Device and method for measuring Raman spectrum

Abstract

An apparatus (100) for measuring time-resolved spectroscopy is disclosed, the apparatus comprising a light source (102) for generating light pulses directed toward a target (110). The apparatus further comprises: a sensor arrangement (118, 200) for collecting emitted optical radiation, shaping and manipulating the emitted optical radiation, and measuring the intensity of the optical radiation; and a controller (120, 228) operably coupled to the light source and the sensor arrangement. The sensor arrangement comprises at least one optical delay element (212, 214, 402, 404, 406) for providing a time delay to a first portion (208, 508, 604) of the emitted optical radiation (210, 302, 412, 706). The sensor arrangement further comprises: a spectral disperser (220) for separating the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths; and a sensor element (226, 314, 426, 612) configured to receive each wavelength of the dispersed radiation in a different spatial region thereof and to measure the light intensity associated with each wavelength of the dispersed radiation. Furthermore, the controller is operated to collect the amount of light intensity associated with each wavelength of the dispersed radiation measured by the sensor element to form a time-resolved spectrum.

Description

Technical Field

[0001] The present disclosure relates generally to spectroscopy; more particularly, to time-resolved spectroscopy; and more particularly, to time-gated Raman spectroscopy. In addition, the present disclosure relates to an apparatus for measuring time-resolved spectroscopy, or more particularly, to an apparatus for measuring time-gated Raman spectroscopy. In addition, the present disclosure relates to a method for measuring time-resolved spectroscopy, or more particularly, to a method for measuring time-gated Raman spectroscopy. Background Art

[0002] Spectroscopy is the study of the interaction between matter and light, especially electromagnetic radiation. Types of spectroscopy generally include, but are not limited to: atomic spectroscopy, ultraviolet and visible spectroscopy, infrared spectroscopy, Raman spectroscopy, etc. Raman spectroscopy is based on the phenomenon that when light (such as laser light) is incident on a substance, it causes the molecules to vibrate and undergo inelastic scattering. This scattered light is detected by a Raman spectrometer, based on which the substance and spectral information related to the substance can be determined.

[0003] Raman spectroscopy can be used in a variety of applications, such as identifying molecules, studying chemical and intramolecular bonds, characterizing materials, discovering the crystal orientation of substances, observing low-frequency excitations of solids, identifying active pharmaceutical ingredients and their polymorphs, etc. Conventional analysis for basic substance identification usually requires low or moderate resolution. In contrast, characterizing polymorphs and crystallinity usually requires high spectral resolution because these phenomena show subtle changes in the Raman spectrum that are not visible in low-resolution Raman spectra. Spectrometers based on angular dispersion are able to achieve good spectral resolution while also being able to measure the entire spectrum at the same time. This is a beneficial property of spectrometers that are not available in scanning monochromators based on, for example, Fabry-Perot filters, rotating gratings, etc.

[0004] Typically, fluorescence and background light or thermal emission of the target that occurs when measuring Raman spectra can result in a loss of spectral information, making it impossible to accurately characterize the material. Time-gated Raman spectroscopy can improve the measurement. In one type of time-gated Raman spectroscopy, the sensor array is operated in an on state only during a specific period of time to measure Raman scattering. On the other hand, when other phenomena other than Raman scattering are observed, the sensor array remains in an off state. For example, fluorescence can have a longer lifetime compared to Raman scattering, so time-gated Raman spectroscopy can be used to reject a significant portion of the fluorescence emission, thereby mitigating the signal distortion associated with it. However, time-gated Raman spectroscopy has its own disadvantages.

[0005] It is noteworthy that when a target is excited with a short laser pulse (e.g., a light pulse with a temporal width of 100 picoseconds), the emitted Raman scattered pulses have approximately the same temporal width, assuming that the target is optically thin and does not cause temporal broadening such as elastic diffusion. Therefore, ideally, the on-states of the sensor array will have the same duration. The spectrometer associated with the present disclosure uses angular dispersion to form a spectrum on the sensor array. Angular dispersion in high-throughput spectrometers leads to excessive temporal broadening of the received light emission pulses. It is noteworthy that when a polychromatic light beam is spectrally resolved, a certain degree of temporal broadening is inevitable, but at the same time, the demand for high throughput (large light spread) will also lead to what is called excessive temporal broadening in the present disclosure. It is noteworthy that in some time-gated methods, time gating of the optical pulse is performed before the pulse enters the spectrometer. In these methods, the temporal broadening caused by the spectrometer is not a problem. The present disclosure only relates to those methods of time-gated spectroscopy, which perform time gating on the light pulse after the light pulse leaves the spectrometer. In these systems, excessive temporal stretching will lead to a reduction in temporal resolution, which is detrimental to many applications of time-resolved spectroscopy. In particular, this leads to a reduction in the effectiveness of time gating, which in turn results in a reduction in the signal-to-noise ratio of time-gated Raman spectroscopy, compared to the case where excessive temporal stretching is completely avoided.

[0006] The problem in the prior art is the increase in temporal broadening and the reduction in signal-to-noise ratio, which reduces the effectiveness of measuring time-gated Raman spectroscopy. Therefore, there is a need to overcome the problems of excessive temporal broadening and reduced signal-to-noise ratio in time-gated Raman spectroscopy methods (these methods use angular dispersion and time gating is performed by or at the detection element). Summary of the invention

[0007] The present disclosure seeks to provide a device for measuring time-resolved light emission spectra. The present disclosure also seeks to provide a method for measuring time-resolved light emission spectra. When applied to a time-resolved spectrometer, the present disclosure seeks to provide a solution to the problem of reduced time resolution in high-throughput spectrometers in the prior art. The purpose of the present disclosure is to provide a solution that at least partially overcomes the problems encountered in the prior art and to provide a device for effectively measuring time-resolved spectra.

[0008] In one aspect, an embodiment of the present disclosure provides an apparatus for measuring time-gated Raman spectroscopy, the apparatus comprising:

[0009] - a light source for generating a light pulse directed towards a target, wherein the target will subsequently emit light radiation comprising at least a first portion and a second portion;

[0010] - a sensor arrangement for measuring the intensity of the optical radiation; and

[0011] - a controller operatively coupled to the light source and the sensor arrangement;

[0012] The sensor arrangement comprises:

[0013] - at least one optical delay element for providing a time delay to a first portion of the emitted optical radiation, wherein a second portion of the emitted optical radiation bypasses the at least one optical delay element;

[0014] a spectral disperser for dispersing the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation is split into angularly different directions, and wherein each portion of the dispersed radiation leaves the spectral disperser with a predetermined relative delay; and

[0015] - a sensor element configured to receive each wavelength of the dispersed radiation over a different spatial region of the sensor element and to measure the light intensity associated with each wavelength of the dispersed radiation; and

[0016] Therein, the controller is operated to record the measured light intensity associated with each wavelength of the dispersed radiation measured by the sensor element to form a time resolved spectrum.

[0017] In another aspect, the present disclosure provides a method for measuring time-resolved spectroscopy, wherein the method comprises:

[0018] - generating a light pulse directed towards a target, wherein the target will then emit light radiation comprising at least a first portion and a second portion;

[0019] - providing a time delay to a first portion of the emitted optical radiation, wherein a second portion of the emitted optical radiation bypasses the at least one optical delay element;

[0020] - dispersing the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation is split into angularly different directions, and wherein each portion of the dispersed radiation leaves the spectral disperser with a predetermined relative delay; and

[0021] - receiving each wavelength of the dispersed radiation in a different spatial region of the sensor element and measuring the light intensity associated with each wavelength of the dispersed radiation;

[0022] - recording the measured light intensity associated with each wavelength of the dispersed radiation measured by the sensor element to form a time resolved spectrum.

[0023] Embodiments of the present disclosure substantially eliminate or at least partially solve the problem of excessive time broadening in the prior art, and provide an apparatus and method for measuring time-resolved spectroscopy. Such an apparatus employs an optical delay element to manipulate a light radiation beam in a manner that enhances time-resolved spectroscopy measurements. Therefore, the present disclosure provides an apparatus for measuring time-resolved spectroscopy. In addition, the present disclosure provides effective and accurate improvements to the measurement of time-gated Raman spectroscopy, and provides enhanced time resolution.

[0024] Additional aspects, advantages, features and objects of the present disclosure will become apparent from the accompanying drawings and detailed description of illustrative embodiments interpreted in conjunction with the appended claims.

[0025] It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] When read in conjunction with the accompanying drawings, the above-described summary of the invention and the detailed description of the illustrative embodiments hereinafter will be better understood. In order to illustrate the present disclosure, exemplary structures of the present disclosure are shown in the accompanying drawings. However, the present disclosure is not limited to the specific methods and tools disclosed herein. In addition, those skilled in the art will appreciate that the accompanying drawings are not drawn to scale. Where possible, similar elements may be represented by the same numerals.

[0027] Embodiments of the present disclosure will now be described, by way of example only, with reference to the following drawings, in which:

[0028] Figure 1 A block diagram of an apparatus for measuring time-resolved spectroscopy according to an embodiment of the present disclosure is shown;

[0029] Figure 2 The embodiment according to the present disclosure is shown in Figure 1 Schematic diagram of a sensor arrangement implemented in a device for measuring time-resolved spectroscopy shown;

[0030] Figure 3 shows a schematic diagram depicting an arrangement in which collimated emitted optical radiation is separated into dispersed radiation when passing through a diffraction grating according to an embodiment of the present disclosure;

[0031] Figure 4A-4B A schematic diagram showing an arrangement employing light transmission segmentation according to an embodiment of the present disclosure, including an optical delay element as a glass block;

[0032] Figure 5A-Figure 5B A schematic diagram showing an arrangement employing light transmission segmentation according to an embodiment of the present disclosure, including an optical delay element as a reflector;

[0033] Figure 6 A schematic diagram showing an arrangement using light reflection segmentation according to an embodiment of the present disclosure is shown;

[0034] Fig. 7A , Figure 7B and Figure 7C A schematic diagram showing an arrangement using light splitting according to an embodiment of the present disclosure; and

[0035] Fig. 8A and Figure 8B A schematic diagram of an arrangement for setting up light delay segmentation for non-collimated emitted optical radiation is shown.

[0036] In the drawings, underlined numbers are used to indicate the item in which the underlined number is located or the item to which the underlined number is adjacent. Non-underlined numbers are associated with the item identified by the line connecting the non-underlined number to the item. When a number is non-underlined and is accompanied by an associated arrow, the non-underlined number is used to identify the general item to which the arrow points. DETAILED DESCRIPTION

[0037] The following detailed description describes embodiments of the present disclosure and ways in which these embodiments can be implemented. Although some ways of implementing the present disclosure have been disclosed, those skilled in the art will recognize that other ways for executing or implementing other embodiments of the present disclosure are also possible.

[0038] In one aspect, an embodiment of the present disclosure provides an apparatus for measuring time-resolved spectroscopy, the apparatus comprising:

[0039] - a light source for generating light pulses directed towards a target, wherein the target will then emit light radiation;

[0040] - a sensor arrangement for measuring the intensity of the optical radiation; and

[0041] - a controller operatively coupled to the light source and the sensor arrangement;

[0042] The sensor arrangement comprises:

[0043] - at least one optical delay element for providing a time delay to a first portion of the emitted optical radiation, wherein the emitted optical radiation also comprises a second portion bypassing the at least one optical delay element;

[0044] a spectral disperser for dispersing the delayed first and second portions of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation is split into angularly different directions, and wherein each portion of the dispersed radiation exits the spectral disperser with a predetermined relative delay; and

[0045] - a sensor element configured to receive each wavelength of the dispersed radiation over a different spatial region of the sensor element and to measure the light intensity associated with each wavelength of the dispersed radiation; and

[0046] Therein, the controller is operated to record the measured light intensity associated with each wavelength of dispersed radiation measured by the sensor element to form a time resolved spectrum.

[0047] In another aspect, the present disclosure provides a method for measuring time-resolved spectroscopy, wherein the method comprises:

[0048] - generating a light pulse directed towards a target, wherein the target will then emit light radiation;

[0049] - providing a time delay to a first portion of the emitted optical radiation, wherein the emitted optical radiation also comprises a second portion bypassing the at least one optical delay element;

[0050] - dispersing the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation is split into angularly different directions, and wherein each portion of the dispersed radiation leaves the spectral disperser with a predetermined relative delay; and

[0051] - receiving each wavelength of the dispersed radiation in a different spatial region of the sensor element and measuring the light intensity associated with each wavelength of the dispersed radiation;

[0052] - Recording the measured light intensity associated with each wavelength of the dispersed radiation measured by the sensor element to form a time-resolved spectrum.

[0053] Throughout this disclosure, the term "target" refers to a material that can emit optical radiation when illuminated by light (e.g., laser light), including but not limited to Raman scattered light. In fact, when illuminated by light, all materials can emit light by Raman scattering, such as when the material includes molecules and / or crystal structures with vibrational energy levels. In addition to emitting light by Raman scattering, some molecules can also emit light by fluorescence. For example, when illuminated by light, organic molecules can emit light by fluorescence as well as by Raman scattering. For example, organic molecules containing conjugated aromatic rings can emit light by fluorescence as well as by Raman scattering. It should be understood that fluorescence may interfere with the measurement of Raman spectroscopy and thus reduce the quality (e.g., signal-to-noise ratio) of the obtained Raman spectrum. Such fluorescence can be reduced or eliminated by using time-gated Raman spectroscopy. The form of time-gated Raman spectroscopy related to the present disclosure uses a time-resolved detector (e.g., a sensor element) that is configured to remain in an "on state" for a short period of time for measuring the dispersed radiation falling thereon, while these time-resolved detectors are configured to remain in an "off state" during the time when most of the fluorescence or other non-Raman light emission is observed. It is noteworthy that light emission by fluorescence is generally a longer-lived process than the emission of Raman radiation. Therefore, the "on-state" associated with the sensor element is ideally equal to the temporal width of the laser pulse, e.g., 100 picoseconds (ps), during which Raman radiation will be observed. This arrangement using time-gated Raman spectroscopy eliminates some of the effects of fluorescence (particularly the tail of fluorescence).

[0054] Raman scattering generally includes two types of radiation, Stokes Raman scattering and anti-Stokes Raman scattering. Stokes Raman scattering is an inelastic scattering process in which photons of irradiating light (e.g., laser light) may lose energy, thereby changing the vibrational and / or rotational state of the target; that is, the difference between the energy of the incident photon and the energy of the corresponding scattered photon is positive. Photons of irradiating light may lose energy, thereby changing the vibrational state of the target and changing the rotational state of the target. Anti-Stokes Raman scattering is an inelastic scattering process in which scattered photons may gain energy from changes in the vibrational state of the target; that is, the difference between the energy of the incident photon and the energy of the corresponding scattered photon is negative. Photons of scattered light may gain energy from changes in the vibrational state and from changes in the rotational state of the target. Time-gated Raman spectra of a target can be used, for example, to provide information about the molecular composition of the target. This information can be used, for example, for qualitative chemical analysis of the target, quantitative chemical analysis of the target, and / or for analyzing the crystal structure of the target. In addition, industrial processes can be controlled based on this information. This information can also be used, for example, for judicial purposes, such as evidence in court.

[0055] The device for measuring the time-resolved spectrum includes a light source for generating a light pulse (also called an excitation pulse) directed to the target. An example of a light source is a laser. In fact, the device for measuring the time-resolved spectrum can utilize a strong monochromatic light source, such as a laser source for generating light pulses. The light source is used to preferably emit light pulses in the visible light range, ultraviolet light range or near-infrared outer region of the electromagnetic spectrum. Optionally, the light source can be a laser diode, a solid-state laser, etc. More optionally, the light source can be a Q-switched laser capable of emitting short pulses of light to the target. In addition, the target scattering will then (after the light (excitation) pulse hits the target) emit light radiation. A portion of the emitted light radiation can be in the form of Raman radiation. The light pulse can be set to irradiate the target, such as causing inelastic scattering of photons from the target. Specifically, a portion of the light pulse can excite Raman scattering from the target. In addition, the light pulse may cause fluorescence radiation to be emitted as light radiation from the target. The target may include, for example, an inorganic material. The target may include, for example, an organic material and / or a biological material. The target may include, for example, an aromatic compound, which may emit light by Raman scattering and fluorescence. The target may include, for example, a gas, a solid and / or a liquid. The target may include, for example, a heterogeneous mixture. The target may include, for example, a non-homogeneous mixture, which includes particles suspended in a liquid or suspended in a gas. The particles may be, for example, solid particles, liquid particles and / or biological cells. The target may include, for example, single crystal materials, polycrystalline materials or amorphous materials. The target may, for example, be supported on a support. The target may, for example, be contained in a sample unit. The emitted optical radiation may include Raman scattered light and / or elastic scattered light. The elastic scattered light may include Rayleigh scattered light from a homogeneous substance. The elastic scattered light may include Mie scattered light from target particles. The elastic scattered light may include Rayleigh scattered light from a suspended medium and / or Mie scattered light from one or more particles. The elastic scattered light and reflected light may include Fresnel reflected light from various boundaries between media with different refractive indices in the target, in the sample unit and in all intervening components in the optical path. When irradiated by a light pulse, the target may provide elastic scattered light (as emitted optical radiation), and when irradiated by a light pulse, the material may provide Raman scattered light (as emitted optical radiation). The wavelength of the elastic scattered light may be equal to the wavelength of the light pulse.

[0056] Optionally, the device for measuring time-resolved spectroscopy also includes at least one optical component to gather the generated light pulses from the light source and focus the generated light pulses toward the target. The at least one optical component can be, for example, an optical lens that gathers the light pulses from the light source and focuses the light pulses toward the target. More optionally, the at least one optical component can be a beam splitter to direct a portion of the light pulses to a synchronization sensor element (e.g., a single reverse-biased photodiode) and another portion of the light pulses to the target. The synchronization sensor element can generate a synchronization signal for controlling the operating timing of the sensor element of the time-resolved spectroscopy. The synchronization signal can also be referred to as, for example, a timing signal. The synchronization signal can include a timing pulse. The synchronization signal can be referred to as a timing pulse.

[0057] Furthermore, the device for measuring a time-resolved spectrum comprises a sensor arrangement for measuring a time-resolved optical radiation spectrum. The sensor arrangement processes the measured optical radiation to obtain a time-resolved spectrum and thus measures a time-resolved spectrum.

[0058] In addition, the apparatus for measuring time-resolved spectroscopy includes a controller that is operably coupled to the light source and the sensor arrangement. Throughout this disclosure, the term "controller" refers to a hardware device or software that manages, commands, directs, or regulates the operation of other devices or systems such as light sources and sensor arrangements. The controller may include auxiliary devices such as clocks, auxiliary triggering devices, and the like. For example, the controller may be implemented via a microcontroller, a programmable logic controller, or the like. A controller that is operably coupled to the light source enables the light source to generate light pulses based on a trigger signal provided by the controller. For example, the trigger signal may be generated by a clock, or by an auxiliary triggering device. The controller, clock, or auxiliary triggering device may be configured to send a trigger signal to the light source, such as to trigger the generation of light pulses as required. The light source may be configured to generate a sequence of light pulses based on the trigger signal. The repetition rate of the light pulses may be, for example, between 1 Hz and 10 7Hz. Optionally, the repetition rate of the light pulses may be in the range of 1 Hz, 10000 Hz, 20000 Hz, 30000 Hz, 40000 Hz, 50000 Hz, 60000 Hz, 70000 Hz, 80000 Hz, 90000 Hz, 100000 Hz, 200000 Hz, 300000 Hz, 400000 Hz, 500000 Hz, 600000 Hz, 700000 Hz, 800000 Hz, 900000 Hz, 1000000 Hz, 2000000 Hz, 3000000 Hz, 4000000 Hz, 5000000 Hz, 6000000 Hz, 7000000 Hz, 8000000 Hz or 9000000 Hz. z Up to the range of 10000Hz, 20000Hz, 30000Hz, 40000Hz, 50000Hz, 60000Hz, 70000Hz, 80000Hz, 90000Hz, 100000Hz, 200000Hz, 300000Hz, 400000Hz, 500000Hz, 600000Hz, 7000000Hz, 8000000Hz, 9000000Hz or 10000000Hz. Preferably, the repetition rate of the light pulse can be, for example, in the range of 10kHz to 1000kHz. Optionally, the repetition rate of the light pulse can be from 10kHz, 100kHz, 200kHz, 300kHz, 400kHz, 500kHz, 600kHz, 700kHz, 800kHz, 900kHz up to 100kHz, 200kHz, 300kHz, 400kHz, 500kHz, 600kHz, 700kHz, 800kHz, 900kHz or 1000kHz. The light source can be arranged to generate a single light pulse. The working life of the light source can depend on the maximum intensity of the light pulse and the time width of the light pulse. In addition, generating short and strong light pulses may be associated with the risk of damaging the key components of the light source or any auxiliary equipment (such as focal length lens) related to the damage light source. The light source can be arranged to provide a light pulse so that when the maximum intensity of the light pulse is within a predetermined range, the time width of the light pulse is greater than a predetermined limit, thereby providing a specific minimum working life for the light source.

[0059] The temporal width of the light pulse may be, for example, in the range of 10 to 2000 ps (picoseconds). In practice, when the light pulse is longer than, for example, 2000 ps, ​​an optical delay element is generally not required. The temporal width of the light pulse may be, for example, longer than or equal to 50 ps to reduce the risk of damaging the light source and auxiliary equipment associated therewith.

[0060] Optionally, the sensor arrangement further comprises at least one collimating element to collimate the optical radiation emitted from the target. The optical radiation emitted from the target is in a scattered form, so that the optical radiation emitted from the target initially has a spherical wavefront. At least one collimating element for collimating the optical radiation emitted from the target can be arranged in an optical path between the target and the at least one delay element. In this example, a collimated beam of optical radiation is provided to the delay element. Optionally, at least one collimating element for collimating the optical radiation emitted from the target can be arranged in an optical path between the at least one delay element and the sensor element.

[0061] Optionally, at least one collimating element comprises, for example, at least one of the following: a lens arrangement, a mirror arrangement, an aperture combined via a pinhole or a slit, or in an optical waveguide. The collimating element can be a lens, such as a convex lens, which collimates the optical radiation emitted by the target with a spherical wavefront into an emitted optical radiation with a plane wavefront.

[0062] The sensor arrangement further comprises at least one optical delay element to provide a time delay to the first portion of the emitted optical radiation. In addition, the emitted optical radiation further comprises a second portion bypassing the at least one optical delay element. As described above, the emitted optical radiation passing through the collimating element has a plane wavefront. The optical delay element is arranged in the optical path of the first portion of such emitted optical radiation. According to one embodiment, at least the first portion of the emitted optical radiation is arranged to pass through the at least one optical delay element multiple times. In a first example, the first portion of the emitted optical radiation passes through the optical delay element, which slows down the first portion of the optical radiation compared to the second portion bypassing the optical delay element. In a second example, the first portion of the emitted optical radiation is arranged to travel a longer optical path compared to the second portion of the emitted optical radiation. In a third example, a combination of an optical delay for slowing down and a longer optical path may be used. Therefore, in general, the time taken for the first portion to travel after leaving the optical delay element is greater than the time taken for the second portion bypassing the optical delay element. It should be understood that the first portion may be further divided into a plurality of portions, such that each of the plurality of portions is provided with a different number or size of optical delay elements, thereby providing a different time delay to each of the plurality of portions. In addition, the optical delay elements in each section may have different shapes and sizes, thereby providing different time delays to each section. In addition, the optical delay elements in each section may be made of different materials, so that the speed of the optical radiation passing through each optical delay element is different, thereby providing different time delays to each of the multiple sections. In addition, in the context of "bypassing at least one optical delay element", the term "bypassing" refers to a portion of the emitted optical radiation not passing through at least one optical delay element. The second portion bypassing at least one optical delay element may be arranged to pass through another optical delay element different from the at least one optical delay element. That is, different delays may be set for the first portion and the second portion. The number of sections in the present disclosure may be two or more. In addition, as an example, the optical delay element may provide a time delay to the first portion of the emitted optical radiation when operating, and the first portion of the emitted optical radiation has a shorter optical path than the second portion of the emitted optical radiation. In addition, the optical path of the second portion of the emitted optical radiation does not have an optical delay element, so that the second portion can travel without any time delay. Therefore, the delayed first portion and the second portion can leave the spectral disperser in the form of dispersed radiation traveling with a predetermined relative time delay. Thus, multiple wavelengths of dispersed radiation are received by the sensor element in a controlled manner (e.g., at different times or at the same time), so that the sensor element can accurately measure the light intensity associated with each of the multiple wavelengths within a short period of time (e.g., tens of picoseconds) during its "on state."Such optical delay elements enhance the temporal resolution associated with time-resolved spectroscopy. Furthermore, it will be appreciated that temporal broadening due to the tilting of the optical pulse front associated with dispersed radiation deteriorates fluorescence rejection of time-gated Raman spectroscopy. Thus, the optical delay element, sensor element, and spectral disperser utilizing angular spectral dispersion enhance temporal resolution while also not negatively impacting the spectral resolution associated with time-gated Raman spectroscopy.

[0063] In order to overcome the problem of excessive time broadening and reduced signal-to-noise ratio when measuring time-gated Raman spectra, at least one optical delay element can be used, at least one optical delay element provides a time delay to the first part of the emitted optical radiation, and the second part will bypass the at least one optical delay element, so that the sensor element can receive multiple wavelengths in a controlled manner in a short period of time. The first part of the emitted optical radiation will pass through the optical delay element; the optical delay element will delay the first part compared to the second part that bypasses the optical delay element, so that the time taken by the first part to travel after leaving the optical delay element is greater than the time taken by the second part that bypasses the optical delay element. The delay of the first part can be adjusted so that it eliminates the average delay between the first part and the second part caused by the pulse front delay tilt caused by the angular dispersion in the spectrometer. Multiple wavelengths will be received by the sensor element in a controlled manner, so that the sensor element can accurately measure the light intensity of multiple wavelengths in a short time. Compared with Raman scattering, fluorescence has a longer lifetime, so measuring the light intensity in a short time will reject a considerable portion of the fluorescence emission, thereby improving the signal-to-noise ratio.

[0064] Optionally, at least one optical delay element comprises at least one of the following: a length of free space, a prism made of glass, a cuboid made of glass, a Dove prism made of glass, a pentaprism made of glass, a prism made of crystal material, a cuboid made of crystal material, a Dove prism made of crystal material, a pentaprism made of crystal material, a mirror arrangement, a lens, an optical fiber. The optical delay element may be a length of free space traveled by a portion of the emitted optical radiation. If the length is longer, the delay is longer. The optical delay element may be a glass that is a transparent glass block so that the emitted optical radiation can pass through. The optical delay element may be an optical lens so that the wavefront of the optical radiation can remain unchanged when passing through the lens. It should be understood that the first portion of the emitted optical radiation may pass through multiple optical delay elements. In one example, the first portion may pass through glass and a lens. In another example, the first portion may pass through a lens, a crystal, and an optical fiber. It is noteworthy that by increasing the number of optical delay elements in the optical path of the first portion, the time delay associated therewith may be increased. In another optional embodiment, the optical delay element may be a mirror arrangement. The mirror arrangement may include one or more plane mirrors. Alternatively or additionally, the reflector arrangement may include one or more non-planar reflectors. In such a reflector arrangement, an optical delay is provided by arranging a first portion of the uncollimated emitted optical radiation to travel a longer optical path than a second portion of the uncollimated emitted optical radiation. Typically, the reflector arrangement may be configured to provide an equivalent effect compared to a dove prism using a pentaprism. In a further embodiment, at least a first portion of the emitted optical radiation may pass through at least one optical delay element multiple times. Thus, a single optical delay element may be used to multiply the delay based on the number of times the emitted optical radiation passes through at least one optical delay element. In an alternative embodiment, the second portion does not pass through the optical delay element. If in another alternative embodiment, the second portion may pass through another optical delay element, the optical delay element will provide a delay different from that of the at least one optical delay element.

[0065] In another optional or alternative embodiment, an optical delay element is arranged using reflective-refractive splitting. The arrangement includes a glass element and a reflector element. In this arrangement, the emitted optical radiation is arranged to pass through the glass block multiple times (twice, four times, etc.). As an example, the first part of the emitted optical radiation is configured to pass through the first glass element, and the second part of the emitted optical radiation is configured to pass through the second glass element at a certain angle. The first glass element is thicker than the second glass element. After passing through the first glass element or the second glass element, each part of the emitted optical radiation will be reflected back using the first reflector to pass through the glass element again. In this way, the delay caused by the glass element can be increased without adding additional glass elements (light will pass through the glass element twice). If the emitted optical radiation is arranged to have an angle relative to the glass block and the first reflector, the first part and the second part are offset from each other (expanding the total pupil width). In addition, the reflected part and the delayed part of the emitted optical radiation can be further reflected back to the glass element using the second reflector to obtain additional delay, and the offset of the first part relative to the other part can also be compensated. When the first reflector and the second reflector are arranged at different angles relative to the glass block, compensation can be performed.

[0066] In another optional arrangement, the optical delay element can be arranged to have a reflector arrangement, which includes a first spherical reflector with a radius of curvature r1 and a second spherical reflector with a radius of curvature r2 (r2=r1 / 2), wherein the two spherical reflectors have a common center of curvature. This arrangement makes it possible to eliminate the need for a collimating element, that is, to use the uncollimated emitted optical radiation for the sensor arrangement. Since the two spherical mirrors have a common center of curvature in this arrangement, the two spherical mirrors form an image of the input beam to the same output position. The input beam of the arrangement is a focused beam of emitted optical radiation, and the output is again a focused beam of emitted optical radiation, which is directed to a spectral disperser of the sensor arrangement (as described later). In this way, the first part of the input beam reflected from the first spherical mirror will obtain an optical path length of 2r1 from input to output, while the second part of the input beam reflected from the second spherical mirror will obtain an optical path length of 2r2=r1 from input to output. In fact, if a concave grating is used, a split spectrometer can be realized by passing through an uncollimated beam.

[0067] The sensor arrangement further comprises a spectral disperser for dispersing the delayed first and second portions of the emitted optical radiation into dispersed radiation having a plurality of wavelengths. Furthermore, each wavelength of the dispersed radiation is split into angularly different directions, wherein each wavelength of the dispersed radiation is split into angularly different directions, and wherein the dispersed radiation of each portion leaves the spectral disperser with a predetermined relative delay.

[0068] The spectral disperser refracts and disperses the emitted optical radiation passing therethrough so that the delayed first and second parts of the emitted optical radiation are split into dispersed radiation having a plurality of wavelengths. Thus, each wavelength of the dispersed radiation is divided into spatially separated directions. The optical delay element provides a time delay to the first part of the emitted optical radiation so that the delayed first and second parts of the emitted optical radiation can leave the spectral disperser in the form of dispersed radiation having a predetermined relative delay when passing through the spectral disperser. As an example, at least one delay element is a cuboid made of glass having a thickness of 5 cm and a refractive index of 1.5 (in the direction of travel of the first part of the emitted optical radiation). The first part of the emitted optical radiation is arranged to travel through the cuboid made of glass, and the second part is arranged to bypass at least one delay element and travel the same distance in the air. The first part travels 5 cm at a speed c / 1.5, and the second part travels at a speed c (where c is the speed of light). That is, the delay time of the first part relative to the second part is 5cm / (c / 1.5)−5cm / c=8.3x10^-11 seconds (83ps).

[0069] Optionally, the apparatus for measuring time-resolved spectroscopy further comprises a first optical fiber and a second optical fiber, the first optical fiber being used to direct the generated light pulses from the light source to the target, and the second optical fiber being used to direct the emitted optical radiation from the target to the spectral disperser. The first optical fiber is arranged in the optical path between the generated light pulses and the target to minimize light loss. Optionally, a second optical fiber may be provided to provide an optical path for the emitted optical radiation so that the optical radiation enters at least one collimating element.

[0070] Optionally, the spectral disperser comprises at least one of: a diffraction grating, a prism or a Fabry-Perot etalon. If the angular dispersion of the dispersed radiation of the diffraction grating and the prism and the etalon is the same, then the pulse front tilt associated with the dispersed radiation in the diffraction grating and the prism and the etalon is the same. However, the nature of the pulse front tilt is different for the diffraction grating and the prism. In the case of a prism used as a spectral disperser, the phase front of each wavelength of the dispersed radiation remains perpendicular thereto, while the wave packets associated with each wavelength of the dispersed radiation acquire different amounts of group delay depending on their optical path length within the prism. In the case of a diffraction grating used as a spectral disperser, the phase front of each wavelength of the dispersed radiation becomes tilted relative to its cross-section.

[0071] More optionally, for a polychromatic light beam, multiple monochromatic components such as multiple wavelengths associated therewith can obtain lateral shifts and positive chirps or negative chirps therebetween. In one example, the prism used as an optical delay element can be a dove prism, a pentaprism, etc. It is worth noting that the dove prism provides lateral color shift and inversion, but the angular dispersion and pulse front tilt are zero. The pentaprism also does not provide angular dispersion or pulse front tilt, but it turns the light beam to one side 90 degrees, and different wavelength components will obtain lateral shifts.

[0072] The trade-off between pulse front tilt and spectral resolution is described in detail below for the case of spectrometers built using planar diffraction gratings.For the purposes of this disclosure, the case of spectrometer designs involving concave diffraction gratings, prisms, and etalons is similar to that of planar gratings.

[0073] The selection of the type of grating used as a diffraction grating for a spectral disperser is an important aspect. The diffraction orders of a diffraction grating are represented by integers "m", typically |m|=1.

[0074] The total number of lines in the diffraction grating is denoted by "N." The diffraction grating is assumed to be completely filled with the collimated emitted optical radiation having the delayed first and second portions.

[0075] The line spacing between gratings of the diffraction grating is expressed as "d" (millimeters). Therefore, the line density (ie, the number of lines per millimeter ((1 / mm))) = 1 / d.

[0076] The total width (w) of the diffraction grating is expressed as:

[0077] w=Nd

[0078] The resolving power (R) of a diffraction grating is expressed as:

[0079] R=λ / Δλ=|m|N

[0080] Where λ is the wavelength.

[0081] The maximum possible resolution (R) of a diffraction grating with width (w) max )for:

[0082] R max =2w / λ

[0083] The pulse front tilt caused by the diffraction grating can be characterized in spatial terms or in temporal terms. In spatial terms, the pulse front tilt is equal to the total number of diffraction orders in the diffraction grating times the wavelength, which is equal to Rλ. The temporal pulse front tilt, which is the same as the total temporal broadening of the incremental pulse, is equal to the spatial tilt divided by the speed of light = Rλ / c, where c is the speed of light.

[0084] The angular dispersion (dθ) / (dλ) associated with dispersed radiation is expressed as:

[0085] (dθ) / (dλ)=(1 / cosθ)(m / d)

[0086] Here, θ is the diffraction angle.

[0087] The incident angle is constant θ 0 . It is worth noting that the angular dispersion will increase as the line spacing of the diffraction grating (d) decreases. In addition, the diffraction efficiency of a diffraction grating of diffraction order "m" is a function of wavelength. The free spectral range depends on the wavelength range and the diffraction order. It is worth noting that in the case of |m|=1, the free spectral range of wavelengths in the visible range of the electromagnetic spectrum covers the entire range. Therefore, no order sorting filter is required for the first order. The diffraction pattern produced by a truly collimated beam of emitted optical radiation with a delayed first part and a second part on the diffraction grating is the sinc of the angle 2 function. It will be appreciated that the greater the resolution, the narrower the central maximum of the pattern. Angular resolution can be estimated using angular dispersion and resolution.

[0088] It is worth noting that Δθ≈(dθ) / (dλ)Δλ

[0089] And Δλ=λ / R=λ / |m|N

[0090] Therefore, |Δθ|≈λ / (N cosθ).

[0091] Furthermore, if the full spectral resolution of the diffraction grating is to be exploited, the slits (e.g., the apertures combined via the slits) need to be very narrow. Specifically, the width of the slits must be such that the entire diffraction grating can fit within the central maximum of the Fraunhofer diffraction pattern of the slits. Typically, the slits are much wider than this to increase the light throughput. Therefore, a monochromatic light beam (e.g., a light pulse) filling the slit is converted by a collimating element into a wide beam with a small but finite angular spread denoted by δθ. Let w 1 is the input slit width, F C is the focal length of the collimator.

[0092] Tan(δθ / 2)=w 1 / (2F C )

[0093] If w 1 ﹤﹤F C

[0094] δθ≈w 1 / F C

[0095] where w 1 is the width of the slit, FC is the focal length of the collimating element.

[0096] It is understood that assuming the diffraction pattern (i.e. sinc 2 function) is still narrower than the image of the slit, then the image of the slit in the spectral plane is one of the main factors determining the spectral resolution. The image of a slit for a monochromatic beam is approximated as the convolution of the diffraction pattern with a boxcar function, which represents the image of the slit assuming perfect imaging quality. In actual spectrometers, the imaging quality is not perfect, and the final input slit image on the detector is further blurred by the point spread function of the system.

[0097] It should be understood that in order to obtain a sufficiently large angular dispersion of the dispersed radiation, the grating constant must be small. In addition, in order to obtain a sufficient throughput, the width of the diffraction grating must be large. Therefore, the resolving power of the diffraction grating is usually better than the final optical resolution defined by the width of the image of the slit.

[0098] Therefore, R=|m|N=|m|(w / d) becomes larger.

[0099] On the other hand, assuming that the slit width is infinitely narrow, we can calculate 0 Get a given resolution Δλ at 0 The minimum required resolution (R). As shown in the figure, resolution R = |m|N = λ / Δλ.

[0100] Therefore, R eq =λ 0 / (Δλ 0 ).

[0101] Among them, Δλ 0 is the resolution limited by the slit.

[0102] If sinc 2 The pattern is at least three times narrower than the image of the slit, so the image of the slit mainly determines the resolution. The minimum equivalent grating resolution to achieve the above resolution is:

[0103] R' eq =(3λ 0 ) / (Δλ 0 )

[0104] The ratio between the minimum resolution and the actual resolution is defined as the excess resolution, i.e.:

[0105] Er=R / R' eq =(|m|NΔλ 0 ) / (3λ 0 )

[0106] In addition, the optical path difference over the entire diffraction grating is defined as Δs=Rλ, and accordingly, the minimum equivalent optical path difference is defined as Δs' eq =R' eq λ. The excess optical path difference is defined as Δs = E R Δs' eq , the excess time broadening can be defined as Δt = E R Δt' eq It is worth noting that if the excess time broadening factor E R >1, then the temporal pulse broadening is greater than absolutely required for the target wavelength resolution.

[0107] Therefore, Δk = Δλ / λ 2 .

[0108] where Δk is the wavenumber resolution.

[0109] Therefore, due to uncertainty relations based on Fourier transform mathematics, Δs = 1 / Δk and ΔsΔk = 1. Based on the above equations, the temporal broadening caused by a Fourier transform spectrometer and a spectrometer based on angular diffraction or dispersion can be compared. In a Fourier transform spectrometer with a perfectly collimated beam (e.g., a light pulse), the wavenumber resolution (Δk) results in a pulse broadening of Δt = Δs / c = 1 / cΔk, which means that there is no excessive temporal broadening.

[0110] Optionally, the collimated emitted optical radiation received from the target is configured to be directed to the sensor element through a spectral disperser using a diffraction grating, which uses at least one of the following: light transmission segmentation, light reflection segmentation or spectroscopic segmentation. In fact, according to one embodiment, the spectral disperser includes a diffraction grating, and the delayed first part of the emitted optical radiation and the second part of the emitted optical radiation are configured to be directed to the sensor element through a spectral disperser using a diffraction grating, which uses at least one of the following: light transmission segmentation, light reflection segmentation, spectroscopic segmentation. The basic requirements of a compact time-gated Raman spectrometer for low-light applications are large aperture and large angular dispersion. This requirement may lead to a large excess resolving power (ER) and, therefore, excessive pulse front tilt. However, in order to maintain a large aperture, the excess resolving power provided by the diffraction grating can be utilized. The original large grating of the diffraction grating can be divided into segments with a smaller but sufficient number of grating lines. Furthermore, each such segment may be fed with a slice of the original monochromatic beam with an appropriate relative optical path difference.

[0111] It should be understood that the optical path length of the collimated emitted optical radiation entering the inner side of the spectral disperser using a diffraction grating (e.g., the first part of the collimated emitted optical radiation) is shorter than the optical path length of the collimated emitted optical radiation entering the outer side of the diffraction grating (e.g., the second part of the collimated emitted optical radiation). In the light transmission splitting, in order to balance the optical path length difference, an optical delay element (e.g., a glass block) can be added to the optical path of the first part. It is worth noting that time broadening is associated with pulse front tilt. Therefore, in the absence of an optical delay element, the pulse front tilt angle is Rλ. In one example, the width of the first part of the collimated emitted optical radiation with the optical delay element is twice that of the second part. In such an example, the diffraction grating segment corresponding to the second part has one-third of the grating lines. In addition, the first part can be divided into two parts, so that each part of the first part has one-third of the diffraction lines. Therefore, the pulse front tilt associated with each part (i.e., the two parts of the first part and the second part) is Rλ / 3. The optical thickness of the optical delay element is selected in such a way that the inclined pulse fronts of each sub-portion of the first part and the second part leave the spectral disperser and travel in unison after dispersion. This arrangement reduces the temporal broadening by a factor of three. Furthermore, assuming that the obtained resolving power R / 3 is still greater than the resolution given by the slit width, the spectral resolution is not deteriorated by the splitting. More optionally, a Dove prism can be used as the optical delay element. An equivalent of a Dove prism including a reflector can be used, which provides the additional advantage of eliminating the chromaticity effects that a Dove prism may experience. More optionally, a pentaprism can be used as the optical delay element. The advantage of using light transmission splitting is that the optical delay element can be easily removed from the optical path of the first part of the collimated light beam when good temporal resolution is not required and the spectrometer cost and complexity must be reduced.

[0112] The light reflection splitting can be used to direct the collimated emitted light radiation to the sensor element via the diffraction grating. Such an arrangement comprising light reflection splitting has the advantage that no dispersive effects such as group velocity dispersion or wavelength-dependent lateral shifts have been observed.

[0113] Spectral splitting is a type of light reflection splitting that includes the use of more than one detector (e.g., sensor element) and more than one spectral disperser. Spectral splitting includes various splitting designs based on the arrangement of beam reflectors (e.g., mirrors) that reflect the light beam (the beam of emitted optical radiation) in the desired direction of each spectral disperser, which is used to receive the light beam (the beam of emitted optical radiation) and disperse the received (polychromatic) emitted optical radiation (essentially the beam of emitted optical radiation) into dispersed radiation with multiple wavelengths propagating to different angles. In one example, the spectroscopic splitting used by the diffraction grating includes a first-order "spruce" design so that the collimated emitted optical radiation is split into two directions, called the two branches of the spruce. In such an example, the temporal broadening is halved, while the wavelength resolution remains unchanged. In another example, the spectroscopic splitting used by the diffraction grating includes a second-order "spruce" design so that the collimated optical radiation is split into four beams. In such an example, the temporal broadening is reduced by a factor of four, while the wavelength resolution is intact. In another example, the spectral splitting used by the diffraction grating includes an "oak tree" design, which is a recursive generalization of a first-order "spruce" design. In practice, the spectral disperser is configured to disperse the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation is split into angularly different directions.

[0114] The sensor arrangement also includes a sensor element configured to receive each wavelength of the dispersed radiation in different spatial regions thereof. In addition, the sensor element is also configured to measure the light intensity associated with each wavelength of the dispersed radiation. The spectral disperser can separate the delayed first part of the collimated emitted optical radiation and the second part of the collimated emitted optical radiation into dispersed radiation with multiple wavelengths, so that each wavelength corresponds to a spectral component. The optical disperser element can guide the spectral components to different spatial regions of the sensor element. The sensor element is configured to measure the spectral intensity (e.g., light intensity) associated with each spectral component at different wavelengths. The potential advantage of the dispersed radiation leaving the spectral disperser at the same time is that the signal-to-noise ratio associated with the sensor element can be improved. As an example, the light intensity associated with each wavelength can refer to the number of photons received by each sensor element during the measurement. In the present disclosure, light intensity generally refers to an absolute value or relative value that can be used to form a time-resolved spectrum. In addition, the term "each wavelength of the dispersed radiation in different spatial regions" refers to a wavelength range in the emitted optical radiation toward an angle associated with an angular direction. As an example, the wavelength range within the first angular range in the direction of the first angular direction may be between the first wavelength and the second wavelength. Depending on the structure of the optical disperser and the geometry of the sensor arrangement, the difference between the first wavelength and the second wavelength may be, for example, 0.001 nm, 0.1 nm, 1 nm, 10 nm, or 100 nm. In addition, the wavelength range within the second angular range in the direction of the second angular direction may be between the third wavelength and the fourth wavelength. Depending on the structure of the optical disperser and the geometry of the sensor arrangement, the difference between the third wavelength and the fourth wavelength may be, for example, 0.001 nm, 0.1 nm, 1 nm, 10 nm, or 100 nm. As another example, the wavelength within the first angle in the first angular direction may be in the range from 800 nm to 801 nm (excluding 801 nm), and the wavelength within the second angle in the second angular direction may be in the range from 801 nm to 802 nm. In other words, the difference between two consecutive "per wavelength" ranges may be, for example, up to 0.001 nm, 0.01 nm, 0.1 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm or 50 nm. According to this example, the first sensor of the sensor element is thus configured to receive photons associated with wavelengths of the first wavelength range (from 800 nm to 801 nm, excluding 801 nm). Furthermore, the second sensor of the sensor element is configured to receive photons associated with wavelengths of the second wavelength range (from 801 nm to 802 nm). According to this example, the first sensor element and the second sensor element are thus arranged spatially adjacent to each other.The measured photons associated with the first range and the second range of wavelengths are used as a measure of the light intensity associated with each wavelength of the dispersed radiation (i.e., the intensity associated with the first range and the second range). In practice, the sensor element is configured to receive each wavelength of the dispersed radiation in a different spatial region thereof, wherein a first spatial region of the sensor element is configured to receive the first wavelength range and a second spatial region of the sensor element is configured to receive the second wavelength range in a second spatial region. In one embodiment, the sensor element comprises two or more sensors.

[0115] Optionally, when the sensor element receives the dispersed radiation, the sensor element is configured or operated to be in an "on state" for a predetermined time period. Optionally, the predetermined time period is defined as the amount of time that the target emits Raman radiation when the target is excited by the incident laser pulse. This amount of time is generally less than the radiation generated by other photons (such as fluorescence emitted by the target). Other radiation hinders the measurement of Raman radiation, so other radiation needs to be avoided when measuring Raman radiation. In one example, the predetermined time period is 100ps, which can be equal to the time width of the laser pulse to excite the target. The sensor element can be in an "on state" for a predetermined time period of 100ps to receive the dispersed radiation associated with the Raman radiation emitted by the target. The sensor element can be in an "off state" for a period of time, during which other unwanted radiation, such as fluorescence, will be observed. In addition, in an exemplary embodiment, the controller synchronizes the sensor elements of the sensor arrangement with the generated light pulses. For example, the controller provides a signal to the sensor element to start measuring at the expected time of the arrival of the photon associated with the Raman spectrum and stop measuring before the trailing fluorescence emission arrives. For example, if the distance between the target and the laser is 1 meter, and the distance from the target to the sensor element is also 1 meter, the total time for the light pulse to travel from the laser to the sensor element is t=2m / c=6.671 nanoseconds (ns), where c=the speed of light. Since fluorescence phenomena generally have a longer lifetime than Raman radiation, shutting off the sensor element, for example 100ps after the start time, will effectively reduce interference from the fluorescence radiation. In this example, the sensor element is in the "on state" for a period of time from 6.671ns to 6.771ns after the start of each pulse generation (measurement window). Typically, the observation time for fluorescence radiation is several thousand picoseconds, for example 10000ps. Therefore, the sensor element is configured to be in the "off state" for a period of time, for example 10000ps, during which fluorescence is observed. In this way, photons associated with the time period during the off state are not measured. In an optional or additional embodiment, the start time of the measurement window after the generation of the light pulse can be adjusted to generate a time-based measurement histogram. Using the 2 meter example above, the start time from the moment the light pulse is generated may be 6.671ns, 6.68ns, 6.69ns, etc. Furthermore, the predetermined time period of the "on state" may be set according to the measurement conditions and the speed and sensitivity of the sensor element. Optionally, the length of the predetermined time period may be in the range of 1ps to 100ps.In one example, the predetermined time period may be in the range of from 1 ps, 10 ps, ​​20 ps, ​​30 ps, ​​40 ps, ​​50 ps, ​​60 ps, ​​70 ps, ​​80 ps, ​​90 ps, ​​100 ps, ​​110 ps, ​​120 ps, ​​130 ps, ​​140 ps, ​​150 ps, ​​160 ps, ​​170 ps, ​​180 ps, ​​190 ps or 200 ps. The predetermined time period of the "on state" may also be, for example, 1 to several nanoseconds, and within this time period, a time-to-digital converter combined with a detection element may be used to determine the impact time of a photon in the detector within a resolution of, for example, 30 picoseconds to 100 picoseconds. In this case, the predetermined time period of the "on state" may be in the range from 1, 2, 3, 4, 5, 6, 7 or 8 nanoseconds to 3, 4, 5, 6, 7, 8, 9 or 10 nanoseconds.

[0116] Optionally, the sensor element also includes a plurality of pixels in each spatial region located in different spatial regions. The plurality of pixels in each spatial region are configured to receive separated wavelengths of dispersed radiation and measure the amount of light intensity associated with each wavelength of dispersed radiation. Each of the plurality of pixels of the sensor element can be arranged to measure the spectral intensity of each spectral component at different wavelengths. For example, the first spectral component can point to pixel P1, the second spectral component can point to pixel P2, the third spectral component can point to pixel P3, and so on. Each pixel of the sensor element can be arranged to measure the light intensity of spectral components at different wavelength bands. The sensor element can provide a plurality of measurement values ​​indicating the light intensity of the measured spectral component. Each measurement value can indicate the spectral intensity of scattered light at different wavelengths. The sensor element can optionally include a memory for storing measurement values. The memory can be referred to as a buffer memory, for example. Specifically, the sensor element can include an array of, for example, single photon avalanche diodes (SPADs). The spectral intensity distribution of scattered Raman radiation can be measured by using a sensor element including SPADs. Using a SPAD detector makes it possible, for example, to reduce the noise level of the measurement value. Optionally, the device may also include one or more filters to filter out unwanted spectral components of the dispersed radiation.

[0117] In addition, the device for measuring the time-gated Raman spectrum includes a controller, which is operated to collect the amount of light intensity associated with each wavelength of the dispersed radiation measured by the sensor element to form a time-gated Raman spectrum. The operation timing of the sensor element can be controlled based on the timing signal. The operation of the sensor element can be enabled and disabled based on the timing signal. In particular, the SPAD detector may include a group of counters. The operation of the group of counters can be enabled and disabled based on the timing signal. For example, the timing signal can be formed by using a beam splitter and an auxiliary photodetector in the excitation laser beam. The sensor element can provide a detector signal. The detector signal may include a plurality of measured light signal values. Each light signal value may indicate the spectral intensity of the light radiation, such as Raman scattered light at different spectral regions. Such light signal values ​​can be used to form a time-gated Raman spectrum, or, generally, a time-resolved spectrum associated with a target.

[0118] Furthermore, the device for measuring the time-resolved spectrum may include a data processing unit for processing the measured values ​​obtained from the sensor element. The device may include a memory for storing output values ​​determined based on the measured values. The output values ​​may specify the time-resolved spectrum of the measured target. The data processing unit may be configured to determine the measured time-resolved spectrum or the usual time-resolved light emission spectrum based on the measured values ​​obtained from the sensor element.

[0119] The device may include a control unit for controlling the operation of the device and / or for processing the measured values ​​obtained from the sensor element. The device may also include a memory for storing a computer program. The computer program, when executed by one or more data processors, may cause the device to perform, for example, measuring light signal values ​​and / or processing light signal values.

[0120] The apparatus may include a memory for storing operating parameters. The operating parameters may specify, for example, the duration of an integration period for a plurality of pixels of a sensor element and the number of excitation laser pulses used to generate optical radiation (including Raman scattered light) in a target during a measurement.

[0121] The device may include a user interface for providing information to a user and / or for receiving user input from a user. The user interface may include, for example, a display, a touch screen and / or a keyboard. For example, the user interface may be configured to graphically display the measured time-resolved spectrum. For example, the user interface may be configured to display a graph representing the measured time-resolved spectrum, such as a histogram.

[0122] The device may include a communication unit for sending and / or receiving data. The communication unit may be arranged to communicate with a local area network, the Internet and / or a mobile communication network. The device may also be arranged to perform data processing in a distributed manner, for example by using an Internet server.

[0123] The time-resolved spectrum measured by the device can be compared with reference data, for example, to identify the target. The time-resolved spectrum measured by the device can be compared with reference data to determine the chemical composition of the target. The height and / or position of one or more spectral peaks of the measured time-resolved spectrum can be used to estimate the concentration of the substance in the target. The spectral and temporal shape of the measured light emission pulse can be used to determine, for example, the photoluminescence decay shape.

[0124] According to one embodiment, the time resolved spectrum is a time gated Raman spectrum. In this embodiment, the measured spectrum is a time gated Raman spectrum.

[0125] The present disclosure also relates to a method as described above. The various embodiments and variations disclosed above apply mutatis mutandis to the method.

[0126] A method for measuring time-resolved spectroscopy comprises: generating an optical pulse directed to a target, wherein the target emits optical radiation; providing a time delay to a first portion of the emitted optical radiation that passes through at least one optical delay element, wherein the emitted optical radiation also includes a second portion that bypasses the at least one optical delay element; dispersing the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation is separated into angularly different directions, and wherein each portion of the dispersed radiation leaves the spectral disperser with a predetermined relative delay; and receiving each wavelength of the dispersed radiation in different spatial regions of a sensor element and measuring the light intensity associated with each wavelength of the dispersed radiation; and collecting the amount of light intensity associated with each wavelength of the dispersed radiation to form a time-gated spectrum. According to one embodiment, the time-gated spectrum is a time-gated Raman spectrum.

[0127] Optionally, the method for measuring time-resolved spectroscopy further comprises directing the generated light pulses from the light source to the target using a first optical fiber, and directing a portion of the light radiation from the target to the spectrometer using a second optical fiber.

[0128] Optionally, the method for measuring time-resolved spectroscopy further comprises collecting the generated light pulses from the light source and focusing the generated light pulses toward the target using at least one optical component.

[0129] Optionally, the sensor element further comprises a plurality of pixels in each of the different spatial regions, and wherein the plurality of pixels in each spatial region receive separate wavelengths of dispersed radiation and measure the amount of light intensity associated with each wavelength of the dispersed radiation. Further optionally, when the sensor element receives the dispersed radiation, the sensor element remains in an "on state" for a predetermined period of time. Optionally, the method of measuring time-resolved spectroscopy refers to measuring time-gated Raman spectroscopy. Further optionally, a laser is used to generate the light pulses.

[0130] Detailed description of the drawings

[0131] Reference Figure 1 , a block diagram of an apparatus 100 for measuring time-gated Raman spectroscopy according to an embodiment of the present disclosure is shown. The apparatus 100 for measuring time-gated Raman spectroscopy (as a specific example of measuring time-resolved spectroscopy) includes: a light source 102 for generating light pulses. The apparatus 100 also includes: a first optical fiber 104 for providing an optical path to the generated light pulses from the light source 102. In addition, the apparatus 100 includes an optical component 106 for collecting the generated light pulses from the first optical fiber 104 and focusing the collected light pulses 108 toward a target 110. In addition, the apparatus 100 includes: an optical device 112, such as a lens for collecting emitted light radiation, the emitted light radiation including the emitted Raman scattered light 114 emitted by the target 110; and a second optical fiber 116 for directing the light radiation to a sensor arrangement 118. In addition, the apparatus 100 includes a controller 120, which is operably coupled to the light source 102 and the sensor arrangement 118. The controller 120 is operated to collect quantities of light intensity associated with each wavelength of the dispersed radiation 122 measured by the sensor arrangement 118 to form a time-gated Raman spectrum.

[0132] Reference Figure 2 , showing the embodiment according to the present disclosure Figure 1Schematic diagram of a sensor arrangement 200 implemented in an apparatus 100 for measuring time-gated Raman spectra is shown. A second optical fiber 202 provides an optical path for emitted optical radiation 204. The emitted optical radiation 204 is received by a collimating element 206 to collimate the emitted optical radiation 204. An optical delay element 212 and an optical delay element 214 are arranged on the optical path of a first portion 208 of the collimated emitted optical radiation 210 to provide a time delay to the first portion 208. A second portion 216 of the collimated emitted optical radiation 210 bypasses (i.e. does not pass through) the optical delay elements 212 and 214. The delayed first portion 218 and the second portion 216 are simultaneously received by a spectral disperser 220, so that the delayed first portion 218 and the second portion 216 can leave the spectral disperser 220 in a consistent manner in the form of dispersed radiation including a first spectral component 222 having a first wavelength and a second spectral component 224 having a second wavelength. The sensor element 226 receives the dispersed radiation with a predetermined delay. The controller 228 receives measured spectral values ​​associated with the dispersed radiation. Furthermore, a third portion of the collimated emitted optical radiation 209 is provided with an optical delay element 214 to form a third delayed portion 219 .

[0133] Reference Figure 3 , a schematic diagram of an arrangement 300 is shown according to an embodiment of the present disclosure, which depicts that a collimated beam of optical radiation 302 is separated into dispersed radiation when passing through a diffraction grating 304. The collected optical radiation 306 is received by a spectrometer via an input slit 308. The emitted optical radiation 306 is collimated by passing the emitted optical radiation 306 through a collimating element 310. In addition, the collimated emitted optical radiation 302 passes through the diffraction grating 304 so that the collimated emitted optical radiation 302 can be separated into dispersed radiation. As shown, spectral components 312 are received at one spatial region of a sensor element 314, while spectral components 316 are received at another spatial region of the sensor element 314 to form a time-gated Raman spectrum.

[0134] refer to Figure 4A-4B , shows schematic diagrams of arrangements 400A and 400B employing light transmission segmentation according to embodiments of the present disclosure, wherein optical delay elements 402, 404, and 406 are included as glass blocks. The collected emitted light radiation 408 is received via an aperture 410 representing an input slit of a spectrometer. The collimated light radiation 412 received from the collimating element 414 is divided into three parts, namely a lower part 416, a middle part 418, and an upper part (not shown). The lower part 416 and the middle part 418 correspond to a first part of the collimated light radiation 412, while the upper part corresponds to a second part of the collimated light radiation 412. As shown in FIG. Figure 4AAs shown, the optical path of the lower portion 416 includes two consecutive optical delay elements 402 and 404, which are combined into a glass block to provide a time delay to the lower portion 416. Figure 4B As shown, the optical path of the middle portion 418 includes an optical delay element 406 incorporated as a glass block to provide a time delay to the middle portion 418. It should be understood that the optical path of the lower portion 416 is smaller than the optical path of the middle portion 418, and therefore, the lower portion 416 will be provided with more time delay than the middle portion 418. This arrangement 400A and 400B of the optical delay elements 402, 404 and 406 allows the delayed first part and the second part to be received by the diffraction grating 420 with appropriate relative delays. The delayed first part and the second part are received by the diffraction grating 420 with such relative delays that the delayed first part and the second part travel with a predetermined relative delay after leaving the diffraction grating 420. In the same figure, two example portions of the dispersed radiation including a first spectral component 422 with a first wavelength and a second spectral component 424 with a second wavelength in a predetermined relative delay are also shown. The dispersed radiation is received by the sensor element 426 with a predetermined delay to measure the time-resolved spectrum by controlling the sensor element.

[0135] refer to Figure 5A-Figure 5B , schematic diagrams of arrangements 500A and 500B using light transmission segmentation according to an embodiment of the present disclosure are shown, including optical delay elements as reflectors 502, 504, and 506. Figure 5A As shown, three mirrors 502, 504 and 506 are arranged in the optical path of the first portion 508 of the collimated emitted optical radiation. The arrangement 500A of the mirrors 502, 504 and 506 allows the mirrors 502, 504 and 506 to represent the pure reflection equivalent of a Dove prism. Using this arrangement 500A allows a portion of the first portion 508 to have less optical path than another portion of the first portion 508 to achieve more time delay, such as to be uniformly received by the sensor element. Figure 5B As shown, three reflectors 502, 504 and 506 are arranged in the optical path of the first portion 508 of the collimated emitted optical radiation. The arrangement 500B of the reflectors 502, 504 and 506 enables the reflectors 502, 504 and 506 to provide the equivalent effect of a dove prism and a folding reflector. In addition, the reflectors 504 and 506 are formed as the reflective equivalent of a pentaprism.

[0136] Reference Figure 6, shows a schematic diagram of an arrangement 600 employing light reflection segmentation according to an embodiment of the present disclosure. As shown, a series of reflectors 602 in a trapezoidal configuration are placed in the optical path of the collimated emitted optical radiation. A first portion 604 of the collimated emitted optical radiation reaches each of the series of reflectors 602 and is reflected toward a diffraction grating 606. Such reflectors 602 provide a time delay to the first portion 604 of the collimated optical radiation. Thus, the delayed first portion and the second portion (not shown) leave the diffraction grating 606 in unison. Thus, the spectral components 608 and 610 of the dispersed radiation arrive at the sensor element 612 in unison.

[0137] refer to Figures 7A-7C , schematic diagrams of arrangements 700A-700C using light splitting according to an embodiment of the present disclosure are shown. Fig. 7A As shown, arrangement 700A includes two mirrors 702 and 704, such as plane mirrors, that split incident collimated optical radiation 706 into two portions. A first portion 708 of the split collimated optical radiation is received by a first diffraction grating 710, while a second portion 712 of the split collimated optical radiation is received by a second diffraction grating 714. This arrangement 700A, which replicates the "spruce" design, reduces temporal broadening by half while maintaining wavelength resolution. Figure 7B As shown, arrangement 700B includes a series of reflective surfaces, such as mirror 716. This arrangement 700B requires four separate diffraction gratings 718, 720, 722 and 724, and therefore requires four sensor elements (not shown). Figure 7C As shown, arrangement 700C includes six mirrors 728, 730, 732, 734, 736 and 738. Two mirrors 728 and 730 are arranged to split the collimated emitted optical radiation (not shown) into two parts. In addition, each part of the separated collimated emitted optical radiation is further split into two parts by using mirrors 732 and 734 on one side and mirrors 736 and 738 on the other side. In addition, four diffraction gratings (e.g. Figure 7B 718, 720, 722 and 724 in the diffraction gratings to receive the collimated emitted light radiation of the four parts. It is worth noting that for such a system including four diffraction gratings (e.g. Figure 7B 700C of the arrangement of diffraction gratings 718, 720, 722 and 724), four sensor elements (not shown) are required to measure the light intensity associated with the dispersed radiation.

[0138] Fig. 8A and 8B An arrangement using a first spherical mirror 802 having a radius of curvature r1 and a second spherical mirror 804 having a radius of curvature r2 as optical delay elements is shown. Fig. 8Ais a view from the side of the arrangement, Figure 8B It is a view from the AA direction of the arrangement. The collected optical radiation is received via the slit 810. The emitted optical radiation input from the slit 810 is a divergent beam. The first part 816 of the emitted optical radiation (marked with a solid line in the figure) travels an optical length of 2xr1 when traveling from the input slit 810 via the first reflector 802 to the output 822. The second part 818 (marked with a dotted line in the figure) travels an optical length of 2xr2 from the input slit 810 via the reflector 804 to the output 822. The first spherical mirror 802 and the second spherical mirror 804 have a common center of curvature 820. For example, if r1 is 30 cm and r2 is 15 cm, the optical delay between the first part and the second part is (30x2-15x2) cm / (3x10^8 m / s)=1 ns.

[0139] The embodiments disclosed above may be modified without departing from the scope of the present disclosure as defined by the appended claims. Expressions such as "comprising," "including," "combining," "having," etc. are used to describe, and the claims of the present invention are intended to be interpreted in a non-exclusive manner, i.e., allowing for the presence of items, components, or elements that are not explicitly described. References to the singular are also interpreted as relating to the plural.

Claims

1. A device (100) for measuring time-gated Raman spectroscopy, the device (100) comprising: A light source (102) for generating a light pulse directed toward a target (110), wherein the target will subsequently emit optical radiation comprising at least a first portion (208, 508, 604) and a second portion (216) of a plane wavefront of the emitted optical radiation; a sensor arrangement (118, 200) for measuring the intensity of said optical radiation; and a controller (120, 228) operably coupled to the light source (102) and the sensor arrangement; Wherein, the sensor arrangement comprises: at least one optical delay element (212, 214, 402, 404, 406) for providing a time delay to a first portion (208, 508, 604) of the emitted optical radiation (210, 302, 412, 706), wherein a second portion (216) of the emitted optical radiation bypasses the at least one optical delay element; a spectral disperser (220) for dispersing the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation (122) is separated into angularly different directions, and wherein each portion of the dispersed radiation leaves the spectral disperser with a predetermined relative delay; and a sensor element (226, 314, 426, 612) configured to receive each wavelength of the dispersed radiation over a different spatial region of the sensor element and to measure the light intensity associated with each wavelength of the dispersed radiation; and Therein, the controller is operated to record the measured light intensity associated with each wavelength of the dispersed radiation measured by the sensor element to form a time resolved spectrum.

2. The device (100) according to claim 1, wherein: The device for measuring the time-resolved spectrum also includes: a first optical fiber (104) for directing the generated light pulses from the light source (102) to the target (110); and a second optical fiber (116, 202) for directing the emitted optical radiation (204, 210, 302, 412, 706) to the spectral disperser (220).

3. The device (100) according to any one of the preceding claims, wherein: The apparatus for measuring time-resolved spectroscopy further comprises at least one optical member (106) for collecting the generated light pulses from the light source (102) and focusing the generated light pulses toward the target (110).

4. The device (100) according to claim 1 or 2, wherein: The at least one optical delay element (212, 214, 402, 404, 406) includes at least one of the following: a free space length, a prism made of glass, a cuboid made of glass, a Dove prism made of glass, a pentaprism made of glass, a prism made of crystal material, a cuboid made of crystal material, a Dove prism made of crystal material, a pentaprism made of crystal material, a mirror arrangement, a lens, an optical fiber.

5. The device (100) according to claim 1 or 2, wherein: At least a first portion of the emitted optical radiation is arranged to pass through at least one optical delay element a plurality of times.

6. The device (100) according to claim 1 or 2, wherein: The spectral disperser (220) includes at least one of the following: a diffraction grating (304, 420, 606, 710, 714, 718, 720, 722, 724), a prism, and a Fabry-Perot etalon.

7. The device (100) according to claim 6, wherein: The spectral disperser (220) includes: a diffraction grating (304, 420, 606, 710, 714, 718, 720, 722, 724), and the delayed first part of the emitted optical radiation and the second part of the emitted optical radiation are configured to be directed to the sensor element (226, 314, 426, 612) through the spectral disperser using the diffraction grating, and the diffraction grating uses at least one of the following: light transmission segmentation, light reflection segmentation, and light splitting.

8. The device (100) according to claim 1 or 2, wherein: The sensor element (226, 314, 426, 612) also includes: a plurality of pixels located on each of the different spatial regions, and wherein the plurality of pixels located on each of the spatial regions are configured to receive separated wavelengths of the dispersed radiation and measure the light intensity associated with each wavelength of the dispersed radiation.

9. The device (100) according to claim 1 or 2, wherein: When the sensor element receives the dispersed radiation, the sensor element (226, 314, 426, 612) is operated to be in an "on state" for a predetermined period of time.

10. The device (100) according to claim 1, further comprising: At least one collimating element (206, 310, 414) is used to collimate the optical radiation received from the target, the at least one collimating element being arranged in an optical path between the target and the at least one delay element.

11. The device (100) according to claim 1, further comprising at least one collimating element (206, 310, 414) for collimating the optical radiation received from the target, the at least one collimating element being arranged in an optical path between the at least one delay element and the sensor element.

12. The device (100) according to claim 10 or 11, wherein: The at least one collimating element comprises at least one of: a lens arrangement, a mirror arrangement, an aperture (308, 410) combined via a pinhole or a slit, an optical waveguide.

13. The device (100) according to claim 1 or 2, wherein: The light source (102) is a laser.

14. A method for measuring time-gated Raman spectroscopy, wherein: The method comprises: generating a light pulse directed toward a target (110), wherein the target will subsequently emit optical radiation comprising at least a first portion (208, 508, 604) and a second portion (216) of a plane wavefront of the emitted optical radiation; providing a time delay to a first portion (208, 508, 604) of the emitted optical radiation (210, 302, 412, 706), wherein a second portion (216) of the emitted optical radiation bypasses at least one optical delay element (212, 214, 402, 404, 406); dispersing the delayed first portion of the emitted optical radiation and the second portion of the emitted optical radiation into dispersed radiation having a plurality of wavelengths, wherein each wavelength of the dispersed radiation (122) is separated into angularly different directions, and wherein each portion of the dispersed radiation exits the spectral disperser (220) with a predetermined relative delay; and receiving each wavelength of the dispersed radiation in a different spatial region of a sensor element and measuring the light intensity associated with each wavelength of the dispersed radiation; and The measured light intensity associated with each wavelength of the dispersed radiation measured by the sensor element (226, 314, 426, 612) is recorded to form a time resolved spectrum.

15. The method according to claim 14, wherein: The method for measuring the time-resolved spectrum also includes directing the generated light pulses from the light source (102) to the target (110) using a first optical fiber (104), and directing the emitted optical radiation (204, 210, 302, 412, 706) to the spectral disperser (220) using a second optical fiber (116, 202).

16. The method according to claim 14 or 15, wherein: The method for measuring the time-resolved spectrum also includes collecting the generated light pulses from the light source (102) and focusing the generated light pulses toward the target (110) using at least one optical component (106).

17. The method according to claim 14 or 15, wherein: The sensor element (226, 314, 426, 612) also includes: a plurality of pixels located on each of the different spatial regions, and wherein the plurality of pixels located on each of the spatial regions receive separated wavelengths of the dispersed radiation and measure the light intensity associated with each wavelength of the dispersed radiation.

18. The method according to claim 14 or 15, wherein: When the sensor element receives the dispersed radiation, the sensor element (226, 314, 426, 612) is in an "on state" for a predetermined period of time.

19. The method of claim 14 or 15, further comprising collimating the optical radiation.

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