Flex-spectrum optical detector

Abstract

To provide an optical system that can detect responses from a sample over a full spectrum with high sensitivity and high resolution.SOLUTION: An optical system 100 includes an optical source 102 to provide excitation light 150 and a collecting element to direct an optical signal 160 received from a sample in response to incidence of the excitation light on a sample 155, to an optical device 110. The optical device includes: a separating element to separate the optical signal into a plurality of spectral bands that are spatially or angularly separated along a band separation direction; a dispersive element having a dispersive region to disperse spectral components of a spectral band along a dispersion direction to form a dispersed spectral band; and an optical element to manipulate the dispersed spectral band in association with imaging the spectral band onto a detector area of a detector array. The optical system includes a controller 122 to obtain one or more read-out signals from the detector array.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] Cross - Reference to Related Applications This patent application claims priority to U.S. Provisional Patent Application No. 63 / 620,080, filed on January 11, 2024, with the title "FLEX SPECTRUM SPECTROMETRY". The disclosure of the prior application is considered a part of this application and is incorporated herein by reference.

[0002] This disclosure generally relates to optical detectors and flex - spectrum optical detectors.

Background Art

[0003] In spectroscopy, conventionally, by dispersing the full - spectrum response, the dispersed spectrum is formed into the shape of a continuous elongated (high width - to - height aspect ratio) beam composed of dispersed spectral bands. Conventionally, the dispersed spectral bands are imaged such that only one spectral band is imaged in a direction perpendicular to the dispersion direction for any detector pixel position along the dispersion direction from one end of the beam to the other end, and they are arranged in a "linear" one - dimensional (1D) sequence. When performing spectroscopy, it is generally desired to detect the response from a sample with high sensitivity and high resolution over the full spectrum (e.g., for a Raman spectrometer, a spectral range of more than 100 nanometers (nm) in wavelength or more than 3000 inverse centimeters (cm−1) in wavenumber).

Summary of the Invention

Means for Solving the Problems

[0004] In one form, an optical system includes a light source that provides excitation light, a collection element that directs an optical signal received in response to the incidence of the excitation light on a sample toward an optical device, the optical device including a separation element that separates the optical signal into a plurality of spectrally separated bands that are spatially or angularly separated along a band separation direction, where each of the plurality of spectrally separated bands has a different spectral range, a dispersion element having a plurality of dispersion regions, where one of the plurality of dispersion regions forms a dispersed spectral band by dispersing spectral components of one of the plurality of spectrally separated bands along a dispersion direction, a plurality of optical elements, where one of the plurality of optical elements operates on the dispersed spectral band in connection with imaging the spectral band onto a detector area of a detector array, a detector array including the detector area, and a controller that obtains one or more readout signals from the detector array.

[0005] In one form, an optical system includes a light source that provides excitation light and a collection element that directs an optical signal received in response to the incidence of the excitation light on a sample toward an optical device, where the optical device separates the optical signal into a plurality of spectrally separated bands that are spatially or angularly separated along a band separation direction, where each of the plurality of spectrally separated bands has a different spectral range, forms a dispersed spectral band by dispersing spectral components of one of the plurality of spectrally separated bands along a dispersion direction, and operates on the dispersed spectral band in connection with imaging the spectral band onto a detector area of a detector array of the optical device, and a controller that obtains one or more readout signals from the detector array.

[0006] In one form, the optical system includes a light source that provides excitation light, a collection element that directs an optical signal received in response to the incidence of the excitation light on the sample toward an optical device, an optical device that is a separation element that separates the optical signal into a plurality of spectral bands, wherein the spectral ranges are different between each of the plurality of spectral bands, a dispersion element having a dispersion region, the dispersion region forming a dispersed spectral band by dispersing the spectral components of one of the plurality of spectral bands, an optical element that operates on the dispersed spectral band in relation to imaging the spectral band on a detector area of a detector array, a detector array including the detector area, and a controller that coordinates the operation of the light source with the operation of one or more elements of the collection element or the optical device such that the reception timing of the optical signal is synchronized with the timing of an acquisition period of the detector area.

Brief Description of the Drawings

[0007]

Figure 1A

Figure 1B

Figure 1C

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Embodiments for Carrying Out the Invention

[0008] With reference to the accompanying drawings, the exemplary embodiments will be described in detail below. The same reference numerals in different drawings may indicate the same or similar elements.

[0009] In spectroscopy, spectrometers have conventionally been designed to provide light in the form of a single, non - split, linear light beam that includes the full spectral range being investigated by the spectrometer, using a dispersive element of the spectrometer. The dispersive element disperses the light, and the dispersed light is projected onto the detector of the spectrometer as a continuous, non - split, linear image. Here, the dispersed spectrum conventionally consists of dispersed spectral components that form a continuous, elongated (high width - to - height aspect ratio) beam shape, where only one spectral component is imaged in a direction perpendicular to the dispersion direction, from one end of the beam to the other without any interruption or for any detector pixel position along the dispersion direction, arranged in a "linear" 1D sequence. When performing spectroscopy, generally, it is desirable to detect the response from a sample with high sensitivity and high resolution over the full spectrum (e.g., for a Raman spectrometer, a spectral range of more than 100 nanometers (nm) in wavelength or more than 3000 inverse centimeters (cm−1) in wavenumber). However, it is difficult to actually do this efficiently. For example, if a high - sensitivity, high - resolution detector array over the full spectrum is required, the physical design of the detector needs to include a high width - to - height aspect ratio. This results in inefficient use of the physical space within the spectrometer system. Therefore, it would be advantageous to abandon the 1D shape of the conventionally dispersed spectrum, avoid the high aspect ratio of the detector, and accommodate a more general 2D imaging detector array.

[0010] Furthermore, every dispersed spectrum has two important attributes: spectral range and spectral resolution. These attributes are incompatible with a fixed spectral physical width. That is, for a given spectral range, there is a given spectral resolution. Increasing the resolution increases the spectral width for a fixed spectral range or decreases the spectral range for a fixed spectral width. Such a limitation exists for the 1D spectrum imaged on the detector. When performing spectroscopic analysis, it is generally desirable that the sensitivity and the degree of resolution of all spectral bands within the full spectral response be substantially the same. On the other hand, many conventional spectroscopic analysis systems are aimed at identifying specific characteristics such that one or more specific spectral bands can provide more useful specific information while another spectral band can provide minimal specific information. In this case, if the sensitivity and resolution of all spectral bands are the same, the use of the detector may become inappropriate. Therefore, it would be advantageous to increase the sensitivity and resolution of the spectral bands that provide more useful and higher specific information and decrease the sensitivity and resolution of the spectral bands that provide more useful and lower specific information. Similarly, some spectral bands of the full spectrum may not provide any useful information, and it may be useful not to image such spectral bands on the detector.

[0011] Conventional two-dimensional (2D) techniques can be used to split the full spectrum, in some cases (e.g., via a beam splitter), into multiple beams, each containing the full spectrum range. Subsequently, different spectral range portions of each beam are imaged onto different detectors. In particular, according to this conventional 2D technique, each beam contains a full spectrum of a portion of the original power, and only a portion of different spectral bands from each beam is imaged onto the detector. This is a waste of power because the original power is split into each full-spectrum beam, and the portion of each beam that is not imaged onto the detector is wasted. Thus, even for a spectral range that is imaged onto a portion of the detector, the spectral range contains only a small portion of the original power. By wasting power, the sensitivity also decreases. Therefore, it would be advantageous to image as much of the power from the full-spectrum response as possible onto the detector.

[0012] The embodiments described herein provide techniques and apparatus for measuring a spectral response that can split a full-spectrum response into spectral bands (e.g., sub-spectra of any spectral range, resolution, or dynamic range). While preserving the power of the full-spectrum response, each spectral band can be oriented to a desired physical location on a detector array through dispersion. In other words, the techniques and apparatus described herein are realizable to separate the full-spectrum response with minimal power loss into a group of distinct spectral bands (e.g., sub-spectra) with respect to wavelength or wave number. These spectral bands can then be independently manipulated or repositioned before spectral dispersion and imaging onto a detector (e.g., a 2D detector). The techniques and apparatus described in this specification avoid power loss when splitting the full-spectrum response, remove the constraints on the bandwidth, resolution, and dynamic range of each spectral band, improve the utilization efficiency of the 2D detector, and enable a smaller spectrometer.

[0013] The techniques and apparatus described herein separate the full spectrum of incident light into spectral bands without losing power (except for power losses caused by non-idealities of the optical components performing the separation function), and spatially rearrange (e.g., stack) the spectral bands before sending them to a dispersive element, enabling a relatively smaller spectrometer. Such a design allows for a higher optical resolution per spectral band from the dispersive element, and in some designs, may allow for a reduction in the size of the dispersive element in the dispersion direction. After dispersion, the dispersed spectral bands are projected and (e.g., stacked and) imaged onto a 2D detector array. Thus, a higher detector resolution is enabled, and the utilization efficiency of the active area of the detector array is improved.

[0014] The techniques and apparatus described herein include spectral banding at the front end. This involves dividing the full spectral range into multiple spectral bands (e.g., sets of adjacent, sequential, or different spectral ranges) before dispersion. In some forms, the spectral bands may not overlap, or may overlap partially (e.g., minimally), or may overlap substantially (e.g., to account for manufacturing redundancy or tolerance when trying to create non-overlapping or adjacent spectral bands). In some forms, a 2D spectral band arrangement can be created by rearranging the spectral bands in space and stacking them on the dispersive element in a non-dispersion direction (e.g., a direction perpendicular to the dispersion direction). In some forms, the dispersive element can comprise a plurality of dispersion regions (e.g., each having different dispersion characteristics) that can be mapped to the incident spectral width. Thus, each dispersion region of the dispersive element can disperse and redirect the incident light independently of the other dispersion regions.

[0015] After dispersion, the spatial arrangement of the dispersed spectral bands may be maintained, or further rearrangement may occur when the dispersed spectral bands are oriented onto the detector array. For example, in some forms, the dispersed spectral bands are arranged in space and may be stacked on a 2D detector array in the band separation direction. The rearrangement of the spectral bands can be done in various ways (e.g., depending on the selected spectral range division and the resolution target). In general, the number of spectral bands, the spectral range of the spectral bands, and the spectral resolution of the spectral bands can be freely and independently changed and set according to the desired performance goals for a given application (e.g., Raman, time-gated Raman, spatially offset Raman spectroscopy (SORS), or fluorescence, etc.). For example, the spectrum formed by the sum of all spectral bands can be discontinuous (e.g., interrupted by one or more gaps), or can have different spectral resolutions for each sub-spectrum. Additionally or alternatively, the dynamic range and sensitivity required for the measurement of each spectral band can be freely set independently of other spectral bands by controlling the "height" (e.g., the direction orthogonal to the dispersion direction) in which each spectral band is imaged onto the detector. Increasing the detector area illuminated by a particular spectral band does not change the total amount of photons within that spectral band. On the other hand, increasing the detector area increases the dynamic range achievable in that spectral band and increases the saturation limit of the detector for wavelengths within that spectral band. This is because the photons spread over more pixels of the detector. In some forms, one or more spectral bands (e.g., one or more non-interested spectral bands) can be excluded by the techniques and apparatus described herein. For example, one or more spectral bands can be excluded from the imaging on the detector during spectral splitting, dispersion, or spatial or angular rearrangement (e.g., before or after dispersion).

[0016] In particular, the techniques and apparatus described herein enable full-spectrum splitting in a manner different from the above-described conventional 2D techniques. In some forms, the full spectrum is split into spectral bands with different wavelength / wavenumber ranges, and then they are spatially reconfigured such that the multiple spectral bands (which can together cover the full spectrum range and can include substantially all of the power of the original spectrum) are stacked in a direction perpendicular to the dispersion direction to result in a 2D arrangement. In such an arrangement, a higher resolution can be achieved compared to a 1D arrangement of the same width (i.e., on a 1D detector). By way of comparison, (assuming, for example, that all spectral bands are of the same width and cover the same spectral range), to achieve the same full spectrum range with an increased resolution with a linear 1D response, a detector with a spectral dispersion dimension increased by a factor equal to the number of spectral bands created is required. Compared to conventional 2D techniques, since the full spectrum is split into individual, (optionally) non-overlapping spectral bands that include substantially all of the power of the full spectrum, the power loss is minimized. This flex-spectrum spectroscopy technique enables the maximum utilization of the active area of the detector and allows for a rectangular-shaped (e.g., with a low width-to-height ratio) 2D detector array. In some forms, the full spectrum can be spatially reconfigured and separated into individual non-overlapping spectral bands that are aligned and stacked on the active area of a 2D detector array with a low width-to-height ratio.

[0017] With the same physical size as conventional 1D techniques, the technologies and apparatuses described herein can achieve higher resolution and / or cover a larger spectral range. Alternatively, the technologies and apparatuses described herein can typically achieve the same performance by reducing the width of the detector in the dispersion direction, which is the maximum dimension of the detector typically used in spectroscopic analysis, to a fraction of the physical size of conventional 1D techniques. Splitting the spectrum to reduce the width, while increasing the height by rearrangement in a direction perpendicular to the dispersion direction (i.e., the band separation direction) of the split spectral bands, results in a detector shape that is advantageous in terms of enabling a spectrometer or spectroscopic analysis system of compact size (e.g., volume), or in terms of affinity with a wider selection of commercially available large pixel count detector arrays (e.g., SPAD arrays). Increasing the height of the detector to cover additional spectral width results in only a slight or no increase in the height of the spectrometer. On the other hand, reducing the width of the detector reduces the angular spread of the dispersed sub-spectra and the width of the detector on its plane, significantly reducing the installation area. As a result of the reduced detector width, the sizes of the optical and mechanical components within the spectrometer also become smaller, realizing a reduction in the size, weight, and (potentially) power consumption of the spectrometer system.

[0018] As described above, for a given detector width along the dispersion direction, the techniques and apparatus described herein can achieve higher resolution and / or cover a larger spectral range. There is no longer a fixed or limiting of the performance attributes of the spectrometer by the detector width. This flexibility is made possible by adding a second dimension to the spectral layout. With the techniques and apparatus described herein, the detection dynamic range and sensitivity can be varied over the full spectral range. By splitting the spectrum, each spectral band can be adjusted to cover any particular height (i.e., the number of pixels in the band separation direction) on the active area of the detector. Thus, for example, the detection dynamic range and sensitivity (which increase or decrease according to the height of the spectral components on the active area of the detector) can be modulated over the various spectral bands to reflect the relative importance of the various spectral bands in a spectroscopic measurement target.

[0019] In practice, the spectrometer can be used in applications such as Raman spectroscopic analysis that utilize the time-gate principle. The time-gate principle in Raman spectroscopic analysis is utilized to suppress fluorescence and phosphorescence generated by sampling during the measurement process, and further to maintain a sufficiently high signal-to-noise ratio (SNR) while suppressing other potential continuous disturbances (such as ambient light or thermal radiation). Time-gated Raman spectroscopic analysis is an effective technical solution to the problem of fluorescence generated by sampling that can mask Raman signals during spectrum detection. Conventional optical systems for performing time-gated Raman spectroscopic analysis use conventional spectrometers that implement the above-described 1D technology. In this case, as a result of the method of manipulating light (e.g., dispersion into a single non-segmented linear light beam including the full spectral range and projection as a continuous non-divided linear image onto the detector), a problem of trade-off between performance and size occurs. As described above, this technology requires a wide dispersion element (dispersion direction) for the same dispersion power to achieve a given spectral resolution, and further requires a wide detector area to cover the full spectral range for a given spectral range and resolution. Instead of widening the detector area to cover the full spectral range for a given spectral range and resolution, it is also possible to use a relatively small 1D detector array to continuously stitch together spectra by stepping or scanning the incident angle to the dispersion element.

[0020] In some forms, the compact spectrometers described herein can be included in optical systems used in other types of spectroscopic analysis applications, such as time-gated Raman spectroscopic analysis applications, time-resolved fluorescence spectroscopic analysis applications, dynamic real-time spatial offset Raman spectroscopic analysis (SORS) applications, laser-induced breakdown spectroscopic analysis (LIBS) applications, or photoacoustic spectroscopic analysis applications. Generally, for a given application, the number of spectral bands provided by the spectrometer can be variable, and the spectral range and / or spectral resolution of a given spectral band can be set independently of other spectral bands freely. Thereby, the optical system may be able to meet the performance goals of the optical system in a given application. Further details will be described later.

[0021] Figures 1A - 1C are diagrams showing examples related to an optical system 100 including a flex - spectrum optical detector 110 described in this specification. As shown in FIG. 1A, the optical system 100 may include a light source 102, a collection element 104, a filter 106, a slit 108, a flex - spectrum optical detector 110 (referred to as optical device 110 in this specification), and a controller 122. As shown in the figure, depending on the design of the optical system 100, the optical system 100 may include one or more other elements associated with the manipulation or direction of light, such as one or more directing elements (e.g., one or more mirrors) or one or more lenses (not labeled in FIG. 1A). In one example, the optical system 100 includes a small - sized Raman spectroscopy engine that can be used for desktop, portable, or built - in applications. In some forms, one or more elements of the optical system 100 may be included in a hermetic package. In one exemplary form, elements of the optical system 100 other than the light source 102 may be housed in a hermetic package. For example, the hermetic package may be a sealed metal housing. In some forms, hermetic sealing can improve the reliability of one or more elements of the optical system 100, particularly the collection element 104 in the form of a MEMS device or a thermoelectric cooler (TEC) used for laser cooling (not shown in FIG. 1A). Further, in some forms, hermetic sealing can improve the wavelength stability of diffraction grating dispersion (i.e., calibration).

[0022] The light source 102 comprises one or more elements that provide the excitation light 150. In some forms, the light source 102 can be a pulsed laser source. In some forms, the light source 102 can provide the excitation light 150 such that the excitation light 150 includes optical pulses having a high repetition rate (e.g., greater than about 500 kilohertz (kHz)), low energy (e.g., less than about 100 nanojoules (nJ)), and a narrow linewidth (e.g., less than about 0.1 nanometer (nm)) for a given wavelength. In some forms, the wavelength of the excitation light 150 can be approximately equal to 532 nm. However, in practice, the light source 102 can be designed to provide the excitation light 150 at virtually any wavelength. In some forms, the light source 102 can reduce the timing jitter in the excitation light 150 or can perform synchronization taking into account the jitter in the excitation light 150. That is, in some forms, the light source 102 can be a low-jitter laser source. The light source 102 can be controlled by the controller 122 to achieve the functions described above.

[0023] In some forms, the light source 102 may be a plurality of light sources 102, and each light source of the plurality of light sources 102 may, for example, emit light at different wavelengths, generate excitation light 150 having different pulse characteristics (such as pulse width, repetition rate, or pulse energy, etc.), or be configured to operate in different operating modes (such as continuous wave (CW), Q-switching, or mode-locking, etc.). In some forms, as shown in FIG. 1A, the excitation light 150 is provided such that the excitation light 150 is incident on the sample 155. In some forms, the use of a plurality of light sources 102 can contribute to better utilization of the spectral range detected by the optical system 100. For example, in Raman spectroscopy, a "silent region" exists in the Raman shift spectrum, typically in the range of about 1800 cm-1 to about 2800 cm-1. In some such applications, the (second) light source 102 can provide another excitation wavelength to fill the spectral band with Raman shifts from the target spectral region. Different excitation wavelengths produce different interactions with the sample material and affect important measurement parameters such as Raman scattering efficiency, the amount of fluorescence background generated, and the damage threshold in various ways. Thus, a combination of a plurality of light sources 102, each providing each (narrow-band) excitation light 150, can be used to improve the optical system 100 for a given application. In some forms, the light source 102 of the optical system 100 may be included in a hermetic package that houses one or more other elements of the optical system 100. Incorporating the light source 102 into a hermetic package can be advantageous, for example, to achieve a desirable form of integration (e.g., within a single package) of the optical system 100. Additionally or alternatively, the light source 102 of the optical system 100 may be external to a hermetic package that houses one or more other elements of the optical system 100. In such a form, the light source 102 may be stored in a second hermetic package (i.e., a hermetic package separate from the one that stores one or more other elements of the optical system 100).A light source 102 located outside the hermetic package can be advantageous in terms of, for example, facilitating thermal management (e.g., since the light source 102 may be a major heat source of the optical system 100), facilitating replacement or exchange of the light source (e.g., with another light source 102 having a different laser type or different characteristics), or increasing the degree of freedom in laser design.

[0024] The collection element 104 includes one or more elements for directing an optical signal 160 received from the sample 155 towards the optical device 110 in response to the incidence of the excitation light 150 on the sample 155. For example, the collection element 104 may have one or more reflective elements such as one or more microelectromechanical systems (MEMS) mirrors. In some forms, the collection element 104 in the form of a MEMS mirror can be used to scan the pulses of the excitation light 150 over a 1D or 2D region of the sample 155, or to dither the excitation light 150 to avoid damage or heating of the sample 155. In some forms, the collection element 104 can be omitted from the optical system 100 (i.e., the collection element 104 may not be included in some forms of the optical system 100). As an example of such a form, the excitation light 150 can be transmitted through the filter 106 and incident on the sample 155, and the optical signal 160 from the sample 155 can be reflected on the optical path by the filter 106 and directed towards the optical device 110.

[0025] The filter 106 has one or more elements for removing one or more excitation wavelengths from the optical signal 160. For example, as shown in FIG. 1A, the filter 106 may include an element that reflects light at the excitation wavelength (e.g., 532 nm) and transmits light at other wavelengths.

[0026] The slit 108 has one or more elements related to the definition of the optical throughput and the optical resolution of the optical system 100 (in combination with the optical device 110). In some forms, the slit 108 is a mechanical feature such as an opening in a light-shielding screen (e.g., a rectangular opening). In some forms, the optical signal 160 is focused by one or more other elements of the optical system 100 such that the transmission of the optical signal 160 through the slit 108 is maximized.

[0027] Note that the example of the optical path shown in FIG. 1A is provided for illustrative purposes, and other forms are possible. For example, on the optical path of the excitation light 150 shown in FIG. 1A, the excitation light 150 is reflected by the filter 106 and guided to the sample 155 by the collection element 104. Further, as shown in FIG. 1A, on the optical path of the optical signal 160, the optical signal 160 is reflected by the collection element 104, transmitted through the filter 106, and guided to the optical device 110 by the reflection element. In this example, the collection element 104 and the filter 106 are present in both the optical path of the optical signal 160 and the optical path of the excitation light 150. However, in another exemplary form, the optical path of the optical signal 160 and the optical path of the excitation light 150 may be separate and independent optical paths.

[0028] The optical device 110 includes the flexible spectrum optical detector described in this specification. FIG. 1B is a diagram showing an exemplary form of the optical device 110. As shown in FIG. 1B, the optical device 110 includes a separation element 112, a dispersion element 114, a plurality of optical elements 116 (for example, including optical element 116a, optical element 116b, and optical element 116c), and a detector array 118 including a set of detector areas 120 (for example, detector area 120a, detector area 110b, detector area 120c). The upper diagram of FIG. 1B shows an example of a diagram of the optical device 110 along the dispersion direction (that is, the direction in which the dispersion element 114 disperses the spectral band 165 as described later), and the lower diagram of FIG. 1B shows an example of a diagram of the optical device 110 along the band separation direction (that is, the direction in which the separation element 112 separates the optical signal 160 into a plurality of spectral bands 165 as described later). As shown in FIG. 1B, the optical signal 160 emitted from the sample 155 (for example, an altered transmission signal from the light source 102, or a signal generated by the sample 155 as a result of excitation by the excitation light 150, etc.) includes spectral information (that is, spectral response) directed towards the optical device 110.

[0029] The separation element 112 includes one or more elements for separating the optical signal 160 into a plurality of spectral bands 165. That is, the separation element 112 includes one or more elements that divide (e.g., for each spectral range) and re-arrange (e.g., spatially / angulary) the spectral response from the sample 155 into spectrally band-separated and spatially and / or angularly re-arranged spectral bands (e.g., spectral band 165a, spectral band 165b, spectral band 165c, and spectral band 165d). In some forms, the direction in which the separation element 112 separates the optical signal 160 into a plurality of spectral bands 165 spatially or angularly is referred to as the band separation direction. In some forms, the band separation direction is perpendicular to the dispersion direction (e.g., the direction in which the dispersion element 114 disperses the spectral band 165). Although a band separation direction perpendicular to the dispersion direction can be used for practical purposes, in some forms (e.g., depending on the shape of the detector), a shape in which the band separation direction is not perpendicular to the dispersion direction can also be utilized. In some forms, the separation of the optical signal 160 (e.g., spectral splitting and re-arrangement) is performed in a single direction, i.e., the band separation direction. In one example, the separation element 112 can change the angle of the wavelength of the optical signal 160 to generate a continuous spatial spectral spread in the band separation direction.

[0030] The separation element 112 can be configured to provide any number of spectral bands having different characteristics (e.g., physical size and orientation in space, spectral range, and / or spectral width). In some forms, the spectral range varies between each of the plurality of spectral bands 165 of the plurality of spectral bands 165. In some forms, the spectral bands 165 within the plurality of spectral bands 165 may not substantially overlap (e.g., each spectral band 165 covers a substantially different frequency range, etc.). Such forms can be utilized, for example, to maximize the spectral range covered by the banding of the optical signal 160 provided by the separation element 112. In some of such forms, a given pair of adjacent spectral bands 165 may overlap slightly (e.g., the overlap ranges from about 2% to about 10% at most). Such overlap can be utilized, for example, to avoid gaps between spectral bands 165 that may arise from design or manufacturing non-idealities. Additionally or alternatively, the spectral bands 165 within the plurality of spectral bands 165 may overlap significantly to provide significant spectral redundancy (e.g., an overlap of a frequency range exceeding about 10%). As an example, depending on the application, the same sub-band spectral range (e.g., an overlap of about 100%) detected by two different detector areas 120 of the detector array 118 may be required (e.g., when the detector characteristics of the two detector areas 120 are different, or when the power of each "identical" spectral band 165 is intentionally made different when incident on each dedicated detector area 120, etc.).

[0031] In one form, the separating element 12 may be configured such that the optical power varies between the spectral bands 165 (e.g., the optical power of a given spectral band 165 is controlled to be different from the optical power of another spectral band 165 to a desired extent or intentionally). Such a form may be utilized, for example, when different detector areas 120 have different input optical power saturation levels (or thresholds) and it is desirable for the different detector areas 120 to operate similarly. As another example, such a form may be utilized when it is desirable to use detector areas 120 at different input power levels to explore the detector areas 120 in different input optical power saturation regions (e.g., a plurality of spectral bands 165 having different optical powers but the same spectral range may be transmitted to a plurality of nominally identical detector areas 120).

[0032] In one form, the separation element 112 can split the optical signal 160 into spectral bands without power loss (e.g., except for power losses caused by component non-ideality). Note that conventional techniques are based on power splitting rather than spectral separation. In other words, conventional techniques split an optical signal into N (N>1) substantially equal sub-beams, and each sub-beam has one Nth of the power of each spectral band of the full spectrum. On the other hand, the separation provided by the separation element 112 separates the optical signal 160 into a plurality of spectral bands 165 that have all of the power from their respective bands and no power from other bands (within a reasonable range of component non-ideality). Thus, the separation provided by the separation element 112 preserves the power corresponding to each spectral band, enables an improvement in throughput, and thus an improvement in sensitivity. Further, by preserving the power associated with each spectral band, the measurement speed of spectroscopic analysis can be improved. For example, the SNR of a given detected spectral component (e.g., a Raman peak within a portion of a spectrum) at a given detection time (i.e., photon collection time) is approximately proportional to the square root of the number of detected Raman photons. For a given excitation pulse energy and number of excitation pulses (or detection period), there are significantly more Raman photons reaching the detector within that spectral component. Thus, spectral splitting achieves a higher SNR (compared to power splitting). This means that for the same SNR, the number of pulses required for spectral splitting is reduced, and thus the detection period is shortened, which is equivalent to an improvement in measurement speed.

[0033] The dispersive element 114 includes one or more elements that disperse the spectral components of the spectral band 165 to form a dispersed spectral band 165. That is, the dispersive element 114 includes one or more elements that disperse the spectral band 165 (e.g., spectral bands 165a to 165d), and forms a plurality of dispersed spectral bands 165 (e.g., in the example shown in FIG. 1B, the dispersed spectral band 165a, the dispersed spectral band 165c, the dispersed spectral band 165d). In some forms, the dispersive element 114 may include one element that can spatially separate incident light into different spectral components (e.g., wavelengths). For example, the dispersive element 114 may include a diffraction grating, a prism, or any other wavelength dispersive element. In one exemplary form, the spatially separated spectral bands 165 are incident on a diffraction grating having spatially separated portions (which may or may not be continuous), and each portion is designed to operate at the corresponding incident spectral band 165. In some forms, the direction in which the dispersive element 114 disperses the spectral band 165 is referred to as the dispersion direction. In some forms, the dispersive element 114 includes a plurality of dispersion regions (e.g., each dispersing one of the plurality of spectral bands 165). In some forms, the plurality of dispersion regions may be stacked along a band separation direction (e.g., perpendicular to the dispersion direction). In some forms, a given dispersion region of the dispersive element 114 disperses the incident spectral band 165 independently of the dispersion by other dispersion regions of the dispersive element 114. For example, in some forms, the plurality of dispersion regions are monolithically patterned (or mechanically laid) on a single dispersive element 114, and each dispersion region has a set of respective (e.g., different) dispersion characteristics.

[0034] In operation, the dispersive element 114 serves to physically separate spectral components that form a given spectral band 165, and the spectral components of the given spectral band 165 emerge from the dispersive element 114 at different angles and positions, thereby forming a dispersed spectral band 165. In some forms, the dispersion region of the dispersive element 114 may operate differently on each spectral band 165 to produce a dispersed spectral band 165 having different optical properties (e.g., physical size and orientation in space, spectral range, spectral width, or spectral resolution, etc.). For example, a given dispersion region of the dispersive element 114 can divide or separate an angular and spatially continuous spatial spectrum into individual bands. In some forms, the dispersive element 114 may define the spectral range of a given spectral band 165.

[0035] The plurality of optical elements 116 includes one or more elements for manipulating the dispersed spectral band 165 in connection with imaging the spectral band 165 onto the detector area 120 of the detector array 118. In some forms, the plurality of optical elements 116 comprises an imaging subsystem for the spectral band 165 that is imaged onto the detector array 118. In some forms, the plurality of optical elements 116 includes a plurality of elements operable to manipulate the position, size, and / or orientation / direction of the spectral band 165 in order to image one or more spectral bands 165 from the plurality of spectral bands 165 onto the detector array 118 in a particular arrangement (e.g., determined by the size of the detector array 118 and / or performance attributes and / or functional criteria). For example, a given optical element 116 may include one or more of a lens, prism, wedge, mirror, diffraction grating, or bulk optical element, and combinations thereof. In some forms, a given optical element 116 can preserve one or more characteristics of a given spectral band 165 (e.g., spectral range, spectral resolution, detection dynamic range and sensitivity, or physical size or position on the plane of the detector array 118) and image such characteristics onto a particular detector area 120 of the detector array 118. Additionally or alternatively, a given optical element 116 can modify one or more characteristics of a given spectral band 165. For example, the optical element 116 can be designed to fill the width of the detector array 118 so as to provide the highest resolution and / or to determine the height of the detector array 118 used for each spectral band 165 (e.g., to control the dynamic range and sensitivity). In some forms, the plurality of optical elements 116 can serve to arrange the dispersed spectral bands 165 in order to optimize the use of the detector array 118 (e.g., to maximize the area utilized by the detector array 118, to maximize the optical resolution, or to utilize a particular detector area 120 on the detector array 118 for a particular spectral band 165).For example, the plurality of optical elements 116 can expand the spectral bands 165 dispersed according to the width of the detector array 118 and stack each spectral band 165 on the detector area 120 at its respective height on the detector array 118. In some forms, the plurality of optical elements 116 can manipulate (e.g., orient, operate, focus, collimate, converge, or expand, etc.) the dispersed spectral bands 165 such that the images of the spectral bands 165 are stacked along the band separation direction in the plane of the detector area 120. For example, in some forms, the plurality of optical elements 116 can effect a spatial rearrangement of the plurality of spectral bands 165 on the plane of the detector area 120. In some forms, one of the optical elements 116 within the plurality of optical elements 116 can manipulate (e.g., expand) the dispersed spectral bands 165 such that the size of the dispersed spectral bands 165 along the dispersion direction matches the size of the detector area 120 along the dispersion direction (e.g., the area of the detector array 118 that images the spectral bands 165). Similarly, in some forms, the optical element 116 can manipulate (e.g., expand) the dispersed spectral bands 165 such that the size of the dispersed spectral bands 165 in the band separation direction matches the size of the detector area 120 along the band separation direction. In this way, the spatial arrangement of the dispersed spectral bands 165 in the detector area 120 can be controlled to make maximum use of a particular detector shape (e.g., a rectangular 2D detector array 118).

[0036] The detector array 118 includes one or more detector areas 120 on which one or more spectral bands 165 are imaged. In some forms, as shown in FIG. 1B, the detector area 120 may include a plurality of detector areas 120 stacked along the band separation direction. In some forms, the detector array 118 may include a 2D array (e.g., a 2D array of detector areas 120). Additionally or alternatively, the detector array 118 may include a plurality of 1D detector arrays (e.g., a plurality of 1D detector arrays stacked along the band separation direction). According to such forms, for example, the detection capabilities (e.g., spectral range, spectral resolution, detection dynamic range, or detection sensitivity, etc.) of the optical device 110 can be extended. In some forms, the detector array 118 may include a single photon avalanche diode (SPAD) array (e.g., a high dynamic range and sensitivity, high time resolution (sub-nanosecond) SPAD array). Additionally or alternatively, the detector array 118 may include an array of time-resolved photon counting detectors (e.g., an array of areas that can associate a time stamp with each photon detected by a given area). Such detectors may be referred to as time-binned photon counting detectors or time-tagged photon counting detectors. Alternatively, the detector array 118 may include a detector array including photon detectors using another type of technology (e.g., an array of photon detectors that may or may not include time-resolved photon counting detectors). In some forms, the size of the first detector area 120 of the plurality of detector areas 120 is different from the size of the second detector area 120 of the plurality of detector areas 120. In some forms, the detector areas 120 of the detector array 118 can be used for a plurality of spectral bands 165. For example, by multiplexing in the time domain in combination with an active element that can select the spectral band 165 that is operated and imaged on a given detector area 120 at a given time, the detector area 120 can be reused.

[0037] In one form, the size of the detector array 118 in the dispersion direction of the first detector area 120 matches the size of the detector array 118 in the dispersion direction of the second detector area 120, and the size of the first detector area 120 in the band separation direction is different from the size of the second detector area 120 in the band separation direction. In such a form, a greater sensitivity is achieved for the spectral band 165 imaged on the first detector area 120 of relatively large size. Thus, by controlling the "height" in the band separation direction in which each spectral band 165 is imaged on the detector array 118, the desired dynamic range and sensitivity for the measurement of each spectral band 165 can be freely set independently of the other spectral bands 165. Increasing the size of the detector area 120 irradiated by a particular spectral band 165 does not change the total amount of photons within that spectral band 165, but the increase in size improves the dynamic range and sensitivity achievable in that spectral band 165 (e.g., by reducing the effect of the reset "dead time" that occurs after a pixel detection event in an SPAD array), and since the photons spread over more pixels of the detector array 118, the saturation limit of the detector array 118 increases with respect to the wavelength within the spectral band 165. In some forms, a given detector area 120 of the detector array 118 can be associated with different spectral bands 165, respectively. In some forms, a given detector area 120 can include a plurality of pixels in the dispersion direction and a plurality of pixels in the separation direction (e.g., to avoid saturation, increase the detector count per pulse, or improve the signal quality, etc.). In some forms, the pixels of a given detector area 120 can be grouped into a plurality of macro-pixels (e.g., to adjust the trade-off between detection efficiency and spectral resolution).

[0038] In some forms, the placement of spectral band 165 on detector area 120 of detector array 118 can be controlled (e.g., dynamically) such that a particular spectral band 165 impinges on a particular detector area 120, or such that a particular spectral band 165 impinges on a detector area 120 that is remote from a particular detector area 120. For example, spectral band 165 can be arranged such that the spectral band 165 of particular interest impinges on the detector area 120 corresponding to the first row of detector array 118 to enable a “quick” readout from detector array 118. In some forms, detector area 120 can assist in the division into particular blocks of pixels. Here, the readout timing can be programmable for each block of pixels. As another example, if a particular pixel of detector array 118 is suffering from noise or another performance issue, the spectral band 165 of particular interest can be arranged to impinge on a detector area 120 that is not close to the particular pixel where the performance issue is occurring. In some forms, the placement of spectral band 165 on detector area 120 as described in the above examples can be configured dynamically. This means that during operation of optical device 110, the placement of spectral band 165 on detector area 120 can be updated, modified, or changed (e.g., based on control signals provided by controller 122). In some forms, such dynamic control can be achieved by adjusting the position, alignment, rotation, or other characteristics of one or more elements of optical system 100, such as, for example, collection element 104, filter 106, separation element 112, dispersion element 114, one or more optical elements 116, detector array 118, one or more detector areas 120, and / or one or more other elements associated with the manipulation or direction of light in optical system 100 (e.g., one or more directing elements, or one or more lenses, etc.).

[0039] In the example shown in FIG. 1B, the separation element 112 provides four spectral bands 165 (i.e., four sub-spectra), three of which (e.g., spectral band 165a, spectral band 165c, spectral band 165d) are directed to the dispersive element 114. These are dispersed and then manipulated by their respective optical elements 116 for imaging in three different shapes (e.g., different heights of each spectral band 165). An example of the result of arranging the optical signal 160 in these three spectral bands 165 having different characteristics (e.g., dynamic range and sensitivity depending on height, spectral range, spectral width covered, spectral resolution) is shown in FIG. 1B and Table 1 below. In this example, spectral band 165b is not imaged on the detector array 118. That is, in some forms, at least one spectral band 165 of the plurality of spectral bands 165 may not be imaged on any detector area 120 of the detector array 118. Such a form can be utilized, for example, when it is not necessary to measure or detect a part of the full spectrum (e.g., spectral band 165b). In some forms, the ability to have such a spectral gap in the detection by the detector array 118 may enable enhancement of one or more other attributes of the detected spectral bands 165 (e.g., improvement in resolution, redundancy, or readout speed, etc.). Thus, in some forms, the spectrum formed by the combination of the spectral bands 165 imaged on the detector array 118 is discontinuous (e.g., includes one or more spectral gaps). In some forms, the optical power of a given spectral band 165 of the plurality of spectral bands 165 in the detector array 118 exceeds 90% of the optical power of the spectral band 165 before the separation element 112. That is, the spectral band 165 can be imaged on the detector array 118 without power loss or with minimal power loss (excluding power loss caused by the non-ideality of the optical components performing the separation function).

[0040] In particular, when imaging onto the detector array 118 (e.g., a 2D detector array), since the spectral bands 165 can be stacked, the angular range required for the elements of the optical device 110 and the optical system is significantly reduced in the dispersion direction (e.g., as compared to conventional devices using a relatively long 1D detector). This reduces the physical size of the optical device 110 and enables miniaturization of the optical engine. Further, the optical device 110 is applicable to many existing spectroscopic analysis techniques. For example, the optical device 110 can be used for Raman and fluorescence spectroscopic analysis, and the readout time of the detector array 118 can be time-gated and / or correlated to the exposure of the sample 155 to the excitation light 150.

[0041] Furthermore, according to the techniques described herein, in some forms, a given spectral band 165 can be directed to any detector area 120 of the detector array 118. The active area of the detector array 118 need not be the same as the area dimensioned by the sum of the areas of all spectral bands 165 detected in the plane of the detector array 118. In some forms, the spectral band 165 can be arranged to fit the width of the active area of the detector array 118 and the scanning mechanism is used to move the spectral band 165 in the band separation direction to reach the detector area 120, or move the detector array 118 in the band separation direction to enter the field of view of the desired spectral band 165. This can enable measurement of the entire spectrum (e.g., the sum of all spectral bands 165) using a miniaturized detector array 118 (e.g., a miniaturized 1D array or 2D array with a reduced number of detector regions) having a width set to the width of a single spectral band 165.

[0042] In one form, one or more elements of the optical device 110 can be configured statically (e.g., using a conventional optical system). Additionally or alternatively, for example, one or more elements of the optical device 110 can be configured dynamically such that, for example, the number of spectral bands 165 generated, the spectral range of each spectral band 165, the dynamic range and sensitivity (or height on the detector array 118) applied to each spectral band 165, and / or the position at which each spectral band 165 is imaged onto the detector array 118 can be configured dynamically. The dynamic configuration can enable different spectral bands 165 from different pulses to be imaged onto the detector array 118. In some forms, the readout of one or more detector areas 120 of the detector array 118 can be performed using various techniques, such as using a global shutter or a rolling shutter. Further, in some forms, one or more spectral bands 165 can be removed by the separation element 112 (e.g., as shown in FIG. 1B). Additionally or alternatively, one or more other elements of the optical device 10, such as the dispersion element 114 or one or more optical elements 116, can be configured to remove one or more spectral bands 165 (e.g., such that one or more spectral bands 165 are not imaged onto the detector array 118).

[0043] The optical resolution is achieved by the dispersive element 114 (e.g., diffraction grating resolution), regardless of the characteristics of the detector array 118. The detector resolution is what is achieved by the detector array 118 (e.g., the pixel size of the detector array 118) and is similarly independent of the dispersive element 114. The system resolution is a combination of the optical resolution and the detector resolution. The best result achievable with the optical device 110 is the optical resolution. Even if better detector resolution is achieved, the detector array 118 cannot perform sampling at a higher resolution than that achieved by the spectral band 165 dispersed by the dispersive element 114. A realistic goal is to match the detector resolution to the optical resolution so as to avoid a decrease in the optical resolution without unnecessary pixels. In some forms, the spectral resolution of the first spectral band 165 among the plurality of spectral bands 165 is different from the spectral resolution of the second spectral band 165 among the plurality of spectral bands 165.

[0044] The spectral range is realized by the range of wavenumbers or wavelengths included within a particular spectral response, signal, band, or sub - spectrum. The spectral range is similar to the bandwidth with respect to wavelength. In the case of Raman spectroscopy, an exemplary spectral range of the optical signal 160 can be greater than about 100 nm (in wavelength) or greater than about 3000 cm−1 (in wavenumber). Further, an exemplary spectral range of a given spectral band 165 can be between about 400 and 700 in wavenumber. In some forms, the spectral range of the first spectral band 165 among the plurality of spectral bands 165 can be different from the spectral range of the second spectral band 165 among the plurality of spectral bands 165.

[0045] The dynamic range is the range of values that can be ascertained from a set of pixels of the detector array 118 for a particular wavelength / wavenumber of the spectral band 165. In some forms, by increasing the number of pixels per wavelength / wavenumber, (e.g., by reducing the effect of the reset “dead time” that occurs after a pixel detection event in a SPAD array), the dynamic range for that wavelength / wavenumber can be increased.

[0046] Returning to FIG. 1A, the controller 122 is an element for acquiring one or more readout signals from the detector array 118. The readout signal is a signal corresponding to the amount of photons detected by a given detector area 120 of the detector array 118 during an acquisition period associated with the given detector area 120. Here, each detector area 120 is associated with a respective spectral band 165, and thus the readout signal associated with a given detector area 120 may correspond to the amount of photons in the spectral band 165 associated with the given detector area 120 for a given time frame. In some forms, in connection with the acquisition of one or more readout signals, the controller 122 may be configured to coordinate the operation of the light source 102 and the operation of one or more other elements of the optical system 100. For example, the controller 122 may be configured to coordinate the operation of the light source 102 and the operation of the detector array 118 such that the timing of the reception of the optical signal 160 (in the form of an optical pulse or a burst of photons) from the sample 155 in response to the excitation light 150 provided by the light source 102 is synchronized with the timing of the acquisition period of one or more detector areas 120 of the detector array 118 that acquire one or more readout signals. In some forms, such coordination may involve one or more other elements of the optical system 100. For example, if the collection element 104 includes a mechanical moving mirror or shutter, the controller 122 may be configured to control the collection element 104 to enable the scanning or dithering of the excitation light 150 across a region of the sample 155. As another example, the controller 122 may be configured to control a scanning element (e.g., a mechanical moving mirror) that enables directing the optical signal 160 towards one or more detector areas 120 during the acquisition period. In some forms, this scanning element may be separate from the collection element 104 (e.g., the scanning element may be included in the optical device 110 on the detection optical path after the slit 108). Such forms may be utilized, for example, when the optical path of the optical signal 160 and the optical path of the excitation light 150 are separate and independent optical paths, or when the optical path of the optical signal 160 and the optical path of the excitation light 150 share a subset of the optical elements of the optical system 100.Alternatively, in some forms, the scanning element may be included in or integrated with the collection element 104 (e.g., the collection element 104 may be controlled by the controller 122 to enable both scanning or dithering of the excitation light 150 over a region of the sample 155 and directing of the optical signal 160 towards one or more detector areas 120). Such a form may be utilized, for example, when the collection element 104 is in both the optical path of the optical signal 160 and the optical path of the excitation light 150).

[0047] In practice, separating Raman and fluorescence signals requires synchronization and timing to sub-nanosecond resolution, which means that signal delays need to be taken into account. Such signal delays can be caused, for example, by the dynamics of the laser cavity that cause delays or jitter between an electrical drive signal and the emission of an optical pulse, the propagation delay of the transmitted optical pulse to or from the sample 155, the timing of detection relative to the arrival of the laser pulse at the detector array 118 (e.g., the time bin of the SPAD), or the timing enabling photon detection. In some forms, the controller 122 may be configured to set the synchronization of the (optimal) operating parameters with the scanning or attenuation elements of the optical system 100 to avoid undesirable effects such as damage or heating of the sample 155 (which can change or shift the measurement spectrum), saturation of the detector, or photobleaching (which can change the measurement spectrum).

[0048] In some forms, controller 122 may acquire a plurality of readout signals, each readout signal being acquired during a different acquisition period among a plurality of acquisition periods. That is, in some forms, controller 122 may be configured to read one spectral band 165 at a time from detector array 118 (e.g., in a rolling window fashion). In some forms, controller 122 may control the length of a given acquisition period to be different in length among the plurality of acquisition periods. For example, the time length of a first acquisition period associated with a first readout signal may be different from the time length of a second acquisition period associated with a second readout signal. Thus, the time taken for measuring a given spectral band 165 can be controlled (e.g., made longer compared to others), and the measurement of a relatively higher priority spectral band 165 can be improved. Additionally or alternatively, controller 122 may acquire a plurality of readout signals, each readout signal being acquired simultaneously during a single acquisition period (e.g., in a global shutter fashion).

[0049] In some forms, controller 122 may be configured to coordinate the sampling of one of the one or more readout signals with the excitation of sample 155 to enable time-resolved Raman spectroscopy. Additionally or alternatively, controller 122 may be configured to coordinate the time sampling of one of the one or more readout signals with the excitation of sample 155 to enable time-resolved fluorescence spectroscopy. Thus, in some forms, optical system 100 may be configured for use, for example, in time-gated Raman spectroscopy applications (e.g., time-resolved measurement and time discrimination of Raman signals and fluorescence signals), time-resolved fluorescence spectroscopy applications (e.g., fluorescence lifetime imaging spectroscopy (FLIM), etc.), dynamic real-time SORS applications, LIBS applications, or photoacoustic spectroscopy applications, etc.

[0050] In some forms, the controller 122 may be configured to perform synchronization taking into account the timing jitter in the excitation light 150. For example, in some forms, the controller 122 may use a separate photodetector to detect the timing of the pulses of the excitation light 150 and control the timing of the detector array 118 accordingly. In some forms, such synchronization can be performed in addition to, or as an alternative to, the timing jitter control performed by the light source 102.

[0051] In some forms, the optical system 100 may include one or more other elements not shown in FIGS. 1A - 1B. For example, in some forms, the optical system 100 may include a scanning element that performs dithering or scanning of the excitation light 150 incident on the sample 155. In one example, the scanning element may be a MEMS device having 1D or 2D scanning capabilities. In some forms, the scanning element may be integrated with the collection element 104. In some forms, such a scanning element can also be used to disable the laser output. That is, the scanning element may "stay" in a position (or state) that does not provide scanning and prevents the excitation light 150 from exiting the housing of the optical system 100.

[0052] As another example, in some forms, the optical system 100 can include a shift element for dynamically adjusting the spatial separation between the illumination optical path of the optical system 100 (e.g., the path through which the excitation light 150 is provided to the sample 155) and the detection optical path of the optical system 100 (e.g., the path through which the optical signal 160 is supplied to the optical device 110). As an example, the shift element can be included (e.g., in a probe attachment inside or outside the optical system 100) and used to enable dynamic and spatially resolved Raman and fluorescence spectroscopy. Such a function allows the positions of the illumination optical path and / or the detection optical path on the sample 155 to be dynamically shifted. This dynamic change in the separation between the illumination optical path and the detection optical path enables probing of Raman signals and fluorescence signals from different depth layers of the sample 155, provides measurement functions and attributes similar to SORS technology, and at the same time enables dynamic change in the position of the area or layer of the sample 155 being probed. In some such forms, the shift element can be integrated with the collection element 104 and / or the scanning element, specifically for dithering or scanning the excitation light 150 incident on the sample 155, or can be a separate element.

[0053] As another example, in some forms, the optical system 100 can include a sampling interface implemented in a hermetic package that houses one or more elements of the optical system 100 (e.g., the optical device 110). In some forms, the sample interface can, for example, be a fiber probe, an optical relay system (e.g., for adjusting the beam size and working distance), or enable external SORS applications.

[0054] In some forms, the optical system 100 described herein differs from conventional techniques in that the optical system 100 enables (1) simultaneous time-resolved measurement and time discrimination of Raman and fluorescence, (2) improved sensitivity and measurement speed, (3) improved resolution and spectral range, (4) improved size, weight, power (SWAP), (5) reduced sample damage, and (6) expansion to dynamic spatially offset Raman spectroscopy.

[0055] Regarding (1), when an optical pulse is incident on a substance, both Raman signals and fluorescence signals are generated. The lifetime of Raman scattering is short (e.g., on the order of sub-picoseconds (ps)), while fluorescence processes involve actual electronic excited states with a finite measurable lifetime (e.g., on the order of several picoseconds to microseconds (μs)). Therefore, using an optical pulse as an excitation source enables the separation of Raman signals and fluorescence signals in the time domain. In some forms, the time-resolved measurement and time discrimination of Raman signals and fluorescence signals can be achieved by the optical system 100 through the use of the detector array 118 in the form of a 2D SPAD array detector that enables both high-sensitivity, high-time-resolution (e.g., sub-nanosecond) time binning and time-gated detection, as illustrated in FIG. 1C. As shown in FIG. 1C, the time bin transmits both Raman signals and fluorescence signals whose relative amplitudes change over time. Thereby, both signals can be measured simultaneously. Analyzing the initial time bin (e.g., corresponding to pulsed laser excitation), it is found that the Raman signal with the highest amplitude-to-background ratio, which is substantially the fluorescence ratio, is obtained. As time elapses (e.g., after pulsed laser excitation), the Raman photons in the time bin will be negligible or absent, and the detected signal will be occupied by fluorescence. This enables time-resolved fluorescence spectroscopy. In some forms, as described above, the controller 122 can be configured to coordinate the operation of one or more elements of the optical system 100. Therefore, in some forms, the controller 122 can coordinate the operation of one or more elements of the optical system 100, such as the light source 102 and the detector array 118, to enable time-resolved measurement and time discrimination of Raman signals and fluorescence signals. In some forms, the optical system 100 can utilize time gating to exclude signals outside a set detection period (e.g., when the SPAD is disabled).

[0056] Regarding (2), a combination of a high repetition rate laser and a detector array 118 (e.g., a high-sensitivity SPAD array), and time binning / time gating detection (e.g., this suppresses the fluorescence background and improves the SNR) can achieve improved sensitivity and measurement speed. Here, since the SNR is proportional to the square root of the number of detected photons (i.e., optical pulses), increasing the laser repetition rate increases the SNR for a fixed measurement time (or conversely, if the SNR is fixed, the measurement speed increases). When the SNR is high, the sensitivity to detect weak Raman signals that would otherwise be hidden by the background signal (i.e., the fluorescence signal) at low SNR increases. In some forms, the optical signal 160 is split into spatially separated spectral bands 165 and imaged in a 2D arrangement on the detector array 118 without significant power loss as described herein, which can enable the optical system 100 to improve sensitivity and measurement speed.

[0057] Regarding (3), if the size is the same as the conventional method, the optical system 100 can achieve higher resolution and / or cover a larger spectral range. Alternatively, the optical system 100 described herein can achieve performance equivalent to the conventional method with a smaller installation area. This is made possible by a spectral banding optical design (e.g., in combination with a capable 2D SPAD array detector) that separates the optical signal including the full spectral range into spectral bands 165 and rearranges the spectral bands 165 to maximize the use of the active area of the detector array 118 as described herein. As described herein, the spectral bands 165 can be rearranged in various ways depending on, for example, the spectral range target and / or the spectral resolution target. In general, the number of spectral bands 165 can be variable, and the spectral range covered or the spectral range of each spectral band 165 can be freely set independently of the other spectral bands 165 (e.g., to meet performance goals).

[0058] (4) Regarding the size, the improvement in size can be defined as the reduction of the installation area of the optical system (including, for example, the condensing optical system and the spectroscope), which can be made possible by the spectral banding optical design approach described in this specification. As a result of the reduction in the installation area, the sizes of the optical components and mechanical components can also be reduced, thereby reducing the overall weight of the spectroscopic analysis engine. According to the latter, the smaller the installation area and / or the lighter the optical system, the shorter the time required for temperature setting or maintenance, which can also lead to a reduction in power consumption. In some forms, the optical layout of the optical system 100 can contribute to reducing the installation area or weight of the optical system 100. For example, the layout of the optical system 100 can be configured such that one or more elements are used in both the detection optical path (for example, the optical path of the optical signal 160) and the illumination optical path (for example, the optical path of the excitation light 150). This means that the detection optical path and the illumination optical path overlap at least partially. Such an optical layout can reduce the installation area by using the same physical space for a part of the plurality of optical paths, and can also reduce the weight by using one or more of the same optical elements for the plurality of optical paths. Other components of the system that can contribute to SWAP (size, weight, power) improvement can include the laser source and the detector array. In some forms, the laser source can be, for example, a highly integrated small microchip device that supplies optical pulses of a specific wavelength (for example, 532 nm) with a high repetition rate (for example, at least about 500 kilohertz (kHz)), low energy (for example, less than about 100 nanojoules (nJ)), and narrow linewidth (for example, less than about 0.1 nm). In some forms, the detector array can be a high-sensitivity 2D SPAD array having a pixel size and number of pixels that enable a high (for example, less than about 10 cm-1 wavenumber) spectral resolution. In some forms, the pixel size and 2D array shape can be selected to reduce the overall ground area of the system. Further, when configured to operate at visible wavelengths, the SPAD detector can be used with almost maximum efficiency and minimum noise. This means that the frequency of requiring thermal cooling can be reduced (compared to, for example, other Raman spectroscopic analysis instruments). As a result, the power consumption can also be reduced.

[0059] (5) Regarding this, by using a detector array 118 in the form of a low-energy pulse, high-sensitivity SPAD detector and a beam scanning mechanism such as a MEMS scanner, it is possible to reduce sample damage. Furthermore, by separating the spectral band 165 without generating power loss (excluding the power loss caused by the non-ideality of optical components), the optimization of detection in a given spectral band 165 is promoted and the SNR is improved. This means that the sample 155 can be illuminated with low power, thus reducing the possibility of damage to the sample 155.

[0060] (6) Regarding this, as described above, the shift element can be incorporated into the optical system 100 or an external probe attachment and used to enable dynamic, spatially resolved Raman and fluorescence spectroscopy.

[0061] As described above, FIGS. 1A-1C are provided as examples. Other examples may differ from those described with respect to FIGS. 1A-1C. Further, the number and arrangement of the elements shown in FIGS. 1A-1B are provided as examples. In practice, there may be additional elements, fewer elements, different elements, or elements with a different arrangement, compared to those shown in FIGS. 1A-1B. For example, the physical layout of the optical system 100 (e.g., the layout of the light source 102, the collection element 104, the filter 106, or the optical device 110, etc.) provides the functions described in this specification using free-space optics. The power and pulse energy of the light source 102 can be relatively high, and the use of free-space optics is advantageous in terms of power handling. Further, free-space optics is efficient for collecting relatively weak reflected Raman signals. However, in some forms, the physical layout of the optical system 100 can be designed to provide the functions described in this specification in another way, such as using a fiber-based or waveguide-based optical system (instead of, or in addition to, free-space optics). In some forms, the choice of technology used to provide the functions of the optical system 100 can be a design requirement in a given application, such as optical performance, size, power consumption, or mechanical stability. Note that two or more of the elements shown in FIGS. 1A-1B may be implemented within a single element, or a single element shown in FIGS. 1A-1B may be implemented as a plurality of distributed elements. Additionally or alternatively, a set of elements (e.g., one or more elements) shown in FIGS. 1A-1B may perform one or more functions described as being performed by another set of elements shown in FIGS. 1A-1B.

[0062] FIG. 2 shows an example related to an optical device 110 that realizes a flexible split and arrangement of a full spectrum in combination with Table 1 (below). In the example shown in FIG. 2, the spectral bands 165 are arranged such that the spectral band 165 is imaged with stacking in the detector array 118 in the band separation direction (e.g., a direction orthogonal to the dispersion direction). As described above, the spectral bands 165 can be arranged in various ways, for example, according to the spectral range, spectral resolution, and / or detection dynamic range and target sensitivity. In some forms, the number and area of the spectral bands 165 can be variable, and the spectral range, resolution, dynamic range, and / or sensitivity of each spectral band 165 can be set independently of those of the other spectral bands 165 (e.g., to achieve the specific performance goals of a given application). For example, in some forms, a portion of the full spectrum that need not be measured or detected (e.g., spectral band 165b) can be skipped (e.g., avoided or rejected). As another example, specific pixels or detector areas 120 that are not usable or should not be used in the detector array 118 can be avoided.

[0063]

Table 1

[0064] Table 1 shows numerical examples of the attributes of different spectral bands 165 imaged on a 2D detector array 118 including three detector areas 120, as shown in FIG. 2. In this example, the height of the exemplary detector area 120 is 700 pixels, and the exemplary spectral range (expressed as a spectral shift from the excitation wavelength) is 0 to 1600 wavenumbers. Here, a spectral band 165b as part of the full spectrum is not imaged on the detector array 118 because it is not being measured or monitored. On the other hand, the remainder of the full spectrum is divided into spectral band 165a, spectral band 165c, and spectral band 165d. These have different spectral ranges, resolutions, dynamic ranges, and sensitivities (e.g., increasing or decreasing according to the height of the detector array 118 and referred to as band height in Table 1), and are imaged on different detector areas 120 of the detector array 118.

[0065] As described above, FIG. 2 is provided as an example. Other examples may differ from those described with respect to FIG. 2.

[0066] FIGS. 3 and 4 are diagrams regarding the improvement of the dynamic range and sensitivity enabled by the optical device 110. In some forms, it is possible to improve the dynamic range and sensitivity without changing the front-end light collection and spectral splitting. In one exemplary form, the back-end imaging optics (e.g., one or more optical elements 116) can be designed such that, for a detector area of fixed size, the energy within one spectral band 165 is imaged on the detector array 118 at a different, larger height by reducing the height or number of the other spectral bands 165. Alternatively, in another exemplary form, two or more spectral bands 165 can be made identical (e.g., spectral band 165a and spectral band 165d in FIG. 3), and the power of those spectral bands 165 can be evenly divided.

[0067] In the example of detector array 118 shown in FIG. 3, spectral band 165c has a height that is twice that of spectral band 165a in detector array 118 (e.g., 200 pixels versus 100 pixels) (e.g., the height of detector area 120 in which spectral band 165c is imaged is twice the height of detector area 120 in which spectral band 165a is imaged). Here, when the energy (e.g., power or throughput) of the entire spectral band 165 is equal, spectral band 165c has a pulse energy per pixel that is reduced by a factor of 2 compared to spectral band 165a (and spectral band 165d). The figure of FIG. 4 shows the effect of the reduction in energy density (e.g., energy per pixel) on detector array 118 for two channel sizes: a spectral channel of a particular width and 100 pixels in height and a spectral channel of a particular width and 200 pixels in height. As shown in FIG. 4, the higher channel (i.e., the spectral channel 200 pixels in height) has a greater dynamic range for count detection. This leads to an improvement in sensitivity. In the figure shown in FIG. 4, as the pulse energy further increases, the detection count per pulse ultimately saturates detector array 118, which means that detector array 118 can no longer perform further count detection even as the pulse energy increases. In some forms, increasing the height (e.g., and number of pixels) assigned to a given spectral band 165 can increase sensitivity and the saturation limit.

[0068] In one form, a first spectral band 165x with a relatively small bandwidth can be imaged on a first detector area 110x of the detector array 118, and a second spectral band 165y with a relatively large bandwidth can be imaged on a second detector area 110y of the detector array 118. Here, in the dispersion direction, the total width and pixel size (i.e., resolution) of the first detector area 110x match the total width and pixel size (i.e., resolution) of the second detector area 110y in the dispersion direction. In this way, when the optical resolution of the first spectral band 165x matches the optical resolution of the second spectral band 165y, the first spectral band 165x can have a higher spectral resolution than the second spectral band 165y (for example, because each detector pixel receives fewer wave numbers for the first spectral band 165x with a relatively small bandwidth).

[0069] As described above, FIGS. 3 and 4 are provided as examples. Other examples may differ from those described with respect to FIGS. 3 and 4.

[0070] FIGS. 5-7 are diagrams showing exemplary forms of the separation element 112 described herein. In some forms, as described above, the separation element 112 can include one or more elements that spatially or angularly separate the optical signal 160 into a plurality of spectral bands 165 such that each spectral band 165 is spatially or angularly separated from the other spectral bands 165. In some forms, the separation element 112 can include a plurality of thin film interference filters, each associated with a different spectral band 165 of the plurality of spectral bands 165. FIG. 5 is a diagram showing an exemplary form of the separation element 112 including a plurality (e.g., four) of thin film interference filters 502. Additionally or alternatively, these can include diffraction gratings. FIGS. 6 and 7 are diagrams showing exemplary forms of the separation element 112 including diffraction gratings 602. Additionally or alternatively, the separation element 112 can include one or more other types of optical elements.

[0071] In one form, the light of the optical signal 160 having a wavelength near the boundary between two spectral bands 165 can be split by the splitting element 112 such that each portion of the light enters a plurality of spectral bands 165. Thus, in some forms, the spectral components at or near the boundary between a first spectral band 165 of the plurality of spectral bands 165 and a second spectral band 165 of the plurality of spectral bands 165 can be split such that a first portion of the spectral component is within the first spectral band 165 and a second portion of the spectral component is within the second spectral band 165. Here, the sum of the power of the first portion and the power of the second portion is the total power of the spectral component.

[0072] In the example shown in FIG. 5, the optical signal 160 includes the full spectrum generated from the sample 155 (e.g., as shown in FIG. 1B). Here, each thin-film interference filter 502 reflects only a portion of the full spectrum (e.g., spectral band 165) and transmits the rest. In some forms, as shown in FIG. 5, a sequence of a plurality (e.g., four) of interference filters 502, followed by a mirror 504, splits the full spectrum into a plurality (e.g., five) of spatially separated spectral bands 165. Then, they are incident on the focusing lens 506. Thereby, the spatial separation (e.g., offset) is converted into an angular separation (e.g., angle) of different spectral bands 165. Then, the spectral bands 165 can be imaged onto a plane for further optical processing. With respect to the optical device 110 described in FIG. 1B, the spatially / angulary separated spectral bands 165 are then directed towards the dispersive element 114.

[0073] In the example shown in FIGS. 6 and 7, an optical signal 160 including a full spectrum generated from sample 155 (e.g., as shown in FIG. 2) is collimated by lens 604 and directed towards a diffraction grating 602 that separates the incident light into different spectral components (e.g., wavelengths). The diffracted light resulting from diffraction grating 602 is focused by lens 606 and imaged to generate spectrally separated bands 165 that are spatially and angularly separated. The imaging system shown in FIG. 7 includes a wedge 702 and prisms 704a and 704b that serve to change the optical path length and propagation angle of the beams in spectral band 165 such that the resulting spectral beams appear to arrive at a single focal plane from different angles (e.g., similar to that realized in the example shown in FIG. 5). With respect to the optical device 110 described in FIG. 1B, the spectrally separated bands 165 that are spatially / angle separated are then directed towards the dispersive element 114.

[0074] As described above, FIGS. 5-7 are provided by way of example. Other examples may differ from those described with respect to FIGS. 5-7. The number and arrangement of the elements shown in FIGS. 5-7 are provided as an example. In practice, there may be additional elements, fewer elements, different elements, or elements in a different arrangement with respect to what is shown in FIGS. 5-7. Further, two or more of the elements shown in FIGS. 5-7 may be implemented within a single element, or a single element shown in FIGS. 5-7 may be implemented as a plurality of distributed elements. Additionally or alternatively, a set of elements (e.g., one or more elements) shown in FIGS. 5-7 may perform one or more functions as described to be performed by a different set of elements shown in FIGS. 5-7.

[0075] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Modifications and variations may be made in light of the above disclosure, or may be realized from the practice of the forms. Further, any forms described herein may be combined unless the foregoing disclosure clearly indicates a reason that one or more forms may not be combined.

[0076] Particular combinations of features are recited in the claims and / or disclosed in the specification, but these combinations are not intended to limit the disclosure in various forms. In fact, many of these features can be combined in ways not specifically recited in the claims and / or disclosed in the specification. Each of the dependent claims listed below may depend directly on only one claim, but the disclosure in various forms includes each dependent claim combined with each other claim within the set of claims. As used herein, the phrase "at least one of" a list of items refers to any combination of these items, including a single member. By way of example, "at least one of a, b, or c" is intended to cover a, b, c, a and b, a and c, b and c, and a and b and c, as well as any combination with multiple of the same items.

[0077] When one component or more than one component (e.g., one optical element or more than one optical element) is described or claimed as performing or being configured to perform a plurality of operations (within one claim or across a plurality of claims), this expression is intended to broadly cover various configurations and environments. For example, unless otherwise explicitly stated (e.g., by the use of "a first component" and "a second component" in the claim or other expressions differentiating components), this expression is intended to cover a single component that performs or is configured to perform all operations, a group of components that collectively perform or are configured to perform all operations, a first component that performs or is configured to perform a first operation, and a second component that performs or is configured to perform a second operation, or any combination of components that perform or are configured to perform operations. For example, if a claim is in the form "one or more components configured to perform X, perform Y, and perform Z", the claim should be interpreted to mean "one or more components configured to perform X, one or more (which may be different) components configured to perform Y, and one or more (likewise, which may be different) components configured to perform Z".

[0078] Any element, act, or instruction used in this specification should not be construed as essential or critical unless so expressly indicated. Further, as used in this specification, the articles "a" and "an" are intended to include one or more items and may be used interchangeably with "one or more." Further, as used in this specification, the article "the" is intended to include one or more items referred to in combination with the article "the" and may be used interchangeably with "the one or more." Further, as used in this specification, the term "set" is intended to include one or more items (e.g., related items, unrelated items, or a combination of related and unrelated items) and may be used interchangeably with "one or more." The expression "only one" or a similar expression is used when only one item is intended. Further, as used in this specification, terms such as "has," "have," or "having" are intended as open-ended terms. Further, the expression "based on" is intended to mean "at least in part based on" unless so expressly indicated. Further, as used in this specification, the term "or" is intended to be inclusive when used in a series, and may be used interchangeably with "and / or" unless so expressly indicated (e.g., when used in combination with "either" or "only one of"). Further, terms related to space such as "below," "lower," "above," and "upper" may be used in this specification for convenience in describing the relationship of one element or feature to another illustrated element or feature. Terms related to space are intended to include different orientations of the devices, devices, and / or elements being used or operating in addition to the illustrated orientation. This device may be oriented in another form (rotated 90 degrees or in another direction). Accordingly, the descriptions related to space used in this specification may be interpreted similarly.

Explanation of Signs

[0079] 100 Optical system 102 Light source 104 Collection element 106 Filter 108 Slit 110 Optical device 112 Separation element 114 Dispersion element 116 Optical element 118 Detector array 120 Detector area 122 Controller 150 Excitation light 155 Sample 160 Optical signal 165 Spectral band 502 Thin-film interference filter 504 Mirror 506 Focusing lens 602 Diffraction grating 604, 606 Lenses 702 Wedge 704a, 704b Prisms

Claims

1. A light source that provides excitation light, A collection element that directs an optical signal received from the sample in response to the incidence of the excitation light on the sample towards an optical device, The optical device, A separation element that separates the optical signal into a plurality of spectral bands spatially or angularly separated along a band separation direction, wherein the spectral ranges are different between each of the plurality of spectral bands, A dispersion element having a plurality of dispersion regions, wherein one of the plurality of dispersion regions forms a dispersed spectral band by dispersing the spectral components of one of the plurality of spectral bands along a dispersion direction, A plurality of optical elements, wherein one of the plurality of optical elements operates on the dispersed spectral band in relation to imaging the spectral band on a detector area of a detector array, The detector array including the detector area, The optical device comprising the above, A controller that obtains one or more readout signals from the detector array, An optical system comprising the above.

2. The optical system according to claim 1, wherein the light source is a pulsed laser source such that the excitation light includes optical pulses having a high repetition rate, low energy, and a narrow linewidth.

3. The optical system according to claim 1, wherein the light source is configured to reduce timing jitter in the excitation light or to perform synchronization in consideration of the jitter in the excitation light.

4. The optical system according to claim 1, wherein the light source is one of a plurality of light sources, and each light source is configured to emit light at a different wavelength, generate excitation light having different pulse characteristics, or operate in a different operation mode.

5. The optical system according to claim 1, further comprising a scanning element that performs dithering or scanning of the excitation light incident on the sample.

6. The optical system according to claim 1, wherein the one or more readout signals include a plurality of readout signals, and each of the plurality of readout signals is obtained during a different acquisition period among a plurality of acquisition periods.

7. The optical system according to claim 6, wherein the time length of the first acquisition period among the plurality of acquisition periods is different from the time length of the second acquisition period among the plurality of acquisition periods.

8. The optical system according to claim 1, wherein the one or more readout signals include a plurality of readout signals, and each of the plurality of readout signals is acquired simultaneously during a single acquisition period.

9. The optical system according to claim 1, wherein the controller is configured to perform synchronization in consideration of timing jitter in the excitation light.

10. The optical system according to claim 1, wherein the controller is configured to coordinate the sampling of the readout signal among the one or more readout signals with the excitation of the sample in order to enable time-resolved Raman spectroscopy.

11. The optical system according to claim 1, wherein the controller is configured to coordinate the time sampling of one of the one or more readout signals with the excitation of the sample in order to enable time-resolved fluorescence spectroscopy.

12. The optical system according to claim 1, wherein the detector array is divided into a plurality of detector areas, and each detector area is associated with a different spectral band among the plurality of spectral bands.

13. The optical system according to claim 1, wherein the detector area includes a plurality of pixels in the dispersion direction and a plurality of pixels in the band separation direction.

14. The optical system according to claim 1, wherein the pixels of the detector area are grouped into a plurality of macro pixels.

15. The optical system is configured to synchronize an acquisition period associated with the acquisition of one or more readout signals to the excitation light and one or more other elements of the optical system associated with the operation of at least one of the excitation light, the optical signal, one or more of the plurality of spectral bands, or one or more of the plurality of optical elements. The optical system according to claim 1.

16. The optical system according to claim 15, wherein the optical system is configured to synchronize the acquisition period with one or more other elements associated with the implementation of time-gated Raman spectroscopy, time-resolved fluorescence spectroscopy, dynamic real-time spatial offset Raman spectroscopy (SORS), laser-induced breakdown spectroscopy (LIBS), or photoacoustic spectroscopy.

17. The optical system according to claim 1, further comprising a sampling interface mounted on an airtight package that houses the optical device or houses the optical device, the collection element, and the light source.

18. The optical system according to claim 1, further comprising a shift element for dynamically adjusting the spatial separation between the illumination optical path and the detection optical path of the optical system.

19. The optical system according to claim 1, further comprising a filter for removing one or more excitation wavelengths from the optical signal.

20. A light source that provides excitation light, A collection element that directs an optical signal received in response to the incidence of the excitation light on a sample towards an optical device, The optical device, A plurality of spectral bands spatially or angularly separated along a band separation direction, wherein each spectral band of the plurality of spectral bands separates the optical signal into a plurality of spectral bands having different spectral ranges, Forming a dispersed spectral band by dispersing the spectral components of one of the plurality of spectral bands along a dispersion direction, Operating the dispersed spectral band in relation to imaging the spectral band on a detector area of a detector array of the optical device The optical device, A controller that obtains one or more readout signals from the detector array, An optical system comprising.

21. A light source that provides excitation light, A collection element that directs an optical signal received in response to the incidence of the excitation light on a sample towards an optical device, The optical device, A separation element that separates the optical signal into a plurality of spectral bands, wherein the spectral range is different between each spectral band of the plurality of spectral bands, A dispersion element having a dispersion region, wherein the dispersion region forms a dispersed spectral band by dispersing the spectral components of one of the plurality of spectral bands, An optical element that operates the dispersed spectral band in relation to imaging the spectral band on a detector area of a detector array, The detector array including the detector area, The optical device comprising. A controller that coordinates the operation of the light source with the operation of one or more elements of the collection element or the optical device so that the reception timing of the optical signal is synchronized with the timing of the acquisition period of the detector area; An optical system comprising the same.

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