Switchable brightfield and darkfield microscope with kÖhler illumination

Abstract

A microscope is configured for brightfield and darkfield illumination using Kohler illumination. An illuminator provides a first radiation pattern that passes through the microscope's objective lens for brightfield illumination and provides at least one second radiation pattern that also passes through the objective lens for darkfield illumination.

Description

Switchable Brightfield and Darkfield Microscope with Kohler IlluminationCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the priority benefit, under 35 U.S. C. 119(e), of U.S. Application No. 63 / 722,348, filed November 19, 2024, which application is incorporated herein by reference in its entirety for all purposes.BACKGROUND

[0002] In the semiconductor industry, there are automated tools for inspecting microfabricated structures on semiconductor wafers and integrated circuit (IC) chips at different stages of the manufacturing process. Some of these tools employ various types of optical systems to perform automated visual inspection of the structures. One such visual inspection tool is the optical microscope which can observe features with imaging resolution down to about 250 nm. As feature sizes in ICs continue to shrink, it is desirable to employ microscopes with increasingly higher magnification and optical resolution in order to resolve and detect the defects in the microfabricated structures.

[0003] To detect a wide variety of defects on semiconductor wafers and IC chips, two types of optical inspection techniques are employed: brightfield microscopy and darkfield microscopy. Brightfield microscopy employs brightfield illumination in which the illuminating radiation is incident on the sample along the same axis used for imaging the sample. The radiation is reflected and scattered from the sample and a portion of the returned radiation is gathered by the imaging optics to form a brightfield image of the sample. The brightfield image can have a bright background with some features showing up as dark images on the higher intensity background.

[0004] Darkfield microscopy employs darkfield illumination in which the illuminating radiation is incident on the sample off axis (i.e., at an angle to the axis used for imaging the sample) such that reflected radiation from the plane of the sample is not collected by the imaging optics. Instead, the radiation that is scattered from features on the sample is gathered by the imaging optics to form a darkfield image of the sample. The darkfield image can have a dark background with some features showing up as bright images on the lower intensity background.

[0005] Brightfield illumination is typically coupled into the microscope and fed through the microscope’s objective lens (using an illumination technique which is referred to as “Kohler illumination”). To obtain the wide-angle illumination for darkfield microscopy, the darkfield illumination is usually made incident on the sample via an external path that does not pass through the objective lens.SUMMARY

[0006] Described herein are optical systems and methods for an optical microscope that can be readily switched between brightfield and darkfield microscopy modes. In both microscopy modes, illumination of the sample is through the objective lens using a Kohler illumination scheme. An illuminator for the microscope can provide a first radiation pattern that passes through the microscope’s objective lens for brightfield illumination. The illuminator can further provide at least one second radiation pattern that also passes through the objective lens for darkfield illumination.

[0007] Some implementations relate to illuminators to provide spatially distinct radiation patterns for a microscope. Such illuminators can comprise: a first optical fiber bundle comprising first optical fibers, the first optical fiber bundle having a first length, a first proximal end, and a first distal end separated from the first proximal end by the first length; a second optical fiber bundle comprising second optical fibers, the second optical fiber bundle having a second length, a second proximal end, and a second distal end separated from the second proximal end by the second length; and an output element containing the first distal end of the first optical fiber bundle and the second distal end of the second optical fiber bundle. The first proximal end of the first optical fiber bundle can be configured to receive first radiation. The second proximal end of the second optical fiber bundle can be configured to receive second radiation. The first optical fibers at the first distal end of the first optical fiber bundle can be arranged in a first shape at the output element to emit the first radiation in a first pattern to provide brightfield illumination to a sample, and the second optical fibers at the second distal end of the second optical fiber bundle can be arranged in a selected shape at least partially around the first optical fibers to emit the second radiation in a selected pattern corresponding to the selected shape to provide at least darkfield illumination to the sample.

[0008] Some implementations relate to optical systems for brightfield imaging and darkfield imaging of a sample. Such optical systems can comprise: an objective lens; an illuminator to output first radiation in a first pattern to the objective lens for the brightfield imaging and to output second radiation in at least one second pattern to the objective lens for at least the darkfield imaging; an objective lens aperture to limit a transverse extent of one or both of the first radiation and the second radiation from the illuminator incident on the objective lens; an illuminator optical system arranged to relay a first image of the first pattern to a location of the objective lens aperture, to relay a second image of the at least one second pattern to the location of the objective lens aperture, and to couple the first radiation and the second radiation from the illuminator onto an imaging optical path of the optical system; an image relay optic arranged on the imaging optical path to relay an image of the objective lens aperture to an intermediate focal plane located along the imaging optical path; and an intensity mask located essentially at the intermediate focal plane to block at least a geometric portion of the second radiation from the at least one second pattern that passes through the objective lens to illuminate the sample, specularly reflects from the sample, passes again through the objective lens, and propagates along the imaging optical path.

[0009] Some implementations relate to optical microscopes comprising an illuminator comprising: a first optical fiber bundle comprising first optical fibers, the first optical fiber bundle having a first length, a first proximal end, and a first distal end separated from the first proximal end by the first length; a second optical fiber bundle comprising second optical fibers, the second optical fiber bundle having a second length, a second proximal end, and a second distal end separated from the second proximal end by the second length; and an output element containing the first distal end of the first optical fiber bundle and the second distal end of the second optical fiber bundle. The first proximal end of the first optical fiber bundle can be configured to receive first radiation. The second proximal end of the second optical fiber bundle can be configured to receive second radiation. The first optical fibers at the first distal end of the first optical fiber bundle can be arranged in a first shape at the output element to emit the first radiation in a first pattern, and the second optical fibers at the second distal end of the second optical fiber bundle are arranged in a selected shape at least partially around the first optical fibers to emit the second radiation in a selected pattern corresponding to the selected shape. The optical microscopes can further comprise: an objective lens arranged to receive the firstradiation and the second radiation from the illuminator to illuminate a sample; an imaging array arranged at an image plane of the optical microscope to receive an image formed, at least in part, by the objective lens; an objective lens aperture for the objective lens arranged to limit a transverse extent of at least one of the first radiation and the second radiation propagating from the illuminator to the objective lens; an image relay optic located along an optical path between the objective lens aperture and the imaging array, the image relay optic arranged to relay an image from the objective lens aperture to an intermediate focal plane along the optical path; and an intensity mask located at the intermediate focal plane, the intensity mask configured to block specularly reflected second radiation from the sample from propagating to the imaging array.

[0010] Some implementations relate to methods for inspecting a sample with an optical system. Such methods can comprise an act of illuminating the sample with radiation from an illuminator, wherein the illuminator is configured to: output first radiation having a first pattern for forming a brightfield image of the sample under inspection by the optical system; and output second radiation having at least one second pattern for forming a darkfield image of the sample under inspection by the optical system. Example methods can further comprise acts of: receiving, with an objective lens, the first radiation from the illuminator to illuminate the sample; receiving, with the objective lens, specularly reflected first radiation from the sample to form the brightfield image of the sample; capturing, with an imaging array, the brightfield image of the sample; receiving, with the objective lens, the second radiation from the illuminator to illuminate the sample; limiting, with an objective lens aperture, a transverse extent of the second radiation received by the objective lens; receiving, with the objective lens, scattered second radiation and specularly reflected second radiation from the sample; blocking at least a portion of the specularly reflected second radiation from propagating to the imaging array with an intensity mask located between the objective lens and the imaging array; and capturing, with the imaging array, the darkfield image of the sample formed from at least a portion of the scattered second radiation from the sample.

[0011] Some implementations relate to methods of inspecting a sample with a microscope. Such methods can comprise acts of: illuminating the sample with darkfield illumination from an illuminator output element that is optically conjugate to an objective lens aperture of an objective lens of the microscope so that at least a portion of the darkfield illumination passes through the objective lens; detecting a darkfield image of the sample with an imaging array located in asample image plane of the microscope; forming an image of the objective lens aperture at an intermediate focal plane along an optical path of the microscope between the objective lens and the imaging array; and filtering, at the intermediate focal plane, a portion of the darkfield illumination that is specularly reflected by the sample and passes through the objective lens.

[0012] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and / or structurally similar elements).

[0014] FIG. 1 depicts an example of darkfield illumination with radiation that does not pass through the objective lens of the system.

[0015] FIG. 2A depicts an example of an optical system that can be switched between a brightfield microscopy mode and a darkfield microscopy mode in which both modes use the Kohler illumination scheme.

[0016] FIG. 2B depicts a darkfield imaging mode of the optical system of FIG. 2A.

[0017] FIG. 2C depicts another arrangement of the optical system of FIG. 2A.

[0018] FIG. 2D depicts another arrangement of the optical system of FIG. 2A.

[0019] FIG. 2E depicts another arrangement of the optical system of FIG. 2 A.

[0020] FIG. 3 depicts an example of an illuminator for the microscopy system of FIG. 2A.

[0021] FIG. 4A illustrates example arrangements of distal ends of optical fibers for two optical fiber bundles of the illuminator of FIG. 3.

[0022] FIG. 4B illustrates examples of output radiation patterns that can be produced with the illuminator of FIG. 3.

[0023] FIG. 4C illustrates another example of output radiation patterns that can be produced with an illuminator like that of FIG. 3.

[0024] FIG. 4D illustrates another example of output radiation patterns that can be produced with an illuminator like that of FIG. 3.

[0025] FIG. 5A depicts an example of an annular light source that can be used in the optical system of FIG. 2A to produce additional output radiation patterns.

[0026] FIG. 5B is a cross-section view of the light source of FIG. 5A further including optical fibers coupled to the light source.

[0027] FIG. 5C illustrates further examples of output radiation patterns that can be produced with an illuminator of the disclosed implementations.

[0028] FIG. 6A depicts an example of an intensity mask that can be used in the optical systems of FIG. 2 A through FIG. 2D.

[0029] FIG. 6B depicts another example of an intensity mask that can be used in the optical systems of FIG. 2 A through FIG. 2D.DETAILED DESCRIPTION

[0030] 1. Difficulty with Darkfield Illumination at High Magnification

[0031] The inventors have recognized and appreciated that illuminating a sample off axis for darkfield microscopy becomes very challenging at high magnification for high-resolution imaging. To obtain high-resolution images, an objective lens with a high magnification power (e.g., 50 or 100 ) and large numerical aperture (NA) value is used. Such objective lenses entail a short working distance from the objective lens 103 to the sample 102 being inspected, resulting in the optical arrangement 100 depicted in FIG. 1. Off-axis darkfield illumination 101 that is provided external to the objective lens 103 can be undesirably blocked and / or vignetted by the objective lens 103. Thus, high- resolution imaging conflicts with darkfield illumination that is external to the objective lens 103.

[0032] The inventors have further recognized and appreciated that using a ring pattern of radiation that passes through the objective lens 103 (e.g., near a periphery of the objective lens) for darkfield microscopy also has problems. Some of the reflected rays from the sample 102 can be collected by the objective lens 103 superimposing a brightfield image on the darkfield image.

[0033] 2. Switchable Brightfield / Darkfield Optical System

[0034] FIG. 2A illustrates an optical system 200 that can be readily switched between a brightfield microscopy mode and a darkfield microscopy mode in which both modes use a Kohler illumination scheme. In both the brightfield microscopy mode and the darkfield microscopy mode, radiation from the illuminator 201 to illuminate the sample 102 passes through the system’s objective lens 103, which can have a NA of no less than 0.5 in some cases, or no less than 0.6 in some cases. In some implementations, the NA of the objective lens 103 can be no less than 0.7, no less than 0.75, no less than 0.8, or even no less than 0.85. The optical system 200 is configured to avoid the problems of external, off-axis darkfield illumination and superposition of a brightfield image onto the darkfield image described above. The optical system 200 can be implemented in a microscope and in an inspection tool for inspecting structures on semiconductor wafers and IC chips.

[0035] The optical system 200 comprises an illuminator 201 that outputs radiation patterns (which may be referred to as a “Kohler inputs”) for both brightfield microscopy and darkfield microscopy with the optical system 200. The optical system 200 further comprises an illumination collection and relay system 220 to (1) relay an image of the illuminator’s output (the Kohler inputs) to the location of an objective lens aperture 206 (e.g., which can be at or near a back focal plane of the objective lens 103) and to (2) couple radiation from the illuminator 201 onto the imaging optical path 230 of the optical system 200. The imaging optical path 230 runs through the objective lens 103. The optical system 200 further comprises the objective lens 103, an image relay optic 240, an intensity mask 211, and an imaging lens 212. The optical system can further comprise an imaging array 250 located at an image plane 213 of the optical system 200 to detect and capture brightfield images and darkfield images formed at the image plane 213. However, an imaging array may not be present in some implementations of the optical system. Instead, an eyepiece may be arranged for human viewing of the sample image.

[0036] In some implementations, the optical system 200 can further comprise at least one controller 260 that is communicatively coupled to the illuminator 201 and the imaging array 250.The controller(s) 260 can control the illuminator to output a selected radiation pattern and can control the imaging array 250 to capture images of the sample 102. At least one controller 260 can further be configured to record the captured images in memory. The memory can be included with the controller 260 or remote to the controller. The controller(s) 260 can comprise at least one processor. A processor can comprise a microcontroller, a microprocessor, a programmable logic unit (PLU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), custom digital circuitry, or some combination thereof. The controller can be a packaged, stand-alone device included with or integrated in the optical system 200 and that can communicatively couple to the optical system 200 with a wired or wireless link. If multiple controllers are used, they can be packaged together in a single unit or packaged separately as individual controllers (e.g., one for illumination control and another for image acquisition). In some implementations, system control can be implemented, at least in part, with a single, packaged, stand-alone device (e.g., circuity comprising a microcontroller or microprocessor and a touchscreen). In some implementations, system control can be implemented, at least in part, with a personal computer or laptop computer which functions as the controller 260 for the optical system 200. Alternatively, system control can be implemented with a distributed controller, with at least some components located at different and separated physical locations from each other but communicating over a network. In some implementations, a first controller can be used to control the illuminator 201 and a second controller, which may or may not be communicatively coupled to the first controller, can be used to control the imaging array 250. The second controller could be a personal computer that can be communicatively coupled to the imaging array 250 (e.g., with a USB cable).

[0037] In the illustrated example, the collection and relay system 220 comprises a first relay lens 202 and a second relay lens 203 arranged to relay and magnify the image of the illuminator’s output radiation patterns to the location at or near (e.g., within ±5 mm) the objective lens aperture 206. As such, the illuminator’s output is approximately or exactly optically conjugate to the objective lens aperture 206 for Kohler illumination. In the example of FIG. 2A, the first relay lens 202 and the second relay lens 203 magnify the output from the illuminator 201 such that the radiation pattern from the illuminator 201 fills the objective lens aperture. Other schemes are also possible (e.g., unity magnification and demagnification by the first relay lens 202 and the second relay lens 203).

[0038] The illuminator optical system 220 further comprises a mirror 204 and a beamsplitter 205 to couple radiation from the illuminator 201 onto the imaging optical path 230 of the optical system 200. In some implementations, the mirror 204 may not be used. Instead, the illuminator 201, first relay lens 202 and a second relay lens 203 can be arranged in the optical system such that radiation from the illuminator 201 is not folded along the illumination optical path 270 before hitting the beamsplitter 205. For example, the illumination optical path 270 could be oriented such that it travels only along a direction approximately or exactly orthogonal to the imaging optical path 230 or at some other angle in a range from 50 degrees to 85 degrees with respect to the imaging optical path 230.

[0039] According to some implementations, the illuminator 201 outputs radiation having a bandwidth of wavelengths. The bandwidth of wavelengths can comprise a portion of wavelengths in a range of wavelengths from 350 nanometers to 2 microns. The illuminator 201 can include one or more light sources. When a plurality of light sources is used, at least some of the light sources in the plurality can emit a different bandwidth of wavelengths than other light sources in the plurality of light sources (e.g., a broader bandwidth and / or different range of wavelengths). In some cases, at least some of the light sources of the illuminator 201 are lightemitting diodes. In some cases, at least some of the light sources of the illuminator 201 are broadband white light emitters (such as a halogen bulb or arc lamp). Other light sources that can be used include, but are not limited to, lasers, electroluminescent devices, super luminescent diodes (SLDs), filaments, incandescent lights, high intensity discharge light sources, and deuterium lamps.

[0040] In some implementations, the optical system 200 includes one or more optical bandpass wavelength filters 207 to filter emission from the illuminator 201 and select a bandwidth of radiation for illuminating the sample 102. The bandpass filters can be inserted into the illumination optical path 270.

[0041] In some implementations, one or more optical polarization components 208 (e.g., polarizers, half-wave plates, quarter-wave plates) can be placed in the illumination optical path 270 and / or imaging optical path 230 to manipulate the polarization of the radiation and / or of the reflected or scattered radiation from the sample 102. Such polarization components can be used for polarized light microscopy.

[0042] The first relay lens 202 can be a single lens or a multi-lens element (compound lens). Similarly, the second relay lens 203 can be a single lens or a compound lens. The first relay lens 202 and the second relay lens 203 can have antireflection coatings to reduce unwanted Fresnel reflections from surfaces of the lenses. The mirror 204 can be a metallic mirror or a multi-layer dielectric mirror.

[0043] The beamsplitter 205 can be a partially-silvered beamsplitter or a dielectric beamsplitter. The back surface or non-reflecting surface of the beamsplitter 205 can have an antireflection coating to reduce unwanted Fresnel reflections from the surface. Further, the back surface or non-reflecting surface can be oriented at an angle with respect to the reflecting surface of the beamsplitter 205.

[0044] As described above, output radiation patterns from the illuminator 201 are relayed by the first relay lens 202 and second relay lens 203 to approximately or exactly the location of the objective lens aperture 206 for the objective lens 103. Either one or both of the first relay lens 202 and the second relay lens 203 can comprise a single optical lens or a compound lens. The objective lens aperture 206 can limit a transverse extent (or beam size) of at least one of the first radiation and the second radiation propagating from the illuminator 201 to the objective lens 103. Radiation passing through the objective lens aperture 206 propagates through the objective lens to the sample 102, reflects and / or scatters from the sample 102, and at least a portion of the returned radiation (reflected and / or scattered back from the sample 102) travels back through the objective lens 103. At least some of the returned radiation that passes through the objective lens aperture 206 can be received by the image relay optic 240. The reflected radiation carries amplitude and phase information for forming a brightfield image of at least a portion of the sample 102. The scattered radiation carries amplitude and phase information for forming a darkfield image of at least a portion of the sample 102.

[0045] The image relay optic 240 images the objective lens aperture 206 approximately or exactly onto an intermediate focal plane 219 at which the intensity mask 211 is approximately or exactly located. As such, the intensity mask 211 is approximately or exactly at a location that is optically conjugate to the objective lens aperture 206. “Approximately” in these cases can mean within ±1 mm, within ±2 mm, or even within ±3 mm. The image relay optic 240 can comprise a first lens 209 and a second lens 210, each of which can be a single lens or compound lensassembly. The function of the intensity mask 211 is described in the following section pertaining to darkfield imaging.

[0046] Returned radiation from the sample 102 that passes the intensity mask 211 is focused by the imaging lens 212 onto the image plane 213. The imaging lens 212 can be a single lens or a compound lens. An imaging array 250 (e.g., a CCD or CMOS imaging array) or another image-capture device can be located at the image plane 213 to detect and capture an image of the sample 102. According to some implementations, a second beamsplitter 285 and an auxiliary viewer 280 (e.g., a microscope eyepiece or camera that is connectable to a video display) can be included in the optical system 200 for manual viewing of the sample 102 in real time. An eyepiece, if used for the auxiliary viewer 280, can comprise a single lens or a compound lens. The second beamsplitter 285 and auxiliary viewer 280 can be arranged at other locations in the optical system 200. FIG. 2C depicts an arrangement where the second beamsplitter 285 is located between the intensity mask 211 and the imaging lens 212. A focusing lens 214 (used for the implementation of FIG. 2C) may or may not be added between the second beamsplitter 285 and the auxiliary viewer 280 for image formation. FIG. 2D depicts an arrangement where the second beamsplitter 285 is located between the second lens 210 and the intensity mask 211. An additional intensity mask 211a can be added at a second intermediate focal plane 219a between the beamsplitter 285 and the auxiliary viewer 280 for the implementation of FIG. 2D to block the specularly reflected rays 276 reflected from the sample 102 and the beamsplitter 285 when using the optical system 200 in darkfield imaging mode. When the auxiliary viewer 280 is implemented as a camera, it can be communicatively coupled to and controlled by the controller 260 for image capture.

[0047] FIG. 2E depicts another arrangement of the optical system 200 of FIG. 2A in which a spatial light modulator 292 is used to form the intensity mask 211 and / or phase mask for the optical system 200. For the illustrated arrangement, the SLM 292 is used in reflection mode, which can provide better performance than transmission-mode SLMs. However, the optical system 200 can use an SLM 292 in transmission mode (e.g., by placing a transmission mode SLM in the imaging optical path 230 between the second lens 210 and the imaging lens 212 at, or approximately at, the second intermediate focal plane 219 where the intensity mask is located in FIG. 2A). For the implementation of FIG. 2E, at least one reflective optic 286 can be installed between the image relay optic 240 and the imaging lens 212 to redirect image-formingrays to the SLM 292 and to receive and redirect image-forming rays reflected from the SLM 292 to the imaging lens 212 and imaging array 250. In some cases, the reflective optic 286 comprises two or more mirrors. The SLM 292 can utilize liquid crystal technology to modulate the intensity, phase, or both intensity and phase of light interacting with and reflecting from the SLM 292. As such, the SLM 292 can be used in the optical system 200 for a phase mask and / or apodizer.

[0048] The SLM 292 can be communicatively coupled to and controlled by the system controller 260 in some implementations. When computer controlled, intensity and / or phase modulation by the SLM 292 can be readily changed and different modulations tried (e.g., to improve imaging or to prototype different operating modes). In this regard, the SLM 292 can operate as an adaptive optical component to improve image quality (e.g., testing variations of intensity and / or phase modulation to improve image quality).

[0049] Though not shown in FIG. 2E, the apparatus for the auxiliary viewer 280 can be added to the optical system 200 in any of the configurations shown in FIG. 2A through FIG. 2D.

[0050] 3. Brightfield Imaging

[0051] To obtain a brightfield image with the optical systems of FIG. 2A through FIG. 2E, the intensity mask 211 or SLM 292 may or may not be used. In some implementations, the intensity mask 211 comprises a circular aperture having an open center for radiation to pass through (depicted as intensity mask 211-1 in FIG. 2A). In some cases, the intensity mask 211 can be easily placed in the imaging optical path 230 and easily removed from the imaging optical path 230 (e.g., slid into and removed from a receptacle) by a user of the system during operation of the system (e.g., to switch between brightfield and darkfield imaging modes). In some implementations, the intensity mask 211 comprises an adjustable iris which can be open and closed to change the diameter of the iris’ open center through which radiation passes. Other implementations of the intensity mask include a phase mask, an amplitude mask, an apodizer, a spatial light modulator as described above in connection with FIG. 2E (which could be connected to and controlled by a system controller 260), or some combination of the foregoing intensity mask implementations. The spatial light modulator (SLM) can control intensity and / or phase of light incident on the SLM. In some implementations, the intensity mask 211 has an opaque central portion surrounded by an annular open portion to block central rays near the optical axis of the system and allow passage of rays in an annular ring around the central portion(depicted as intensity mask 211-2 in FIG. 2A). The intensity mask 211-2 can block brightfield illumination, regardless of the state of the illuminator (e.g., outputting both brightfield and darkfield illumination).

[0052] In brightfield imaging, light rays (indicated with both dashed and solid lines in the example of FIG. 2A) can propagate from the illuminator 201 along the illumination optical path 270 and imaging optical path 230, reflecting from the sample 102, as shown in FIG. 2A. If the intensity mask 211 is present in the imaging optical path 230, it can be used to geometrically block outer or wide-angle rays that contribute to high-resolution brightfield imaging. Blocking these rays can reduce resolution of the microscope but increase the depth of field of the microscope. For high resolution imaging, the intensity mask 211 can be removed from the imaging optical path 230 or opened (if an iris) to allow the outer rays, indicated with the dashed lines, to pass through the imaging lens 212 and participate in image formation. In some implementations, the intensity mask 211 can be annular such that the outer rays (high-resolution rays) pass through the mask and the inner rays (lower resolution rays) are geometrically blocked by the intensity mask 211. Rays that pass the intensity mask 211 will be focused by the imaging lens 212 to form an image of the sample 102 at the image plane 213 (and at the subject’s retina if a subject is viewing the sample through the eyepiece of the auxiliary viewer 280). In some brightfield imaging applications, the outer rays (dashed) can be omitted from the illumination optical path 270 (e.g., not emitted from the illuminator 201 as described further below or blocked) and would thus be absent from the drawings of FIG. 2A through FIG. 2E. Operation of the illuminator 201 and image acquisition of brightfield images by the imaging array 250 can be controlled, at least in part, by the controller 260.

[0053] 4. Darkfield Imaging

[0054] FIG. 2B illustrates the optical system of FIG. 2A operated in the darkfield imaging mode. The wavelength filter(s) 207 and polarization component(s) 208 are not shown in FIG. 2B but could be present and used during darkfield imaging. In this operating mode, the illuminator 201 is controlled (e.g., by the controller 260) to emit outer rays 275 and not to emit rays close to an optical axis 272 of the illumination optical path 270. The pattern of radiation emitted from the illuminator 201 can be annular, for example, producing a cylindrical shell of radiation propagating along the illumination optical path 270. The outer rays 275 propagate along the illumination optical path 270 and are eventually focused and redirected onto the sample102 at a large incident angle (e.g., 45 degrees or larger) by the objective lens 103 to produce scattered rays 235 from features on the sample 102. The scattered rays 235 and outer specularly reflected rays 276 are collected by the objective lens 103 and redirected along the imaging optical path 230 toward the relay 240.

[0055] The scattered rays 235 and outer specularly reflected rays 276 pass through the image relay optic 240 and propagate toward the imaging lens 212. However, the intensity mask 211 or SLM 292 geometrically blocks the outer specularly reflected rays 276 thereby preventing these specularly reflected rays 276 from contributing to the image formed at the image plane 213.Accordingly, the specularly reflected rays 276 of incident radiation can be completely blocked or nearly completely blocked (e.g., at least 90% blocked) such that the image formed in darkfield imaging mode can be formed completely or nearly completely from scattered rays 235 from the sample 102 and a negligible or no amount of specularly reflected radiation is permitted to pass through the imaging lens 212 to form a brightfield image of the sample 102. The illumination of the sample with outer rays 275 for darkfield imaging can be done with each of the implementations of FIG. 2A through FIG. 2E.

[0056] 5. Illuminator

[0057] FIG. 3 depicts an example illuminator 201 that can be used in the optical systems 200 of FIG. 2 A through FIG. 2E. The illuminator 201 is configured to output first radiation in a first radiation pattern for brightfield illumination during operation of the optical system 200 in brightfield microscopy mode. The illuminator 201 is further configured to output second radiation in at least one second radiation pattern for darkfield illumination during operation of the optical system 200 in darkfield microscopy mode (as illustrated in FIG. 2B).

[0058] In the example illumination system, optical fiber bundles 322, 324 carry radiation from two light sources 362, 364 to an output element 340 of the illuminator 201. The first light source 362 can emit first radiation and the second light source 364 can emit second radiation, which may or may not comprise the same wavelengths as the first radiation. For example, the first radiation can comprise first wavelengths of light extending over a range of wavelengths, and the second radiation can comprise at least a band of wavelengths that are different from the first wavelengths. In some implementations, the first light source 362 and the second light source 364 emit radiation having the same band of wavelengths. The intensity of radiation emitted by the first light source 362 and the second light source 364 can be the same or different.The angular distribution of light emitted by the first light source 362 and the second light source 364 can be the same or different.

[0059] The first light source 362 can comprise one or more LEDs or any other suitable light emitter, such as a halogen bulb or arc lamp. Similarly, the second light source 364 can comprise one or more LEDs or any other suitable light emitter, such as a halogen bulb or arc lamp. The first light source 362 and the second light source 364 can each be controlled independently of each other by the controller 260 to at least turn the respective light source on and off and, in some cases, to further adjust the output intensity of the light source (e.g., by controlling the amount of electrical power delivered to each light source).

[0060] First radiation output from the first light source 362 can be coupled into a proximal end of the first optical fiber bundle 322 by a first optical coupler 312. Similarly, the second radiation output from the second light source 364 can be coupled into a proximal end of the second optical fiber bundle 324 by a second optical coupler 314. Optical fibers in the first optical fiber bundle 322 and in the second optical fiber bundle 324 can be arranged in any pattern or shape (e.g., circular, square, rectangle, oval, etc. . The arrangements of the optical fibers at the proximal ends can be selected to match the shape of light output from the respective light sources 362, 364 and improve optical coupling efficiency between the light source and fiber bundle. For example, if the first light source 362 comprises an array of LEDs arranged in a square pattern on a substrate, the optical fibers at the proximal end of the first optical fiber bundle 322 can be arranged in a square pattern.

[0061] The first optical fiber bundle 322 can comprise a first plurality of optical fibers and have a first length. The second optical fiber bundle can comprise a second plurality of optical fibers and have a second length. The first optical coupler 312 and second optical coupler 314 can each be implemented with one or more lenses, a graded-refractive index lens, one or more lensed fibers, or some combination thereof. In some implementations, the first optical coupler 312 and second optical coupler 314 can be implemented by directly butt coupling ends of optical fibers to the respective light source.

[0062] FIG. 4A illustrates example arrangements of distal ends of optical fibers for two optical fiber bundles of the illuminator of FIG. 3. The first optical fiber bundle 322 can be combined with the second optical fiber bundle 324 at a junction 330 into a combined optical fiber bundle 335 that terminates at the output element 340. The output element 340 can be configured toinsert into an illumination port for an optical microscope or inspection tool having the optical system 200 described above, such that an output face 345 of the output element 340 is at a desired location for a Kohler input of the tool (e.g., at the location of the optical output from the illuminator 201.

[0063] According to some implementations as depicted in FIG. 4A, distal ends of second optical fibers 325 (illustrated as black circles) at a distal end of the second optical fiber bundle 324 (also at the distal end of the combined optical fiber bundle 335) can be arranged in a second shape or pattern at the output element 340. The second shape can extend at least partially around first optical fibers 323 (illustrated as gray circles) at a distal end of the first optical fiber bundle 322. In the illustrated example, the second shape is annular and completely surrounds the first shape. However, other shapes are possible.

[0064] FIG. 4B crudely depicts an output radiation pattern 400 that can be emitted from an output face 345 of the output element 340 when both light sources 362, 364 are emitting. The first radiation from the first light source 362 can be emitted in a first pattern 410 (e.g., a circle) from the first optical fibers 323 and the second radiation from the second light source 364 can be emitted in a second pattern 420, (e.g., an annulus) from the second optical fibers 325. The first pattern 410 is spatially distinct from the second pattern 420.

[0065] Since the light sources 362, 364 can be controlled independently via the controller 260, either one of the two output radiation patterns 410, 420 can be provided from the output element at a time. For example, the first radiation emitted in a first pattern 410 for brightfield microscopy can be produced by turning on the first light source 362 and turning off the second light source 364. The second radiation in a second pattern 420 for darkfield microscopy can be produced by turning off the first light source 362 and turning on the second light source 364. Of course, the light sources could be switched at the inputs of the first optical coupler 312 and second optical coupler 314, such that the second optical source could be turned on to produce the first pattern 410.

[0066] By turning on the first light source 362 and turning off the second light source 364, the optical system can be placed in a first microscopy mode (brightfield or darkfield depending on the coupling of the light sources 362, 364 to the first optical fiber bundle 322 and the second optical fiber bundle 324). By simply turning off the first light source 362 and turning on the second light source 364, the optical system can be switched to the other microscopy mode(darkfield or brightfield). This may be done without making any other adjustments to the optical system.

[0067] In some implementations, the illuminator 201 is configured and operable to turn on the first light source 362 and turn on the second light source 364 at the same time, giving a mix of brightfield and darkfield imaging. The relative intensities of the two light sources can be adjusted by a user to adjust the mix of brightfield and darkfield imaging characteristics. Such a mixed imaging mode can be implemented without changing lenses or apertures in the microscope, and by merely turning on the other light source. Such an imaging mode can be beneficial for further distinguishing features in an image that may not be clearly distinguished with only brightfield illumination or only darkfield illumination.

[0068] The illuminator 201 is not limited to two patterns and can be further adapted to output more than two radiation patterns. For example, a third optical fiber bundle and third light source could be added to the illuminator 201. Optical fibers from the third optical fiber bundle can be distributed adjacent to the second optical fibers 325 (e.g., in a second annular arrangement or other arrangement). FIG. 4C depicts patterns 450 for a second annular arrangement of optical fibers at the output element 340. The patterns 450 include a circular first pattern 410, an annular second pattern 421, and an annular third pattern 422.

[0069] FIG. 4D depicts spatially distinct patterns 452 for a third annular arrangement of optical fibers at the output element 340. For this implementations, the optical fibers are arranged in two annular patterns. A first annular pattern 441 lies inside a second annular patter 442. The central region 445 of the light source can be empty, according to some embodiments. For example, there may be no optical fibers in the central region 445.

[0070] Other light source configurations and patterns are possible for the illuminator 201. FIG. 5A depicts an annular LED light source 510 comprising a plurality of LEDs 512. The plurality of LEDs can be disposed on an annular substrate (e.g., printed circuit board) to form the annular LED light source 510. There can be tens, hundreds, or even thousands of LEDs disposed on the substrate and each LED can be coupled to a proximal end of a second optical of the plurality of second optical fibers 325, as shown in FIG. 5B. Accordingly, the second optical fibers 325 for the second optical fiber bundle 324 can be coupled to the plurality of LEDs 512 of the annular LED light source 510.

[0071] In some implementations, the individual LEDs and / or groups of the LEDs in the plurality of LEDs 512 used for the second light source 364 can be controlled independently of one another by the controller 260. As such, virtually any pattern can be produced with the annular LED light source 510. Similarly, individual LEDs and / or groups of the LEDs in a plurality of LEDs used for the first light source 362 (when coupled to a plurality of first optical fibers 323) can be controlled independently of one another by the controller 260 to produce virtually any light pattern for the first pattern 410. FIG. 5C depicts an example of spatially distinct output radiation patterns 500 that can be produced using the annular LED light source 510. If all LEDs in the plurality of LEDs 512 are turned on, then an annular pattern is produced like that shown in FIG. 4B. If groups of the plurality of LEDs 512 are individually turned on, different sectional patterns 423, 424, 425, 426 (segments of the annular pattern) can be output from the output element 340. In the illustration of FIG. 5C, arcuate sections of an annulus are depicted, though other shapes are possible for the sectional patterns. Further, the groups of LEDs can be turned on and off independently of each other and independently of the first pattern 410. In some cases, the first pattern 410 can also be segmented into two or more sectional patterns of virtually any shape by selectively turning on and off LEDs coupled to the first optical fibers 323.

[0072] The sectional patterns 423, 424, 425, 426 can be used for different darkfield illumination schemes (e.g., from different incident angles, subtending different azimuthal angles, and incident from different directions). Radiation for darkfield imaging can have an incident angle of at least 45 degrees or larger using the sectional patterns 423, 424, 425, 426. According to some implementations, LEDs in different groups of the annular LED light source 510 can emit at different wavelengths, so that the sample can be illuminated with different colors or wavelengths.

[0073] Instead of using an annular LED light source 510 to produce the different sectional patterns 423, 424, 425, 426 shown in FIG. 5C, it is possible to use different light sources and different optical fiber bundles to produce each of the sectional patterns. In the illustrated example of FIG. 5C, four different light sources (each comprising one or more light emitters) can be used that are each coupled to a different optical fiber bundle. The four light sources can be separated from one another (e.g., separately packaged emitters). The optical fibers of the four optical fiber bundles can be arranged at the output element 340 in the shapes of the differentsectional patterns 423, 424, 425, 426. For example, optical fibers of a first optical fiber bundle can be arranged such that the ends of the optical fibers at the output element 340 are in a first sectional pattern 423. Optical fibers of a second optical fiber bundle can be arranged such that the ends of the optical fibers at the output element 340 are in a second sectional pattern 424, and so on for the other two optical fiber bundles. The light sources for the four optical fiber bundles can be turned on and off independently of each other to produce a desired output sectional pattern. Since the distal ends of the optical fibers can be arranged in any desired manner at the output element 340, virtually any pattern can be obtained with each optical fiber bundle.

[0074] 6. Increased Depth of Focus

[0075] Referring again to FIG. 2A, imaging capability of the optical system 200 can be improved by placing a phase mask 290 at the location of the intermediate focal plane 219, where the intensity mask 21 lean also be located. The phase mask 290 can be a separate optical component from the intensity mask 211 in some implementations or may be combined with the intensity mask 211 in some cases. In some cases, the phase mask 290 and the intensity mask 211 may be placed adjacent to each other (e.g., within 5 mm of each other, within 2 mm of each other, or even within 1 mm of each other) at the intermediate focal plane 219 (e.g., on either side of the intermediate focal plane 219). In some cases, the intensity mask 211 and the phase mask 290 can be implemented on a single optical component and co-located at the intermediate focal plane 219 (e.g., both functionalities encoded on the same optical component). The intermediate focal plane 219 is essentially a location where an image from the objective lens aperture 206 is relayed to by the image relay optic 240. The phase mask 290 can be used to modulate the phase of a wavefront passing through the phase mask 290. The phase mask 290 can be designed to encode any desired phase modulation onto the wavefront (e.g., to achieve extended depth of focus, depth encoding, or a desired point-spread function). In some implementations, the phase mask 290 can be used to increase the depth of focus of the optical system, particularly when a high-magnification objective lens 103 is used. To extend the depth of focus or depth of field of the optical systems 200, a cubic phase mask can be used for the phase mask 290. In such cases, the raw images captured with the imaging array 250 may not appear well focused. However, these images can be processed by a computer (either by the controller 260 or another processing device) to recover a well-focused image over an extended depth of field. The recovery of the image can be done using known methods, to account for the phase profile introduced by thephase mask 290. Such image-recovery methods can involve inverse filtering, decoding methods, classical, deconvolutional methods such as the Lucy-Richardson deconvolution process, machine learning methods, deep learning methods, neural networks, or some combination of these processes to recover well-focused, extended depth-of-focus images from the captured raw images. The phase mask 290 can be used in any of the implementations of the optical system 200 illustrated in FIG. 2A through FIG. 2E.

[0076] 7. Additional Instensity Mask Designs

[0077] FIG. 6A and FIG. 6B depict additional implementations of intensity masks that can be used for the intensity mask 211 and SLM 292 in the above-described optical systems 200 of FIG. 2A through FIG. 2E. These intensity masks could be implemented with the SLM 292 or with fixed light-blocking portions (e.g., patterned in metal on a transparent substrate). These intensity masks can block a first selected amount of the brightfield illumination and a second selected amount of the darkfield illumination. The intensity mask 61 la of FIG. 6 A comprises an outer annular ring 610 (depicted as light-blocking in this configuration) and an inner annular ring 612 (depicted as transparent in this configuration). The outer annular ring 610 and inner annular ring 612 can be sized and located at the intermediate focal plane 219 to block and / or pass at least a portion of the darkfield illumination. For example, the outer annular ring 610 can block a first portion of the outer specularly reflected rays 276 and the inner annular ring 612 can pass a second portion of the specularly reflected rays 276. A circular interior region 614 can be partially transparent and partially opaque. For example, a first pie-shaped section 613 can be transparent and a second pie section 615 can be light-blocking. The interior region 614 can be sized and located at the intermediate focal plane 219 to block and / or pass portions of the brightfield illumination. When implemented as a SLM, the depicted light-blocking portions can be made transparent and the depicted transparent portions can be made light-blocking for other implementations of the intensity mask 611a. Other patterns of light-blocking portions and transmitting portions are possible.

[0078] FIG. 6B depicts another implementation of an intensity mask 61 lb in which the interior region 614 comprises a partially transparent portion 623 and light-blocking portions 625 (circularly shaped in the illustrated example, but other shapes are possible). According to some implementations, the intensity masks 611a, 611b can be rotatably mounted in the optical system 200 such that the intensity masks 611a, 611b can be rotated by the user to change illuminationconditions on the sample 102. The rotation of the intensity masks 611a, 611b can be in a direction that is the plane of the drawing (indicated by the double-ended arrow in FIG. 6A).

[0079] 8. Conclusion

[0080] While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the function and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the inventive teachings is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0081] Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0082] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0083] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0084] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and / or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and / or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0085] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0086] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, inone embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0087] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMS1. An illuminator (201) to provide spatially distinct radiation patterns for a microscope, the illuminator comprising: a first optical fiber bundle (322) comprising first optical fibers (323), the first optical fiber bundle having a first length, a first proximal end, and a first distal end separated from the first proximal end by the first length; a second optical fiber bundle (324) comprising second optical fibers (325), the second optical fiber bundle having a second length, a second proximal end, and a second distal end separated from the second proximal end by the second length; and an output element (340) containing the first distal end of the first optical fiber bundle and the second distal end of the second optical fiber bundle, wherein: the first proximal end of the first optical fiber bundle is configured to receive first radiation, the second proximal end of the second optical fiber bundle is configured to receive second radiation, the first optical fibers (323) at the first distal end of the first optical fiber bundle are arranged in a first shape at the output element to emit the first radiation in a first pattern (410) to provide brightfield illumination to a sample, and the second optical fibers (325) at the second distal end of the second optical fiber bundle are arranged in a selected shape at least partially around the first optical fibers to emit the second radiation in a selected pattern (420, 421, 422, 423, 424) corresponding to the selected shape to provide at least darkfield illumination to the sample.

2. The illuminator of claim 1, wherein the selected shape is an annulus.

3. The illuminator of claim 1, wherein the selected shape is a section of an annulus.

4. The illuminator of claim 1, further comprising: a first optical coupler (312) arranged to optically couple the first radiation from a first light source into the first proximal end of the first optical fiber bundle; anda second optical coupler (314) arranged to optically couple the second radiation from a second light source into the second proximal end of the second optical fiber bundle.

5. The illuminator of claim 4, further comprising: the first light source (362) arranged to deliver the first radiation to the first optical coupler; and the second light source (364) arranged to deliver the second radiation to the second optical coupler.

6. The illuminator of claim 5, wherein at least one of the first light source and the second light source comprises one or more light emitting diodes.

7. The illuminator of claim 5, wherein: the first radiation comprises first wavelengths of light; and the second radiation comprises at least a band of wavelengths that are different from the first wavelengths.

8. The illuminator of claim 5, wherein the second light source comprises an annular LED light source (510), the annular LED light source comprising: an annular substrate; and a plurality of light emitting diodes disposed on the annular substrate, wherein at least a first group of the plurality of light emitting diodes can be controlled independently from a second group of the plurality of light emitting diodes to form two distinct patterns.

9. The illuminator of any one of claims 5 through 8, further comprising a controller (260) communicatively coupled to the illuminator to control independently the first light source and the second light source.

10. The illuminator of claim 1, wherein the selected shape is a first selected shape and the selected pattern is a first selected pattern, the illuminator further comprising: a third optical fiber bundle comprising third optical fibers, the third optical fiber bundle having a third length, a third proximal end, and a third distal end separated from the third proximal end by the third length, wherein:the output element further contains the third distal end of the third optical fiber bundle, the third proximal end of the third optical fiber bundle is configured to receive third radiation, the third optical fibers at the third distal end of the third optical fiber bundle are arranged in a second selected shape at least partially around the first optical fibers to emit the third radiation in a second selected pattern (421, 422, 423, 424) corresponding to the second selected shape.

11. An optical system (200) for brightfield imaging and darkfield imaging of a sample (102), the optical system comprising: an objective lens (103); an illuminator (201) to output first radiation in a first pattern (410) to the objective lens for the brightfield imaging and to output second radiation in at least one second pattern (420, 421, 422, 423, 424) to the objective lens for at least the darkfield imaging; an objective lens aperture (206) to limit a transverse extent of one or both of the first radiation and the second radiation from the illuminator incident on the objective lens; an illuminator optical system (220) arranged to relay a first image of the first pattern to a location of the objective lens aperture, to relay a second image of the at least one second pattern to the location of the objective lens aperture, and to couple the first radiation and the second radiation from the illuminator onto an imaging optical path (230) of the optical system; an image relay optic (240) arranged on the imaging optical path to relay an image of the objective lens aperture to an intermediate focal plane (219) located along the imaging optical path; and an intensity mask (211) located essentially at the intermediate focal plane to block at least a geometric portion of the second radiation from the at least one second pattern (420, 421, 422, 423, 424) that passes through the objective lens (103) to illuminate the sample, specularly reflects from the sample, passes again through the objective lens, and propagates along the imaging optical path (230).

12. The optical system of claim 11, wherein the illuminator and the illuminator optical system are arranged to provide Kohler illumination of the sample for both the first pattern and the second pattern.

13. The optical system of claim 11, wherein the objective lens has a numerical aperture of no less than 0.5.

14. The optical system of claim 11, wherein: the first pattern is circular; and the at least one second pattern includes an annular pattern.

15. The optical system of claim 14, wherein the at least one second pattern further includes an arcuate section of the annular pattern.

16. The optical system of claim 11, wherein: the first pattern is circular; and the at least one second pattern includes an arcuate section of an annular pattern.

17. The optical system of claim 11, wherein the illuminator comprises at least one optical fiber bundle.

18. The optical system of claim 11, wherein the illuminator comprises at least one light emitting diode array arranged in the first pattern or the at least one second pattern.

19. The optical system of claim 11, wherein the illuminator comprises at least one halogen lamp.

20. The optical system of claim 11 , wherein the illuminator comprises at least one laser.

21. The optical system of claim 11, wherein the illuminator comprises at least one super luminescent diode.

22. The optical system of claim 11, wherein the illuminator comprises: a first optical fiber bundle (322) comprising first optical fibers (323), the first optical fiber bundle having a first length, a first proximal end, and a first distal end separated from thefirst proximal end by the first length; a second optical fiber bundle (324) comprising second optical fibers (325), the second optical fiber bundle having a second length, a second proximal end, and a second distal end separated from the second proximal end by the second length; and an output element (340) containing the first distal end of the first optical fiber bundle and the second distal end of the second optical fiber bundle, wherein: the first proximal end of the first optical fiber bundle is configured to receive first radiation, the second proximal end of the second optical fiber bundle is configured to receive second radiation, the first optical fibers (323) at the first distal end of the first optical fiber bundle are arranged in a circular shape at the output element to emit the first radiation in a circular first pattern (410), and the second optical fibers (325) at the second distal end of the second optical fiber bundle are arranged in a selected shape at least partially around the first optical fibers to emit the second radiation in a selected pattern (420, 421, 422, 423, 424) corresponding to the selected shape.

23. The optical system of claim 111, wherein the intensity mask comprises a reflection-mode spatial light modulator.

24. The optical system of claim 11 , further comprising a phase mask (290) located at the intermediate focal plane to modulate the phase of a wavefront passing through the phase mask.

25. The optical system of claim 24, wherein the phase mask is a cubic phase mask.

26. The optical system of claim 11, further comprising: an imaging lens (212); and an imaging array (250) located at a distal end of the imaging optical path to capture an image of the sample formed, at least in part, by the imaging lens on the imaging array.

27. The optical system of claim 26, further comprising: a beamsplitter (285) arranged in the optical path between the imaging lens (212) and theimaging array (250); and an auxiliary viewer (280) arranged to receive light rays from the beamsplitter and provide an auxiliary image of the sample.

28. The optical system of claim 27, wherein the auxiliary viewer comprises a microscope eyepiece.

29. The optical system of claim 26, further comprising: a beamsplitter (285) arranged in the optical path between the intensity mask (211) and the imaging lens (212); and an auxiliary viewer (280) arranged to receive light rays from the beamsplitter and provide an auxiliary image of the sample.

30. The optical system of claim 26, further comprising: a beamsplitter (285) arranged in the optical path between the image relay optic (240) and the intensity mask (211); and an auxiliary viewer (280) arranged to receive light rays from the beamsplitter and provide an auxiliary image of the sample.

31. The optical system of claim 11 , further comprising a controller (260) communicatively coupled to the illuminator and adapted to: control the illuminator at a first time to output the first radiation and first pattern while the second radiation is off; and control the illuminator at a second time to output the second radiation and at least one second pattern while the first radiation is off.

32. The optical system of claim 31, further comprising an imaging array located at an image plane of the optical system, wherein the controller is further communicatively coupled to the imaging array and adapted to: control the imaging array to capture images of the sample; and record the images of the sample captured by the imaging array in memory.

33. An optical microscope comprising: an illuminator (201) comprising:a first optical fiber bundle (322) comprising first optical fibers (323), the first optical fiber bundle having a first length, a first proximal end, and a first distal end separated from the first proximal end by the first length; a second optical fiber bundle (324) comprising second optical fibers (325), the second optical fiber bundle having a second length, a second proximal end, and a second distal end separated from the second proximal end by the second length; and an output element (340) containing the first distal end of the first optical fiber bundle and the second distal end of the second optical fiber bundle, wherein: the first proximal end of the first optical fiber bundle is configured to receive first radiation, the second proximal end of the second optical fiber bundle is configured to receive second radiation, the first optical fibers (323) at the first distal end of the first optical fiber bundle are arranged in a first shape at the output element to emit the first radiation in a first pattern (410), and the second optical fibers (325) at the second distal end of the second optical fiber bundle are arranged in a selected shape at least partially around the first optical fibers to emit the second radiation in a selected pattern (420, 421, 422, 423, 424) corresponding to the selected shape; an objective lens (103) arranged to receive the first radiation and the second radiation from the illuminator to illuminate a sample; an imaging array (250) arranged at an image plane (213) of the optical microscope to receive an image formed, at least in part, by the objective lens; an objective lens aperture (206) for the objective lens arranged to limit a transverse extent of at least one of the first radiation and the second radiation propagating from the illuminator to the objective lens; an image relay optic (240) located along an optical path between the objective lens aperture and the imaging array, the image relay optic arranged to relay an image from the objective lens aperture to an intermediate focal plane along the optical path; and an intensity mask (211) located at the intermediate focal plane, the intensity maskconfigured to block specularly reflected second radiation from the sample from propagating to the imaging array.

34. A method for inspecting a sample with an optical system (200), the method comprising: illuminating the sample with radiation from an illuminator (201), the illuminator configured to: output first radiation having a first pattern for forming a brightfield image of the sample under inspection by the optical system; and output second radiation having at least one second pattern for forming a darkfield image of the sample under inspection by the optical system; receiving, with an objective lens, the first radiation from the illuminator to illuminate the sample; receiving, with the objective lens, specularly reflected first radiation from the sample to form the brightfield image of the sample; capturing, with an imaging array, the brightfield image of the sample; receiving, with the objective lens, the second radiation from the illuminator to illuminate the sample; limiting, with an objective lens aperture, a transverse extent of the second radiation received by the objective lens; receiving, with the objective lens, scattered second radiation and specularly reflected second radiation from the sample; blocking at least a portion of the specularly reflected second radiation from propagating to the imaging array with an intensity mask located between the objective lens and the imaging array; and capturing, with the imaging array, the darkfield image of the sample formed from at least a portion of the scattered second radiation from the sample.

35. A method of inspecting a sample with a microscope, the method comprising: illuminating the sample with darkfield illumination from an illuminator output element that is optically conjugate to an objective lens aperture of an objective lens of the microscope so that at least a portion of the darkfield illumination passes through the objective lens;detecting a darkfield image of the sample with an imaging array located in a sample image plane of the microscope; forming an image of the objective lens aperture at an intermediate focal plane along an optical path of the microscope between the objective lens and the imaging array; and filtering, at the intermediate focal plane, a portion of the darkfield illumination that is specularly reflected by the sample and passes through the objective lens.

36. The method of claim 35, further comprising; terminating the darkfield illumination; and illuminating the sample with brightfield illumination from the illuminator output element so that at least a portion of the brightfield illumination passes through the objective lens.

37. The method of claim 35, wherein the objective lens has a numerical aperture of at least 0.5.

Images