Light extraction probes for electron microscopes and other vacuum chambers

Abstract

A beam extraction system is provided. The beam extraction system includes a first focusing optical element, a second focusing optical element, and an optical relay coupled to the first focusing optical element and the second focusing optical element. The first focusing optical element is configured to form a light beam from light collected from a sample positioned at a focus of the first focusing optical element. The second focusing optical element is configured to couple the light beam to a detector. The optical relay provides an optical path for the light beam from the first focusing optical element to the second focusing optical element.

Description

[Technical field]

[0001] Light extraction probes FIELD OF THE DISCLOSURE The present invention relates to light extraction probes that are configured to extract sample light to and from different environments. [Background technology]

[0002] To perform spectroscopic work within a vacuum chamber, it is often necessary to move a light beam in and out of the chamber so that the sample within the chamber can be observed by an external spectrometer. The optics must maintain imaging quality over a particular field of view without excessive blurring or vignetting. Furthermore, the optics must often share space with other instruments and detectors within the chamber, such as the beam of a Scanning Electron Microscope (SEM).

[0003] U.S. Patent No. 6,885,445 (the '445 patent) describes an Off-Axis Parabolic (OAP) mirror configuration, where one mirror is held above a sample and a hole in the mirror allows the electron beam to pass through. The '445 patent further describes pairing such mirrors such that one mirror cancels the optical aberrations introduced by the other mirror. FIG. 1A shows a first configuration, an optical aberration canceling configuration, including a pair of OAP mirrors 101, 102. Two plane mirrors 104 are also included to redirect light rays 105 in the beam. The OAP mirrors 101, 102 are positioned such that their focal points are in the same horizontal plane 106, whereby the matching OAP mirrors are positioned to focus light to the same horizontal plane 106. 1B illustrates a pairing in which two OAP mirrors 101, 102 are positioned such that the focal point of the OAP mirror 102 is in a horizontal plane 108 that is different from the horizontal plane 106. This second configuration exacerbates optical aberrations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 6,885,445 Summary of the Invention [Problem to be solved by the invention]

[0005] As a pair of focusing optical elements, such as OAP mirrors 101 and 102, are separated by larger and larger distances, the field of view decreases and imaging displays vignetting and blurring. This occurs because a ray 105 introduced along the optical axis passes from one mirror to the other, but off-axis rays 105' as observed over an extended sample area are collected by one mirror and do not strike the other mirror. This is illustrated by FIG. 1C, which shows how, over long distances, off-axis rays 105' from OAP mirror 101 miss OAP mirror 102. This also happens in the reverse direction. For example, in a Raman instrument, the probe laser light is collected by one mirror and misses a second mirror in an imaging experiment.

[0006] Thus, there remains a need for methods and systems for passing a sample light beam over distances to and from different environments while maintaining imaging quality. [Means for solving the problem]

[0007] Systems, methods, and articles of manufacture to address the above identified needs and others are described herein with respect to the following exemplary, non-limiting embodiments. Various alternatives, modifications, and equivalents are possible.

[0008] According to a first aspect, a beam extraction system is provided. The beam extraction system includes a first focusing optical element, a second focusing optical element, and an optical relay coupled to the first focusing optical element and the second focusing optical element. The first focusing optical element is configured to form a light beam from light collected from a sample positioned at a focus of the first focusing optical element. The second focusing optical element is configured to couple the light beam to a detector. The optical relay provides an optical path for the light beam from the first focusing optical element to the second focusing optical element.

[0009] According to a second aspect, there is provided a spectroscopic system. The spectroscopic system includes a housing including a first focusing optical element configured to form a light beam at a focal point of the first focusing optical element from light collected from a sample positioned within the housing. A second focusing optical element of the system is configured to couple the light beam to a detector positioned outside the housing. An optical relay is coupled to the first focusing optical element and the second focusing optical element. The optical relay provides an optical path for the light beam from the first focusing optical element to the second focusing optical element. The system also includes an extraction window in the optical path.

[0010] According to a third aspect, a method of passing sample light between different environments is provided. The method includes positioning a sample in a first environment, focusing a first optical element on the sample, and forming a light beam from sample light received from the sample. The light beam is extended from the first focusing optical element to the second focusing optical element through an optical relay coupled to the first focusing optical element and the second focusing optical element. The light beam is coupled to a detector positioned in the second environment.

[0011] The beam extraction system described herein provides a way to pass a sample light beam over distances and through different environments while maintaining imaging quality.

[0012] The foregoing and other features and advantages of the present embodiments will be more fully understood from the following detailed description of illustrative embodiments taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1A] FIG. 13 shows an optical aberration cancellation configuration using a pair of OAP mirrors. [Figure 1B] 1 is a diagram showing a configuration of a pair of OAP mirrors in which optical aberration occurs. [Figure 1C] FIG. 1 illustrates a pair of focusing optical elements spaced a long distance apart. [Figure 2A] FIG. 1 illustrates a beam extraction system according to some implementations. [Figure 2B] A diagram illustrating a beam extraction system according to some other implementations. [Diagram 3] FIG. 1 illustrates a spectroscopic system according to some implementations. [Figure 4] 1 is a flow diagram describing a method for passing sample light between different environments according to some implementations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The figures referenced above are not necessarily drawn to scale and should be understood to provide representations of particular embodiments, which are conceptual in nature and merely illustrative of the principles involved. The same reference numbers are used in the drawings for similar or identical components and features shown in various alternative embodiments. The beam extraction systems disclosed herein will have configurations and components that are determined in part by the intended application and environment in which they will be used.

[0015] In the description of the invention herein, unless otherwise understood or stated, implicitly or explicitly, it is understood that words appearing in the singular include their plural equivalents and words appearing in the plural include their singular equivalents. Furthermore, unless otherwise understood or stated, implicitly or explicitly, it is understood that for any given component or embodiment described herein, any of the possible candidates or alternatives listed for that component may generally be used individually or in combination with each other. The term "about" as used herein is intended to mean close to or approximately the specified value, within the constraints of practical commercial engineering objectives, cost, manufacturing tolerances, and capabilities in the field of radiometric gauging. The term "substantially" as used herein is intended to mean mostly or nearly the same, within the constraints of practical commercial engineering objectives, cost, manufacturing tolerances, and capabilities in the field of radiometric gauging.

[0016] Thus, unless otherwise indicated to the contrary, the numerical parameters set forth in the specification and appended claims are to be understood as being modified by the term "about" and may vary depending on the desired properties sought to be obtained by the subject matter presented herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed at least in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the subject matter presented herein are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0017] FIG. 2A is a diagram illustrating a beam extraction system 200 according to some implementations. A first focusing optical element 202 forms a light beam 204 from light collected from a sample 206 positioned at a focal point 208 of the first focusing optical element 202. A second focusing optical element 210 couples the light beam 204 to a detector 212. For example, the light beam can be focused onto an objective lens 214 that is part of a Raman spectrometer, a Fourier-Transform Infrared Spectroscopy (FTIR) spectrometer, or a camera that is the detector 212. In some implementations, the light beam 204 is focused directly onto an entrance slit of a spectrometer; in FIG. 2A, the objective lens 214 replaces the entrance slit and the detector 212 is a spectrometer.

[0018] The beam extraction system 200 also includes an optical relay 218. The optical relay 218 is optically coupled to the first focusing optical element 202 and the second focusing optical element 210. The optical relay 218 provides an optical path for the light beam 204 from the first focusing optical element 202 to the second focusing optical element 210. The optical relay 218 may include optical elements such as lenses, mirrors, and combinations thereof that extend the light beam 204. In some implementations, the optical relay 218 collimates or re-collimates the light beam 204 while extending it.

[0019] According to some implementations, the optical relay 218 includes a third focusing optical element 220 having a focal length of F and a fourth focusing optical element 222 also having a focal length of F. The optical relay 218 in combination with the first focusing optical element 202 and the second focusing optical element 210 provides an optical path length of 4F from the first focusing optical element 202 to the second focusing optical element 210. The optical relay 218 is coupled to the first focusing optical element 202 at one end by the third focusing optical element 220 and to the second focusing optical element 210 at a second end by the fourth focusing optical element 222. In some implementations, the sum of the distance from the third focusing optical element 220 to the first focusing optical element 202 and the distance from the fourth focusing optical element 222 to the second focusing optical element 210 is 2F. 2A, the distance from the third focusing optical element 220 to the first focusing optical element 202 and the distance from the fourth focusing optical element 222 to the second focusing optical element 210 are each F. In some implementations, the distance from the third focusing optical element 220 to the fourth focusing optical element 222 is 2F.

[0020] In some implementations, the third focusing optical element 220 is matched to the fourth focusing optical element. As used herein, "matching" optical elements or optical elements that "match" another optical element means that they are selected to function equivalently. For example, for the light of interest (e.g., light beam 204), matching optical elements have the same focal length, transmission, aberration, curvature, reflectivity, reflective surface area, and transmission area. Matching optical elements may be selected by purchasing components from a commercial source, where the components have the same part number and the same specifications.

[0021] In some implementations, as shown by FIG. 2A, the third focusing optical element 220 and the fourth focusing optical element 222 are lenses, such as glass lenses. In some other implementations of the beam extraction system 200, mirrors are used, as illustrated in FIG. 2B. According to this implementation, the optical relay 218 includes a first concave mirror 224 positioned to reflect the light beam 204 formed by the first focusing optical element 202 and a second concave mirror 226 positioned to reflect the light beam 204 to the second focusing optical element 210. The sum of the distance from the first concave mirror 224 to the first focusing optical element 202 and the distance from the second concave mirror 226 to the second focusing optical element 210 is 2F. In some implementations, the first concave mirror 224 is positioned at a distance F from the first focusing optical element 202, and the second concave mirror 226 is positioned at a distance F from the second focusing optical element 210.

[0022] In some implementations, the first concave mirror 224 and the second concave mirror 226 are matched concave mirrors and are positioned substantially back-to-back, where "back-to-back" refers to positioning the first concave mirror 224 as close as possible to the second concave mirror 226, and the back surface of the mirror refers to the non-reflective surface opposite the reflective surface of each mirror. For example, if mounting requirements allow the back surfaces of the concave mirrors 224, 226 to touch, they are positioned in contact with each other. This is often not possible due to some alignment requirements or mounting frame requirements. In some implementations, at least one point on the back surfaces of the concave mirrors 224, 226 is separated by a distance of 1 cm or less (e.g., 0.5 cm or less apart, or 1 mm or less apart).

[0023] The concave mirrors 224 and 226 generally reflect the light beam 204 back in the directions of the first focusing optical element 202 and the second focusing optical element 210, respectively. Thus, the optical relay 218 in this implementation includes a planar mirror relay configured to reflect the light beam 204 from the first concave mirror 224 to the second concave mirror 226 across the distance 2f. The planar mirror relay may include two or more planar mirrors. In some implementations, the planar mirror relay includes a first planar mirror 228 positioned within the light beam 204 at a distance n from the first concave mirror 224 and a second planar mirror 230 positioned within the light beam 204 at a distance F - n from the second concave mirror 226. Here, n is a real number greater than 0 and less than the focal length F of the concave mirrors 224, 226 (i.e., 0 < n < F). In some implementations, n is approximately 0.5. In some implementations, the first planar mirror 228 and the second planar mirror 230 are aligned mirrors.

[0024] The concave mirrors 224, 226 are also angled such that the principal axis is not horizontal with respect to the page of FIG. 2B. In some implementations, the mirrors forming the optical relay 218 are angled such that the mirrors 228 and 230 do not block the light beam 204. That is, for the first concave mirror 224, substantially all of the light reflected from the first concave mirror 224 (e.g., at least 95% or at least 99% of the light) is reflected by the first planar mirror 228, and the first planar mirror 228 is angled such that it does not block the light beam 294 in a first section between the first focusing optical element 202 and the first concave mirror 224. Similarly, for the second concave mirror 226, substantially all of the light reflected from the second concave mirror 226 is reflected by the second planar mirror 230, and the second planar mirror 230 is angled such that it does not block the light beam 204 in a second section between the second focusing optical element 210 and the second concave mirror 226. In some implementations, the axes of the concave mirrors 224, 226 are angled such that the mirrors 228 and 230 are as close as possible to the contact beam 204, i.e., such that the distance 229 is as close as possible to 0 length units. In some implementations, the axes of the concave mirrors 224, 226 are each independently angled by at least 1 degree, at least 2 degrees, at least 5 degrees, at least 10 degrees, at least 20 degrees, or at least 30 degrees from horizontal.

[0025] In some implementations, each of the first focusing optical element 202 and the second focusing optical element 210 is independently selected from an OAP mirror, a Schwarzschild objective lens, and a lens. In some implementations, each of the first focusing optical element 202 and the second focusing optical element 210 is independently selected from an OAP mirror and a Schwarzschild objective lens. As depicted in FIG. 2A and FIG. 2B, the first focusing optical element 202 and the second focusing optical element 210 are OAP mirrors. The selection of the focusing optical element can be selected by a person skilled in the art who is familiar with current optical element technology. For example, a Schwarzschild objective lens, a glass lens, and an OAP mirror can be used to manipulate Raman excitation light, while mirrors are currently known to be most suitable for infrared (IR) light manipulation. Similarly, for light produced by cathodoluminescence, some wavelengths of interest, such as the ultraviolet (UV) range, are significantly attenuated by glass lenses, making mirror and Schwarzschild objective lenses currently a better choice. Similar factors can be taken into consideration when selecting for other optical elements, such as the third focusing optical element 220 and the fourth focusing optical element 222.

[0026] In some implementations, the first focusing optical element 202 and the second focusing optical element 210 are matched OAP mirrors. This provides the option for the first focusing optical element 202 and the second focusing optical element 210 to be positioned to reflect light in the same horizontal plane. That is, the focal point 208 and the objective lens 214 at the focal point of the second focusing optical element 210 are in the same horizontal plane. The advantage of using the same horizontal plane is the reduction of optical aberrations, as previously described with reference to Figures 1A-1C.

[0027] In some implementations, the beam extraction system 200 further includes an extraction window 304 positioned between the first focusing optical element 202 and the second focusing optical element 210. The extraction window 304 is positioned in the path of the light beam 204 and is selected to be at least partially transparent to the light beam 204. For example, the extraction window 304 allows at least 90% (e.g., at least 95% or at least 99%) of the light beam 204 to pass through the window. The extraction window 304 may be attached to a wall that is part of a structure such as a vacuum chamber containing the sample 206, an enclosure containing the detector 212, or a tube surrounding the optical relay 218. The extraction window 304 is designed to be impermeable to fluids (air, gas). In some implementations, the extraction window 304 is designed to be impermeable to high vacuum (e.g., up to 10 -12 Thor)

[0028] Also, according to some implementations, the linear distance between the first focusing optical element 202 and the second focusing optical element 210 is at least 10 cm, e.g., at least 20 cm to 100 cm, or at least 20 cm to 60 cm. In some implementations, the distance between the first focusing optical element 202 and the second focusing optical element 210 is 4F or less. As used herein, a "linear" distance refers to the shortest or straightest path between the first focusing optical element 202 and the second focusing optical element 210.

[0029] Those skilled in the art should recognize that the 4F optical path length and linear distance can be manipulated (i.e., selected) based on the type of optical elements used and the focal distance of the optical elements. For example, if the third focusing optical element 220 and the fourth focusing optical element 222 are selected to be lenses (FIG. 2A), the 4F optical path between the first focusing optical element 202 and the second focusing optical element 210 does not need to be folded as in the case where the concave mirrors 224, 226 (FIG. 2B) are selected. The linear distance can also be manipulated by changing the angle from the horizontal at which the concave mirrors 224, 226 are set. Obviously, the focal distance F selected for the optical elements also determines the 4F optical path length and linear distance. In some implementations, F is selected to be 1 cm to 50 cm.

[0030] Another way to extend the linear distance between the first focusing optical element 202 and the second focusing optical element 210 is to include additional optical relays 218. For example, using two or more optical relays 218 inserted in series between the first focusing optical element 202 and the second focusing optical element 210. In some implementations, the optical relay 218 includes m 4F optical paths from the first focusing optical element 202 to the second focusing optical element 210, where m is an integer greater than 1. In some implementations, M is 2, 3, or 4. Although implementations of more than one 4F optical path add complexity to the system since more mirrors are used, such implementations provide the advantage that smaller diameter meters can be used for an equivalent total extracted beam length of the light beam 204.

[0031] In some embodiments, the beam extraction system 200 is included in a spectroscopic system 300, as shown in FIG. 3. The spectroscopic system 300 includes a housing 302 that includes a first focusing optical element 202 configured to form a light beam 204 positioned within the housing 302 and at a focal point 208 of the first focusing optical element 202. A second focusing optical element 210 is configured to couple the light beam 204 to a detector 212 positioned outside the housing 302. An optical relay 218 is coupled to the first focusing optical element 202 and the second focusing optical element 210 and provides an optical path for the light beam 204 from the first focusing optical element 202 to the second focusing optical element 210. An extraction window 304 is positioned in the light beam 204 between the first focusing optical element 202 and the second focusing optical element 210 along the optical path, as previously described. The extraction window 304 is shown mounted within a structure such as a tube that defines a tunnel 306 that encloses an optical path for the light beam 204. The extraction window 304 may be mounted anywhere within the tunnel 306. The extraction window 304 may also be mounted at an opening 308 in the housing 302 or at a location 309 proximate to the detector 212. The inner wall 303 of the housing 302, the inner wall 311 of the tunnel 306, and the wall 307 of the extraction window 304 define a space that includes a first environment, which is different from a second environment that is outside of the space. As previously mentioned, the extraction window 304 is at least partially transparent to the light beam 204, but impermeable to fluids such as gases. Thus, the extraction window 304 allows the light beam 204 to pass through the extraction window 304, but does not allow fluid to pass through the window 304, resulting in a closed fluid environment in the space defined by the housing 302.

[0032] In some implementations, the enclosure 302 is a controlled atmosphere chamber, providing a controlled atmosphere within the first environment. The controlled atmosphere can be an inert atmosphere including an inert gas such as helium or argon. In some implementations, the controlled atmosphere is a reduced pressure atmosphere relative to the atmosphere outside the enclosure 302. In some implementations, the enclosure 302 is a vacuum chamber, such as a high vacuum chamber in an SEM or a medium vacuum chamber used in an environmental SEM. For example, in some implementations, the enclosure 302 is part of a scanning electron microscope, including an electron beam system 310 and a stage 312 for holding and orienting the sample 206. The first focusing optic 202 can include an opening for the electron beam 314 to pass therethrough. A secondary electron detector 316 and a backscatter detector 318 are also shown. The first focusing optical element 202 is positioned (e.g., above, below, or parallel to the first focusing optical element 202) to minimize interference with or shadowing of the secondary electron detector 316 and the backscatter detector 318.

[0033] In some implementations, the detector 212 includes a spectrometer 320. In some implementations, the second focusing optics 210 focuses the light beam 204 directly onto an entrance slit 322 of the spectrometer 320. In the embodiment shown in FIG. 3, the light beam 204 is shown directed towards the objective lens 214 of the spectrometer 320.

[0034] In some implementations, the detector 212 includes an excitation source 324 that provides an excitation beam 326 that is fused with the light beam 204. The excitation source may include optical elements such as magnifying lenses, collimating lenses, and beam splitters to fuse the excitation beam 326 with the light beam 204. In some implementations, the excitation source may be a laser that provides a Raman excitation beam.

[0035] In some implementations, the detector 212 includes an optical imaging element 328, such as a CCD camera. The optical imaging element 328 may include focusing optics and filters. The optical imaging element may be responsive to UV, IR, and visible light. The CCD camera may be used to detect cathodoluminescence when coupled to the electron beam system 310 through the beam extraction system 200 (FIG. 2B). The cathodoluminescence may also be directed to a spectrometer 320 for spectral analysis. In some implementations, a visible light source 330 is included, providing a visible light beam 331 that is fused with the light beam 204. The light source 330 may provide illumination to the sample 206, which allows the sample 206 to be viewed by the optical imaging element 328.

[0036] FIG. 3 with excitation source 324 shows an embodiment of a Raman spectrometer system. It is understood that not all components of a Raman spectrometer system for a functional Raman spectrometer are included because they are well known in the art. Additional variations known in the art, such as confocal Raman microscopy, shifted-excitation Raman difference spectroscopy (SERDS), surface-enhanced Raman (SERS), and surface-enhanced resonance Raman (SERRS), may also be implemented. It should be noted that this description of Raman spectroscopy should not be construed as a limited use for the beam extraction system 200. Those skilled in the art may envision implementations including transmission FTIR (Fourier transform infrared), reflection FTIR. In transmission FTIR, a light source is directed through the sample, and a light source such as a laser 317 may generally direct a light beam 352 from below the sample. The plane mirror 350 and stage 312 that redirects the light beam may have an aperture aligned with the electron beam 314. The aperture is wide enough to transmit at least a portion of the light beam 352 through the sample 206. Similarly, the housing 302 may be configured for energy-dispersive X-ray (EDS) analysis and as a tunneling electron microscope (TEM). In some implementations, the electron beam system 310 is implemented in a spectroscopy system 300 having a detector 212 that includes only a spectrometer 320 and a light imager 328 to analyze cathodoluminescence. The spectroscopy system 300 may also be implemented to extract light from hazardous environments, such as the high vacuum of outer space, or from toxic environments.

[0037] 4 is a flow diagram describing a method 400, according to some implementations of the present disclosure, for passing sample light between different environments.

[0038] In a first step 402, the sample 206 (FIG. 3) is positioned in a first environment. For example, the enclosure 302 can be the first environment. In some implementations, the sample 206 is illuminated with a transmission light source, such as an IR transmission configuration or a UV-vis transmission configuration. In some implementations, the sample 206 is illuminated by an excitation energy source. In some implementations, the excitation energy source is selected from a visible light source, an IR light source, a UV light source, an electron beam, or a combination thereof. Each of the light sources can be a laser source or a diffuse source. In some implementations, the sample 206 is illuminated by a visible light source. In some implementations, the sample 206 is illuminated by an IR light source. In some implementations, the sample 206 is illuminated by a UV light source. In some implementations, the sample 206 is illuminated by an electron beam to generate cathodoluminescence. In some implementations, the sample 206 is illuminated by a visible light source, which is a laser, such as a Raman excitation laser, and an electron beam at which the sample 206 produces Raman emission light and cathodoluminescence. In some implementations, the excitation energy source is focused at the sample 206 by a first focusing optic 202.

[0039] In a second step 404, the first optical element 202 is focused on the sample 206 and a light beam 204 is formed from sample light received from the sample 206. For example, the sample 206 is positioned such that the focal point 208 is focused on the sample 206. This may include moving the first focusing optical element 202 with respect to the sample 206. In some implementations, the sample 206 is on a stage 312 that may be moved to provide a relative orientation of the sample 206 with respect to the first focusing optical element 202.

[0040] In a third step 406, the light beam 204 is extended from the first focusing optical element 202 to the second focusing optical element 210. This extension of the light beam is provided by an optical relay 218 coupled to the first focusing optical element 202 and the second focusing optical element 210. In some implementations, the optical relay 218 includes a third focusing optical element 220 having a focal length of F and a fourth focusing optical element 222 having a focal length of F, such that the optical relay 218 provides a 4F optical path from the first focusing optical element 202 to the second focusing optical element 210.

[0041] In a final step 408, the light beam is coupled to a detector 212. The detector 212 is positioned in a second environment. In some implementations, the first environment is at a lower pressure than the second environment. For example, the first environment can be the space enclosed by the housing 302 and the tunnel 306 up to the extraction window 304 (left side of FIG. 3), while the second environment can be the space enclosed by the detector 212 and the tunnel 306 up to the extraction window 304 (right side of FIG. 3).

[0042] Those skilled in the art with knowledge gained from this disclosure will recognize that various modifications may be made to the disclosed apparatus and methods in achieving these and other advantages without departing from the scope of the present disclosure. Accordingly, it is to be understood that features described herein may be modified, altered, changed, or substituted. For example, all combinations of elements and / or steps that perform substantially the same function in substantially the same manner to achieve the same results are expressly intended to be within the scope of the embodiments described herein. Substitution of elements from one described embodiment to another is also fully intended and contemplated. The specific embodiments shown and described herein are for illustrative purposes only and are not intended to be limiting as set forth in the appended claims. Other embodiments will be apparent to those skilled in the art. It is to be understood that the foregoing description is provided for clarity only and is merely exemplary. The spirit and scope of the present disclosure is not limited to the above examples, but is encompassed by the following claims. All publications and patent applications cited above are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

Claims

1. A beam extraction system (200), comprising: a first focusing optical element (202) configured to form a light beam (204) from light collected from a sample (206) positioned at a focal point (208) of the first focusing optical element (202); a second focusing optic (210) configured to couple the light beam (204) to a detector (212); and an optical relay (218) coupled to the first focusing optical element (202) and the second focusing optical element (210), the optical relay (218) providing an optical path for the light beam (204) from the first focusing optical element (202) to the second focusing optical element (210); A beam extraction system (200) comprising:

2. 2. The beam extraction system of claim 1, wherein the optical relay includes a third focusing optical element having a focal length of F and a fourth focusing optical element having a focal length of F, the optical relay providing a 4F optical path from the first focusing optical element to the second focusing optical element.

3. The optical relay (218) a first concave mirror (224) positioned to reflect the light beam (204) formed by the first focusing optical element (202); a second concave mirror (226) positioned to reflect the light beam (204) to the second focusing optical element (210); 3. The beam extraction system of claim 2, wherein a sum of a distance from the first concave mirror (224) to the first focusing optical element (202) and a distance from the second concave mirror (226) to the second focusing optical element (210) is 2F.

4. 4. The beam extraction system of claim 3, wherein the first concave mirror (224) is positioned at a distance F from the first focusing optical element (202) and the second concave mirror (226) is positioned at a distance F from the second focusing optical element (210).

5. 4. The beam extraction system of claim 3, wherein the first concave mirror (224) and the second concave mirror (226) are matched concave mirrors and positioned substantially back-to-back.

6. 4. The beam extraction system of claim 3, wherein the optical relay comprises a plane mirror relay configured to reflect the light beam from the first concave mirror to the second concave mirror over a distance of 2f.

7. 7. The beam extraction system of claim 6, wherein the plane mirror relay comprises a first plane mirror (228) positioned in the light beam (204) at a distance n from the first concave mirror, and a second plane mirror (230) positioned in the light beam (204) at a distance F-n from the second concave mirror, where n is greater than 0 and less than F (0<n<F).

8. The beam extraction system of claim 7 , wherein n is 0.

5.

9. The beam extraction system of claim 7 , wherein the first plane mirror (228) and the second plane mirror (230) are matched mirrors.

10. 2. The beam extraction system of claim 1, wherein each of the first focusing optical element (202) and the second focusing optical element (210) is independently selected from an off-axis parabolic (OAP) mirror and a Schwarzschild objective lens.

11. The beam extraction system of claim 10 , wherein the first focusing optical element (202) and the second focusing optical element (210) are matched OAP mirrors.

12. The beam extraction system of claim 11 , wherein the matching OAP mirrors are positioned to focus light in a same horizontal plane (106).

13. The beam extraction system of claim 1 , further comprising an extraction window positioned between the first focusing optical element (202) and the second focusing optical element (210).

14. The beam extraction system of claim 1 , wherein a linear distance between the first focusing optical element (202) and the second focusing optical element (210) is at least 10 cm.

15. 2. The beam extraction system of claim 1, wherein the optical relay comprises m 4F optical paths from the first focusing optical element and the second focusing optical element, where m is an integer greater than 1.

16. A spectroscopic system (300), a housing (302) including a first focusing optical element (202), the first focusing optical element being configured to form a light beam (204) from light collected from a sample (206) positioned within the housing (302) and at a focal point (208) of the first focusing optical element (202); a second focusing optic (210) configured to couple the light beam (204) to a detector (212) positioned outside the housing (302); an optical relay (218) coupled to the first focusing optical element (202) and the second focusing optical element (210), the optical relay (218) providing an optical path for the light beam (204) from the first focusing optical element (202) to the second focusing optical element (210); and A spectroscopic system (300) comprising an extraction window (304) in the optical path.

17. The spectroscopic system of claim 16, wherein the enclosure (302) is a controlled atmosphere chamber.

18. The spectroscopic system of claim 16 , wherein the housing (302) includes an electron beam system (310) configured to provide an electron beam (314) through an opening in the first focusing optical element.

19. The spectroscopic system of claim 16 , wherein the detector comprises a spectrometer (320).

20. The spectroscopic system of claim 16 , wherein the detector (212) includes an excitation source (324) that provides an excitation beam (326) that is fused with the light beam (204).

21. The spectroscopic system of claim 16 , wherein the detector (212) comprises an optical imaging element (328).

22. 1. A method for passing sample light between different environments (400), the method comprising: Positioning the sample in a first environment; focusing a first optical element (202) onto the sample (206) to form a light beam (204) from sample light received from the sample (206); extending the light beam (204) from the first focusing optical element (202) to the second focusing optical element (210) through an optical relay (218) coupled to the first focusing optical element (202) and the second focusing optical element (210); and and coupling the light beam (204) to a detector (212) positioned within a second environment.

23. 23. The method of claim 22, wherein the optical relay (218) includes a third focusing optical element (220) having a focal length of F and a fourth focusing optical element (222) having a focal length of F, the optical relay (218) providing a 4F optical path from the first focusing optical element (202) to the second focusing optical element (210).

24. The method of claim 22, wherein the sample (206) is illuminated by an excitation energy source.

25. 23. The method of claim 22, wherein the first environment is at a lower pressure than the second environment.

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