Flexible spectral optical detector

Abstract

The invention relates to a flexible spectral optical detector. An optical system may include a light source for providing excitation light and a collection element for directing a light signal received from a sample to an optic in response to incidence of the excitation light onto the sample. The optical device may include a separation element for separating the optical signal into a plurality of spectral bands separated spatially or angularly along a band separation direction, a dispersion element comprising a dispersion region for dispersing spectral components of the spectral bands along a dispersion direction to form a dispersed spectral band, and an optical element comprising a plurality of optical elements. An optical element is used to manipulate the dispersive spectral band in association with imaging the spectral band onto a detector region of the detector array. The optical system may include a controller for acquiring one or more readout signals from the detector array.

Description

[0001] Cross - Reference to Related Applications

[0002] 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 hereby incorporated by reference in its entirety and made a part of this patent application. Field of the Invention

[0003] The present disclosure generally relates to optical detectors and flexible spectral optical detectors. Background Art

[0004] In spectroscopic analysis, the full-spectrum response is typically dispersed, such that the dispersed spectrum has the shape of a continuous elongated beam composed of dispersed spectral bands (with a large aspect ratio). Conventionally, for any detector pixel position along the dispersion direction, the dispersed spectral bands are arranged in a "linear" one-dimensional (1D) sequence from one edge of the beam to the other edge of the beam, without any discontinuities, or only one spectral band is imaged in a direction perpendicular to the dispersion direction. When performing spectroscopic measurements, it is generally desirable to detect the response from a sample with high sensitivity and high resolution over the full spectral range (e.g., for a Raman spectrometer, the spectral range is above 100 nanometers (nm) (wavelength) or above 3000 reciprocal centimeters (cm -1 )(wave number)). Summary of the Invention

[0005] In some implementations, an optical system includes a light source, a collection element, an optical device, and a controller. The light source is configured to provide excitation light. The collection element is configured to direct an optical signal received from a sample in response to incidence of the excitation light on the sample to the optical device. The optical device includes a separation element, a dispersion element, a plurality of optical elements, and a detector array. The separation element is configured to separate the optical signal into a plurality of spectrally distinct bands along a band separation direction, where the spectral ranges among the respective bands of the plurality of spectrally distinct bands are different. The dispersion element includes a plurality of dispersion regions, where a dispersion region of the plurality of dispersion regions is configured to disperse spectral components of the spectral bands of the plurality of spectrally distinct bands along a dispersion direction to form dispersed spectral bands. The optical elements of the plurality of optical elements are configured to manipulate the dispersed spectral bands in association with imaging the spectral bands onto detector regions of the detector array. The detector array includes detector regions. The controller is configured to obtain one or more readout signals from the detector array.

[0006] In some implementations, an optical system includes a light source, a collection element, an optical device, and a controller. The light source is configured to provide excitation light. The collection element is configured to direct an optical signal received in response to incidence of the excitation light on a sample to the optical device. The optical device is configured to: separate the optical signal into a plurality of spectrally distinct bands that are spatially or angularly separated along a band separation direction, each of the plurality of spectrally distinct bands having a different spectral range; disperse spectral components of the spectrally distinct bands among the plurality of spectrally distinct bands along a dispersion direction to form dispersed spectral bands; manipulate the dispersed spectral bands in association with imaging the spectral bands onto a detector region of a detector array of the optical device; and the controller is configured to obtain one or more readout signals from the detector array.

[0007] In some implementations, an optical system includes a light source, a collection element, an optical device, and a controller. The light source is configured to provide excitation light. The collection element is configured to direct an optical signal received in response to incidence of the excitation light on a sample to the optical device. The optical device includes a separation element, a dispersion element, an optical element, and a detector array. The separation element is configured to separate the optical signal into a plurality of spectral bands, wherein spectral ranges among each of the plurality of spectral bands are different. The dispersion element includes a dispersion region, wherein the dispersion region is configured to disperse spectral components of the spectral bands among the plurality of spectral bands to form dispersed spectral bands. The optical element is configured to manipulate the dispersed spectral bands in association with imaging the spectral bands onto a detector region of the detector array. The detector array includes a detector region. The controller is configured to coordinate operation of the light source with operation of one or more elements of the collection element or the optical device such that timing of receipt of the optical signal is synchronized with timing of an acquisition window of the detector region. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figures 1A - 1C is a diagram illustrating an example associated with an optical system including a flexible spectral optical detector described herein.

[0009] Figure 2 illustrates an example associated with an optical device providing flexible segmentation and arrangement of a full spectrum.

[0010] Figure 3 and Figure 4 is a diagram associated with an increase in dynamic range and sensitivity achieved by the optical device described herein.

[0011] Figures 5 - 7 is a diagram illustrating an example implementation of the separation element described herein. DETAILED DESCRIPTION

[0012] The following detailed description of example implementations refers to the accompanying drawings. Identical reference numerals in different drawings may identify the same or similar elements.

[0013] In spectroscopic analysis, a spectrometer is typically designed to provide light in the form of a single non-segmented linear beam that encompasses the full spectral range interrogated by the spectrometer at the dispersive element of the spectrometer. The dispersive element disperses the light, and the dispersed light is projected as a continuous non-segmented linear image onto the detector of the spectrometer. Here, for any detector pixel position along the dispersion direction, the dispersed spectrum traditionally has the shape of a continuous elongated beam (with a large aspect ratio) that consists of dispersed spectral components arranged in a "linear" 1D sequence from one edge of the beam to the other edge without any discontinuities, or only one spectral component is imaged in a direction perpendicular to the dispersion direction. When performing spectroscopic measurements, it is generally desirable to detect the response from a sample with high sensitivity and high resolution over the full spectral range (e.g., for a Raman spectrometer, the spectral range is above 100 nanometers (nm) (wavelength) or above 3000 reciprocal centimeters (cm -1 )(wave number)). However, this is difficult to achieve efficiently in practice. For example, if a detector array with high sensitivity and high resolution over the full spectral range is required, the physical design of the detector must accommodate the large aspect ratio, which results in inefficient use of physical space in the spectrometer system. Therefore, it would be advantageous to discard the traditional 1D shape of the dispersed spectrum and avoid the large aspect ratio of the detector, and be compatible with a more typical 2D imaging detector array.

[0014] In addition, any dispersed spectrum has two important properties: spectral range and spectral resolution. For a fixed spectral physical width, these properties are in conflict. That is, for a given spectral range, there is a given spectral resolution. Increasing the resolution results in an increase in the spectral width for a fixed spectral range or a decrease in the spectral range for a fixed spectral width. These constraints exist for the 1D spectrum imaged on the detector. When performing spectroscopic measurements, all spectral bands within the full spectral response typically have nominally the same sensitivity and resolution. However, most traditional spectroscopic measurement systems are designed to identify specific features, where one or more specific spectral bands may provide more useful identification information while other spectral bands may provide little identification information. If all spectral bands have the same sensitivity and resolution, this may result in poor utilization of the detector. Therefore, it would be advantageous to provide higher sensitivity and resolution for spectral bands that provide more useful identification information and lower sensitivity and resolution for spectral bands that provide less useful identification information. Similarly, some spectral bands of the full spectrum may not provide useful information at all, and thus, it would be advantageous to avoid imaging these spectral bands on the detector.

[0015] In some cases, traditional two-dimensional (2D) techniques can be used to divide the full spectrum into several light beams (e.g., via a beam splitter), with each light beam containing the full spectral range. Then, different spectral range portions of each light beam are imaged onto different detectors. Notably, according to this traditional 2D technique, each light beam includes the full spectrum under a small fraction of the original power, and then only a small portion of the different spectral bands in each light beam are imaged onto the detector. This wastes power because the original power is split into each full-spectrum light beam, and then the portions of each light beam that are not imaged onto the detector are wasted. Thus, even the spectral range that is imaged onto a part of the detector only includes a small fraction of the original power within that spectral range. Wasting power also reduces sensitivity. Therefore, it is advantageous to image as much power as possible in the full-spectrum response onto the detector.

[0016] The implementations described herein provide techniques and apparatus for measuring spectral response, where the full-spectrum response can be divided into spectral bands (e.g., sub-spectra of any spectral range, resolution, or dynamic range), and each spectral band can be directed to a desired physical location on a detector array through dispersion while maintaining the power of the full-spectrum response. In other words, the techniques and apparatus described herein can be implemented to separate the full-spectrum response into a set of different spectral bands (e.g., sub-spectra) by wavelength or wave number with minimal power loss, and then these spectral bands can be independently manipulated or rearranged before spectral dispersion and imaging onto a detector (e.g., a 2D detector). The techniques and apparatus described herein avoid power loss when splitting the full-spectrum response; decouple the bandwidth, resolution, and dynamic range constraints of each spectral band; improve the utilization efficiency regarding the 2D detector; and enable a more compact spectrometer.

[0017] The techniques and apparatus described herein achieve a relatively more compact spectrometer by separating the full spectrum of incident light into spectral bands without power loss (except for power loss caused by the non-ideality of the optical elements performing the separation function), and spatially rearranging the spectral bands (e.g., stacking) before delivering the spectral bands to the dispersion element. This design can enable each spectral band from the dispersion element to have a higher optical resolution, and in some designs can reduce the size of the dispersion unit in the dispersion direction. After dispersion, the dispersed spectral bands are transmitted and imaged (e.g., in a stack) onto a 2D detector array, enabling a higher detector resolution and improving the utilization efficiency of the effective area of the detector array.

[0018] The techniques and apparatus described herein combine spectral bands at the front end, which split the full spectral range into multiple spectral bands (e.g., a set of adjacent, contiguous, or distinct spectral ranges) before dispersion. In some implementations, the spectral bands can be non - overlapping, or can partially (e.g., minimally) overlap or hardly overlap (e.g., allowing for manufacturing redundancy or tolerances when attempting to create non - overlapping or adjacent spectral bands). In some implementations, the spectral bands can be re - arranged in space and stacked onto a dispersive element in a non - dispersive direction (e.g., a direction perpendicular to the dispersive direction), thereby creating a 2D arrangement of spectral bands. In some implementations, the dispersive element can include multiple dispersive regions (e.g., each having different dispersive characteristics), which can be mapped to the spectral bands incident thereon. Thus, each dispersive region of the dispersive element can disperse and redirect the light incident thereon independently of the other dispersive regions.

[0019] After dispersion, when the dispersed spectral bands are directed to a detector array, the spatial arrangement of the dispersed spectral bands can be maintained or further re - arranged. For example, in some implementations, the dispersed spectral bands can be arranged in space and stacked onto a 2D detector array in a band - separation direction. The spectral bands can be re - arranged in various ways (e.g., depending on the selected spectral range partitioning and resolution objectives). Generally, the number of spectral bands, the spectral ranges of the spectral bands, and the spectral resolution of the spectral bands can vary and be set independently of each other according to the desired performance objectives of a given application (e.g., Raman, time - gated Raman, spatially offset Raman spectroscopy (SORS), fluorescence, etc.). For example, the spectrum formed by the sum of all spectral bands may be discontinuous (e.g., interrupted by one or more gaps), or may have different spectral resolutions for different sub - spectra. Additionally or alternatively, by controlling the “height” (e.g., in a direction orthogonal to the dispersive direction) at which each spectral band is imaged onto the detector, the desired dynamic range and sensitivity for the measurement of each spectral band can be set independently of the other spectral bands. While increasing the detector area illuminated by a particular spectral band does not change the total number of photons in that spectral band, increasing the detector area increases the dynamic range that can be achieved for that spectral band and increases the saturation limit of the detector for the wavelengths in that spectral band, as the photons spread over more pixels of the detector. In some implementations, the techniques and apparatus described herein are capable of removing one or more spectral bands (e.g., one or more spectral bands of no interest). For example, during spectral splitting, during dispersion, or during spatial or angular re - arrangement (e.g., before or after dispersion), one or more spectral bands can be removed from the imaging on the detector.

[0020] It should be noted that the techniques and devices described herein can segment the full spectrum in a different manner from the above-described conventional 2D techniques. In some implementations, the full spectrum is separated into spectral bands that differ in wavelength / wavenumber range and then spatially rearranged to have a 2D arrangement in which multiple spectral bands (which together can cover the full spectrum range and include almost all of the power of the original spectrum) are stacked in a direction perpendicular to the dispersion direction. In this arrangement, a higher resolution can be achieved compared to a 1D arrangement of the same width (i.e., on a 1D detector). For comparison, achieving the same full spectrum range with a linear 1D response to increase resolution would require a detector with a spectral dispersion size increased by a factor equal to the number of spectral bands created (e.g., assuming all spectral bands have the same width and cover the same spectral range). Compared to conventional 2D techniques, since the full spectrum is divided into separate (optional) non-overlapping spectral bands that include almost all of the power of the full spectrum, the power loss is minimal. This flexible spectral analysis technique allows for maximum utilization of the effective area of the detector, which can be a rectangular (e.g., low aspect ratio) 2D detector array. In some implementations, the full spectrum can be separated into separate non-overlapping spectral bands that are spatially rearranged to be aligned and stacked onto the low aspect ratio effective area of a 2D detector array.

[0021] For the same physical size as a conventional 1D solution, the techniques and devices described herein can achieve a higher resolution and / or cover a larger spectral range. Alternatively, the techniques and devices described herein can achieve the same performance with a reduced width of the detector in the dispersion direction, which is typically the largest dimension of the detector used in spectral analysis and is a fraction of the physical size of conventional 1D techniques. The spectrum is segmented to reduce the width while increasing the height by rearranging the segmented spectral bands in a direction perpendicular to the dispersion direction (i.e., the band separation direction) to obtain a favorable detector geometry for implementing a compact size (e.g., volume) spectrometer or spectral analysis system, or for compatibility with a wider range of commercially available large pixel count detector arrays (e.g., SPAD arrays). Increasing the height on the detector to cover additional spectral bands results in a slight or no increase in the height of the spectrometer, while the reduction in detector width significantly reduces the footprint since the angular distribution of the sub-spectra of the dispersion is smaller and their width on the detector plane is also smaller. Due to the reduction in the width of the detector, the size of the optical and mechanical components within the spectrometer also decreases, which results in a reduction in the size, weight, and (potentially) power consumption of the spectrometer system.

[0022] 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. The performance attributes of the spectrometer are no longer fixed or limited by the detector width. Adding a second dimension in the spectral arrangement allows for this flexibility. The techniques and apparatus described herein can vary the detection dynamic range and sensitivity across the entire spectral range. Since the spectrum is segmented, each spectral band can be adjusted to cover any particular height (i.e., multiple pixels in the band separation direction) on the effective area of the detector. Thus, the detection dynamic range and sensitivity (which are proportional to the height of the spectral components on the detector effective area) can be modulated on individual spectral bands to reflect, for example, the relative importance of the individual spectral bands in a spectral measurement.

[0023] In practice, a spectrometer can be used, for example, in Raman spectroscopy applications using the time-gating principle. The time-gating principle in Raman spectroscopy is used to suppress sample-induced fluorescence and phosphorescence during measurement, and to maintain a sufficiently high signal-to-noise ratio (SNR) while suppressing other potential continuous interferences (e.g., ambient light, thermal emission, etc.). Time-gated Raman spectroscopy is an effective technical solution for addressing the problem of sample-induced fluorescence, which may mask the Raman signal during spectral detection. Conventional optical systems for performing time-gated Raman spectroscopy use conventional spectrometers implementing the above-described 1D techniques, and thus result in a trade-off between performance and size due to the way light is manipulated (e.g., dispersion as a single non-segmented linear beam covering the entire spectral range; and transmission as a continuous non-segmented linear image on the detector). As described above, for the same dispersion power, this technique requires a wide dispersion element (in the dispersion direction) to achieve a given optical spectral resolution, and furthermore, for a given spectral range and resolution, a wide detector area is also required to cover the entire spectral range. As an alternative to a wide detector area, to cover the entire spectral range for a given spectral range and resolution, the angle of incidence at the dispersion element can be stepped or scanned, and a relatively small 1D detector array can be used to stitch the spectra together sequentially.

[0024] In some implementations, the compact spectrometers described herein can be included in an optical system for time-gated Raman spectroscopy applications or another type of spectroscopy application, such as time-resolved fluorescence spectroscopy applications, dynamic real-time spatially offset Raman spectroscopy (SORS) applications, laser-induced breakdown spectroscopy (LIBS) applications, or photoacoustic spectroscopy applications, etc. Generally, for a given application, the number of spectral bands provided by the spectrometer can vary, and the spectral range and / or optical spectral resolution of a given spectral band can be freely set independently of other spectral bands. In this way, the optical system can be capable of meeting the performance goals of the optical system in a given application. Additional details are provided below.

[0025] Figures 1A - 1C FIG. is a diagram illustrating an example associated with an optical system 100 including a flexible spectral optical detector 110 described herein. As Figure 1A shown, the optical system 100 may include a light source 102, a collection element 104, a filter 106, a slit 108, a flexible spectral optical detector 110 (referred to herein as the optical device 110), and a controller 122. As shown, depending on the design of the optical system 100, the optical system 100 may include one or more other elements associated with manipulating or guiding light, such as one or more guiding elements (e.g., one or more mirrors) or one or more lenses ( Figure 1A not labeled in the figure). In one example, the optical system 100 includes a compact Raman spectroscopy engine that can be used for benchtop, handheld, or embedded applications. In some implementations, one or more elements of the optical system 100 may be included in a hermetic package. In one example implementation, the elements of the optical system 100 other than the light source 102 may be housed in a hermetic package. The hermetic package may be, for example, a sealed metal enclosure. In some implementations, the hermetic seal may improve the reliability of one or more elements of the optical system 100, such as the collection element 104 in the form of a MEMS device or a thermoelectric cooler (TEC) ( Figure 1A not shown in the figure), etc. Additionally, in some implementations, the hermetic seal may improve the wavelength stability (i.e., calibration) of grating dispersion.

[0026] The light source 102 includes one or more elements for providing excitation light 150. In some implementations, the light source 102 may be a pulsed laser source. In some implementations, the light source 102 may provide 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 narrow linewidth (e.g., less than about 0.1 nanometer (nm)) for a given wavelength. In some implementations, the wavelength of the excitation light 150 may be approximately equal to 532 nm. However, in practice, the light source 102 may be designed to provide excitation light 150 at any practical wavelength. In some implementations, the light source 102 may be capable of reducing timing jitter in the excitation light 150, or may be capable of performing synchronization to account for jitter in the excitation light 150. That is, in some implementations, the light source 102 may be a low-jitter laser source. The light source 102 may be controlled by the controller 122 to achieve the above functions.

[0027] In some implementations, the light source 102 can be multiple light sources 102, where each light source among the multiple light sources 102 is configured to emit, for example, at different wavelengths, generate excitation light 150 with different pulse characteristics (e.g., pulse width, repetition rate, pulse energy, etc.), or operate in different operation modes (e.g., continuous wave (CW), Q-switching, mode-locking, etc.). In some implementations, as Figure 1A shown, the excitation light 150 is provided such that the excitation light 150 is incident on the sample 155. In some implementations, the use of multiple light sources 102 can be used to better utilize the spectral range detected by the optical system 100. For example, in Raman spectroscopy, there is a "silent region" in the Raman shift spectrum, which is 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 this spectral band with Raman shifts from the spectral region of interest. Different excitation wavelengths interact differently with the sample material, thus affecting important parameters measured in different ways, such as Raman scattering efficiency, the amount of generated fluorescence background, damage threshold, etc. Therefore, a combination of multiple light sources 102 can be used to improve the optical system 100 for a given application, where each light source provides the corresponding (narrowband) excitation light 150. In some implementations, the light source 102 of the optical system 100 can be included in a hermetic package that houses one or more other elements of the optical system 100. For example, the light source 102 inside the hermetic package can facilitate the realization of the integration of the desired optical system 100 (e.g., in a single package). Additionally or alternatively, the light source 102 of the optical system 100 can be located outside the hermetic package that houses one or more other elements of the optical system 100. In such an implementation, the light source 102 can be housed in a second hermetic package (i.e., a hermetic package separate from the hermetic package that houses one or more other elements of the optical system 100). The light source 102 outside the hermetic package can be advantageous, for example, to facilitate thermal management (e.g., because the light source 102 can be the main heat source of the optical system 100), promote the replacement or exchange of the light source (e.g., with a different laser type or another light source 102 with different characteristics), or increase the flexibility of the laser design.

[0028] The collection element 104 includes one or more elements for directing an optical signal 160 received from the sample 155 in response to the incidence of the excitation light 150 on the sample 155 to the optical device 110. For example, the collection element 104 may include one or more reflective elements, such as one or more microelectromechanical systems (MEMS) mirrors. In some implementations, the collection element 104 in the form of a MEMS mirror may be used to scan 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 implementations, the collection element 104 may be omitted from the optical system 100 (i.e., some implementations of the optical system 100 may not include the collection element 104). In an example of one such implementation, the excitation light 150 may pass through the filter 106 to be incident on the sample 155, and the optical signal 160 from the sample 155 may be reflected by the filter 106 on the optical path towards the optical device 110.

[0029] The filter 106 includes one or more elements for removing one or more excitation wavelengths from the optical signal 160. For example, as Figure 1A shown, the filter 106 may include an element that reflects light at an excitation wavelength (e.g., 532 nm) and transmits light at other wavelengths.

[0030] The slit 108 includes one or more elements associated with defining the optical throughput and optical resolution of the optical system 100 (in combination with the optical device 110). In some implementations, the slit 108 is a mechanical feature, such as an opening (e.g., a rectangular opening) in a mask. In some implementations, the optical signal 160 is focused by one or more other elements of the optical system 100 to maximize the transmission of the optical signal 160 through the slit 108.

[0031] Notably, Figure 1A the example optical paths shown are for illustrative purposes only, and other implementations are possible. For example, in Figure 1A the optical path of the excitation light 150 shown, the excitation light 150 is reflected by the filter 106 and directed to the sample 155 by the collection element 104. Additionally, in the optical path of the optical signal 160 as shown in Figure 1A , the optical signal 160 is reflected by the collection element 104, transmitted by the filter 106, and directed to the optical device 110 by a reflective element. In this example, the collection element 104 and the filter 106 are located on both the optical path of the optical signal 160 and the optical path of the excitation light 150. However, in another example implementation, the optical path of the optical signal 160 and the optical path of the excitation light 150 may be separate and independent optical paths.

[0032] The optical device 110 includes a flexible spectral optical detector as described herein. Figure 1B is a diagram illustrating an example implementation of the optical device 110. As Figure 1B shown, the optical device 110 includes a separation element 112, a dispersion element 114, a plurality of optical elements 116 (e.g., including optical element 116a, optical element 116b, and optical element 116c), and a detector array 118 that includes a set of detector regions 120 (e.g., detector region 120a, detector region 120b, detector region 120c). Figure 1B The upper diagram in illustrates an example of a view of the optical device 110 along the dispersion direction (i.e., the direction along which the dispersion element 114 disperses the spectral band 165, as described below), while Figure 1B the lower diagram of illustrates an example of a view of the optical device 110 along the band separation direction (i.e., the direction along which the separation element 112 separates the optical signal 160 into a plurality of spectral bands 165, as described below). As Figure 1B shown, the optical signal 160 from the sample 155 (e.g., an altered transmission signal from the light source 102, a signal generated by the sample 155 due to excitation by the excitation light 150, etc.) includes spectral information (i.e., spectral response) that is directed to the optical device 110.

[0033] 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 segment (e.g., by spectral range) and rearrange (e.g., spatially / angulary) the spectral response from the sample 155 into spectrally bands that are rearranged spatially and / or angulary (e.g., spectral band 165a, spectral band 165b, spectral band 165c, and spectral band 165d). In some implementations, the direction along which the separation element 112 separates the optical signal 160 spatially or angulary into a plurality of spectral bands 165 is referred to as the band separation direction. In some implementations, the band separation direction is perpendicular to the dispersion direction (e.g., the direction along which the dispersion element 114 disperses the spectral band 165). It is noted that while a band separation direction perpendicular to the dispersion direction can be used for practical purposes, in some implementations (e.g., depending on the detector geometry), a geometry where the band separation direction is not perpendicular to the dispersion can be used. In some implementations, the separation of the optical signal 160 (e.g., spectral segmentation and rearrangement) is performed in a single direction (the band separation direction). As an example, the separation element 112 can change the wavelength angle of the optical signal 160 to produce a continuous spatial spectral spread in the band separation direction.

[0034] The separating 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 implementations, the spectral ranges of the individual spectral bands 165 among the plurality of spectral bands 165 are different. In some implementations, the spectral bands 165 among the plurality of spectral bands 165 may substantially not overlap (e.g., such that each spectral band 165 covers a substantially different frequency range). Such an implementation can be used, for example, to maximize the spectral range covered by the bands of the optical signal 160 provided by the separating element 112. In some such implementations, the overlap between a given pair of adjacent spectral bands 165 can be small (e.g., the maximum overlap is in the range of about 2% to about 10%). For example, this overlap can be utilized to avoid gaps between the spectral bands 165 that might otherwise be created due to design or manufacturing non-idealities. Additionally or alternatively, the spectral bands 165 among the plurality of spectral bands 165 may substantially overlap (e.g., the overlap within the frequency range is greater than about 10%) to provide significant spectral redundancy. For example, an application may require that two different detector regions 120 of the detector array 118 detect the same sub-band spectral range (e.g., about 100% overlap) (e.g., when the two detector regions 120 have different detector characteristics, when the power in each "same" spectral band 165 is intentionally made different when incident on the respective dedicated detector regions 120, etc.).

[0035] In some implementations, the separating element 112 can be configured such that the optical power between the spectral bands 165 is different (e.g., such that the optical power of a given spectral band 165 is controlled to a desired degree or is intentionally different from the optical power of another spectral band 165). For example, this implementation can be used when different detector regions 120 have different input optical power saturation levels (or thresholds) and it is desired for the different detector regions 120 to have similar behavior. As another example, this implementation can be used when it is desired to use the detector regions 120 at different input power levels to probe the detector regions 120 in different input optical power saturation states (e.g., multiple spectral bands 165 having the same spectral range but different optical powers can be sent to multiple nominally identical detector regions 120).

[0036] In some implementations, the separating element 112 can segment the optical signal 160 into spectral bands without power loss (e.g., except for power loss caused by component non-ideality). Notably, traditional techniques are based on power splitting rather than spectral separation. In other words, traditional techniques split the optical signal into N (N>1) approximately equal sub-beams, where the power of each sub-beam is 1 / N of each spectral band of the full spectrum. In contrast, the separation provided by the separating element 112 separates the optical signal 160 into multiple spectral bands 165, where all the power comes from its corresponding band without power from other bands (within reasonable non-ideal components). Thus, the separation provided by the separating element 112 preserves the power associated with each spectral band, which can increase throughput and thus increase sensitivity. Additionally, preserving the power associated with each spectral band enables an increased measurement speed for spectral analysis. For example, the signal-to-noise ratio of a given detected spectral component (e.g., a Raman peak within a portion of the spectrum) within 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 equivalent detection time window), relatively more Raman photons reach the detector within this spectral component, and thus, a higher signal-to-noise ratio is achieved through spectral splitting (compared to power splitting). This means that for the same signal-to-noise ratio, spectral splitting requires fewer pulses and thus a shorter detection time window, which is equivalent to an increased measurement speed.

[0037] The dispersive element 114 includes one or more elements for dispersing spectral components of the spectral band 165 to form a dispersed spectral band 165. That is, the dispersive element 114 includes dispersing the spectral band 165 (e.g., spectral bands 165a to 165d) to form multiple dispersed spectral bands 165 (e.g., Figure 1BOne or more elements of the dispersion spectral bands 165a, 165c, and 165d) in the illustrated example. In some implementations, the dispersion element 114 can include one or more elements capable of spatially separating incident light into different spectral components (e.g., wavelengths). For example, the dispersion element 114 can include a diffraction grating, a prism, or any other wavelength dispersion element. In one example implementation, the spatially separated spectral bands 165 are incident on a diffraction grating having spatially separated portions (which can be continuous or not), each portion being designed to operate with a corresponding incident spectral band 165. In some implementations, the direction along which the dispersion element 114 disperses the spectral bands 165 is referred to as the dispersion direction. In some implementations, the dispersion element 114 includes a plurality of dispersion regions (e.g., each dispersion region is for dispersing a corresponding spectral band among the plurality of spectral bands 165). In some implementations, the plurality of dispersion regions can be stacked along the band separation direction (e.g., perpendicular to the dispersion direction). In some implementations, a given dispersion region of the dispersion element 114 disperses the spectral band 165 incident thereon independently of the dispersion performed by other dispersion regions of the dispersion element 114. For example, in some implementations, the plurality of dispersion regions can be monolithically patterned (or mechanically pieced together) onto a single dispersion element 114, each dispersion region having a corresponding (e.g., different) set of dispersion characteristics.

[0038] In operation, the dispersion element 114 is used to physically separate the spectral components forming a given spectral band 165 such that the spectral components of the given spectral band 165 exit the dispersion element 114 at different angles and positions, thereby forming the dispersion spectral band 165. In some implementations, the dispersion regions of the dispersion element 114 can operate differently on each spectral band 165 to produce dispersion spectral bands 165 having different optical characteristics (e.g., physical size and orientation in space, spectral range, spectral width, spectral resolution, etc.). For example, a given dispersion region of the dispersion element 114 can segment or separate a continuous spatial spectrum angularly and spatially into individual bands. In some implementations, the dispersion element 114 can define the spectral range of a given spectral band 165.

[0039] The plurality of optical elements 116 includes one or more elements for manipulating the dispersed spectral band 165 associated with imaging the spectral band 165 onto the detector region 120 of the detector array 118. In some implementations, the plurality of optical elements 116 includes an imaging subsystem for imaging the spectral band 165 onto the detector array 118. In some implementations, the plurality of optical elements 116 includes a plurality of elements capable of manipulating the position, size, and / or orientation / direction of the spectral band 165 to image one or more of the plurality of spectral bands 165 onto the detector array 118 and having a particular arrangement (e.g., determined by the size and / or performance attributes and / or functional criteria of the detector array 118). For example, a given optical element 116 can include one or more lenses, prisms, wedges, mirrors, diffraction gratings, bulk optical devices, etc. and combinations thereof. In some implementations, 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, physical size or position on the plane of the detector array 118, etc.), and image such characteristics onto a particular detector region 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 such that the width of the detector array 118 is filled to provide the highest resolution and / or determine the height of the detector array 118 for each corresponding spectral band 165 (e.g., to control the dynamic range and sensitivity). In some implementations, the plurality of optical elements 116 can be used to arrange the dispersed spectral band 165 to optimize the use of the detector array 118 (e.g., maximize the area used on the detector array 118, maximize the optical resolution, use a particular detector region 120 on the detector array 118 for a particular spectral band 165, etc.). For example, the plurality of optical elements 116 can expand the dispersed spectral band 165 to match the width of the detector array 118, and stack each spectral band 165 at a corresponding height in the detector region 120 on the detector array 118. In some implementations, the plurality of optical elements 116 can manipulate (e.g., direct, steer, focus, collimate, converge, expand, etc.) the dispersed spectral band 165 such that the images of the spectral band 165 are stacked along the band separation direction at the plane of the detector region 120. For example, in some implementations, the plurality of optical elements 116 can provide a spatial rearrangement of the plurality of spectral bands 165 on the plane of the detector region 120. In some implementations, an optical element 116 among the plurality of optical elements 116 can manipulate (e.g., expand) the dispersed spectral band 165 such that the size of the dispersed spectral band 165 along the dispersion direction matches the size of the detector region 120 along the dispersion direction (e.g., the region of the detector array 118 onto which the spectral band 165 is to be imaged).Similarly, in some implementations, the optical element 116 can manipulate (e.g., expand) the dispersion spectral band 165 such that the size of the dispersion spectral band 165 in the band separation direction matches the size of the detector region 120 along the band separation direction. In this way, the spatial arrangement of the dispersion spectral band 165 at the detector region 120 can be controlled to maximize the use of a particular detector geometry (e.g., rectangular 2D detector array 118).

[0040] The detector array 118 includes one or more detector regions 120 on which one or more spectral bands in the spectral band 165 are imaged. In some implementations, as Figure 1B shown, the detector region 120 can include a plurality of detector regions 120 stacked along the band separation direction. In some implementations, the detector array 118 can include a 2D array (e.g., a 2D array of detector regions 120). Additionally or alternatively, the detector array 118 can include a plurality of 1D detector arrays (e.g., a plurality of 1D detector arrays stacked along the band separation direction). For example, such an implementation can expand the detection capabilities of the optical device 110 (e.g., spectral range, spectral resolution, detection dynamic range, detection sensitivity, etc.). In some implementations, the detector array 118 can 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 can include a time-resolved photon counting detector array (e.g., an area array capable of associating a timestamp with each photon detected by a given area). Such a detector can also be referred to as a time-binned photon counting detector or a time-tagged photon counting detector. Alternatively, the detector array 118 can include a detector array that includes photon detectors using another technique (e.g., a photon detector array that may or may not include a time-resolved photon counting detector). In some implementations, the size of the first detector region 120 among the plurality of detector regions 120 is different from the size of the second detector region 120 among the plurality of detector regions 120. In some implementations, the detector regions 120 of the detector array 118 can be used for a plurality of spectral bands 165. For example, through time-domain multiplexing and in combination with an effective element capable of selecting the spectral band 165, reuse of the detector region 120 can be achieved, where the spectral band is manipulated and imaged onto a given detector region 120 at a given time point.

[0041] In some implementations, the size of the first detector region 120 of the detector array 118 in the dispersion direction matches the size of the second detector region 120 of the detector array 118 in the dispersion direction, and the size of the first detector region 120 in the band separation direction is different from the size of the second detector region 120 in the band separation direction. In this implementation, higher sensitivity is provided for the spectral band 165 that is imaged onto the first detector region 120 having a relatively larger size. In this way, by controlling the "height" of each spectral band 165 in the band separation direction onto which it is imaged onto 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. Although increasing the size of the detector region 120 illuminated by a particular spectral band 165 does not change the total number of photons in that spectral band 165, the increase in size increases the dynamic range and sensitivity that can be achieved for that spectral band 165 (e.g., by reducing the effect of the reset "dead time" that occurs after a pixel detection event in the SPAD array), and increases the saturation limit of the detector array 118 for the wavelengths in that spectral band 165 because the photons are spread over more pixels of the detector array 118. In some implementations, a given detector region 120 of the detector array 118 can be associated with different respective spectral bands 165. In some implementations, a given detector region 120 can include multiple pixels in the dispersion direction and multiple pixels in the separation direction (e.g., to avoid saturation and allow for more detector counts per pulse, improve signal quality, etc.). In some implementations, the pixels of a given detector region 120 can be grouped into multiple macro-pixels (e.g., to adjust the trade-off between detection efficiency and spectral resolution).

[0042] In some implementations, the arrangement of spectral bands 165 on detector region 120 of detector array 118 can be (e.g., dynamically) controlled such that a particular spectral band 165 is incident on a particular detector region 120, or such that a particular spectral band 165 is incident on a detector region 120 remote from a particular detector region 120. For example, spectral bands 165 can be arranged such that spectral bands 165 of particular interest are incident on detector regions 120 corresponding to the first row of detector array 118 to enable “fast” reads from detector array 118. In some implementations, detector regions 120 can support partitioning into specific pixel blocks, each having programmable readout timing. As another example, if a particular pixel of detector array 118 is experiencing noise or another performance issue, spectral bands 165 of particular interest can be arranged to be incident on detector regions 120 not proximate to the particular pixel experiencing the performance issue. In some implementations, the arrangement of spectral bands 165 on detector regions 120 (such as those described in the examples above) can be dynamically configured, which means that the arrangement of spectral bands 166 on detector regions 120 can be updated, modified, or changed during operation of optical device 110 (e.g., based on control signals provided by controller 122). In some implementations, such dynamic control can be achieved, for example, by adjusting the position, alignment, rotation, or other characteristics of one or more elements of optical system 100, such as collection element 104, filter 106, separation element 112, dispersion element 114, one or more optical elements 116, detector array 118, one or more detector regions 120, and / or one or more other elements associated with manipulating or guiding light in optical system 100 (e.g., one or more guiding elements, one or more lenses, etc.).

[0043] In Figure 1B In the example shown, separation element 112 provides four spectral bands 165 (i.e., four sub - spectra), three of which (e.g., spectral band 165a, spectral band 165c, and spectral band 165d) are directed to dispersion element 114 for dispersion and then manipulated by corresponding optical elements 116 to be imaged in three different geometries (e.g., different heights of respective spectral bands 165). Figure 1BShown in Table 1 below are resulting examples of arranging the optical signal 160 into these three spectral bands 165 having different attributes (e.g., highly correlated dynamic range and sensitivity, spectral range, spectral width covered, spectral resolution). It is noted that in this example, spectral band 165b is not imaged at the detector array 118. That is, in some implementations, at least one of the multiple spectral bands 165 may not be imaged onto any detector region 120 of the detector array 118. For example, this implementation can be used when certain portions of the full spectrum (e.g., spectral band 165b) do not need to be measured or detected. In some implementations, the ability to have such spectral gaps when detecting at the detector array 118 can enable enhancing one or more other characteristics of the detected spectral bands 165 (e.g., increased resolution, redundancy, readout speed, etc.). Thus, in some implementations, the spectrum formed by the sum of a set of spectral bands 165 imaged on the detector array 118 is discontinuous (e.g., includes one or more spectral gaps). In some implementations, the optical power of a given spectral band 165 among the multiple spectral bands 165 at the detector array 118 is greater than 90% of the optical power of the spectral band 165 before the separation element 112. That is, the spectral band 165 can be imaged at the detector array 118 with no or only minimal power loss (except for power loss caused by the non-ideality of the optical elements performing the separation function).

[0044] It is noted that since the spectral bands 165 can be stacked when being imaged onto the detector array 118 (e.g., a 2D detector array), the angular range required for the elements of the optical device 110 and the optical device in the dispersion direction is significantly reduced (e.g., compared to conventional devices using a relatively long 1D detector). This reduces the physical size of the optical device 110, thus enabling a more compact optical engine. In addition, the optical device 110 can be applied to many existing spectral measurement techniques. For example, the optical device 110 can be used for Raman spectroscopy and fluorescence spectroscopy measurements, and the readout time of the detector array 118 can be time-gated and / or related to the time when the sample 155 is exposed to the excitation light 150.

[0045] In addition, according to the techniques described herein, in some implementations, a given spectral band 165 can be directed to any detector region 120 of the detector array 118. The active area of the detector array 118 need not have the same dimensions as the area given by the sum of the areas of all spectral bands 165 to be detected at the plane of the detector array 118. In some implementations, the spectral bands 165 can be arranged to fit the width of the active area of the detector array 118, and a scanning mechanism can be used to move the spectral bands 165 in the band separation direction to cause them to fall on the detector regions 120, or to move the detector array 118 in the band separation direction to cause it to fall within the field of view of the desired spectral band(s) 165. This can allow the use of a detector array 118 of reduced size (e.g., a reduced-size 1D array or a 2D array with fewer detector regions), whose width is set by the width of a single spectral band 165, to measure an entire spectrum (e.g., the sum of all spectral bands 165).

[0046] In some implementations, one or more elements of the optical device 110 can be statically configured (e.g., using conventional optics). Additionally or alternatively, one or more elements of the optical device 110 can be dynamically configured, e.g., to allow dynamic configuration of 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 on the detector array 118 at which each spectral band 165 is imaged. Dynamic configuration can allow different spectral bands 165 from different pulses to be imaged onto the detector array 118. In some implementations, the readout of one or more detector regions 120 of the detector array 118 can be performed using various techniques, such as using a global shutter or a rolling shutter. Additionally, in some implementations, the separating element 112 can remove one or more spectral bands 165 (e.g., as Figure 1B shown). Additionally or alternatively, one or more other elements of the optical device 110 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), such as the dispersive element 114 or one or more optical elements 116.

[0047] The optical resolution is given by the dispersive element 114 (e.g., grating resolution) and is independent of the characteristics of the detector array 118. The detector resolution is given by the detector array 118 (e.g., pixel size of the detector array 118) and is similarly independent of the dispersive element 114. The system resolution combines the optical resolution and the detector resolution. In the optical device 110, the best result that can be achieved is the optical resolution because even if better detector resolution is provided, the detector array 118 cannot sample at a resolution higher than that provided by the dispersive spectral band 165 provided by the dispersive element 114. In practice, the goal is to match the detector resolution with the optical resolution to avoid reducing the optical resolution without having unnecessary pixels. In some implementations, 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.

[0048] The spectral range is given by the wave number or wavelength range included in a specific spectral response, signal, band, or sub-spectrum. The spectral range is similar to the wavelength bandwidth. In the case of Raman spectroscopy measurements, an example spectral range of the optical signal 160 can be greater than about 100 nm (wavelength) or greater than about 3000 cm -1 (wave number). Additionally, an example spectral range of a given spectral band 165 can be between about 400 and 700 wave numbers. In some implementations, 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.

[0049] The dynamic range is the range of values that can be reported from a set of pixels of the detector array 118 relative to a specific wavelength / wave number in the spectral band 165. In some implementations, the dynamic range for that wavelength / wave number (e.g., by reducing the impact of the reset "dead time" that occurs after a pixel detection event in the SPAD array) can be increased by increasing the number of pixels for each wavelength / wave number.

[0050] Back to Figure 1A, the controller 122 is an element for obtaining 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 region 120 of the detector array 118 during an acquisition window associated with the given detector region 120. Here, each detector region 120 may be associated with a corresponding spectral band 165, and thus, the readout signal associated with a given detector region 120 may correspond to the amount of photons in the spectral band 165 associated with the given detector region 120 within a given time window. In some implementations, in association with obtaining one or more readout signals, the controller 122 may be configured to coordinate the operation of the light source 102 and 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 detector array 118 such that the timing of receiving the optical signal 160 (in the form of light pulses or photon bursts) 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 window of one or more detector regions 120 of the detector array 118, from which one or more readout signals can be obtained. In some implementations, such coordination may involve one or more other elements of the optical system 100. For example, in the case where the collection element 104 includes a mechanically movable mirror or shutter, the controller 122 may be configured to control the collection element 104 so as to enable scanning or perturbing the excitation light 150 over the region of the sample 155. As another example, the controller 122 may be configured to control a scanning element (e.g., a mechanically movable mirror) that can direct the optical signal 160 towards one or more detector regions 120 during the acquisition window. In some implementations, the scanning element may be separate from the collection element 104 (e.g., the scanning element may be included in the optical device 110 in the detection optical path after the slit 108). For example, this implementation can be used when the optical path of the optical signal 160 and the optical path of the excitation light 150 are separate 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 implementations, the scanning element may be included in or integrated with the collection element 104 (e.g., under the control of the controller 122, the collection element 104 can enable scanning or perturbing the excitation light 150 over the region of the sample 155 and direct the optical signal 160 towards one or more detector regions 120). For example, this implementation can be used when the collection element 104 is located on both the optical path of the optical signal 160 and the optical path of the excitation light 150).

[0051] In practice, separating Raman signals and fluorescence signals requires synchronization and down-timing to sub-nanosecond resolution, which means that signal delays need to be considered. Such signal delays can be caused by, for example: laser cavity dynamics (laser cavity dynamics result in a delay or jitter between an electrical drive signal and the emission of an optical pulse), propagation delays of transmitted optical pulses to and from the sample 155, detection timing relative to the arrival of a laser pulse at the detector array 118 (e.g., SPAD time intervals), or the timing enabling photon detection. In some implementations, the controller 122 can be configured to set (optimal) operating parameters and synchronization with the scanning or attenuation elements of the optical system 100 to avoid unnecessary effects such as damage or heating of the sample 155 (which may change or shift the measured spectrum), detector saturation or photobleaching (which may alter the measured spectrum).

[0052] In some implementations, the controller 122 can acquire multiple readout signals, where each readout signal is acquired during a different acquisition window among a plurality of acquisition windows. That is, in some implementations, the controller 122 can be configured to read one spectral band 165 at a time from the detector array 118 (e.g., in a rolling window manner). In some implementations, the controller 122 can control the length of a given acquisition window such that the lengths between multiple acquisition windows can be different. For example, the time length of a first acquisition window associated with a first readout signal can be different from the time length of a second acquisition window associated with a second readout signal. In this way, the amount of time used to measure a given spectral band 165 (e.g., increased relative to other spectral bands) can be controlled in order to improve the measurements made for relatively higher-priority spectral bands 165. Additionally or alternatively, the controller 122 can acquire multiple readout signals, where each readout signal is acquired simultaneously during a single acquisition window (e.g., in a global shutter manner).

[0053] In some implementations, the controller 122 can be configured to coordinate the sampling of readout signals in one or more readout signals with the excitation of the sample 155 to achieve time-resolved Raman spectroscopy. Additionally or alternatively, the controller 122 can be configured to coordinate the temporal sampling of readout signals in one or more readout signals with the excitation of the sample 155 to achieve time-resolved fluorescence spectroscopy. Thus, in some implementations, the optical system 100 can be configured for, for example, time-gated Raman spectroscopy applications (e.g., time-resolved measurement and 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.

[0054] In some implementations, controller 122 may be configured to perform synchronization to account for timing jitter in the excitation light 150. For example, in some implementations, controller 122 may use a separate optical detector to detect the timing of the pulses of the excitation light 150 and accordingly control the timing of detector array 118. In some implementations, such synchronization may be performed as a supplement to or an alternative to the timing jitter control performed by light source 102.

[0055] In some implementations, optical system 100 may include Figures 1A - 1B one or more other elements not shown. For example, in some implementations, optical system 100 may include a scanning element for perturbing or scanning the excitation light 150 incident on sample 155. In one example, the scanning element may be a MEMS device having 1D or 2D scanning capabilities. In some implementations, the scanning element may be integrated with collection element 104. In some implementations, such a scanning element may also be used to disable the laser output, which means that the scanning element will not provide scanning but will be "parked" in a position (or state) that prevents the excitation light 150 from leaving the enclosure of optical system 100.

[0056] As another example, in some implementations, optical system 100 may include a shifting element for dynamically adjusting the spatial separation between the illumination light path of optical system 100 (e.g., the path through which excitation light 150 is provided to sample 155) and the detection light path of optical system 100 (e.g., the path through which the optical signal 160 is provided to optical device 110). In one example, a shifting element may be included (e.g., inside optical system 100 or in an external probe attachment), and the shifting element may be used to implement dynamic, spatially resolved Raman and fluorescence spectroscopy. With this capability, the position of the illumination light path and / or the detection light path on sample 155 can be dynamically shifted. This dynamic change in the separation between the illumination light path and the detection light path allows Raman and fluorescence signals to be probed from different depth layers of sample 155 and provides measurement capabilities and attributes similar to those of SORS technology, while also allowing for dynamic variation in the position of the probed region or layer of sample 155. In some such implementations, the shifting element may be integrated with collection element 104 and / or with the scanning element for perturbing or scanning the excitation light 150 incident on sample 155, or may be a separate element.

[0057] As another example, in some implementations, optical system 100 may include a sampling interface mounted on a hermetic package that houses one or more elements of optical system 100 (e.g., optical device 110). In some implementations, the sampling interface may implement, for example, a fiber optic probe, an optical relay system (e.g., for adjusting beam size and working distance), or an external SORS application.

[0058] In some implementations, the optical system 100 described herein differs from conventional solutions in that the optical system 100 is capable of (1) performing time-resolved measurements and time-resolved Raman and fluorescence simultaneously, (2) improving sensitivity and measurement speed, (3) improving resolution and spectral range, (4) improving size, weight, and power (SWAP), (5) reducing sample damage, and (6) extending to dynamic spatially offset Raman spectroscopy.

[0059] Regarding point (1), when an optical pulse is incident on a material, both Raman and fluorescence signals are generated. Although the lifetime of Raman scattering is very short (e.g., on the order of sub-picoseconds (ps)), the fluorescence process involves real electronic excited states with a finite measurable lifetime (e.g., on the order of a few ps to microseconds (μs)). Therefore, when an optical pulse is used as the excitation source, the Raman and fluorescence signals can be separated in the time domain. In some implementations, the time-resolved measurement and time-resolved Raman and fluorescence can be achieved by the optical system 100 by using a detector array 118 in the form of a high-sensitivity, high-time-resolution (e.g., sub-ns) 2D SPAD array detector, which is capable of both time interval (bin) detection and time-gated detection, as exemplified Figure 1C shown. As Figure 1C shown, the time interval carries both Raman and fluorescence signals, and the relative amplitude of the signal varies with time, which enables the simultaneous measurement of these two signals. Analysis of the early time intervals (e.g., consistent with pulsed laser excitation) reveals the Raman signal with the maximum amplitude-to-background ratio (which is actually the fluorescence ratio). At a later time (e.g., after pulsed laser excitation), the time interval has a negligible amount of Raman photons or no Raman photons, and the detected signal is dominated by fluorescence, which enables time-resolved fluorescence spectroscopy. In some implementations, 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 implementations, 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 achieve time-resolved measurement and time-resolved Raman and fluorescence. In some implementations, the optical system 100 can use time gating to reject signals outside a set detection window (e.g., when the SPAD is disabled).

[0060] Regarding point (2), by combining high-repetition-rate laser with a detector array 118 (e.g., a high-sensitivity SPAD array) and time binning / time gating detection (e.g., which suppresses the fluorescence background and improves the SNR), the sensitivity and measurement speed can be increased. 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 constant measurement time (or conversely, increases the measurement speed for a constant SNR). A higher SNR results in higher sensitivity for detecting weak Raman signals that would otherwise be obscured by the background signal (i.e., the fluorescence signal). In some implementations, higher sensitivity and measurement speed can be achieved by the optical system 100 by splitting the optical signal 160 into spectrally separated spectral bands 165, which are imaged onto the detector array 118 arranged in a 2D layout, as described herein, without significant power loss.

[0061] Regarding point (3), for the same size as the conventional solution, the optical system 100 can achieve higher resolution and / or cover a larger spectral range. Alternatively, the optical system 100 described herein can achieve the same performance as the conventional solution but with a smaller footprint. This is achieved by a spectral band optical design that separates the optical signal including the full spectral range into spectral bands 165 and rearranges the spectral bands 165 to maximize the utilization of the effective area of the detector array 118, as described herein (e.g., in combination with a capable 2D SPAD array detector). As described herein, the spectral bands 165 can be rearranged in various ways according to, for example, spectral range targets and / or spectral resolution targets. Generally, the number of spectral bands 165 can vary, and the spectral range covered or the spectral range of each spectral band 165 can be freely set independently of the spectral bands 165 (e.g., to meet performance goals).

[0062] Regarding point (4), the size improvement can be defined as a reduction in the footprint of an optical system (e.g., including collection optics and a spectrometer), which can be achieved by the spectral band optical design method described herein. Due to the reduction in footprint, the sizes of the optical and mechanical components can also be reduced, thereby reducing the overall weight of the spectral engine. The latter can also reduce power consumption because it takes less time to set or maintain the temperature of an optical system with a smaller footprint and / or reduced weight. In some implementations, the optical layout of the optical system 100 can be used to achieve a reduction in the footprint 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 for both the detection light path (e.g., the light path of the optical signal 160) and the illumination light path (e.g., the light path of the excitation light 150), which means that the detection light path and the illumination light path at least partially overlap. This optical layout achieves a smaller footprint by using the same physical space for a portion of multiple light paths, and can also reduce weight by using one or more identical optical elements on multiple light paths. Other components of a system that contribute to improving SWAP (size, weight, and power) can include a laser source and a detector array. In some implementations, the laser source can be a highly integrated compact microchip device that delivers light pulses of a specific wavelength (e.g., 532 nm) at a high repetition rate (e.g., at least about 500 kilohertz (kHz)), low energy (e.g., less than about 100 nanojoules (nJ)), and narrow linewidth (e.g., less than about 0.1 nm). In some implementations, the detector array can be a high-sensitivity 2D SPAD array whose pixel size and pixel count enable high (e.g., less than about 10 cm -1 wave number) spectral resolution. In some implementations, the pixel size and 2D array geometry can be selected to reduce the footprint of the entire system. Additionally, if configured to operate at visible wavelengths, the SPAD detector can be used with near-maximum efficiency and minimum noise, which means that frequent thermal cooling (e.g., compared to other Raman spectroscopy instruments) may not be required. As a result, power consumption can be reduced.

[0063] Regarding point (5), sample damage can be reduced by using low-energy pulses, a detector array 118 in the form of a high-sensitivity SPAD detector, and a beam scanning mechanism such as a MEMS scanner. Additionally, by separating the spectral band 165 without power loss (except for power loss caused by the non-ideality of optical elements), the detection optimization in a given spectral band 165 is increased, and the SNR is improved, which means that a lower power illumination can be used to illuminate the sample 155, thereby reducing the likelihood of damaging the sample 155.

[0064] Regarding point (6), the shift element can be integrated into the optical system 100 or within an external probe attachment and can be used to implement dynamic, spatially resolved Raman and fluorescence spectroscopy, as described above.

[0065] As described above, Figures 1A - 1C is provided only as an example. Other examples can be different from those regarding Figures 1A - 1C described. In addition, Figures 1A - 1B the number and arrangement of the elements shown are provided only as an example. In practice, there can be more elements, fewer elements, different elements, or differently arranged elements compared to those Figures 1A - 1B shown. For example, the physical layout of the optical system 100 (e.g., the layout of the light source 102, collection element 104, filter 106, optics 110, etc.) provides the functions described herein using free-space optics. The power and pulse energy of the light source 102 can be relatively high, and using free-space optics is advantageous in terms of power handling. In addition, free-space optics is efficient in collecting relatively weak reflected Raman signals. However, in some implementations, the physical layout of the optical system 100 can be designed to provide the functions described herein in another way, such as by using fiber-based or waveguide-based optics (as an alternative or supplement to free-space optics). In some implementations, the choice of technology for providing the functions of the optical system 100 can be a design requirement in a given application, such as optical performance, size, power consumption, mechanical stability, etc. In addition, Figures 1A - 1B two or more of the elements shown can be implemented within a single element, or Figures 1A - 1B a single element shown can be implemented as multiple distributed elements. Additionally or alternatively, Figures 1A - 1B a set of elements (e.g., one or more elements) shown can perform one or more functions described as being performed by Figures 1A - 1B another set of elements shown.

[0066] In conjunction with Table 1 (below), Figure 2 illustrates an example associated with the optics 110 that provides flexible segmentation and arrangement of the full spectrum. In Figure 2In the example shown, the spectral bands 165 are arranged such that the spectral bands 165 are stacked and imaged at the detector array 118 in a band separation direction (e.g., a direction perpendicular to the dispersion direction). As described above, the spectral bands 165 can be arranged in various ways according to, for example, spectral range, spectral resolution, and / or detection dynamic range and sensitivity objectives. In some implementations, the number and regions of the spectral bands 165 can vary, and the spectral range, resolution, dynamic range, and / or sensitivity of each spectral band 165 can be set independently of the other spectral bands 165 (e.g., for the purpose of meeting the specific performance objectives of a given application). For example, in some implementations, portions of the full spectrum that are not desired to be measured or detected (e.g., spectral band 165b) can be skipped (e.g., avoided or rejected). As another example, specific pixels or detector regions 120 of the detector array 118 that cannot or should not be used can be avoided.

[0067]

[0068] Table 1

[0069] Table 1 gives a numerical example that illustrates the properties of different spectral bands 165 imaged on a 2D detector array 118, which includes three detector regions 120, as Figure 2 shown. In this example, the height of the example detector region 120 is 700 pixels, and the example spectral range (expressed as a spectral shift from the excitation wavelength) is from 0 to 1600 wave numbers. Here, a portion of the full spectrum (i.e., spectral band 165b) is not measured or monitored and thus not imaged onto the detector array 118, while the remainder of the full spectrum is divided into spectral band 165a, spectral band 165c, and spectral band 165d, which have different spectral ranges, resolutions, dynamic ranges, and sensitivities (e.g., scaled with height on the detector array 118, referred to as band height in Table 1), and are imaged onto different detector regions 120 of the detector array 118.

[0070] As described above, Figure 2 is provided as an example. Other examples can be different from those Figure 2 described.

[0071] Figure 3 and Figure 4A diagram associated with the increase in dynamic range and sensitivity achieved through the optical device 110. In some implementations, the dynamic range and sensitivity can be increased without changing the front-end light collection and spectral splitting. In one example implementation, the back-end imaging optics (e.g., one or more optical elements 116) can be designed such that the energy in one spectral band 165 is imaged on the detector array 118 at a different and greater height, at the cost of a reduced height or number of other spectral bands 165 for a fixed-size detector region. Alternatively, in another example implementation, two or more spectral bands 165 can be made the same (e.g., spectral band 165a and spectral band 165d in Figure 3 ), and the power in these spectral bands 165 can be split equally.

[0072] In Figure 3 the example detector array 118 shown, the height of spectral band 165c at the detector array 118 is twice that of spectral band 165a (e.g., 200 pixels versus 100 pixels) (e.g., the height of the detector region 120 on which spectral band 165c is imaged is twice the height of the detector region 120 on which spectral band 165a is imaged). Here, if all spectral bands 165 have equal energy (e.g., power or throughput), the per-pixel pulse energy of spectral band 165c will be reduced by a factor of 2 compared to spectral band 165a (and spectral band 165d). In Figure 4 the diagram shown, the impact of reducing the energy density (e.g., energy per pixel) on the detector array 118 is calculated for two channel sizes: one is an optical spectral channel with a specific width and a 100-pixel height, and the other is an optical spectral channel with a specific width and a 200-pixel height. As Figure 4 shown, the higher channel (i.e., the optical spectral channel with a height of 200 pixels) has a greater counting detection dynamic range, thus improving the sensitivity. In Figure 4 the diagram shown, if the pulse energy is further increased, the detection count per pulse will eventually saturate the detector array 118, which means that despite the increase in pulse energy, the detector array 118 cannot detect more counts. In some implementations, the sensitivity and saturation limit can be improved by increasing the height (e.g., and number of pixels) allocated to a given spectral band 165.

[0073] In some implementations, a first spectral band 165x having a relatively small bandwidth can be imaged on a first detector region 110x of a detector array 118, and a second spectral band 165y having a relatively large bandwidth can be imaged on a second detector region 110y of the detector array 118, while the total width and pixel size (i.e., resolution) of the first detector region 110x in the dispersion direction match the total width and pixel size (i.e., resolution) of the second detector region 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 be provided with a higher spectral resolution than the second spectral band 165y (e.g., because for the first spectral band 165x having a relatively small bandwidth, each detector pixel receives fewer wave numbers).

[0074] As described above, Figure 3 and Figure 4 are provided only as examples. Other examples may differ from those regarding Figure 3 and Figure 4 described.

[0075] Figures 5 - 7 FIG. is a diagram illustrating an example implementation of the separation element 112 described herein. In some implementations, as described above, the separation element 112 can include one or more elements capable of spatially or angularly separating an 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 implementations, the separation element 112 can include a plurality of thin-film interference filters, each of the plurality of thin-film interference filters being associated with a different spectral band 165 among the plurality of spectral bands 165. Figure 5 FIG. is a diagram illustrating an example implementation of the separation element 112 including a plurality (e.g., four) thin-film interference filters 502. Additionally or alternatively, these can include diffraction gratings. Figure 6 and Figure 7 FIG. is a diagram illustrating an example implementation of the separation element 112 including a diffraction grating 602. Additionally or alternatively, the separation element 112 can include one or more other types of optical elements.

[0076] In some implementations, light having a wavelength near the boundary between two spectral bands 165 of the optical signal 160 can be split by the splitting element 112 such that corresponding portions of the light enter multiple spectral bands 165. Thus, in some implementations, spectral components at or near the boundary between a first spectral band 165 and a second spectral band 165 among the multiple spectral bands 165 can be split such that a first portion of the spectral component lies in the first spectral band 165 and a second portion of the spectral component lies in 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.

[0077] In Figure 5 the example shown, the optical signal 160 includes a full spectrum (e.g., as Figure 1B shown) originating from the sample 155. Here, each thin-film interference filter 502 reflects only a portion of the full spectrum (e.g., spectral band 165) and transmits the remainder. In some implementations, as Figure 5 shown, a series of multiple (e.g., four) interference filters 502 (followed by a mirror 504) divide the full spectrum into multiple (e.g., five) spatially separated spectral bands 165, which then impinge on a focusing lens 506 to convert the spatial separation (e.g., offset) into an angular separation (e.g., angle) of the different spectral bands 165. The spectral bands 165 can then be imaged onto a plane for further optical processing. In Figure 1B the context of the optical device 110 described in

[0078] In Figure 6 and Figure 7 the example shown, the optical signal 160 (including the full spectrum originating from the sample 155 (as Figure 2 shown)) is collimated by a lens 604 and then directed onto a diffraction grating 602, which separates the incident light into different spectral components (e.g., wavelengths). The diffracted light exiting the diffraction grating 602 is then focused by a lens 606 and imaged to produce spectrally separated spectral bands 165 in space and angle. Figure 7 The imaging system shown includes a wedge 702 and prisms 704a and 704b, which are used to change the optical path length and propagation angle of the beams of the spectral bands 165 such that the exiting spectral beams appear to be from a single focal plane rather than from different angles (e.g., similar to what is achieved in the example shown in Figure 5 )). In Figure 1B the context of the optical device 110 described in

[0079] As described above,Figures 5 - 7 are provided as examples. Other examples may be different from those described with respect to Figures 5 - 7 the different. Figures 5 - 7 The number and arrangement of the elements shown are provided only as examples. In practice, compared with those Figures 5 - 7 shown, there may be more elements, fewer elements, different elements, or elements arranged differently. In addition, Figures 5 - 7 two or more of the elements shown may be implemented within a single element, or Figures 5 - 7 a single element shown may be implemented as multiple distributed elements. Additionally or alternatively, Figures 5 - 7 a set of elements (e.g., one or more elements) shown may perform one or more functions described as being performed by Figures 5 - 7 another set of elements shown.

[0080] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the implementation to the precise forms disclosed. Modifications and variations may be made in light of the foregoing disclosure, or may be obtained from the practice of the implementation. In addition, any implementations described herein may be combined, unless the foregoing disclosure expressly provides a reason why one or more implementations cannot be combined.

[0081] Although specific combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of the various implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and / or not expressly disclosed in the specification. Although each dependent claim listed below may depend directly on only one claim, the disclosure of the various implementations includes the combination of each dependent claim with every other claim in the claim set. As used herein, the phrase "at least one" in reference to a list of items means any combination of those items, including a single member. For example, "at least one of a, b, or c" is intended to cover a, b, c, a - b, a - c, b - c, and a - b - c, as well as combinations of multiple occurrences of the same item.

[0082] When a component or one or more components (e.g., an optical element or one or more optical elements) are described or claimed (within a single claim or across multiple claims) as performing multiple operations or being configured to perform multiple operations, such language is intended to broadly cover a variety of architectures and environments. For example, unless otherwise expressly claimed (e.g., by using "a first component" and "a second component" or other language that differentiates components in a claim), such language is intended to cover a single component performing or being configured to perform all operations, a group of components jointly performing or being configured to perform all operations, a first component performing or being configured to perform a first operation and a second component performing or being configured to perform a second operation, or any combination of components performing or being configured to perform the operations. For example, when a claim is in the form "one or more components are configured to: perform X; perform Y; and perform Z", the claim should be interpreted as "one or more components are configured to perform X; one or more (possibly different) components are configured to perform Y; and one or more (also possibly different) components are configured to perform Z."

[0083] Unless expressly stated otherwise, any element, act, or instruction used herein should not be construed as critical or essential. Also, as used herein, the articles "a" and "an" are intended to include one or more items and may be used interchangeably with "one or more". Also, as used herein, the article "the" is intended to include one or more items referenced in conjunction with the article "the" and may be used interchangeably with "one or more". Also, the term "set" as used herein 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". If only one item is intended, the phrase "only one" or similar language is used. Also, as used herein, the terms "having", "including", "containing", etc. are intended to be open-ended terms. Also, unless expressly stated otherwise, the term "based on" is intended to mean "at least partially based on". Also, as used herein, the term "or" when used in series is inclusive and may be used interchangeably with "and / or" unless expressly stated otherwise (e.g., if used in combination with "any one of... " or "only one of... "). Also, for ease of description, spatial relative terms (such as "below", "lower", "above", "upper", etc.) may be used herein to describe the relationship of one element or feature to other elements or features shown in the figures. Except for the orientation shown in the figures, spatial relative terms are intended to cover different orientations of the device, apparatus, and / or element in use or operation. The device may be oriented otherwise (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein may be interpreted accordingly.

Claims

1. An optical system, comprising: A light source for providing excitation light; A collection element for: Guiding an optical signal received from the sample in response to incidence of the excitation light on the sample to an optical device; The optical device, comprising: A separation element for separating the optical signal into a plurality of spectral bands along a band separation direction, the plurality of spectral bands being separated spatially or angularly, wherein spectral ranges among respective ones of the plurality of spectral bands are different, A dispersion element including a plurality of dispersion regions, wherein a dispersion region among the plurality of dispersion regions is for dispersing a spectral component of a spectral band among the plurality of spectral bands along a dispersion direction to form a dispersed spectral band, A plurality of optical elements, wherein an optical element among the plurality of optical elements is for manipulating the dispersed spectral band in association with imaging the spectral band onto a detector region of a detector array, and The detector array including the detector region; And A controller for obtaining one or more readout signals from the detector array.

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 perform synchronization to account for jitter in the excitation light.

4. The optical system according to claim 1, wherein the light source is a light source among a plurality of light sources, each of the plurality of light sources being configured to perform at least one of the following: emit at different wavelengths, generate excitation light having different pulse characteristics, or operate in different operation modes.

5. The optical system according to claim 1, further comprising a scanning element for perturbing or scanning 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, each of the plurality of readout signals to be obtained during a different acquisition window among a plurality of acquisition windows.

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

8. The optical system according to claim 1, wherein the one or more readout signals include a plurality of readout signals, each of the plurality of readout signals to be obtained simultaneously during a single acquisition window.

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

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

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

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

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

15. The optical system according to claim 1, wherein the optical system is configured to synchronize an acquisition window with the excitation light and one or more other elements of the optical system, the acquisition window is associated with obtaining one or more readout signals, and the one or more other elements are associated with manipulating at least one of the following: the excitation light, the optical signal, one or more spectral bands among the plurality of spectral bands, or one or more optical elements among the plurality of optical elements.

16. The optical system according to claim 15, wherein the optical system is configured to synchronize the acquisition window with the one or more other elements in association with performing time-gated Raman spectroscopy, time-resolved fluorescence spectroscopy, dynamic real-time spatially 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 shifting element for dynamically adjusting the spatial interval between the illumination light path and the detection light 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. An optical system, comprising: a light source for providing excitation light; a collection element for guiding an optical signal received in response to the incidence of the excitation light on a sample to an optical device; the optical device for: separating the optical signal into a plurality of spectral bands along a band separation direction, the plurality of spectral bands being separated spatially or angularly, and each of the plurality of spectral bands having a different spectral range; dispersing spectral components of the spectral bands among the plurality of spectral bands along a dispersion direction to form dispersed spectral bands; manipulating the dispersed spectral bands in association with imaging the spectral bands onto a detector region of a detector array of the optical device; and a controller for obtaining one or more readout signals from the detector array.

21. An optical system, comprising: a light source for providing excitation light; a collection element for guiding an optical signal received in response to the incidence of the excitation light on a sample to an optical device; the optical device, comprising: A separating element for separating the optical signal into a plurality of spectral bands, wherein the spectral ranges among the individual spectral bands of the plurality of spectral bands are different; A dispersive element including a dispersive region, wherein the dispersive region is for dispersing spectral components of the spectral bands of the plurality of spectral bands to form dispersed spectral bands; An optical element for manipulating the dispersed spectral bands in association with imaging the spectral bands onto a detector region of a detector array, and The detector array including the detector region; and A controller for coordinating the operation of the light source with the operation of one or more elements of the optical device or the collection element such that the timing of reception of the optical signal is synchronized with the timing of an acquisition window of the detector region.

Images