Multiple diffuse reflection optical device with light redirection for collection of spectrometers

Abstract

Aspects relate to a mechanism for enhancing the coupling of scattered light from a sample under test into a spectrometer. The optical device may include a reflective surface positioned separately from the sample and configured to receive a first portion of the scattered light from the sample and to redirect the first portion of the scattered light back to one or more discrete spots on the sample in a non-random manner to produce redirected scattered light from the sample. The spectrometer may then be configured to receive coupled light from the sample, the coupled light comprising at least a portion of the redirected scattered light.

Description

[0001] Priority Statement

[0002] This application claims the priority and benefit of Provisional Application No. 63 / 403,160, filed on September 1, 2022, and Non - Provisional Application No. 18 / 240,595, filed on August 31, 2023, with the United States Patent and Trademark Office, the entire contents of which are incorporated herein by reference as if fully set forth below for all applicable purposes. Technical Field

[0003] The techniques discussed below generally relate to spectra including diffuse reflectance spectra and transmission spectra, and particularly to mechanisms for effectively increasing the collection of spectrometers to better handle non - uniform samples and improve sensitivity. Background Art

[0004] Diffuse reflectance spectroscopy can be used to study the molecular structure of a given material based on its spectral response. In diffuse reflectance spectroscopy, a light source (e.g., a broadband light source) irradiates light onto the material to be measured. The incident light interacts with the material such that part of the light is transmitted, another part of the light is reflected, and another part of the light is scattered. The scattered part is affected by the absorption spectrum of the sample and can be used to identify the material based on its spectral fingerprint. Diffuse reflectance spectroscopy can be used for different forms of materials, such as solids, powders, and liquids.

[0005] Although the absorption spectrum is mainly determined by the material itself, measurement errors can start to occur if the scattered light does not fully represent the measured sample. This can be attributed to many reasons. For example, one reason is related to the use of non - uniform samples. This means that the material has different regions where the absorption spectrum varies depending on the measurement location. Another reason is related to the size and shape of the macroscopic particles of the substance. Various materials can exhibit a wide range of macroscopic particle forms, from fine particles found in powders to large spherical particles with diameters of several millimeters. Materials such as grains (e.g., corn kernels) exhibit non - uniformity and grain size variations. For example, corn can have irregularly shaped grains with lengths ranging from 5 mm to 20 mm. In this example, the scattered light is dominated by the part of the grain that is aligned with the field of view of the spectrometer. This makes a single measurement only representative of a small part of the corn kernel. Generally, depending on the different measurement locations, corn kernels can have different absorption spectra. In addition, due to the limited field of view of the spectrometer, it is difficult to measure multiple grains in the same measurement. Moreover, this irregular shape affects the scattered light that can be collected into the spectrometer, thereby affecting the signal - to - noise ratio (SNR) of the spectrometer measurement.

[0006] Conventional spectrometers can overcome these problems through the initial steps of sample preparation. Such sample preparation steps typically include grinding the material to form a uniform powder. Although such sample preparation processes are feasible in the laboratory, they may not be easy in the field for portable spectrometers or on the production line for quality control. In the past decade, the development of portable and handheld spectrometers has led to improvements in the sample interface, thus overcoming the above problems. For example, one way to overcome the problem of sample non-uniformity is to increase the field of view of the spectrometer. This helps to average the sample response of different non-uniform regions and ensures that the scattered light and collected light within the spectrometer can well represent different regions.

[0007] However, in some cases, increasing the field of view of the spectrometer may not be practical, especially when the acceptance angle and aperture size of the spectrometer are limited. This is the case for handheld and portable spectrometers. Many of these spectrometers are based on MEMS (Micro-Electro-Mechanical System) components, which typically have small optical surfaces, thus limiting the overall light throughput of the spectrometer. Such limitations impose constraints on the field of view with sufficient optical coupling power obtained. For example, increasing the area observed by the spectrometer at a limited light throughput can reduce the coupled optical power, which can result in a decrease in SNR. The reduced SNR can greatly affect material analysis and introduce errors in chemometric models. Summary of the Invention

[0008] The following presents an overview of one or more aspects of the present disclosure to provide a basic understanding of these aspects. This overview is not an extensive review of all the expected features of the present disclosure, and neither aims to identify the key or important elements of all aspects of the present disclosure nor to depict the scope of any or all aspects of the present disclosure. Its sole purpose is to present some concepts of one or more aspects of the present disclosure in a certain form as a prelude to the more detailed description presented later.

[0009] In one example, an optical device is disclosed. The optical device includes a reflective surface that is separated and positioned from the sample and is configured to receive a first portion of the scattered light from the sample and redirect the first portion of the scattered light back onto one or more discrete spots on the sample in a non-random manner to generate redirected scattered light from the sample. The optical device further includes a spectrometer that is configured to receive the coupled light from the sample at its input and obtain the spectrum of the sample based on the coupled light. The coupled light includes at least a portion of the redirected scattered light.

[0010] Another example provides a method for increasing the collection of a spectrometer. The method includes receiving a first portion of scattered light from a sample at a reflective surface positioned separately from the sample, redirecting the first portion of the scattered light in a non-random manner back to one or more discrete light spots on the sample to produce redirected scattered light from the sample, and receiving coupled light from the sample at an input of the spectrometer to obtain a spectrum of the sample based on the coupled light. The coupled light includes at least a portion of the redirected scattered light

[0011] These and other aspects of the present invention can be more fully understood by reading the following detailed description. By reading the following description of specific exemplary embodiments of the present invention in conjunction with the accompanying drawings, other aspects, features, and embodiments of the present invention will become apparent to those of ordinary skill in the art. While the features of the present invention may be discussed with respect to certain embodiments and figures below, all embodiments of the present invention may include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments of the present invention discussed herein. In a similar manner, while exemplary embodiments may be discussed below as device, system, or method embodiments, it should be understood that such exemplary embodiments may be implemented in various devices, systems, and methods BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram illustrating a spectrometer as an optical system according to some aspects

[0013] Figure 2 is a schematic diagram illustrating an example of scattered light coupled into a spectrometer according to some aspects

[0014] Figure 3 is a schematic diagram illustrating an example of an optical device with light redirection for spectrometer collection according to some aspects

[0015] Figure 4 is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects

[0016] Figure 5 is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects

[0017] Figure 6 is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects

[0018] Figure 7FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0019] Figure 8 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0020] Figure 9 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0021] Figure 10A and Figure 10B FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0022] Figure 11 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0023] Figure 12 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0024] Figure 13 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0025] Figure 14 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0026] Figure 15 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects.

[0027] Figure 16 FIG. is a flowchart of an exemplary method of light redirection for spectrometer collection from a sample according to some aspects. DETAILED DESCRIPTION

[0028] The detailed description set forth below in connection with the appended drawings is intended to describe various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0029] For example, spectroscopy can be used to characterize the chemical composition of solids, liquids, and gases. A spectrometer uses various mechanisms (e.g., transmission or diffuse reflection sampling) to analyze and interact with a sample to be measured. Transmission is typically used for liquid or gas samples. In this configuration, light passes through the sample to be measured and is then coupled into the spectrometer after interacting with the sample molecules. In diffuse reflection sampling, light is incident on the sample to be measured, and the scattered light from the sample is collected and coupled into the spectrometer. Diffuse reflection is mainly used for solids.

[0030] In both cases, the light collected by the spectrometer interacts with only a limited portion of the sample. In some applications, the sample is not uniform and can have a large particle size. In this case, measuring a small spot size may not be representative of the spectral properties of the sample. This can be observed in the measured spectrum because the variation at different positions on the sample is large. For example, in particle analysis, the particle size can vary between 5 mm and 20 mm. Therefore, the optical system of the spectrometer should be able to accommodate such a large spot size. In most of the existing systems on the market, the sample is measured several times at different positions, and then the readings are averaged together. In the present disclosure, a technique is provided to increase the spot size of the spectrometer and ultimately increase the accuracy of the chemometric model to simultaneously couple light from different positions of the sample.

[0031] In particular, aspects are directed to techniques for redirecting scattered light from a sample to one or more spots on the sample in a non-random manner to increase the effective spot size area. In some examples, a portion of the scattered light from a spot on the sample can be directly coupled into the spectrometer, while the remaining portion of the scattered light can be redirected back to the spot on the sample to increase the effective size of the spot and also increase the optical power of the optical device. In other examples, the scattered light from a first spot on the sample outside the field of view of the spectrometer can be redirected to a second spot on the sample within the field of view of the spectrometer, where the first spot and the second spot together form an extended spot region on the sample.

[0032] Figure 1 FIG. 10 is a schematic diagram of a spectrometer 104 as an optical system according to some aspects. The spectrometer 104 can be, for example, a Fourier transform infrared (FTIR) spectrometer. In some examples, the spectrometer 104 can include a Michelson interferometer or a Fabry - Perot interferometer.

[0033] The spectrometer f04 as an optical system can be simplified to an aperture f06 having a specific size (e.g., diameter) and a receiving angle θ. The acceptance angle θ represents the angle at the head of the light cone by which light from the illumination spot 102 on the sample is optically coupled into the spectrometer 104. For example, light passing through the sample or reflected from the sample (e.g., scattered from the sample) can be optically coupled from the illumination spot 102 towards the spectrometer 104.Figure 1 The throughput of the spectrometer 104 shown can be written as:

[0034] Throughput ∝ Aperture diameter 2 × sin 2 (θ). (Equation 1)

[0035] The distance between the sample interface and the spectrometer input surface can be denoted as X, as Figure 1 shown. If the distance X is large compared to the diameter of the aperture 106, and the collected spot area of the illumination spot 102 is much larger than the area of the aperture 106, the effective area (e.g., the field of view) seen by the spectrometer can be approximated by the following relationship:

[0036] Spot diameter ≈ 2X tan(θ). (Equation 2)

[0037] Based on the above Equation 1 and Equation 2, the key limitation of the spectrometer optical system in terms of the collected spot size can be considered to be the acceptance angle θ of the system. In a miniaturized spectrometer with a small-area and small acceptance angle input aperture 106, the performance of such spectrometers can be limited to uniform samples having an almost constant spectral response at different positions of the sample.

[0038] Figure 2 is a schematic diagram illustrating an example of scattered light coupled into the spectrometer 204 according to some aspects. The spectrometer 204 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflection mode. In some examples, the spectrometer 204 can include a Michelson interferometer or a Fabry - Perot interferometer. As described in the example Figure 1 shown, based on the diffuse reflection of light scattered (e.g., reflected) from the sample, light can be optically coupled from the illumination spot 202 on the sample towards the spectrometer 204 into the spectrometer 204. As Figure 2 shown, the scattered light from the sample can include a first portion of scattered light 208 and a second portion of scattered light 210. The first portion of scattered light 208 is scattered outside the aperture 206 and acceptance angle θ of the spectrometer 204, and thus does not reach the input of the spectrometer 204. Therefore, the first portion of scattered light 208 represents useless scattered light from the sample. Based on the aperture 206 and acceptance angle θ, the second portion 210 of the scattered light is directly coupled into the spectrometer 204, and thus represents useful scattered light from the sample.

[0039] In various aspects of the present disclosure, techniques are provided to redirect unwanted scattered light 208 from a sample back to the sample surface to increase the interaction of light with the sample and collect more information from the sample, thereby averaging the measured spectra, which results in enhanced coupling of light to the spectrometer 204. Various aspects provide different mechanisms to extend the coupling spot size and effectively achieve a larger field of view. In some examples, coupling spots can be simultaneously formed at different locations on the sample, which can reduce the measurement time if the sample is non-uniform because less averaging is required to cover the entire sample.

[0040] In some aspects, a reflective surface is used to redirect scattered light 208 that would otherwise miss within the input aperture and acceptance angle of the spectrometer back to the sample. The redirected light interacts with the sample again, and a portion of the scattered light that is scattered back is coupled into the spectrometer. The coupled power entering the spectrometer includes contributions from first and second sample reflections. Depending on the material properties of the reflective surface and the sample under test, light can be trapped between the reflective surface and the sample. In this example, light can be coupled after multiple reflections from the sample.

[0041] Figure 3FIG. is a schematic diagram illustrating an example of an optical device with light redirection for spectrometer collection according to some aspects. The optical device 300 includes a spectrometer 304 configured to receive coupled light from a sample 306 at its input and obtain a spectrum of the sample 306 based on the coupled light. The spectrometer 304 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflection mode. For example, the spectrometer 304 can include an FTIR interferometer configured to generate an interferogram that can be detected by a detector. The output of the detector can be processed to obtain a spectrum of the detected light, which can then be used to identify various parameters associated with the sample 306 to be measured. In some examples, the spectrometer 304 can include an interferometer (e.g., a Michelson interferometer and / or a Fabry - Perot interferometer), which can be implemented as, for example, a microelectromechanical system (MEMS) spectrometer. As used herein, the term MEMS refers to the integration of mechanical elements, sensors, actuators, and electronics on a common substrate through microfabrication techniques. For example, microelectronic devices are typically fabricated using integrated circuit (IC) processes, while micromachined components are fabricated using compatible micromachining processes that selectively etch away portions of a silicon wafer or add new structural layers to form mechanical and electromechanical components. An example of a MEMS element is a micro - optical component having a dielectric or metallized surface operating in a reflective or refractive mode. Other examples of MEMS elements include actuators, detector trenches, and fiber trenches. In some examples, the MEMS spectrometer can include one or more micro - optical components (e.g., one or more reflectors or mirrors) that can be movably controlled by a MEMS actuator. For example, a MEMS spectrometer can be fabricated using a deep reactive ion etching (DRIE) process on a silicon - on - insulator (SOI) substrate to produce micro - optical components and other MEMS elements capable of processing free - space light beams propagating parallel to the SOI substrate.

[0042] In Figure 3 the example shown, as described above, based on the input aperture and acceptance angle of the spectrometer 304, light can be coupled from the illumination spot 302 on the sample 306 into the spectrometer 304. For example, light incident on the illumination spot 302 is scattered by the sample 306. The scattered light covers a hemispherical solid angle. The scattered light within the acceptance numerical aperture of the spectrometer 304 is directly coupled into the spectrometer 304 as directly - coupled scattered light 310. However, due to the finite spectrometer numerical aperture, the directly - coupled scattered light 310 represents a small fraction of the total scattered light.

[0043] Thus, in aspects of the present disclosure, as Figure 3As shown, the reflective surface 308 is positioned separated from (e.g., surrounding) the sample 306. The reflective surface 308 has a curvature that is configured to receive a first portion (e.g., missed scattered light) of the scattered light 312 that is scattered outside the numerical aperture of the spectrometer 304, and redirect the missed scattered light 312 as reflected scattered light 314 towards the sample 306 to increase the effective spot size of the spot 302. In this example, the directly coupled scattered light 310 that is directly coupled from the sample 306 into the spectrometer 304 may correspond to a second portion of the scattered light. The reflected scattered light 314 may interact with the sample 306 again to generate redirected scattered light, which may be coupled into the spectrometer 304 as indirectly coupled redirected scattered light 316. Thus, based on the redirected scattered light 314, the spot 302 may have an expanded spot size (e.g., due to light incident on the sample 306 at different angles and then being coupled into the spectrometer 304). The reflective surface 308 may also have apertures 318 for coupling the scattered light including the directly coupled scattered light 310 and the indirectly coupled redirected scattered light 316 into the spectrometer 304. In Figure 3 the example shown, the reflective surface 308 is a hemisphere.

[0044] In some examples, the redirected scattered light may produce a scattering pattern that covers a hemispherical solid angle. Portions of these scattered rays (e.g., the indirectly coupled redirected scattered light 316) may be coupled into the spectrometer acceptance angle, while the remaining portion of the redirected scattered light (e.g., additional missed scattered light) may be collected again by the reflective surface 308 and redirected again towards the sample 306 to produce additional redirected scattered light that may be coupled into the spectrometer 304. For multiple redirections of the missed scattered light, the same process may occur multiple times; however, each time the power coupled may be less due to light leaking through the sample 306 and the coupling aperture 318 into the spectrometer 304. Thus, the coupled light (coupled power) into the spectrometer 304 may be expressed as:

[0045] Coupled power = directly coupled scattered light from the first interaction + indirectly coupled redirected scattered light from the second interaction (Equation 3)

[0046] However, more generally, the spectrometer 304 is configured to receive coupled light that includes a second portion of the scattered light (e.g., the directly coupled scattered light 310) and at least a portion of the redirected scattered light (e.g., the indirectly coupled redirected scattered light 316), which may include redirected scattered light from multiple subsequent interactions with the sample.

[0047] Figure 4FIG. is a schematic diagram showing another example of an optical device with light redirection for spectrometer collection. The optical device 400 includes a spectrometer 404 configured to receive coupled light from a sample 406 at its input and obtain a spectrum of the sample 406 based on the coupled light. The spectrometer 404 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in diffuse reflection mode. In Figure 4 In the example shown, the light incident on the illumination spot 402 on the sample 406 can be scattered by the sample 406. The scattered light within the acceptance numerical aperture of the spectrometer 404 is directly coupled into the spectrometer 404 as directly coupled scattered light 410.

[0048] In addition, in Figure 4 the example shown, the scattered light covers the entire spherical solid angle. Thus, as Figure 4 shown, the reflective surface 408 can have a curvature designed to receive the missed scattered light 412 scattered in all directions outside the numerical aperture of the spectrometer 404 and redirect the missed scattered light 412 as reflected scattered light 414 towards the sample to produce redirected scattered light, at least a portion of which can be coupled into the spectrometer 404 as indirectly coupled redirected scattered light 416. The reflective surface 408 can also have an aperture 418 for coupling the scattered light including the directly coupled scattered light 410 and the indirectly coupled redirected scattered light 416 into the spectrometer 404. In Figure 4 the example shown, the reflective surface 408 is a sphere. By using the spherical reflective surface 408 to redirect the missed scattered light from the sample 406 in all directions, the coupled spot size can be increased, thereby effectively achieving a larger field of view of the spectrometer 404. In addition, using the spherical reflective surface 408 can result in an increase in coupled power and an improvement in sample representation.

[0049] Figure 5 FIG. is a schematic diagram showing another example of an optical device with light redirection for spectrometer collection. The optical device 500 includes a spectrometer 504 configured to receive coupled light from a sample 506 at its input and obtain a spectrum of the sample 506 based on the coupled light. The spectrometer 504 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in diffuse reflection mode. In Figure 5In the example shown, light is incident on a plurality of illumination spots 502a - 502e on the sample 506, where at least one spot (e.g., spots 502b - 502e) has a sample region that is outside or at least partially outside the field of view of the spectrometer 504. In this example, the scattered light scattered from the spot (e.g., spot 502a) within the acceptance numerical aperture of the spectrometer 504 can be directly coupled into the spectrometer 504 as directly coupled scattered light 510.

[0050] The light scattered from other spots on the sample 506 (e.g., spots 502b - 502e) can be trapped between the sample 506 and the reflective surface 508 for redirecting the scattered light towards a spot (e.g., spot 502a) on the sample 506 within the field of view of the spectrometer 504. For example, the reflective surface 508 can have a curvature that is configured to collect scattered light (e.g., scattered light 512) from an illumination spot (e.g., spot 502d) outside the field of view of the spectrometer 504, and redirect (reflect) the scattered light as reflected scattered light 514 to another spot (e.g., spot 502a) on the sample 506 within the field of view of the spectrometer 504, where the light is scattered a second time to produce redirected scattered light, which can be coupled into the spectrometer 504 as indirectly coupled redirected scattered light 516. In this example, the first spot 502d and the second spot 502a form an extended spot region on the sample 506. The reflective surface 508 can also have a hole 518 for coupling the scattered light including the directly coupled scattered light 510 and the indirectly coupled redirected scattered light 516 into the spectrometer 504.

[0051] In some examples, the light can be redirected multiple times. For example, the reflective surface 508 can be configured to receive scattered light (e.g., scattered light 512) from a first illumination spot (e.g., spot 502e) outside the field of view of the spectrometer 504, and redirect (reflect) the scattered light as reflected scattered light 514 to a second spot (e.g., spot 502d) on the sample 506, which is also outside (or at least partially outside) the field of view of the spectrometer 504. Then, the light can be scattered a second time to produce redirected scattered light 512, which can be redirected by the reflective surface 508 again to a third spot (e.g., spot 502a) within the field of view of the spectrometer 504, where the light is scattered a third time to produce redirected scattered light, and at least a portion of the redirected scattered light can be coupled into the spectrometer 504 as indirectly coupled redirected scattered light 516.

[0052] Figure 6FIG. 0 is a schematic diagram showing another example of an optical device with light redirection for spectrometer collection. The optical device 600 includes a spectrometer 604 configured to receive coupled light from a sample 606 at its input and obtain a spectrum of the sample 606 based on the coupled light. The spectrometer 604 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in diffuse reflection mode. In Figure 6 In the example shown, the optical device 600 also includes a reflective surface 608 and an illumination system 616 (e.g., one or more light sources 620a and 620b) between the reflective surface 608 and the sample 606. The illumination system 616 is configured to irradiate a spot 602 on the sample 606 with the input light 618 directly and / or via reflection of the input light 618 from the reflective surface 608. Then, the input light 618 can be reflected and scattered from the spot 602 on the sample 606 to produce scattered light. The scattered light within the acceptance numerical aperture of the spectrometer 604 can be directly coupled into the spectrometer 604 as directly coupled scattered light 610.

[0053] The reflective surface 608 can include a first section 608a adjacent to the illumination system 616, the first section having a first curvature configured to couple the input light 618 to the spot 602 on the sample 606; and a second section 608b having a second curvature different from the first curvature and configured to collect scattered light (e.g., scattered light 612) from the illuminated spot 602 and redirect (reflect) the scattered light as reflected scattered light 614 back to the spot 602 on the sample 606, thereby increasing the effective spot size of the spot 602 (e.g., due to light incident on the sample at different angles). Here, the light is scattered a second time to produce redirected scattered light, which can be coupled into the spectrometer 604 as indirectly coupled redirected scattered light 624 to increase the illumination power in the throughput-limited effective area coupled into the spectrometer 604. In this example, the first section 608a includes two outer sections 622a and 622b, and the illumination system includes two light sources 620a and 620b, each light source being positioned adjacent to one of the outer sections 622a and 622b. There can also be holes 626 in the reflective surface 608 for coupling scattered light including directly coupled scattered light 610 and indirectly coupled redirected scattered light 624 into the spectrometer 604. It should be understood that the present disclosure is not limited to any particular number or configuration of the light sources 620a and 620b, or the number or configuration of the outer sections 622a and 622b. For example, based on the configuration of the optical device 600, the positions and numbers of the light sources 620a and 620b and the outer sections 622a and 622b can vary.

[0054] Figure 7FIG. is a schematic diagram showing another example of an optical device with light redirection for spectrometer collection according to some aspects. The optical device 700 includes a spectrometer 704 configured to receive coupled light from a sample 706 at its input and obtain a spectrum of the sample 706 based on the coupled light. The spectrometer 704 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflection mode. In Figure 7 In the example shown, the optical device 700 also includes a reflective surface 708, an illumination system 716 (e.g., one or more light sources 720a and 720b) between the reflective surface 708 and the sample 706, and diffuse reflection materials 726 on each side of the sample 706. The illumination system 716 is configured to illuminate a spot 702 on the sample 706 with the input light 718 directly and / or via reflection of the input light 718 from the reflective surface 708. Then, the input light 718 can be reflected and scattered from the spot 702 on the sample 706 to produce scattered light. The scattered light within the acceptance numerical aperture of the spectrometer 704 can be directly coupled into the spectrometer 704 as directly coupled scattered light 710.

[0055] The reflective surface 708 can include a first section 708a adjacent to the illumination system 716, the first section having a first curvature configured to couple the input light 718 to the spot 702 on the sample 706; and a second section 708b having a second curvature different from the first curvature and configured to collect scattered light (e.g., scattered light 712) from the illuminated spot 702 and redirect (reflect) the scattered light as reflected scattered light 714 back to the spot 702 on the sample 706. Here, the light is scattered a second time to produce redirected scattered light, which can be coupled into the spectrometer 704 as indirectly coupled redirected scattered light 724 to increase the effective spot size of the spot 702 (e.g., due to light incident on the sample at different angles) and increase the illumination power in the throughput effective area coupled into the spectrometer 704. In this example, the first section 708a includes two outer sections 722a and 722b, and the illumination system includes two light sources 720a and 720b, each light source being positioned adjacent to one of the outer sections 722a and 722b. There can also be holes 730 in the reflective surface 708 for coupling scattered light including directly coupled scattered light 710 and indirectly coupled redirected scattered light 724 into the spectrometer 704. It should be understood that the present disclosure is not limited to any particular number or configuration of the light sources 720a and 720b, or the number or configuration of the outer sections 722a and 722b. For example, based on the configuration of the optical device 700, the positions and numbers of the light sources 720a and 720b and the outer sections 722a and 722b can vary.

[0056] In addition, in Figure 7 the illustrated example, the diffuse reflection material 726 is configured to reflect at least a portion of the input light 718a radiated from the light sources 720a and 720b to the side of the sample 706 as the reflected light 728 back to the reflective surface 708. This reflected light 728 can then be redirected (e.g., via the first section 708a or the second section 708b) by the reflective surface 708 to the light spot 702 on the sample 706 to generate additional redirected scattered light that can be coupled into the spectrometer 704, thereby increasing the light coupled into the spectrometer 704. In some examples, the diffuse reflection material 726 is a high-diffuse reflection material, such as Spectralon / polytetrafluoroethylene (PTFE).

[0057] Figure 8 is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects. The optical device 800 includes a spectrometer 804 that is configured to receive coupled light from a sample 806 at its input and obtain a spectrum of the sample 806 based on the coupled light. The spectrometer 804 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflection mode. In Figure 8 the illustrated example, the optical device 800 also includes a reflective surface 808 and an illumination system 816 (e.g., one or more light sources 824a and 824b) between the reflective surface 808 and the sample 806. The illumination system 816 is configured to illuminate the light spot 802 on the sample 806 with the input light 818 directly and / or via reflection of the input light 818 from the reflective surface 808. Then, the input light 818 can be reflected and scattered from the light spot 802 on the sample 806 to generate scattered light. The scattered light within the acceptance numerical aperture of the spectrometer 804 can be directly coupled into the spectrometer 804 as directly coupled scattered light 810.

[0058] In addition, in Figure 8 the illustrated example, the reflective surface 808 can be designed to receive the missed scattered light 812 scattered in all directions outside the numerical aperture of the spectrometer 804 and redirect the missed scattered light 812 back to the sample as the reflected scattered light 814 to generate redirected scattered light, at least a portion of which can be coupled into the spectrometer 804 as indirectly coupled redirected scattered light 822. In Figure 8 the illustrated example, the reflective surface 808 completely surrounds the sample 806 on all sides and includes a first section 808a, a second section 808b, and a third section 808c.

[0059] The first section 808a is adjacent to the illumination system 816 and has a first curvature that is configured to couple the input light 818 to the spot 802 on the sample 806. For example, the first section 808a includes two outer sections 826a and 826b, and the illumination system includes two light sources 824a and 824b, each of which is positioned adjacent to one of the outer sections 826a and 826b (e.g., between the reflective surface 808 of the outer sections 826a and 826b and the sample 806). The second section 808b is between the two outer sections 826a and 826b of the first section 808a in front of the sample 806 (e.g., on the same side of the spectrometer 804), and has a second curvature different from the first curvature. The third section 808c is between the two outer sections 826a and 826b behind the sample 806 (e.g., on the opposite side of the spectrometer 804), and has a third curvature different from the first curvature and the second curvature.

[0060] Both the second section 808b and the third section 808c are configured to collect scattered light (e.g., scattered light 812) from the spot 802 on the sample 806 or other spots on the sample 806 (e.g., other spots radiated by the light sources 824a and 824b) in all directions, and redirect (reflect) the scattered light as reflected light 814 to the spot 802 on the sample 806 to increase the effective spot size of the spot 802 (e.g., due to different angles of light incident on the sample). Here, the light is scattered a second time to produce redirected scattered light, which can be coupled into the spectrometer 804 as indirectly coupled redirected scattered light 822. The reflective surface 808 may also have holes 828 for coupling the scattered light including directly coupled scattered light 810 and indirectly coupled redirected scattered light 822 into the spectrometer 804. It should be understood that the present disclosure is not limited to any particular number or configuration of the light sources 824a and 824b, or the number or configuration of the outer sections 826a and 826b. For example, based on the configuration of the optical device 800, the positions and numbers of the light sources 824a and 824b and the outer sections 826a and 826b may vary. In addition, the shapes and curvatures of the sections 808a, 808b, and 808c of the reflective surface 808 may vary depending on the desired coupling to the spectrometer 804.

[0061] The optical device 800 may further include a sample holder 820 that is configured to hold the sample 806. In Figure 8 the example shown, the sample holder 820 may extend in a first direction parallel to the plane of the substrate including the spectrometer 804.

[0062] Figure 9FIG. is a schematic diagram showing another example of an optical device with light redirection for spectrometer collection. The optical device 900 includes a spectrometer 904 configured to receive coupled light from a sample 906 at its input and obtain a spectrum of the sample 906 based on the coupled light. The spectrometer 904 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflection mode. In Figure 9 the example shown, the optical device 900 further includes a reflective surface 908 and an illumination system 916 (e.g., one or more light sources 924a and 924b) between the reflective surface 908 and the sample 906, similar to Figure 8 that shown. For example, the illumination system 916 is configured to illuminate a spot 902 on the sample 906 with the input light 918 directly and / or via reflection of the input light 918 from the reflective surface 908. Then, the input light 918 can be reflected and scattered from the spot 902 on the sample 906 to generate scattered light. The scattered light within the acceptance numerical aperture of the spectrometer 904 can be directly coupled into the spectrometer 904 as directly coupled scattered light 910.

[0063] In addition, in Figure 9 the example shown, the reflective surface 908 can be designed to receive missed scattered light 912 scattered in all directions outside the numerical aperture of the spectrometer 904 and redirect the missed scattered light 912 back to the sample as reflected scattered light 914 to generate redirected scattered light, at least a portion of which can be coupled into the spectrometer 904 as indirectly coupled redirected scattered light 922. In Figure 9 the example shown, the reflective surface 908 completely surrounds the sample 906 on all sides and includes a first section 908a, a second section 908b, and a third section 908c.

[0064] The first section 908a is adjacent to the illumination system 916 and has a first curvature configured to couple the input light 918 to the spot 902 on the sample 906. For example, the first section 908a includes two outer sections 926a and 926b, and the illumination system includes two light sources 924a and 924b, each light source being positioned adjacent to one of the outer sections 926a and 926b (e.g., between the reflective surface 908 of the outer sections 926a and 926b and the sample 906). The second section 908b is between the two outer sections 926a and 926b of the first section 908a in front of the sample 906 (e.g., on the same side as the spectrometer 904) and has a second curvature different from the first curvature. The third section 908c is between the two outer sections 926a and 926b on both sides of the sample 906 (e.g., on the opposite side of the spectrometer 904) and has a third curvature different from the first curvature and the second curvature.

[0065] The second section 908b and the third section 908c are each configured to collect scattered light (e.g., scattered light 912) from the light spot 902 on the sample 906 or other light spots on the sample 906 (e.g., light spots from light sources 924a and 924b or other light spots of reflected light radiation) in all directions, and redirect (reflect) the scattered light as reflected light 914 onto the light spot 902 on the sample 906 to effectively increase the light spot size of the light spot 902 (e.g., due to different angles of light incident on the sample). Here, the light is scattered a second time to produce redirected scattered light, which can be coupled into the spectrometer 904 as indirectly coupled redirected scattered light 922. The reflective surface 908 may also have holes 928 for coupling scattered light including directly coupled scattered light 910 and indirectly coupled redirected scattered light 922 into the spectrometer 904. It should be understood that the present disclosure is not limited to any particular number or configuration of the light sources 924a and 924b, or the number or configuration of the outer sections 926a and 926b. For example, based on the configuration of the optical device 900, the positions and numbers of the light sources 924a and 924b and the outer sections 926a and 926b may vary. Additionally, the shapes and curvatures of the sections 908a, 908b, and 908c of the reflective surface 908 may vary depending on the desired coupling to the spectrometer 904.

[0066] The optical device 900 may also include a sample holder 920 configured to hold the sample 906. Figure 9 In the example shown, the sample holder 920 may extend in a second direction (e.g., a vertical direction) perpendicular to the plane of the substrate including the spectrometer 904. In this example, the second direction of the sample holder 920 is also perpendicular to Figure 8 the first direction of the sample holder 820 shown. It should be understood that the sample holder 920 may extend in any suitable direction depending on the configuration of the light sources 924a and 924b, the spectrometer 904, and the reflective surface 908.

[0067] Figure 10A and Figure 10BFIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection. The optical device 1000 includes a spectrometer 1004 configured to receive at its input coupled light from a sample 1006 and obtain a spectrum of the sample 1006 based on the coupled light. The spectrometer 1004 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflection mode. In the example shown in FIG. 10, the optical device 1000 further includes a reflective surface 1008 and an illumination system 1016 (e.g., one or more light sources 1024a and 1024b) between the reflective surface 1008 and the sample 1006.

[0068] In Figure 10A and Figure 10B the example shown, a multiple reflection, multiple incidence configuration is depicted where light impinges on the sample 1006 multiple times in different spatial regions / spots (e.g., collection spot 1002a and redirected spot 1002b). For example, the input light 1018 from each of the light sources 1024a and 1024b of the illumination system 1016 is configured to illuminate the corresponding redirected spot 1002b on the sample 1006 directly and / or via reflection of the input light 1018 from the reflective surface 1008, outside the field of view of the spectrometer 1004 or at least partially outside the field of view of the spectrometer. The scattered light from the redirected spot 1002b can then be redirected towards the collection spot 1002a on the sample using the reflective surface 1008.

[0069] For example, the reflective surface 1008 may include a first section 1008a adjacent to the illumination system 1016, the first section having a first curvature configured to couple the input light 1018 to a corresponding redirected light spot 1002b on the sample 1006. In this example, the first section 1008a includes two outer sections 1020a and 1020b, and the illumination system includes two light sources 1024a and 1024b, each light source being positioned adjacent to one of the outer sections 1020a and 1020b. The reflective surface 1008 may also include a second section 1008b having a second curvature different from the first curvature and configured to collect scattered light (e.g., scattered light 1012) of the redirected light spot 1002b of illumination outside or partially outside the field of view of the spectrometer 1004, and redirect (reflect) the scattered light as reflected scattered light 1014 to a collection spot 1002a (e.g., collection area) on the sample 1006 within the field of view of the spectrometer 1004. Here, the light is scattered a second time to produce redirected scattered light 1010, which may be coupled into the spectrometer 1004. In this example, the redirected scattered light 1010 may correspond to directly coupled scattered light. The reflective surface 1008 may also have a hole 1022 therein for coupling the scattered light 1010 into the spectrometer 1004.

[0070] Light missed that is scattered outside the acceptance numerical aperture of the spectrometer 1004 may also be redirected again via the second section 1008b of the reflective surface 1008 toward the collection spot 1002a on the sample 1006 and scattered a third time to produce additional redirected scattered light 1010, at least a portion of which may be coupled into the spectrometer 1004 as indirectly coupled redirected scattered light. It should be understood that depending on the configuration of the optical device 1000, the number of bounces may increase. For example, before being directed to the collection spot 1002a within the field of view of the spectrometer 1004, scattered light from the redirected light spot 1002b may be directed to an additional spot (not shown) on the sample 1006 outside or partially outside the field of view of the spectrometer 1004. The multiple reflection configuration shown in FIG. 10 results in an increase in the effective spot size being scanned, resulting in the spectrometer 1004 seeing a large spot size. For example, the collection spot 1002a and the redirected light spot 1002b may form an extended spot region on the sample 1006.

[0071] In some examples, in the presence of the sample S s the power spectral density PSD measured by the spectrometer 1004 is given by:

[0072] S s = R s 2S o , (Equation 1)

[0073] where S o is the reference PSD at the presence of an ideal diffuse reflectance (e.g., spectral reflectance), and R s is the sample reflectance. The square of R s is based on two interactions of light with the sample before being coupled into the spectrometer (as shown in the configuration of Figure 10A ). Then, the apparent reflectance R a measured by the spectrometer can be used to extract R s by taking the square root:

[0074]

[0075] For a non-uniform sample where the spectral characteristics can vary depending on the measurement location on the sample, the light scattered from different spots can experience different reflectances. Therefore, in the configuration shown in Figure 10A , we can express the reflectance extracted by the spectrometer R s,NH as:

[0076]

[0077] where R s1 is the sample reflectance of the right spot, R s2 is the sample reflectance of the left spot, and R s0 is the sample reflectance of the middle spot, as shown in Figure 10A .

[0078] Therefore, it is obvious that the extracted reflectance is the geometric mean of the reflectance in the middle region (e.g., collection spot 1002a) and the mathematical mean of the reflectances in the left and right regions (e.g., redirected spots 1002b). Assuming a random noise effect due to the non-uniformity of the sample, the reflectance of each specific spot can be expressed as:

[0079] R sk = R s,H + n sk , (Equation 4)

[0080] where R sk represents the reflectance from spot k, R s,H is the uniform reflectance of the sample, and n sk is the reflectance noise due to the non-uniformity from different regions / spots. The extracted sample reflectance R s,NH of the non-uniform sample can be expressed as:

[0081]

[0082] For Rs,H >> n s , the l / R can be ignored s,H 2 For the third term under the square root, the expression can be approximated as:

[0083]

[0084] As described above, the noise caused by sample non-uniformity is reduced by about 39%, which is close to the case of three times the spot size, as if the non-uniformity noise is averaged from three different spots, resulting in a noise reduction of about 42%. Extending this concept to M light sources that irradiate the sample at M different spots around the main collection area (collection spot), and the light source is redirected back to the main collection area, the extracted reflectance is expressed as:

[0085]

[0086] As shown in the above equation, the expected non-uniform noise reduction saturates at 50%. Therefore, increasing the number of bulbs and thus increasing the irradiated spots mainly provides an increase in the collected signal level.

[0087] In some examples, the signal-to-noise ratio (SNR) of the spectrometer can be analyzed, considering the spectrometer system noise in addition to the noise caused by sample non-uniformity and the coupled signal level. Figure 10A The multi-incident configuration shown is incorrect! Assuming the same light source, the case where no reference source is found can be compared with the case of directly collecting a spot with a three-fold larger diameter 3D. For the case of direct collection, according to the throughput limit, the coupling efficiency is inversely proportional to the spot area. Therefore, due to a three-fold increase in diameter, the coupling efficiency is reduced by nine times.

[0088] For Figure 10A the multi-incident configuration shown, the coupling efficiency is mainly determined by the size of the collection spot 1002a and is independent of the number of redirected spots 1002b. However, due to multiple incidences on the sample, the signal level is reduced more than normal due to the additional sample reflection response. In this example, as described above, the sample reflectance for a single incidence can be extracted by taking the square root of the measured apparent reflectance (in the case of two incidences). Then, the SNR of the extracted reflection is 2RS of the normal case of a single incidence on the sample, where the system noise is reduced by two times by taking the square root of the signal. Therefore, if R s = 0.5, the same SNR as the single-incidence and D collection diameter spot cases can be achieved, but it is nine times the SNR of the 3D collection diameter. In summary, assuming the same spectrometer light collection rate, using this configuration can also improve the spectrometer SNR.

[0089] Figure 11FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection. Optical device 1100 includes spectrometer 1104, which is configured to receive coupled light from sample 1106 at its input and obtain a spectrum of sample 1106 based on the coupled light. Spectrometer 1104 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in diffuse reflection mode. In Figure 11 In the example shown, optical device 1100 also includes reflective surface 1108 and illumination system 1116 (e.g., one or more light sources 1132a and 1132b) between reflective surface 1108 and sample 1106.

[0090] Figure 11 The example shown in is another example of a multiple reflection, multiple incidence configuration, in which light impinges on sample 1106 multiple times in different spatial regions / spots (e.g., collection spot 1102a and redirected spot 1102b). For example, input light 1118 from each of light sources 1132a and 1132b of illumination system 1116 is configured to illuminate corresponding redirected spots 1102b on sample 1106 directly and / or via reflection of input light 1118 from reflective surface 1108 outside the field of view of spectrometer 1104 or at least partially outside the field of view of the spectrometer. Scattered light from redirected spots 1102b can then be redirected towards collection spot 1102a on the sample using reflective surface 1108.

[0091] For example, the reflective surface 1108 can include a first section 1108a adjacent to the illumination system 1116, the first section having a first curvature configured to couple the input light 1118 to a corresponding redirected light spot 1102b on the sample 1106. In this example, the first section 1108a includes two outer sections 1120a and 1120b, and the illumination system includes two light sources 1132a and 1132b, each light source being positioned adjacent to one of the outer sections 1120a and 1120b. The reflective surface 1108 can also include a second section 1108b having a second curvature different from the first curvature and configured to collect scattered light (e.g., scattered light 1112) of the redirected light spot 1102b that is outside the field of view of the spectrometer 1104 or partially outside the field of view of the spectrometer, and redirect (reflect) the scattered light as reflected scattered light 1114 onto a collection light spot 1102a (e.g., collection area) on the sample 1106 within the field of view of the spectrometer 1104. Here, the light is scattered a second time to produce redirected scattered light 1110, which can be coupled into the spectrometer 1104. In this example, the redirected scattered light 1110 can correspond to directly coupled scattered light. The reflective surface 1108 can also have a hole 1122 therein for coupling the scattered light 1110 into the spectrometer 1104.

[0092] The reflective surface 1108 can also include a third section 1108c (e.g., inner section) having a third curvature different from the first and second curvatures and configured to collect missed scattered light 1124 outside the acceptance numerical aperture of the spectrometer 1104 and redirect the missed scattered light 1124 as missed reflected light 1126 back toward the collection light spot 1102a on the sample 1106. Here, the missed reflected light can be scattered a third time to produce additional redirected scattered light 1128, at least a portion of which can be coupled into the spectrometer 1104 as indirectly coupled redirected scattered light. As Figure 11 shown, the second section 1108b can include two additional sections 1130a and 1130b, each additional section being between a corresponding one of the outer sections 1120a and 1120b and the inner section 1108c. It should be understood that the number of bounces can increase depending on the configuration of the optical device 1100. For example, before being directed to the collection light spot 1102a within the field of view of the spectrometer 1104, the scattered light from the redirected light spot 1102b can be directed to an additional light spot (not shown) on the sample 1106 that is outside the field of view of the spectrometer 1104 or partially outside the field of view of the spectrometer. Figure 11The multiple reflection configuration shown results in an increase in the effective spot size of the scan, causing the spectrometer 1104 to see a large spot size. For example, the collection spot 1102a and the redirected spot 1102b can form an extended spot region on the sample 1106.

[0093] Figure 12 is a schematic diagram showing another example of an optical device with light redirection for spectrometer collection according to some aspects. The optical device 1200 includes a spectrometer 1204 that is configured to receive coupled light from a sample 1206 at its input and obtain a spectrum of the sample 1206 based on the coupled light. The spectrometer 1204 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflection mode. In Figure 12 the example shown, the optical device 1200 also includes a reflective surface 1208 and an illumination system 1216 (e.g., one or more light sources 1232a and 1232b) between the reflective surface 1208 and the sample 1206.

[0094] Figure 12 the example shown is another example of a multiple reflection, multiple incidence configuration in which light impinges on the sample 1206 multiple times in different spatial regions / spots (e.g., the redirected spot 1202 and the collection region 1220). In this example, the collection region 1220 is a diffuse reflection material, such as Spectralon / PTFE. For example, the input light 1218 from each of the light sources 1232a and 1232b of the illumination system 1216 is configured to illuminate a corresponding redirected spot 1202 on the sample 1206 directly and / or via reflection of the input light 1218 from the reflective surface 1208 outside the field of view of the spectrometer 1204 or at least partially outside the field of view of the spectrometer. The scattered light from the redirected spot 1202 can then be redirected towards the collection region 1220 on the sample using the reflective surface 1208.

[0095] For example, the reflective surface 1208 may include a first section 1208a adjacent to the illumination system 1216, the first section having a first curvature configured to couple the input light 1218 to a corresponding redirected light spot 1202 on the sample 1206. In this example, the first section 1208a includes two outer sections 1222a and 1222b, and the illumination system includes two light sources 1232a and 1232b, each light source being positioned adjacent to one of the outer sections 1222a and 1222b. The reflective surface 1208 may further include a second section 1208b having a second curvature different from the first curvature and configured to collect scattered light (e.g., scattered light 1212) of the redirected light spot 1202 that is outside the field of view of the spectrometer 1204 or partially outside the field of view of the spectrometer, and redirect (reflect) the scattered light as reflected scattered light 1214 onto a collection area 1220 (e.g., a diffuse reflective material) on the sample 1206 within the field of view of the spectrometer 1204. Here, the light is reflected to produce redirected scattered light 1210, which can be coupled into the spectrometer 1204. In this example, the redirected scattered light 1210 may correspond to directly coupled scattered light. The reflective surface 1208 may also have a hole 1236 therein for coupling the scattered light 1210 into the spectrometer 1204.

[0096] The reflective surface 1208 may further include a third section 1208c (e.g., an inner section) having a third curvature different from the first and second curvatures and configured to collect missed scattered light 1224 outside the acceptance numerical aperture of the spectrometer 1204 and redirect the missed scattered light 1224 as missed reflected light 1226 back towards the collection area 1220 on the sample 1206. Here, the missed reflected light may be reflected to produce additional redirected scattered light 1228, at least a portion of which may be coupled into the spectrometer 1204 as indirectly coupled redirected scattered light. As Figure 12 shown, the second section 1208b may include two additional sections 1234a and 1234b, each additional section being between a corresponding one of the outer sections 1222a and 1222b and the inner section 1208c. It should be understood that depending on the configuration of the optical device 1200, the number of bounces may increase. For example, before being directed to the collection area 1220 within the field of view of the spectrometer 1204, scattered light from the redirected light spot 1202 may be directed to an additional light spot (not shown) on the sample 1206 that is outside the field of view of the spectrometer 1204 or partially outside the field of view of the spectrometer. Figure 12The multiple reflection configuration shown results in an increase in the effective spot size of the scan, resulting in a large spot size seen by the spectrometer 1204. For example, the redirected spot 1202 can form an extended spot region on the sample 1206.

[0097] Figure 13 FIG. [FIG. number not provided] is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects. The optical device 1300 includes a spectrometer 1306 that is configured to receive coupled light from a sample 1302 at its input and obtain a spectrum of the sample 1302 based on the coupled light. The spectrometer 1306 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in a diffuse reflectance mode. In Figure 13 the example shown, the optical device 1300 also includes a corrugated window 1308 (e.g., a transparent window) and an illumination system formed by a light source 1304 (e.g., a lamp with a surrounding light source reflector 1310). The light source 1304 (with the surrounding light source reflector 1310) can be positioned opposite a first side 1320 of the corrugated window 1308, and the sample 1302 can be positioned on a second side 1322 of the corrugated window 1308 opposite the first side 1320 such that the corrugated window 1308 is positioned between the illumination system 1304 / 1310 and the sample 1302. In some examples, the corrugations in the corrugated window 1308 can be made to be comparable to the diameter of the illumination spot of the light source 1304. More specifically, half of the corrugation period can be made approximately equal to the illumination spot diameter.

[0098] It should be noted that there seems to be a missing figure number in the text for item . Also, the tags -

[0098] are left unchanged as they are likely some specific identifiers within a larger context and not intended for translation themselves.The light source 1304 is configured to irradiate the sample 1302 with the input light 1316 via the corrugated window 1308. For example, the sample 1302 may be positioned on the outer half period of the corrugation such that the incident angle of the input light 1316 is centered at approximately 45°. The input light 1316 incident on the sample 1302 will interact with the sample 1302 at the spot 1328 to generate the first scattered light 1324. A portion of the first scattered light 1324 will strike the sample 1302 at the spot 1330 placed on the other half of the first corrugation period and interact with the sample 1302 to generate the second scattered light 1326. This second scattered light 1326 carries the sample spectral information from both halves of the corrugation period. The right-angle mirror 1314 may be positioned to receive the second scattered light 1326 after two sample strikes and redirect the light 1326 to the next corrugation period. Additionally, one or more lenses (e.g., lens 1312) may be included and configured to increase the collection of the scattered light 1326 to the right-angle mirror 1314 and from the right-angle mirror 1314 to the sample 1302. The scattered light 1326 striking the next corrugation period interacts with the sample 1302 for the third time at the spot 1332 in the first half of this new period and for the fourth time at the spot 1334 in the second half to generate the redirected scattered light 1318. In this example, the redirected scattered light 1318 may include directly coupled scattered light. The redirected scattered light 1318 may then be coupled into the spectrometer 1306. Each of the spots 1328, 1330, 1332, and 113 together forms an extended spot on the sample 1302.

[0099] Figure 14 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects. The optical device 1400 includes a spectrometer 1406 configured to receive coupled light from a sample 1402 at its input and obtain the spectrum of the sample 1402 based on the coupled light. The spectrometer 1406 may be, for example, a Fourier transform infrared (FTIR) spectrometer operating in diffuse reflectance mode. In Figure 14 the example shown, the optical device 1400 further includes a corrugated window 1408 and an illumination system formed by a light source 1404 (e.g., a lamp with a surrounding light source reflector 1416). Similar to the configuration shown in Figure 13 , the light source 1404 (with the surrounding light source reflector 1416) may be positioned opposite the first side 1424 of the corrugated window 1408, and the sample 1402 may be positioned on the second side 1426 of the corrugated window 1408 opposite the first side 1424 such that the corrugated window 1408 is positioned between the illumination system 1404 / 1416 and the sample 1402.

[0100] In addition, similar to Figure 13 the configuration shown, the light source 1404 is configured to irradiate the sample 1402 with the input light 1420 via the corrugated window 1408. For example, the sample 1402 may be positioned on the outer half period of the corrugation such that the incident angle of the input light 1420 is centered at 45°. The input light 1420 incident on the sample 1402 will interact with the sample 1402 at the spot 1432 to generate the first scattered light 1428. A portion of the first scattered light 1428 will strike the sample 1402 on the other half of the first corrugation period and interact with the sample 1402 at the spot 1434 to generate the second scattered light 1430. The second scattered light 1430 carries the sample spectral information from both halves of the corrugation period. The right-angle mirror 1414 may be positioned to receive the second scattered light 1430 after two sample strikes and redirect the light 1430 to the next corrugation period. In addition, one or more lenses 1418 may be included and configured to increase the collection of the scattered light 1430 to the right-angle mirror 1414 and from the right-angle mirror 1414 to the sample 1402. The scattered light 1430 striking the next corrugation period interacts with the sample 1402 for the third time at the spot 1436 in the first half of this new period and for the fourth time at the spot 1438 in the second half to generate the redirected scattered light 1422. In this example, the redirected scattered light 1422 may include directly coupled scattered light. The redirected scattered light 1422 may then be coupled into the spectrometer 1406. The spots 1432, 1434, 1436, and 1438 together form an extended spot region on the sample 1402.

[0101] In addition, in Figure 14In the example shown, a corrugated mirror 1410 can be disposed on top of the sample 1402 such that the sample 1402 is sandwiched between the corrugated mirror 1410 and the corrugated window 1408. Additionally, a heat dissipation element 1412 (e.g., a passive or active cooling system) can be attached to the corrugated mirror 1410 on its top side. In some examples, the corrugated mirror 1410 can be a metal mirror to enhance heat conduction and reduce the overall temperature of the sample 1402. In this configuration, a higher irradiation intensity can be used without burning the sample 1402 as it will be cooled by the heat dissipation element 1412. Additionally, this can help limit the temperature rise of the sample 1402, which typically affects the measured spectral characteristics. This can improve the measurement accuracy and reduce errors caused by temperature variations. Further, the corrugated mirror 1410 can be configured to redirect light leaking between the sample particles back to the lower (first) side 1424 of the corrugated window 1408. A portion of this redirected light can be collected by the right-angle mirror 1414 and interact with the sample 1402 in the next corrugation period, thus increasing the overall efficiency of the system.

[0102] Figure 15 FIG. is a schematic diagram illustrating another example of an optical device with light redirection for spectrometer collection according to some aspects. The optical device 1500 includes a spectrometer 1506 that is configured to receive coupled light from a sample 1502 at its input and obtain a spectrum of the sample 1502 based on the coupled light. The spectrometer 1406 can be, for example, a Fourier transform infrared (FTIR) spectrometer operating in diffuse reflection mode. In Figure 15In the example shown, the optical device 1500 further includes a light source 1504 (e.g., a lamp with a surrounding elliptical reflector 1538 for the light source), which is positioned opposite to one side of the sample 1502. The light source 1504 is configured to irradiate the sample 1502 with input light 1520 at a specific angle at a first spot 1534 on its first side 1528 to generate scattered light 1522. An off-axis parabolic mirror 1510 is positioned to collect the scattered light 1522. More specifically, the center of the irradiation spot (e.g., the focused irradiation spot 1508) on the sample 1502 is positioned at the focus of the mirror 1510 (e.g., the off-axis parabolic mirror focus 1514). Thus, the mirror 1510 will generate a set of parallel light rays 1524 corresponding to the scattered light 1522. Another off-axis parabolic mirror 1512 can be positioned to collect the set of parallel light rays 1524 and direct the reflected scattered light 1526 to a second side 1530 of the sample 1502 opposite to the first side 1528. The off-axis parabolic mirror 1512 can be configured to focus the reflected scattered light 1526 to its focus (e.g., the off-axis parabolic mirror focus 1516). The focused light 1526 interacts with the sample 1502 a second time at a second spot 1536 to generate redirected scattered light 1532. The first spot 1528 and the second spot 1536 together form an extended spot region on the sample 1502.

[0103] A collection optical device (e.g., a lens 1518) is positioned to couple the redirected scattered light 1532 after the second interaction with the sample 1502. In this example, the redirected scattered light 1532 can include directly coupled scattered light. The redirected scattered light 1532 can then be coupled into a spectrometer 1506. As a result, this configuration enables spectroscopic measurements to be performed from both sides 1528 and 1530 of the sample 1502. Additionally, in this configuration, the parallel light rays 1524 generated by the off-axis parabolic mirror 1510 can achieve a longer propagation distance, which can be advantageous for a thick sample 1502.

[0104] Figure 16 is a flowchart of an exemplary method 1600 for redirecting light collected by a spectrometer from a sample according to some aspects. As described below, in certain embodiments within the scope of the present disclosure, some or all of the illustrated features may be omitted, and some of the illustrated features may not be necessary for the implementation of all embodiments. In some examples, the method can be performed by the optical device 300 described above and shown in Figure 3 or by any configuration of the optical device, such as the configuration shown in Figure 3 - 15 shown.

[0105] At block 1602, the optical device may receive a first portion of scattered light from the sample at a reflective surface positioned separately from the sample. In some examples, the reflective surface may include a hemisphere or a sphere.

[0106] At block 1604, the optical device may redirect the first portion of the scattered light back to one or more discrete spots on the sample in a non-random manner to generate redirected scattered light from the sample. Additionally, at block 1606, the optical device may receive coupled light from the sample at an input of a spectrometer to obtain a spectrum of the sample based on the coupled light. The coupled light may include at least a portion of the redirected scattered light.

[0107] In some examples, the optical device may include an illumination system positioned between the reflective surface and the sample for illuminating the sample with input light. The input light may be scattered from the sample as scattered light. In some examples, the coupled light includes a second portion of the scattered light directly coupled from the sample into the spectrometer.

[0108] In some examples, one or more spots include a single spot within the field of view of the spectrometer. Based on the redirected scattered light, the single spot may have an extended spot size. In this example, the optical device may also be configured to receive another portion of the redirected scattered light at the reflective surface and may also redirect other portions of the redirected scattered light back to the single spot on the sample to generate additional redirected scattered light. Here, the coupled light may also include at least a portion of the additional redirected scattered light. In some examples, the optical device may also reflect at least a portion of the input light back to the reflective surface via diffusive reflective materials on each side of the sample for redirecting the input light towards the single spot on the sample.

[0109] In some examples, the optical device may receive a first portion of the scattered light from a first spot on the sample, the spot area of the first spot being at least partially outside the field of view of the spectrometer, and may also redirect the first portion of the scattered light to a second spot on the sample within the field of view of the spectrometer. In this example, the first spot and the second spot form an extended spot area on the sample. In some examples, the optical device may also redirect the first portion of the scattered light to the second spot on the sample via a third spot on the sample, the third spot being at least partially outside the field of view of the spectrometer. In this example, the extended spot area also includes the third spot.

[0110] In some examples, an illumination system can include at least two light sources, each configured to direct a respective portion of input light to a respective spot on a sample. In this example, an optical device can receive a first portion of scattered light from each of the respective spots on the sample at a reflective surface, and redirect the first portion of the scattered light to a collection region on the sample within the field of view of a spectrometer, from which the coupled light is directed to the spectrometer. Here, at least the respective spots on the sample form an extended spot region on the sample. In some examples, the collection region forms a collection spot on the sample, and the extended spot region further includes the collection spot. In some examples, the collection region includes a diffuse reflective material configured to direct the coupled light into the spectrometer.

[0111] In some examples, the reflective surface is a right-angle reflector. In this example, the optical device can also irradiate a first spot on the sample with input light via a corrugated window between the illumination system and the sample. The input light can be scattered from the sample as a first portion of scattered light and directed toward the right-angle reflector via a second spot on the sample. Additionally, the optical device can redirect the first portion of the scattered light from the right-angle reflector back to a third spot on the sample via the corrugated window to produce redirected scattered light, which is coupled into the spectrometer via a fourth spot on the sample. Here, the first spot, the second spot, the third spot, and the fourth spot form an extended spot region on the sample. In some examples, the optical device further includes a corrugated mirror and a heat dissipation element adjacent to the corrugated mirror. In this example, the sample can be sandwiched between the corrugated window and the corrugated mirror.

[0112] In some examples, the reflective surface includes a first off-axis parabolic mirror and a second off-axis parabolic mirror. In this example, the optical device can also receive a first portion of scattered light from a first spot on a first side of the sample at the first off-axis parabolic mirror, direct the first portion of the scattered light as a set of parallel rays from the first off-axis parabolic mirror to the second off-axis parabolic mirror, and direct the reflected scattered light corresponding to the set of parallel rays to a second spot on a second side of the sample opposite the first side to produce redirected scattered light. Here, the first spot and the second spot form an extended spot region on the sample.

[0113] An overview of examples of the present disclosure is provided below.

[0114] Example 1: An optical device, the optical device comprising: a reflecting surface that is positioned separately from the sample and is configured to receive a first portion of scattered light from the sample and redirect the first portion of the scattered light back onto the sample in a non-random manner to one or more discrete light spots to generate redirected scattered light from the sample; and a spectrometer that is configured to receive, at its input, coupled light from the sample and obtain a spectrum of the sample based on the coupled light, the coupled light including at least a portion of the redirected scattered light.

[0115] Example 2: The optical device according to Example 1, the optical device further comprising: an illumination system that is positioned between the reflecting surface and the sample and is configured to illuminate the sample with input light scattered from the sample as the scattered light.

[0116] Example 3: The optical device according to Example 2, wherein the coupled light further includes a second portion of the scattered light that is directly coupled from the sample into the spectrometer.

[0117] Example 4: The optical device according to Example 3, wherein one or more light spots include a single light spot within the field of view of the spectrometer, the single light spot having an extended spot size based on the redirected scattered light, and wherein the reflecting surface is further configured to receive another portion of the redirected scattered light and redirect the other portion of the redirected scattered light back onto the single light spot on the sample to generate additional redirected scattered light, wherein the coupled light further includes at least a portion of the additional redirected scattered light.

[0118] Example 5: The optical device of Example 4, the optical device further comprising: a diffuse reflective material that reflects at least a portion of the input light back onto the reflecting surface on each side of the sample for redirecting the input light toward the single light spot on the sample.

[0119] Example 6: The optical device according to Example 4, wherein the reflecting surface includes a hemisphere or a sphere.

[0120] Example 7: The optical device according to any one of Examples 2 to 6, wherein the reflecting surface includes a first section adjacent to the illumination system and a second section configured to redirect the first portion of the scattered light, wherein the first section has a first curvature and the second section has a second curvature different from the first curvature.

[0121] Example 8: The optical device according to Example 7, wherein the first section includes two outer sections, and the illumination system includes two light sources, each light source being positioned adjacent to one of the two outer sections.

[0122] Example 9: The optical device according to Example 7 or 8, wherein the reflecting surface completely surrounds the sample.

[0123] Example 10: The optical device according to Example 9, the optical device further comprising: a sample holder configured to hold a sample, wherein the sample holder extends in one of two perpendicular directions.

[0124] Example 11: The optical device according to Example 2, wherein the reflective surface is configured to receive a first portion of scattered light from a first light spot on the sample, the first light spot having a light spot region at least partially outside the field of view of the spectrometer, and redirect the first portion of the scattered light to a second light spot on the sample within the field of view of the spectrometer, wherein the first light spot and the second light spot form an extended light spot region on the sample.

[0125] Example 12: The optical device according to Example 11, wherein the reflective surface is further configured to redirect the first portion of the scattered light to the second light spot on the sample via a third light spot on the sample, the third light spot being at least partially outside the field of view of the spectrometer, wherein the extended light spot region further includes the third light spot.

[0126] Example 13: The optical device according to Example 2, wherein the illumination system includes at least two light sources, each light source being configured to direct a corresponding portion of the input light to a corresponding light spot on the sample, and wherein the reflective surface is configured to receive a first portion of the scattered light from each of the corresponding light spots on the sample and redirect the first portion of the scattered light to a collection region within the field of view of the spectrometer, from which the coupled light is directed to the spectrometer, wherein at least the corresponding light spots on the sample form an extended light spot region on the sample.

[0127] Example 14: The optical device according to Example 13, wherein the collection region forms a collection light spot on the sample, and the extended light spot region further includes the collection light spot.

[0128] Example 15: The optical device according to Example 13, wherein the collection region includes a diffuse reflective material configured to direct the coupled light into the spectrometer.

[0129] Example 16: The optical device according to any one of Examples 13 to 15, wherein the reflective surface includes a corresponding outer section, an inner section, and a corresponding additional section between the corresponding outer section and the inner section, each corresponding outer section having one of two light sources positioned adjacent thereto, wherein the inner section and the corresponding additional section are configured to redirect the first portion of the scattered light to the collection region, and wherein the outer section, the additional section, and the inner section each include a different corresponding curvature.

[0130] Example 17: The optical device according to Example 2, wherein the reflective surface includes a right-angle reflector, and further includes: a corrugated window positioned between the illumination system and the positioned sample, wherein the illumination system is configured to irradiate the sample at a first spot on the sample via the corrugated window using input light, the input light is scattered from the sample into a first portion of scattered light, and is guided towards the right-angle reflector via a second spot on the sample, wherein the right-angle reflector is configured to redirect the first portion of the scattered light back to a third spot on the sample via the corrugated window to generate redirected scattered light, the redirected scattered light is coupled into the spectrometer via a fourth spot on the sample, and the first spot, the second spot, the third spot, and the fourth spot form an extended spot region on the sample.

[0131] Example 18: The optical device according to Example 17, the optical device further includes: a corrugated mirror, the sample is sandwiched between the corrugated window and the corrugated mirror; and a heat dissipation element adjacent to the corrugated mirror.

[0132] Example 19: The optical device according to Example 2, wherein the reflective surface includes a first off-axis parabolic mirror and a second off-axis parabolic mirror, the first off-axis parabolic mirror is configured to receive a first portion of the scattered light from a first spot on a first side of the sample and guide the first portion of the scattered light as a set of parallel light rays to the second off-axis parabolic mirror, the second off-axis parabolic mirror is configured to collect the set of parallel light rays and guide the reflected scattered light corresponding to the set of parallel light rays to a second spot on a second side of the sample opposite the first side to generate redirected scattered light, and the first spot and the second spot form an extended spot region on the sample.

[0133] Example 20: A method of increasing the collection of a spectrometer using the optical device according to any one of Examples 1 to 19.

[0134] In this disclosure, the term "exemplary" is used to mean "serving as an example, instance, or illustration". Any embodiment or aspect described herein as "exemplary" is not necessarily to be construed as more preferred or advantageous than other aspects of the disclosure. Similarly, the term "aspect" does not require that all aspects of the disclosure include the recited features, advantages, or modes of operation. As used herein, the term "coupled" refers to a direct or indirect coupling between two objects. For example, if object A physically contacts object B, and object B contacts object C, then objects A and C can still be considered to be coupled to each other—even if they do not directly physically contact each other. For example, a first object can be coupled to a second object even if the first object never directly physically contacts the second object. The terms "circuit" and "circuitry" are used broadly and are intended to include both hardware implementations of electrical devices and conductors that, when connected and configured, perform the execution of the functions described in this disclosure, without limitation to the type of electronic circuit, as well as software implementations of information and instructions that, when executed by a processor, perform the execution of the functions described in this disclosure.

[0135] Figures 1 to 16 One or more of the components, steps, features, and / or functions shown may be rearranged and / or combined into a single component, step, feature, or function, or embodied in several components, steps, or functions. Additional elements, components, steps, and / or functions may also be added without departing from the novel features disclosed herein. Figures 1 to 16 The apparatus, devices, and / or components shown may be configured to perform one or more of the methods, features, or steps described herein. The novel algorithms described herein may also be effectively implemented in software and / or embedded in hardware.

[0136] It should be understood that the particular order or hierarchy of steps in the disclosed methods is an illustration of exemplary processes. Based on design preferences, it should be understood that the particular order or hierarchy of steps in a method can be rearranged. The appended method claims present the elements of the various steps in exemplary order and are not meant to be limited to the particular order or hierarchy presented unless specifically recited therein.

[0137] The foregoing description is intended to enable any person skilled in the art to practice the various aspects described herein. Those skilled in the art will readily appreciate various modifications to these aspects, and the general principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, where the elements in the singular form are not intended to mean "one and only one" but rather "one or more" unless specifically stated otherwise. The term "some" means one or more unless specifically stated otherwise. A phrase referring to "at least one of" a series 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 and b; a and c; b and c; and a, b, and c. All structural and functional equivalents of the elements of the various aspects described in this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be covered by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public, whether or not such disclosure is expressly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for".

Claims

1. An optical device, comprising: a reflective surface that is positioned separately from a sample and is configured to receive a first portion of scattered light from the sample and redirect the first portion of the scattered light back onto the sample in a non-random manner at one or more discrete light spots to generate redirected scattered light from the sample; and a spectrometer that is configured to receive, at its input, coupled light from the sample and obtain a spectrum of the sample based on the coupled light, the coupled light including at least a portion of the redirected scattered light.

2. The optical device according to claim 1, further comprising: an illumination system that is positioned between the reflective surface and the sample and is configured to illuminate the sample with input light scattered from the sample as the scattered light.

3. The optical device according to claim 1, wherein the coupled light further includes a second portion of the scattered light that is directly coupled from the sample into the spectrometer.

4. The optical device according to claim 3, wherein the one or more light spots include a single light spot within the field of view of the spectrometer, the single light spot having a spot size that is extended based on the redirected scattered light, and wherein the reflective surface is further configured to receive another portion of the redirected scattered light and redirect the other portion of the redirected scattered light back onto the single light spot on the sample to generate additional redirected scattered light, wherein the coupled light further includes at least a portion of the additional redirected scattered light.

5. The optical device according to claim 4, further comprising: a diffuse reflective material that, on each side of the sample, reflects at least a portion of the input light back to the reflective surface for redirecting the input light toward the single light spot on the sample.

6. The optical device according to claim 4, wherein the reflective surface includes a hemisphere or a sphere.

7. The optical device according to claim 2, wherein the reflective surface includes a first section adjacent to the illumination system and a second section configured to redirect the first portion of the scattered light, wherein the first section has a first curvature and the second section has a second curvature different from the first curvature.

8. The optical device according to claim 7, wherein the first section includes two outer sections, and the illumination system includes two light sources, each light source being positioned adjacent to one of the two outer sections.

9. The optical device according to claim 7, wherein the reflective surface completely surrounds the sample.

10. The optical device according to claim 9, further comprising: a sample holder that is configured to hold the sample, wherein the sample holder extends in one of two perpendicular directions.

11. The optical device according to claim 2, wherein the reflective surface is configured to receive the first portion of the scattered light from the first light spot on the sample, the first light spot having a light spot region at least partially outside the field of view of the spectrometer, and redirect the first portion of the scattered light to a second light spot on the sample within the field of view of the spectrometer, wherein the first light spot and the second light spot form an extended light spot region on the sample.

12. The optical device according to claim 11, wherein the reflective surface is further configured to redirect the first portion of the scattered light to the second light spot on the sample via a third light spot on the sample, the third light spot being at least partially outside the field of view of the spectrometer, wherein the extended light spot region further includes the third light spot.

13. The optical device according to claim 2, wherein the illumination system includes at least two light sources, each light source being configured to direct a corresponding portion of the input light to a corresponding light spot on the sample, and wherein the reflective surface is configured to receive the first portion of the scattered light from each of the corresponding light spots on the sample and redirect the first portion of the scattered light to a collection region within the field of view of the spectrometer, the coupled light being directed from the collection region to the spectrometer, wherein at least the corresponding light spots on the sample form an extended light spot region on the sample.

14. The optical device according to claim 13, wherein the collection region forms a collection light spot on the sample, and the extended light spot region further includes the collection light spot.

15. The optical device according to claim 13, wherein the collection region includes a diffuse reflective material configured to direct the coupled light into the spectrometer.

16. The optical device according to claim 13, wherein the reflective surface includes corresponding outer sections, inner sections, and corresponding additional sections between the corresponding outer sections and the inner sections, each of the corresponding outer sections having one of the two light sources positioned adjacent thereto, wherein the inner sections and the corresponding additional sections are configured to redirect the first portion of the scattered light to the collection region, wherein the outer sections, the additional sections, and the inner sections each include different corresponding curvatures.

17. The optical device according to claim 2, wherein the reflective surface includes a right-angle reflector, and further includes: a corrugated window positioned between the illumination system and the positioned sample, wherein the illumination system is configured to irradiate the sample with the input light via the corrugated window at a first light spot on the sample, the input light being scattered from the sample as the first portion of the scattered light and being directed toward the right-angle reflector via a second light spot on the sample. The right-angle mirror is configured to redirect the first portion of the scattered light back onto a third light spot on the sample via the corrugated window to generate the redirected scattered light, and the redirected scattered light is coupled into the spectrometer via a fourth light spot on the sample, wherein the first light spot, the second light spot, the third light spot, and the fourth light spot form an extended light spot region on the sample.

18. The optical device according to claim 17, further comprising: a corrugated mirror, with the sample sandwiched between the corrugated window and the corrugated mirror; and a heat dissipation element adjacent to the corrugated mirror.

19. The optical device according to claim 2, wherein the reflective surface comprises a first off-axis paraboloidal mirror and a second off-axis paraboloidal mirror, the first off-axis paraboloidal mirror being configured to receive the first portion of the scattered light from the first light spot on the first side of the sample and direct the first portion of the scattered light as a set of parallel light rays to the second off-axis paraboloidal mirror, the second off-axis paraboloidal mirror being configured to collect the set of parallel light rays and direct the reflected scattered light corresponding to the set of parallel light rays to a second light spot on the second side of the sample opposite the first side to generate the redirected scattered light, wherein the first light spot and the second light spot form an extended light spot region on the sample.

20. A method for increasing the collection of a spectrometer, comprising: receiving a first portion of the scattered light from the sample at a reflective surface positioned separately from the sample; redirecting the first portion of the scattered light back onto one or more discrete light spots on the sample in a non-random manner to generate redirected scattered light from the sample; and receiving at an input of the spectrometer the coupled light from the sample to obtain a spectrum of the sample based on the coupled light, the coupled light including at least a portion of the redirected scattered light.

21. The method according to claim 20, further comprising: irradiating the sample with input light from an illumination system positioned between the reflective surface and the sample, wherein the input light is scattered from the sample as the scattered light.

22. The method according to claim 21, wherein the coupled light further includes a second portion of the scattered light directly coupled from the sample into the spectrometer.

23. The method according to claim 22, wherein the one or more light spots include a single light spot within the field of view of the spectrometer, the single light spot having an extended light spot size based on the redirected scattered light, and further comprising: receiving another portion of the redirected scattered light at the reflective surface; and redirecting the other portions of the redirected scattered light back onto the single light spot on the sample to generate additional redirected scattered light, wherein the coupled light further includes at least a portion of the additional redirected scattered light.

24. The method according to claim 23, further comprising: At least a portion of the input light is reflected back to the reflective surface via the diffuse reflective material on each side of the sample for redirecting the input light toward the single light spot on the sample.

25. The method according to claim 23, wherein the reflective surface comprises a hemisphere or a sphere.

26. The method according to claim 21, further comprising: Receiving, at the reflective surface, the first portion of the scattered light from a first light spot on the sample, the first light spot having a light spot area at least partially outside the field of view of the spectrometer; And Redirecting the first portion of the scattered light to a second light spot on the sample within the field of view of the spectrometer, wherein the first light spot and the second light spot form an extended light spot area on the sample.

27. The method according to claim 26, further comprising: Redirecting the first portion of the scattered light to the second light spot on the sample via a third light spot on the sample, the third light spot being at least partially outside the field of view of the spectrometer, wherein the extended light spot area further comprises the third light spot.

28. The method according to claim 21, wherein the illumination system comprises at least two light sources, each light source being configured to direct a respective portion of the input light to a respective light spot on the sample, and further comprising: Receiving, at the reflective surface, the first portion of the scattered light from each of the respective light spots on the sample; And Redirecting the first portion of the scattered light to a collection area within the field of view of the spectrometer, the coupled light being directed from the collection area to the spectrometer, wherein at least the respective light spots on the sample form an extended light spot area on the sample.

29. The method according to claim 21, wherein the reflective surface comprises a right-angle reflector, and further comprising: Illuminating a first light spot on the sample with the input light via a corrugated window positioned between the illumination system and the sample, the input light being scattered from the sample into the first portion of the scattered light and being directed toward the right-angle reflector via a second light spot on the sample; And Redirecting the first portion of the scattered light from the right-angle reflector back to a third light spot on the sample via the corrugated window to produce the redirected scattered light, the scattered light being coupled into the spectrometer via a fourth light spot on the sample, wherein the first light spot, the second light spot, the third light spot, and the fourth light spot form an extended light spot area on the sample.

30. The method according to claim 21, wherein the reflective surface comprises a first off-axis parabolic mirror and a second off-axis parabolic mirror, and further comprising: Receiving, at the first off-axis parabolic mirror, the first portion of the scattered light from a first light spot on a first side of the sample; Directing the first portion of the scattered light as a set of parallel rays from the first off-axis parabolic mirror to the second off-axis parabolic mirror; And Direct the reflected scattered light corresponding to the set of parallel light rays onto a second light spot on a second side of the sample opposite the first side to produce the redirected scattered light, wherein the first light spot and the second light spot form an extended light spot region on the sample.

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