerable to operational errors from an operator.

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

SUMMARY

The aim of the present disclosure is to provide a method and a system to minimize measurement uncertainty by improving an accuracy of measuring wavelength of emitted light. The aim of the present disclosure is achieved by a method and a system for calibration as defined in the appended independent claims to which reference is made to.

Advantageous features are set out in the appended dependent claims.

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

N steps not explicitly disclosed also to be present. Moreover, the singular 3 encompasses the plural unless the context otherwise requires. In © particular, where the indefinite article is used, the specification is to be

I understood as contemplating plurality as well as singularity, unless the x 25 context requires otherwise. >

N BRIEF DESCRIPTION OF THE DRAWINGS

Al

FIG. 1 illustrates a flowchart depicting steps of a method for calibration, in accordance with an embodiment of the present disclosure;

FIG. 2 illustrates a schematic illustration of a system for calibration, in accordance with an embodiment of the present disclosure;

FIG. 3 illustrates a schematic illustration of a detector unit, in accordance with an embodiment of the present disclosure; and

FIG. 4 illustrates a graphical representation of at least one first peak value and at least one second peak value, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

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.

In a first aspect, the present disclosure provides a method for calibration, the method being implemented by a system comprising a laser source, an optical component, a spectrograph, and a detector unit, wherein the optical component comprises at least one first optical channel and at least one second optical channel, the method comprising: - receiving a reference light emitted by a reference light source, at the spectrograph, via the at least one first optical channel of the optical

S component, wherein the reference light is dispersed by the spectrograph & towards the detector unit; © - measuring at least one first peak value corresponding to the dispersed

I reference light using a predetermined part of the detector unit; 3 25 - emitting a laser light from the laser source towards a sample, wherein

S the sample interacts with the laser light for emitting light;

O - receiving the emitted light from the sample, via the at least one second optical channel of the optical component, at the spectrograph, wherein the emitted light is dispersed by the spectrograph, and directed upon dispersion from the spectrograph towards the detector unit; - measuring at least one second peak value corresponding to the dispersed emitted light using another predetermined part of the detector unit, based on a calibration of the detector unit by adjusting a wavelength axis of the detector unit based on the measured at least one first peak value.

The disclosed method provides calibration of the detector unit for accurate measurement of the at least one second peak value corresponding to the dispersed emitted light. The detector unit is adjusted based on the at least one first peak value, to ensure calibration for accurate data collection and alignment using known wavelengths in the reference light. Beneficially, the calibration ensures the reliability of the measurements. Moreover, the measured spectrum of the emitted light, such as Raman spectrum is used to identify and characterize different chemical compounds, as each molecule has a unique set of vibrational modes that produce a unique Raman spectrum. The position and intensity of the peaks in the Raman spectrum provide information about the strength and symmetry of the vibration and can be used to determine the chemical composition and structure of the molecule. < In a second aspect, the present disclosure provides a system for

S calibration, the system comprising: & - a processing arrangement; © - a reference light source configured to emit a reference light;

E 25 -alaser source configured to emit a laser light towards a sample, wherein 3 the sample interacts with the laser light to emit light;

O - a spectrograph configured to:

O - receive the reference light via at least one first optical channel of an optical component, wherein the reference light is dispersed by the spectrograph, and

- receive the emitted light from the sample, via at least one second optical channel of the optical component, wherein the emitted light is dispersed by the spectrograph; and - a detector unit configured to: 5 - receive the reference light directed upon dispersion from the spectrograph towards the detector unit, wherein a predetermined part of the detector unit is used to measure at least one first peak value, and - receive the emitted light directed upon dispersion from the spectrograph towards the detector unit, wherein another predetermined part of the detector unit is used to measure at least one second peak value; - measure at least one second peak value corresponding to the dispersed emitted light using another predetermined part of the detector unit, based on a calibration of the detector unit by adjusting a wavelength axis of the detector unit based on the measured at least one first peak value, wherein the processing arrangement is configured to calibrate the detector unit.

The disclosed system provides calibration of the detector unit for accurate measurement of the at least one second peak value corresponding to the dispersed emitted light. The detector unit is adjusted based on the at < least one first peak value, to ensure calibration for accurate data

S collection and alignment using known wavelengths in the reference light. 8 Beneficially, the calibration ensures the reliability of the measurements. 3 25 Moreover, the measured spectrum such as Raman spectrum is used to z identify and characterize different chemical compounds, as each molecule 3 has a unique set of vibrational modes that produce a unique Raman

S spectrum. The position and intensity of the peaks in the Raman spectrum

R provide information about the strength and symmetry of the vibration and can be used to determine the chemical composition and structure of the molecule.

Throughout the present disclosure the term "calibration" refers to a process in which a measurement instrument (herein the spectrograph) is calibrated in real-time or on a regular basis during use. It will be appreciated that the calibration involves using the reference light as a known standard to minimize any measurement uncertainty by ensuring that an accuracy of the apparatus is maintained. Typically, the calibration ensures that the measured at least one second peak value is accurate and reliable over time, even after changes in environmental conditions or other factors that can affect the spectrograph performance. Moreover, using calibration, errors, or drift in the measured at least one second peak value can be detected and corrected in real-time, leading to more accurate and precise measurements. It will be appreciated that the calibration quantifies and controls errors or uncertainties in measurement processes to an acceptable level.

The spectrum is a graphical representation of an intensity of emitted light as a function of a frequency shift from an incident light. Typically, a beam of light in the form of laser light is shone onto the sample to obtain the spectrum (such as, the optical spectrum) of the sample. Optionally, the spectroscopy is Raman spectroscopy. A part of the beam of light interacts with the sample to emit the light from the sample. Optionally, the interaction with the sample can be scattering of the light, where the

S emitted light can be scattered light. The emitted light can be either

N elastically scattered, which means that the scattered light has the same 3 frequency as the incident beam of light, or inelastically scattered, which = 25 means that the scattered light has a different frequency than the incident & beam of light. Optionally, the inelastically scattered light is Raman

S scattered light. Optionally, the emitted light is fluorescence emitted light.

N

S The method is being implemented by the system that comprises the laser source. Throughout the present disclosure, the term "/aser source" refers toalight source that emits an intense beam of light that may be focused.

Optionally, the laser source is one of: a pulsed laser source, a continuous- wave laser source. Notably, in the pulsed laser source, the light is generated in brief bursts, typically lasting from a few picoseconds to a few nanoseconds, and then turns off before a next pulse is emitted.

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 ultra-violet 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. Additionally, the laser source may be a Q- switched laser that enables emission of short pulses of light.

Moreover, the method is being implemented by the system that comprises the optical element, wherein the optical component comprises at least one first optical channel and at least one second optical channel.

The optical component may be a fibre splitter (PLC splitter or fused fibre splitter). In another embodiment, the optical component may be substituted with a free-space. Essentially, the optical component is configured to receiving the emitted light and the reference light. The optical component comprises the at least one first optical channel and at least one second optical channel. Each of the at least one first optical channel and at least one second optical channel comprises at least one

S optical fibre. The at least one optical fibre is a thin, flexible strand of

N transparent material that is capable of transmitting the light 3 therethrough. The at least one optical fibre may include a core, which is = 25 surrounded by a cladding layer with a lower refractive index. Further, the & at least one second optical channel is configured to efficiently transmit 2 the emitted light therethrough, with low attenuation and dispersion. 3 Optionally, the at least one second optical channel comprising the at least

N one optical fibre is configured to have a same length to allow the emitted light to be received and delivered at the same time. In an example, the length of the at least one optical fibre is in a range of 1 to 10 meters.

Optionally, the length of the at least one optical fibre lies in the range of 1,2,3,4,5,6, 7, 8 or 9 up to 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 meters.

The method comprises receiving a reference light emitted by a reference light source, at the spectrograph, via the at least one first optical channel of the optical component, wherein the reference light is dispersed by the spectrograph towards the detector unit. Although a single reference light source is used herein, in some embodiments, the method may use multiple reference light sources, providing multiple calibration setups.

Throughout the present disclosure, the term "reference light source" refer to a source of light that is configured to emit the reference light. The reference light source is typically a stable and a known light source.

Optionally, the reference light emitted by the reference light source has, for example, a monochromatic and coherent light. For example, wavelength for a helium-neon reference laser light used as the reference light is 632.8 nm. The reference light source provides a narrow-band excitation peaks in a region of interest of the at least one second peak value that is to be measured corresponding to the dispersed emitted light.

Optionally, the reference light source may emit a broad range of infrared wavelengths. Beneficially, the wavelength content of the reference light is critical for accurate and reproducible measurements. Notably, the wavelength of reference light is selected to be of those one or more

N wavelengths that are to be measured in the emitted light. a 2 Optionally, the reference light source is operable to generate the © reference light in a range of 532 to 900 nanometres (nm). Optionally, the

E 25 reference light may lie in a range of 532, 540, 550, 600, 650, 700, 750, 3 800 or 850 up to 540, 550, 600, 650, 700, 750, 800, 850 or 900 nm.

O Optionally, the reference light source is operable to generate the

N

S reference light in a range of 532 to 1064 nm. A technical effect of the reference light source having wavelength in one of the above-mentioned ranges is that each wavelength of the first wavelength component is in a close proximity to a wavelength range for a specific vibrational mode of the sample's molecules that may carry information about molecular structures, compositions, and/or interactions.

Notably, the reference light is received at the spectrograph by passing the reference light through the at least one first optical channel of the optical component. The reference light source is used to establish a baseline for the measurement and to correct for any drift or variation over time. Throughout the present disclosure, the term "spectrograph" refers to a device that is configured to analyse the spectral properties of light. Notably, the spectrograph works by dispersing any light into wavelengths component and then measuring intensity of that light at each of the wavelength component. Herein the spectrograph is used to disperse the reference light towards a detector unit. The detector unit is used to record the intensity of the reference light. Optionally, the spectrograph may include a collimating lens for collimating the reference light, a diffraction grating for dispersing the collimated reference light, and a focusing lens for focusing the dispersed reference light to record the intensity of the reference light by the detector unit. Notably, dispersion of the reference light refers to a process where the reference light is separated or spread out into various wavelengths by using a dispersive element. The dispersive element may include but not limited

N to a prism or diffraction grating. a 2 Moreover, the method comprises measuring the at least one first peak © value corresponding to the dispersed reference light using the

E 25 predetermined part of the detector unit. The term "detector unit" refers 3 to a device that is configured for measuring signals, such as spectral

O intensity (or light intensity) associated with the reference light. The

N

S detector unit may comprise electronics needed for time-resolved measurement or time-correlated single-photon counting. Notably, after dispersing the reference light from the spectrograph, the dispersed reference light is only directed towards the predetermined part of the detector unit. The term "predetermined part" refers a specific area or part of the detector unit that is designated to capture the dispersed reference light. Throughout the present disclosure, the term "first peak value" refers to the wavelength of the highest intensity point of the dispersed reference light. In other words, the first peak value refers to a specific wavelength component or a set of wavelength components that are related to specific spectral features in the reference lights. It will be appreciated that the dispersed reference light has at least one first wavelength component therein (i.e., one or more wavelengths are present in the dispersed reference light). Subsequently, the at least one first peak value is measured for the corresponding at least one first wavelength component. Moreover, the predetermined part of the detector unit is configured to measure the intensity or amount of light that is received at specific wavelengths, and in particular, to measure the at least one peak value corresponding to the dispersed reference light.

Notably, the detector unit comprises of pixels which are sensitive to light and thus, used to measure wavelength distribution of any light that is incident upon the pixels present in the detector unit. It will be appreciated that the pixels present in the predetermined part of the detector unit are used to measure the at least one first peak value by exposing the pixels present in the predetermined part of the detector unit to the dispersed

S reference light and sensing the at least one first wavelength component & in the dispersed reference light. eo] = 25 Furthermore, the method comprises emitting the laser light from the laser & source towards the sample, wherein the sample interacts with the laser 2 light to emit the light. Throughout the present disclosure, the term 3 "sample" refers to materials that may emit optical radiation, including but

N not limited to the scattered light and fluorescence emitted light, when illuminated with light, such as the laser light. It will be appreciated that all samples may emit the emitted light when illuminated with light, when the sample comprises molecules and/or a crystal structure that has vibrational and/or electronic energy levels. The sample may comprise for example, an organic material and/or biological material. Moreover, the sample may comprise for example, a gas, a solid and/or a liquid. Notably, the sample may be contained for example, in a sample cell. For example, organic molecules containing conjugated aromatic rings may emit light.

The laser light interacts with the vibrational, rotational, and electronic states of the sample, which causes the sample to emit radiation in the form of the emitted light. Throughout the present disclosure, the term "emitted light" refers to a light that is emitted by the molecules of the sample when irradiated (exposed to the radiation) with the laser light.

Optionally, the emitted light comprises scattered light and fluorescence emitted light. When the sample is irradiated with the laser light, the interactions with the molecular, vibrational, and rotational states cause some photons of the emitted light to be shifted in frequency and energy.

In particular, the energy of an incident photons (of the laser light) interacts with the vibrational and rotational energy levels of the molecule of the sample, causing the molecule to undergo a change in its electronic, vibrational, or rotational state. The frequency of the emitted light is shifted by the amount of energy gained or lost during this interaction.

Furthermore, the method comprises receiving the emitted light, via the

S at least one second optical channel of the optical component, at the

N spectrograph, wherein the emitted light is dispersed by the spectrograph, 3 and directed upon dispersion from the spectrograph towards the detector = 25 unit. Herein the spectrograph is configured to disperse the emitted light. & The dispersion of the emitted light refers to a process where the emitted 2 light is separated or spread out into various wavelengths by using a 3 dispersive element. The dispersive element may include but not limited

N to a prism or diffraction grating. Beneficially, analysing the various wavelengths of the emitted light provides valuable insights into the chemical and physical properties of the sample. Optionally, the spectrograph may include a collimating lens for collimating the emitted light, a diffraction grating for dispersing the collimated emitted light, and a focusing lens for focusing the emitted light to record the intensity of the emitted light by the detector unit. Moreover, the emitted light is detected and analysed using the spectrograph and the detector unit. Suitably, the spectrograph separates the various wavelengths of the emitted light to record the spectrum of the emitted light with the detector unit. For example, the Raman spectrum provides information about the vibrational modes of the molecule of the sample, as each peak in the spectrum corresponds to a particular vibrational mode.

Furthermore, the method comprises measuring at least one second peak value corresponding to the dispersed emitted light using another predetermined part of the detector unit, based on a calibration of the detector unit by adjusting a wavelength axis of the detector unit based on the measured at least one first peak value. Throughout the present disclosure, the term "wavelength axis" refers to the scale or reference used by the pixels of the detector unit to associate detected light with specific wavelengths. The at least one first peak value serves as a reference point as the at least one wavelength of the dispersed reference light measured in the at least one peak value is accurately known.

Subsequently, the at least one first peak value is then used as the

S reference to adjust the wavelength axis of the detector unit. Throughout

N the present disclosure, the term "calibrating" refers to correcting or 3 adjusting the detector unit such that the wavelength axis of the pixels of = 25 the detector unit is adjusted according to the at least one first peak value, & to measure any wavelengths of the dispersed emitted light that are in a 2 close range to the at least one first peak value. Therefore, the calibration 3 is done by adjusting or correcting the wavelength axis of the detector

N unit to ensure a correct detection of wavelength by the detector unit.

Once the detector unit is properly calibrated, then the at least one second peak value corresponding to the dispersed emitted light is accurately measured by the another predetermined part of the detector unit.

Throughout the present disclosure, the term "second peak value" refers to wavelength of the highest intensity point in the spectral data associated with the dispersed emitted light. Throughout the present disclosure, the term "another predetermined part of the detector unit" refers to that specific area or part of the detector unit other than the predetermined part of the detector unit, which receives and detects the dispersed emitted light. It will be appreciated that the at least one second peak value that are measured corresponding to the dispersed emitted light, are in a close range of the at least one first peak value that is used for the calibration of the detector unit.

For example, the at least one first peak value corresponding to the dispersed reference light is measured to be of 532 nanometres (nm) using the predetermined part of the detector unit, which is used to calibrate the detector unit to sense wavelengths of light that lie in a close range of 532 nm. Subsequently, based on the calibration of the detector unit, the at least one second peak value corresponding to the dispersed emitted light that lies in the close range of 532 nm is measured using the another predetermined part of the detector unit.

Optionally, the step of receiving the reference light and the step of < receiving the emitted light are performed simultaneously. In this regard,

S both the reference light and the emitted light, respectively, are received & at the spectrograph at a same instance of time. Subsequently, both the © reference light and the emitted light, respectively, are directed upon

E 25 dispersion from the spectrograph towards the detector unit, 3 simultaneously. A technical effect of the step of receiving the reference

O light and the step of receiving the emitted light being performed

N

S simultaneously is that the step of measuring of the at least one first peak value, the step of calibration of the detector unit, and the step of measuring of the at least one second peak value are done simultaneously.

Alternatively, optionally, the step of receiving the reference light and the step of receiving the emitted light are performed at different time instances. In other words, both the reference light and the emitted light, respectively, are received at the spectrograph at a different instance of time (for example, by a difference of just few nanoseconds).

Optionally, the detector unit comprises a set of first detectors in the predetermined part of the detector unit, and a set of second detectors in the another predetermined part of the detector unit, that are to be employed to receive the reference light and the emitted light upon dispersion from the spectrograph, respectively. Throughout the present disclosure, the term "set of first detectors" refers to those detectors in the detector unit which are present in the predetermined part of the detector unit. Throughout the present disclosure, the term "set of second detectors" refers to those detectors in the detector unit which are present in the another predetermined part of the detector unit. A technical effect of the detector unit comprising the set of first detectors and the set of second detectors is that the set of first detectors in the predetermined part of the detector unit are selected to be those detectors that are suitable to receive the reference light. Similarly, the set of second detectors in the another predetermined part of the detector unit are selected to be those detectors that are suitable to receive the emitted 3 light. 2 Optionally, the set of first detectors is selected from at least one of: © charge-coupled device (CCD), complementary metal-oxide

E 25 semiconductor (CMOS) pixel, single photon avalanche diode (SPAD). In 3 this regard, the SPAD is a semiconductor device that is arranged in the

O set of first detectors that is used as a detector for measuring the intensity

O of any light at different wavelengths. Herein, the SPAD is used to measure the intensity of the reference light. In this regard, the CCD is a type of image sensor that may be used in the set of first detectors to measure the intensity of any light at different wavelengths. Herein, the CCD is used to measure the intensity of the reference light. Moreover, the CMOS pixel may be arranged on the set of first detectors and is configured to measure the intensity of the reference light at different wavelengths. The set of first detectors are configured to measure at least one first peak value that corresponds to the dispersed reference light. The set of first detectors may be arranged in an array or any other configuration and may be used to generate the spectrum of the reference light. The first peak value refers to a specific wavelength component or a set of wavelength components that are related to specific spectral features in the reference lights. A technical effect of the above-mentioned is that a variety already known image sensors may be selected to be used as the set of first detectors to accurately measure the at least one first peak value.

Optionally, the set of second detectors is selected from at least one of: charge-coupled device (CCD), complementary metal-oxide semiconductor (CMOS) pixel, SPAD. Herein, the SPAD may be used to detect the wavelength distribution of the at least one second peak value corresponding to the dispersed emitted light. As the dispersed emitted light is directed upon the detector unit by the spectrograph, it is focused onto the another predetermined part of the detector unit comprising the

N SPAD. Moreover, the intensity of the emitted light by the sample produces

N the at least one second peak value. Beneficially, electronics needed for 3 time-resolved measurement or time-correlated single-photon counting = 25 are integrated on the same chip with the set of second detectors, such & as SPADs in a CMOS process. Subseguently, the CMOS-SPADs offers a 2 compact solution to be used in the set of second detectors. Notably, a 3 timing jitter of the time-resolved CMOS-SPADs is typically, in a range of

N 50-100 picoseconds (ps), which is in typical cases good enough to measure the temporal distribution of the emitted light. A technical effect of using the CMOS-SPADs is that the CMOS-SPADs has a low design complexity and a small size in comparison to, for example, time-gated

CCD.

Optionally, - the set of first detectors are arranged in a form of an array, and - the set of second detectors are arranged in a form of an array.

In this regard, both the set of first detectors and the set of second detectors are arranged in the form of array. In an embodiment, the array of sensing elements in both the set of first detectors and the set of second detectors, respectively, may be stacked upon each other. In another embodiment the array of the sensing elements in both the set of first detectors and the set of second detectors, respectively, may be arranged side by side. In yet another embodiment the sensing elements in both the set of first detectors and the set of second detectors, respectively, may be arrange in the combination of stacking and side by side arrangement. Optionally, the array may be a two-dimensional arrangement or three-dimensional array of individual sensing elements, each capable of detecting light. A technical effect of using the array is that it enables to simultaneously capture multiple data points, resulting in enhanced sensitivity, efficiency, and the ability to gather more comprehensive information.

N Optionally, the reference light source is ON continuously for continuously a directing the reference light towards the predetermined area of the = detector unit. In this regard, the reference light source is ON continuously = to ensure accurate and consistent measurements. The reference light is a 25 ON continuously to emit light consistently over a prolonged duration. 3 Operatively, the reference light source is configured to continuously direct 3 the reference light towards the predetermined part of the detector unit

N for calibration. The continuous directing of the reference light towards the predetermined part of the detector unit, enables to obtain measurements that helps in identify any variations or changes that may occur in the detector unit. The continuous emission of reference light ensures that the detector unit remains calibrated and ready for accurate measurements at all times. Any fluctuations, drifts, or changes in the detector unit can be detected by comparing the reference source light readings. A technical effect of the reference light being ON continuously is that it enhances the reliability and precision of measurements by accounting for potential variations in the predetermined area of the detector unit.

Optionally, the laser source is ON intermittently for intermittently directing the emitted light from the sample towards the another predetermined part of the detector unit. In this regard, the laser light source is activated to emit the pulses periodically rather than continuously. Typically, the intermittent activation is to intermittently direct the emitted light from the sample towards the another predetermined part of the detector unit. When the laser source is activated, it produces a burst of high-energy light that interacts with the sample, initiating the emitting phenomenon. The emitted light, which carries information about molecular vibrations and interactions within the sample, is directed towards the detector unit during the intermittent pulses. A technical effect of the intermittent activation of the laser source when coupled with a time-resolved detector unit is that the another predetermined part of the detector unit captures the temporal distribution

S of the emitted light from the sample. This allows to study the temporal

N aspects of the emitted light and to separate the emitted light from 3 background radiation, which improves the signal-to-noise ratio and the = 25 sensitivity of the measurements. x = 3 Optionally, the method further comprises controlling a time-resolved

O operation of the detector unit and a synchronized operation of the laser

O source. In this regard, the time-resolved operation of the detector unit refers to synchronizing the detector unit to be turned on at predefined intervals of time at which the dispersed emitted light is received by the detector unit and the detector unit is arranged to measure the temporal distribution of the photons in the dispersed emitted light. Similarly, the synchronized operation of the laser source refers to synchronizing the laser source to emit the laser light at predefined intervals of time on the sample, which allows for time-resolved measurement by the detector unit. Typically, controlling the time-resolved operation of the detector unit and the synchronized operation of the laser source requires to facilitate an interaction between the detector unit and the laser source, ensuring they operate in synchronization. Notably, the activation and deactivation of the laser source is controlled, ensuring that the laser source emits its bursts of light at appropriate intervals. Additionally, timing of the detector unit is controlled, ensuring that it is ready to capture and analyse the signals from the sample generated by the laser source. Optionally, the time-resolved operation of the detector unit also comprises time-gated operation of the detector unit. In this regard, the time-gated operation of the detector unit refers to synchronizing the detector unit to measure the dispersed emitted light with at least one time window, which allows for time-gated measurement of the at least one second peak value by the detector unit. A technical effect of controlling the time-resolved operation of the detector unit and the synchronized operation of the laser source is that it allows to analyse temporal aspects of the dispersed emitted light, such as fluorescence

S lifetimes, and it helps in separating the emitted light from the background & signals in time-domain, as in time-gated Raman spectroscopy, increasing

D 25 the signal-to-noise ratio of measurements. = + The present disclosure also relates to the system as described above. 3 Various embodiments and variants disclosed above, with respect to the 3 aforementioned method, apply mutatis mutandis to the system. - The term "processing arrangement" refers to a computational element that is operable to respond to and processes instructions that drive the system for to calibrate the detector unit. The processing arrangement includes, but is not limited to, a microprocessor, a microcontroller, a complex instruction set computing (CISC) microprocessor, a reduced instruction set (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or any other type of processing circuit.

Furthermore, the processing arrangement may refer to one or more individual processors, processing devices and various elements associated with a processing device that may be shared by other processing devices. Additionally, the one or more individual processors, processing devices and elements are arranged in various architectures for responding to and processing the instructions that drive the system.

Optionally, the spectrograph is configured to receive the reference light and the emitted light simultaneously.

Optionally, the detector unit comprises a set of first detectors in the predetermined part of the detector unit, and a set of second detectors in the another predetermined part of the detector unit, that are to be employed to receive the reference light and the emitted light upon dispersion from the spectrograph, respectively.

Optionally, the set of first detectors is selected from at least one of: charge-coupled device (CCD), complementary metal-oxide

N semiconductor (CMOS) pixel, single photon avalanche diode (SPAD).

N

8 Optionally, the set of second detectors comprises a SPAD. 3

I Optionally, 3 - the set of first detectors are arranged in a form of an array, and

N 25 - the set of second detectors are arranged in a form of an array.

O

N

R Optionally, the reference light source is ON continuously for continuously directing the reference light towards the predetermined part of the detector unit.

Optionally, the laser source is ON intermittently for intermittently directing the emitted light towards the another predetermined part of the detector unit.

Optionally, the system further comprising a controller configured to control a time-resolved operation of the detector unit and/or a synchronized operation of the laser source. In this regard, the term "controller" refers to an electronic device for managing and regulating the time-resolved operation of the detector unit and the synchronized operation of the laser source. Optionally, the detector unit and/or the laser source comprises timing electronics that enables the controller to control the time-resolved operation of the detector unit and the synchronized operation of the laser source. Optionally, the controllers include but is not limited to, a microcontroller, a processor, a microprocessor, a complex instruction set computing (CISC) microprocessor, a reduced instruction set (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, Field Programmable Gate

Array (FPGA) or any other type of controlling circuit, for example as aforementioned.

Optionally, the reference light source is operable to generate the reference light having the first wavelength component in a range of 532 < to 900 nanometre (nm).

S a DETAILED DESCRIPTION OF THE DRAWINGS

O

2 Referring to FIG. 1, there are shown steps of a method for calibration, in

E accordance with an embodiment of the present disclosure. At step 102, 3 25 a reference light emitted by a reference light source is received, via the

O at least one first optical channel of the optical component, at the

S spectrograph, wherein the reference light is dispersed by the spectrograph, and directed upon dispersion from the spectrograph towards the detector unit. At step 104, at least one first peak value is measured, corresponding to the dispersed reference light using a predetermined part of the detector unit. At step 106, a laser light is emitted from the laser source towards a sample, wherein the sample interacts with the laser light for emitting light. At step 108, the emitted light is received, via the at least one second optical channel of the optical component, at the spectrograph, wherein the emitted light is dispersed by the spectrograph, and directed upon dispersion from the spectrograph towards the detector unit. At step 110, at least one second peak value is measured, corresponding to the dispersed emitted light using another predetermined part of the detector unit, based on a calibration of the detector unit by adjusting a wavelength axis of the detector unit based on the measured at least one first peak value.

The steps 102, 104, 106, 108 and 110 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.

Referring to FIG. 2, illustrated is a schematic illustration of a system 200 for calibration, in accordance with an embodiment of the present disclosure. As shown, the system 200 comprises a processing arrangement 202. Moreover, the system 200 comprises a reference light < source 204 configured to emit a reference light 206. Furthermore, the

S system 200 comprises a laser source 208 configured to emit a laser light & 210 towards a sample 212, wherein the sample 212 interacts with the © laser light 210 to emit light 214. Furthermore, the system 200

E 25 comprises a spectrograph 216 configured to receive the reference light 3 206 via at least one first optical channel 218 of an optical component

O 220, wherein the reference light 206 is dispersed by the spectrograph

N

S 216. Moreover, the spectrograph 216 is configured to receive the emitted light 214, via at least one second optical channel (depicted as a second optical channel 222) of the optical component 220, wherein the emitted light 214 is dispersed by the spectrograph 216. Furthermore, the system 200 comprises a detector unit 224 configured to receive the reference light 206 directed upon dispersion from the spectrograph 216 towards the detector unit 224. Moreover, the detector unit 224 is configured to measure at least one first peak value corresponding to the dispersed reference light using a predetermined part 226 of the detector unit 224. Furthermore, the detector unit 224 is configured to receive the emitted light 214 directed upon dispersion from the spectrograph 216 towards the detector unit 224. Furthermore, the detector unit 224 is configured to measure at least one second peak value corresponding to the dispersed emitted light using another predetermined part 228 of the detector unit 224, based on a calibration of the detector unit 224 by adjusting a wavelength axis of the detector unit 224 based on the measured at least one first peak value, wherein the processing arrangement 202 is configured to calibrate the detector unit 224.

Referring to FIG. 3, illustrated is a schematic illustration of a detector unit 300, in accordance with an embodiment of the present disclosure. As shown, the detector unit 300 comprises a set of first detectors 302 in a predetermined part 304 of the detector unit 300. Moreover, the detector unit 300 comprises a set of second detectors 306 in another predetermined part 308 of the detector unit 300.

N

2 Referring to FIG. 4, illustrated is a graphical representation of at least & one first peak value 400 and at least one second peak value 402, in © accordance with an embodiment of the present disclosure. As shown, x-

E 25 axis depicts wavenumber of the at least one first peak value 400 and the 3 at least one second peak value 402 in a unit of inverse centimetres (cm'

O 1), Moreover, y-axis depicts Arbitrary Units (AU) which represents an

O intensity of the at least one first peak value 400 and the at least one second peak value 402.

Claims

1. A method for calibration, the method being implemented by a system comprising a laser source (208), an optical component (220), a spectrograph (216), and a detector unit (224, 300), wherein the optical component comprises at least one first optical channel (218) and at least one second optical channel (222), the method comprising: - receiving a reference light (206) emitted by a reference light source (204), at the spectrograph, via the at least one first optical channel of the optical component, wherein the reference light is dispersed by the spectrograph towards the detector unit; - measuring at least one first peak value (400) corresponding to the dispersed reference light using a predetermined part (226, 304) of the detector unit; - emitting a laser light (210) from the laser source towards a sample (212), wherein the sample interacts with the laser light for emitting light (214); - receiving the emitted light from the sample, via the at least one second optical channel of the optical component, at the spectrograph, wherein the emitted light is dispersed by the spectrograph, and directed upon dispersion from the spectrograph towards the detector unit; - measuring at least one second peak value (402) corresponding to the N dispersed emitted light using another predetermined part (228, 308) of N the detector unit, based on a calibration of the detector unit by adjusting 3 a wavelength axis of the detector unit based on the measured at least = 25 onefirst peak value. x =

3 2. The method according to claim 1, wherein the step of receiving the O reference light (206) and the step of receiving the emitted light (214) are O performed simultaneously.

3. The method according to any of the preceding claims, wherein the detector unit (224, 300) comprises a set of first detectors (302) in the predetermined part (226, 304) of the detector unit, and a set of second detectors (306) in the another predetermined part (228, 308) of the detector unit, that are to be employed to receive the reference light (206) and the emitted light (214) upon dispersion from the spectrograph (216), respectively.

4. The method according to claim 3, wherein the set of first detectors (302) is selected from at least one of: charge-coupled device (CCD), complementary metal-oxide semiconductor (CMOS) pixel, single photon avalanche diode (SPAD).

5. The method according to claim 3 or 4, wherein the set of second detectors (306) comprises SPAD.

6. The method according to any of the claims 3-5, wherein - the set of first detectors (302) are arranged in a form of an array, and - the set of second detectors (306) are arranged in a form of an array.

7. The method according to any of the preceding claims, wherein the reference light source (204) is ON continuously for continuously directing the reference light (206) towards the predetermined part (226, 304) of the detector unit (224, 300).

8. The method according to any of the preceding claims, wherein the laser N 20 source (208) being a pulsed laser source is ON intermittently for a intermittently directing the emitted light (214) from the sample towards O © the another predetermined part (228, 308) of the detector unit (224, O T 300). =

3 9. The method according to any of the preceding claims, wherein the N 3 25 method further comprises controlling a time-resolved operation of the N detector unit (224, 300) and a synchronized operation of the laser source (208).

10. The method according to any of the preceding claims, wherein the reference light source (204) is operable to generate the reference light (206) in a range of 532 to 900 nanometre (nm).

11. A system (200) for calibration, the system comprising: - a processing arrangement (202); - a reference light source (204) configured to emit a reference light (206); - a laser source (208) configured to emit a laser light (210) towards a sample (212), wherein the sample interact with the laser light to emit light (214); - a spectrograph (216) configured to: - receive the reference light via at least one first optical channel (218) of an optical component (220), wherein the reference light is dispersed by the spectrograph, and - receive the emitted light from the sample, via at least one second optical channel (222) of the optical component, wherein the emitted light is dispersed by the spectrograph; and - a detector unit (224, 300) configured to: - receive the reference light directed upon dispersion from the spectrograph towards the detector unit, - measure at least one first peak value (400) corresponding to the dispersed reference light using a predetermined part (226, 304) of S the detector unit, N - receive the emitted light directed upon dispersion from the 3 spectrograph towards the detector unit, and = 25 - measure at least one second peak value (402) corresponding to & the dispersed emitted light using another predetermined part (228, 2 308) of the detector unit, based on a calibration of the detector unit 3 by adjusting a wavelength axis of the detector unit based on the N measured at least one first peak value, wherein the processing arrangement is configured to calibrate the detector unit.

12. The system (200) according to claim 11, wherein the spectrograph (216) is configured to receive the reference light (206) and the emitted light (214) simultaneously.

13. The system (200) according to claim 11 or 12, wherein the detector unit (224, 300) comprises a set of first detectors (302) in the predetermined part (226, 304) of the detector unit, and a set of second detectors (306) in the another predetermined part (228, 308) of the detector unit, that are to be employed to receive the reference light (206) and the emitted light (214) upon dispersion from the spectrograph (216), respectively.

14. The system (200) according to claim 13, wherein the set of first detectors (302) is selected from at least one of: charge-coupled device (CCD), complementary metal-oxide semiconductor (CMOS) pixel, a single photon avalanche diode (SPAD).

15. The system (200) according to claim 13 or 14, wherein the set of second detectors (306) comprises a single photon avalanche diode (SPAD).

16. The system (200) according to any of the preceding claims 13-15, wherein + 20 - the set of first detectors (302) are arranged in a form of an array, N < - the set of second detectors (306) are arranged in a form of an array. n O ©

17. The system (200) according to any of the preceding claims 11-16, r wherein the reference light source (204) is ON continuously for a 3 continuously directing the reference light (206) towards the & 25 predetermined part (226, 304) of the detector unit (224, 300). 2 N R

18. The system (200) according to any of the preceding claims 11-17, wherein the laser source (208) being a pulsed laser source is ON intermittently for intermittently directing the emitted light (214) from the sample towards the another predetermined part (228, 308) of the detector unit (224, 300).

19. The system (200) according to any of the preceding claims 11-18, wherein the system further comprises a controller configured to control a time-resolved operation of the detector unit (224, 300) and a synchronized operation of the laser source (208).

20. The system (200) according to any of the preceding claims 11-19, wherein the reference light source (204) is operable to generate the reference light (206) in a range of 532 to 900 nanometre (nm). + N O N n <Q 00 O I = + 00 N LO < N O N