Optical-based methods and systems

Abstract

The invention discloses an optical-based method and system. An optically based method includes providing a light guide device (LGA) configured to redirect light incident on the LGA in a direction perpendicular to an exterior surface of a sample into or onto the sample such that a cursor is incident on an interior facet of the sample symmetrically perpendicular to the interior facet; generating a first incident light beam LB directed perpendicular to the exterior surface and a second incident light beam LB parallel to the first incident light beam LB and directed towards the LGA; obtaining a first return LB by reflection of the first incident LB from the outer surface, and obtaining a second return LB by redirecting the second incident LB by the LGA into or onto the sample, reflecting the second incident LB from the inner facet, and reverse redirecting by the LGA; an angular deviation between the return LBs is measured and an actual tilt angle of the inner facet with respect to the outer surface is derived from the angular deviation.

Description

[0001] This application is a divisional application of the Chinese patent application with application number 202180055253.7 and invention name “Optical-based system”. The international filing date of the parent application is November 18, 2021, and the international application number is PCT / IL2021 / 051378. Technical Field

[0002] The present disclosure generally relates to methods and systems for metrology of samples including internal facets. Background Art

[0003] Some transparent optical elements, such as glass prisms and waveguides, may include reflective internal facets. To verify the orientation of such facets with respect to one or more external surfaces of the optical element with high accuracy, current prior art requires high-end optical components and the implementation of complex alignment and calibration procedures. Therefore, there is an unmet need in the art for a simple and easily implementable metrology technique that avoids the use of high-end optical components, thereby addressing large-scale production requirements. Summary of the invention

[0004] According to some embodiments of the present disclosure, aspects of the present disclosure relate to methods and systems for measuring samples including one or more internal facets. More specifically, but not exclusively, according to some embodiments of the present disclosure, aspects of the present disclosure relate to optical-based methods and systems for measuring samples including one or more internal facets.

[0005] Advantageously, the present application discloses a rapid, simple, and accurate method and system for verifying the inclination of an internal facet of a sample, or a plurality of nominally parallel internal facets of a sample, relative to one or more external planar surfaces of the sample.

[0006] Thus, according to an aspect of some embodiments, there is provided an optically based method for verifying the orientation of one or more internal facets of a sample relative to an external planar surface of the sample. The method comprises:

[0007] - providing a sample comprising an outer flat first surface and an inner facet which is tilted at a nominal tilt angle μnominal (tilted by design and manufacturing intent) relative to the first surface.

[0008] - providing a light guiding arrangement (LGA) configured to redirect light incident on the LGA in a direction perpendicular to the first surface into or onto the sample such that light transmitted by the sample into the sample impinges on the inner facet symmetrically perpendicular to the inner facet.

[0009] - generating a first incident light beam (LB) directed towards the first surface in a normal manner to the first surface and a second incident LB parallel to the first incident LB and directed towards the LGA.

[0010] - A first return LB is obtained by reflection of the first incident LB from the first surface.

[0011] - A second return LB is obtained by redirecting the second incident LB into or onto the sample by the LGA, reflecting the second incident LB from the internal facet and redirecting it back by the LGA.

[0012] - Measuring a first angular deviation of the second return LB relative to the first return LB.

[0013] - deducing an actual inclination angle μ′ of the inner facet relative to the first surface based at least on the measured first angular deviation.

[0014] According to some embodiments of the method, the sample includes a first portion and a second portion, and the internal facet extends between the first portion and the second portion. The first portion is located between the external second surface of the sample and the internal facet. The transmission LB constituting a portion of the second incident LB is directly or indirectly transmitted into the sample and enters the sample via the second surface.

[0015] According to some embodiments of the method, the LGA includes a light folding component (LFC) that is nominally configured to fold light at a light folding angle equal to a nominal tilt angle at least when light is projected onto the LFC in a direction perpendicular to the first surface.

[0016] According to some embodiments of the method, the LFC is or comprises a prism, one or more mirrors and / or a diffraction grating.

[0017] According to some embodiments of the method, the light folding angle is insensitive to changes in the pitch of the LFC.

[0018] According to some embodiments of the method, the LFC is or comprises a pentaprism or similar functional prism, or a pair of mirrors arranged at an angle relative to each other, or a similar functional mirror arrangement.

[0019] According to some embodiments of the method, the LGA further comprises a coupling infrastructure configured to direct light folded by the LFC onto or into the sample such that light transmitted by the sample into the sample is incident quasi-normally on the internal facet.

[0020] According to some embodiments of the method, the coupling infrastructure includes a coupling prism (CP). The CP includes an external flat CP first surface, an external flat CP second surface nominally tilted at a nominal tilt angle relative to the CP first surface, and an external CP third surface opposite the CP second surface. The CP has a refractive index that is the same as the refractive index of the first portion of the sample or a refractive index that is close to the refractive index of the first portion of the sample (e.g., within 0.001%, 0.01%, or even 0.1%, each possibility corresponding to a separate embodiment). The CP is arranged so that the CP first surface is parallel to the first surface of the sample, and is also oriented so that the light folded by the LFC is nominally normal to the CP second surface.

[0021] According to some embodiments of the method, the coupling infrastructure further comprises a shape-compliant interface. The shape-compliant interface is arranged between the CP third surface and the sample and has been formed to present a shape such that the CP first surface is parallel to the first surface of the sample.

[0022] According to some embodiments of the method, the shape compliant interface has a refractive index that is the same as, or close to, the refractive index of the first portion of the sample (e.g., within 0.001%, 0.01%, or even 0.1%, each possibility corresponding to a separate embodiment).

[0023] According to some embodiments of the method, the shape compliant interface is or includes a liquid and / or a gel.

[0024] According to some embodiments of the method, the sample can be a prism, a waveguide, or a beam splitter.

[0025] According to some embodiments of the method, the first incident LB and the second incident LB constitute complementary parts of a single collimated light beam, or are prepared by blocking one or more parts of a single collimated light beam.

[0026] According to some embodiments of the method, the first incident LB and the second incident LB are prepared by blocking one or more portions of a single collimated LB.

[0027] According to some embodiments of the method, the single collimating LB is polychromatic.

[0028] According to some embodiments of the method, the single collimated LB is a laser beam.

[0029] According to some embodiments of the method, wherein the coupling infrastructure comprises the CP, the method further comprises an initial calibration phase, wherein the LFC, the CP and / or the orientation of the sample are calibrated using a gold standard sample.

[0030] According to some embodiments of the method, wherein the coupling infrastructure includes the CP, the method further includes generating an additional incident LB, the additional incident LB pointing to the first surface of the CP and parallel to the first incident LB. During the measurement of the first angular deviation, the orientation of the CP is (a) calibrated and / or (b) tested to obtain the correct orientation by measuring the additional angular deviation of the additional return LB relative to the first return LB. The additional return LB is obtained by reflection of the additional incident LB from the first CP surface.

[0031] According to some embodiments, the first angular deviation is obtained based on measured coordinates of a first point and a second point formed on a photosensitive surface of the light sensor by the first return LB and the second return LB, respectively.

[0032] According to some embodiments of the method, the first angular deviation is measured using an autocollimator.

[0033] According to some embodiments of the method, the measured first angular deviation is equal to Δu / f. Δu is the difference between the coordinates of the first point on the photosensitive surface of the autocollimator and the corresponding coordinates of the second point. f is the focal length of the collimating lens of the autocollimator. The first point is formed by the first return LB and the second point is formed by the second return LB.

[0034] According to some embodiments of the method, wherein the coupling infrastructure includes the CP, the actual tilt angle of the internal facet relative to the first surface is obtained based on the measured first angle deviation, the value of the actual tilt angle of the CP second surface relative to the CP first surface and the refractive index of the first portion of the sample and optionally the actual light folding angle of the LFC.

[0035] According to some embodiments of the method, the method further comprises measuring an actual light folding angle of the LFC.

[0036] According to some embodiments of the method, wherein the coupling infrastructure comprises the CP, the method further comprises measuring an actual tilt angle of the second surface of the CP relative to the first surface of the CP.

[0037] According to some embodiments of the method, the nominal tilt angle is an obtuse angle.

[0038] According to some embodiments of the method, the nominal tilt angle is an acute angle.

[0039] According to some embodiments of the method, the nominal tilt angle is 90° and the sample includes an outer third surface that is flat and parallel to the first surface of the sample. The method also includes performing the following operations after measuring the first angular deviation:

[0040] - Flip the sample over to invert the first and third surfaces.

[0041] - generating a third incident LB and a fourth incident LB, wherein the third incident LB is directed to the third surface in a manner perpendicular to the third surface, and the fourth incident LB is parallel to the third incident LB and directed to the LGA.

[0042] - A third return LB is obtained by reflection of the third incident LB from the second surface.

[0043] - A fourth return LB is obtained by redirecting a second incident LB into or onto the sample by the LGA, reflecting it from the internal facets and redirecting it back by the LGA.

[0044] - Measuring a second angular deviation of the fourth return LB relative to the third return LB.

[0045] - deducing an actual inclination angle between the first outer surface and the inner facet based on the measured first angular deviation and the measured second angular deviation.

[0046] According to some embodiments of the method, the coupling infrastructure includes the CP, and the CP also includes a CP fourth surface opposite and parallel to the CP first surface. The flipping of the sample is accompanied by the flipping of the CP, so that the CP first surface and the CP fourth surface are reversed while maintaining the nominal orientation of the CP second surface relative to the sample.

[0047] According to some embodiments of the method, the uncertainty in the parallelism of the first surface of the sample and the third surface of the sample is smaller or even significantly smaller (eg, an order of magnitude or more) than the required measurement accuracy of the actual tilt angle.

[0048] According to some embodiments of the method, wherein the coupling infrastructure includes a CP, the actual inclination angle of the internal facet relative to the first surface is obtained based on the measured first angle deviation, the value of the actual inclination angle of the CP second surface relative to the CP first surface, and the refractive index of the first portion of the sample.

[0049] According to some embodiments of the method, wherein the coupling infrastructure includes a CP, the actual tilt angle is equal to or approximately equal to 90°+(δ1-δ2) / (4n)+Δμ″′·(n-1) / n (for example, the derived actual tilt angle is between 90°+0.95·[(δ1-δ2) / (4n)+Δμ″′·(n-1) / n)] and 90°+1.05·[(δ1-δ2) / (4n)+Δμ″′·(n-1) / n)], between 90°+0.9·[(δ1-δ2) / (4n)+Δμ″′·(n-1) / n)] and 90°+1. 1·[(δ1-δ2) / (4n)+Δμ″′·(n-1) / n], or even between 90°+0.8·[(δ1-δ2) / (4n)+Δμ″′·(n-1) / n)] and 90°+1.2·[(δ1-δ2) / (4n)+Δμ″′·(n-1) / n)], each possibility corresponding to a separate embodiment. δ1 and δ2 are the measured first angle deviation and the measured second angle deviation, respectively. n is the refractive index of the first part of the sample. Δμ″′ is the deviation of the inclination of the CP second surface relative to the CP first surface from 90°. Advantageously, according to some such embodiments, there is no need to know or measure the deviation of the actual light folding angle of the LFC from its nominal inclination angle.

[0050] According to some embodiments of the method, the internal facet extends up to the first surface of the sample.

[0051] According to some embodiments of the method, the sample includes k≥1 additional internal facets nominally parallel to the internal facet. When obtaining the second return LB, the k additional return LBs are obtained by reflecting the k LBs from each of the k additional internal facets, respectively. The k LBs constitute the portion of the second incident LB that is transmitted into the sample and is also transmitted through the internal facet. When measuring the first angular deviation, the k additional angular deviations of the k additional return LBs relative to the first return LB are measured. When deriving the actual tilt angle μ′ of the internal facet, (i) k additional actual tilt angles of each of the k additional internal facets are additionally derived, and / or (ii) an average actual tilt angle is derived, which is equal to or approximately equal to the average of the actual tilt angles of the internal facet and the k additional internal facets. The average actual tilt angle indicates the actual tilt angle μ′ of the internal facet.

[0052] According to some embodiments of the method, k≥2. The first internal facet in the additional internal facets is located between the internal facets and the second internal facet in the additional internal facets. For each m such that 2≤m≤k-1, the mth internal facet in the k additional internal facets is located between the (m-1)th internal facet and the (m+1)th internal facet in the k additional internal facets. According to some such embodiments, each of the k+1 points formed on the photosensitive surface of the light sensor or image sensor by the second return LB and the k additional return LBs, respectively, can be attributed to the corresponding return LB based on the brightness of the point (i.e., identified as being formed by the corresponding return LB). The brightest point among the k+1 points can be attributed to the second return LB, and for each j such that 2≤j≤k+1, the jth brightest point can be attributed to the return LB caused by the reflection of the (j-1)th internal facet in the k additional internal facets.

[0053] According to some embodiments of the method, the interior facet and each of the k additional interior facets are configured to reflect a corresponding spectrum of light. Each spectrum is different from the other spectra to allow differentiation between the second return LB and each of the k additional return LBs.

[0054] According to an aspect of some embodiments, there is provided an optical-based system for verifying the orientation of an internal facet of a sample relative to an external planar surface of the sample. The system comprises:

[0055] - a light guiding arrangement (LGA) configured to redirect light incident on the LGA in a direction perpendicular to an external and flat first surface of the sample into or onto the sample so that light transmitted into the sample by the sample impinges on an internal facet of the sample symmetrically perpendicular to the internal facet.

[0056] - an illumination and collection arrangement (ICA), said ICA comprising:

[0057] A light generating assembly configured to (a) project a first incident light beam (LB) onto a first surface to generate a first return LB by reflection from the first surface, and (b) project a second incident LB onto an LGA parallel to the first incident LB to generate a second return LB by redirecting the second incident LB into or onto a sample by the LGA, reflecting the second LB from an internal facet, and redirecting it in reverse by the LGA.

[0058] • At least one sensor configured to measure a first angular deviation of the second return LB relative to the first return LB, and / or an eyepiece assembly configured to enable manual measurement of the first angular deviation.

[0059] The measured first angular deviation indicates an actual inclination angle of the inner facet relative to the first surface.

[0060] According to some embodiments of the system, the light generating assembly includes a light source and an optical device.

[0061] According to some embodiments of the system, the at least one sensor includes one or more light sensors and / or one or more image sensors (eg, one or more cameras).

[0062] According to some embodiments of the system, the sample includes a first portion and a second portion, and the internal facet extends between the first portion and the second portion. The first portion is located between the external second surface of the sample and the internal facet. The LGA is configured to redirect the second incident LB into or onto the first portion via the second surface.

[0063] According to some embodiments of the system, the LGA includes a light folding component (LFC) that is nominally configured to fold light at a light folding angle equal to the nominal tilt angle at least when the light is projected onto the light folding component in a direction perpendicular to the first surface.

[0064] According to some embodiments of the system, the LFC is or includes a prism, one or more mirrors and / or a diffraction grating.

[0065] According to some embodiments of the system, the light folding angle of the LFC is insensitive to pitch changes of the LFC.

[0066] According to some embodiments of the system, the LFC is or includes a pentaprism or similar functional prism, or a pair of mirrors or similar functional mirror arrangements arranged at an angle relative to each other.

[0067] According to some embodiments of the system, the LGA further comprises a coupling infrastructure configured to direct light folded by the LFC onto or into the sample such that light transmitted by the sample into the sample strikes the internal facet quasi-normally.

[0068] According to some embodiments of the system, the coupling infrastructure includes a coupling prism (CP) including an external flat CP first surface, an external flat CP second surface nominally tilted at a nominal tilt angle relative to the CP first surface, and an external CP third surface (which may be flat or uneven) opposite the CP second surface. The CP has a refractive index that is the same as or close to the refractive index of the first portion of the sample (e.g., within 0.001%, 0.01%, or even 0.1%, each possibility corresponding to a separate embodiment). The CP is arranged so that the CP first surface is parallel to the first surface of the sample, and is also oriented so that the light folded by the LFC is nominally normal to the CP second surface.

[0069] According to some embodiments of the system, the coupling infrastructure further comprises a shape-compliant interface. The shape-compliant interface is arranged between the CP third surface and the sample such that the CP first surface is parallel to the first surface of the sample. The shape-compliant interface has a refractive index that is the same as the refractive index of the first portion of the sample or a refractive index that is close to the refractive index of the first portion of the sample (e.g., within 0.001%, 0.01%, or even 0.1%, each possibility corresponding to a separate embodiment).

[0070] According to some embodiments of the system, the shape compliant interface is or includes a liquid and / or a gel.

[0071] According to some embodiments of the system, the sample can be a prism, a waveguide, or a beam splitter.

[0072] According to some embodiments of the system, wherein the LGA comprises at least one sensor, the system further comprises a calculation module configured to calculate an actual tilt angle based on at least the measured first angular deviation.

[0073] According to some embodiments of the system, the calculation module is further configured to calculate an uncertainty in the calculated value of the actual tilt angle taking into account at least manufacturing tolerances and defects of the LGA and the ICA.

[0074] According to some embodiments of the system, including a CP, the system also includes an oriented base structure, which is configured to orient the sample so that a first incident LB is normally incident on the first surface, and / or a folded LB obtained by folding the second incident LB by the LFC is nominally normally incident on the second surface of the CP.

[0075] According to some embodiments of the system, the system further comprises an autocollimator. The autocollimator comprises a light source, at least one sensor and a collimating lens or a collimating lens assembly.

[0076] According to some embodiments of the system, the ICA further comprises at least two shutters configured to selectively block each of the incident LBs and / or one or more spectral filters configured to at least facilitate distinguishing the returning LBs.

[0077] According to some embodiments of the system, wherein the sample comprises a first portion and a second portion, the nominal tilt angle is 90°, and the sample further comprises an outer flat third surface parallel to the first surface.

[0078] According to some embodiments of the system, the system is configured to facilitate turning the sample.

[0079] According to some embodiments of the system, at least one sensor and a computing module are included, which is configured to additionally consider a measured second angle deviation of the fourth return LB relative to the third return LB to calculate the actual tilt angle. In the case where the sample is flipped so that the first surface and the third surface are reversed, the third return LB and the fourth return LB are obtained by: (a′) projecting a third incident light beam onto the third surface of the sample to generate a third return LB by reflection from the third surface, and (b′) projecting a fourth incident LB parallel to the third incident LB onto the LFC to generate a fourth return LB by redirecting the fourth incident LB into or onto the sample by the LGA, reflecting the fourth incident LB from an internal facet, and reversely redirecting it by the LGA.

[0080] According to some embodiments of the system, the CP further comprises an outer flat CP fourth surface, the outer flat CP fourth surface being parallel to the CP first surface. The CP is mechanically flippable such that the CP first surface and the CP fourth surface can be flipped while maintaining the nominal orientation of the CP second surface relative to the sample.

[0081] According to some embodiments of the system, the measured second angular deviation is obtained when the CP is flipped such that the CP first surface and the CP fourth surface are reversed and the nominal orientation of the CP second surface relative to the sample is maintained.

[0082] According to some embodiments of the system, wherein the system comprises an orientation infrastructure, the calculation module is configured to calculate the uncertainty of the calculated value of the actual tilt angle by additionally taking into account manufacturing tolerances and imperfections of the orientation infrastructure.

[0083] According to some embodiments of the system, wherein the light generating assembly includes a light source and an optical device, the light source is configured to generate a single LB, and the optical device is configured to collimate the single LB.

[0084] According to some embodiments of the system, the first incident LB and the second incident LB are complementary parts of the collimating LB.

[0085] According to some embodiments of the system, the light source is a polychromatic light source.

[0086] According to some embodiments of the system, the light source is configured to generate a laser beam.

[0087] Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be very obvious to those skilled in the art based on the drawings, descriptions, and claims included herein. In addition, although specific advantages are listed above, various embodiments may include all, some, or none of the listed advantages.

[0088] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. In the event of a conflict, the patent specification, including definitions, controls. As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more" unless the context clearly indicates otherwise.

[0089] Unless otherwise specifically noted, as is apparent from the present disclosure, it may be understood that, according to some embodiments, terms such as “process,” “compute,” “calculate,” “determine,” “estimate,” “evaluate,” “measure,” and the like may refer to the action and / or processing of a computer or computing system or similar electronic computing device that manipulates and / or transforms data represented as physical (e.g., electronic) quantities within a computing system register and / or memory into other data similarly represented as physical quantities within a computing system memory, register, or other such information storage, transmission, or display device.

[0090] Embodiments of the present disclosure may include devices for performing the operations herein. These devices may be specially constructed for the desired purpose, or may include a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer-readable storage medium, such as, but not limited to, any type of disk, including a floppy disk, an optical disk, a CD-ROM, a magneto-optical disk, a read-only memory (ROM), a random access memory (RAM), an electrically programmable read-only memory (EPROM), an electrically erasable and programmable read-only memory (EEPROM), a magnetic card or an optical card, or any other type of medium suitable for storing electronic instructions and capable of being coupled to a computer system bus.

[0091] The processing and display proposed here are not inherently related to any specific computer or other equipment. Various general-purpose systems can be used together with the program according to the teaching of this paper, or it can be proved that it is convenient to construct more special-purpose equipment to perform the desired method. From the following description, it can be seen that the desired structure of various these systems. In addition, the embodiments of the present disclosure are not described with reference to any specific programming language. It will be understood that various programming languages ​​can be used to implement the teachings of the present disclosure as described herein.

[0092] Various aspects of the present disclosure may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Typically, program modules include routines, programs, objects, components, data structures, etc., which perform specific tasks or implement specific abstract data types. The disclosed embodiments may also be practiced in a distributed computing environment, where tasks are performed by remote processing devices linked through a communication network. In a distributed computing environment, program modules may be located in both local computer storage media and remote computer storage media, including memory storage devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Some embodiments of the present disclosure are described herein with reference to the accompanying drawings. The description together with the accompanying drawings makes it apparent to one of ordinary skill in the art how some embodiments may be practiced. The accompanying drawings are for the purpose of illustrative description and are not intended to show the structural details of the embodiments in more detail than is necessary for a basic understanding of the present disclosure. For clarity, some objects depicted in the drawings are not drawn to scale. In addition, two different objects in the same figure may be drawn to different scales. In particular, in the same figure, the scales of some objects may be greatly enlarged compared to other objects.

[0094] In the attached picture:

[0095] Figure 1A schematically depicts an optical-based system for internal facet metrology of a sample during inspection of the sample, according to some embodiments;

[0096] Figure 1B schematically depicts a light guide of a system according to some embodiments and the trajectory of a light beam within a sample;

[0097] Figure 1C Schematically depicts a Figure 1A a point on the photosensitive surface of the sensor of the system;

[0098] Figure 2 Schematically depicted is an optically based system for internal facet metrology of a sample during inspection of the sample, the system corresponding to Figure 1A a specific implementation of the system;

[0099] Figure 3 Schematically depicted is an optically based system for internal facet metrology of a sample during inspection of the sample, the system corresponding to Figure 1A a specific implementation of the system;

[0100] Figures 4A to 4D According to some embodiments, a Figure 1A Non-limiting examples of samples for which internal facet metrology is performed by a system;

[0101] Figure 5A and Figure 5B Schematically depicted is an optical-based system for verifying the perpendicularity of an internal facet of a sample relative to two parallel external planar surfaces of the sample during inspection of the sample, the system corresponding to Figure 1A a specific implementation of the system;

[0102] Figure 5C and Figure 5D Schematically depicts a Figure 5A and5B a point on the photosensitive surface of the sensor of the system;

[0103] Fig. 6A Schematically depicts an inspection of a sample comprising a pair of nominally parallel internal facets, the inspection utilizing Figure 1A The system is executed according to the specific implementation of the system;

[0104] Figure 6B Schematically depicts a method for inspecting a Fig. 6A a point of a sample on a photosensitive surface of a sensor of the system;

[0105] Figure 7 presents a flow chart of an optical-based method for internal facet metrology of a sample according to some embodiments;

[0106] Fig. 8A and Figure 8B presents a flow chart of an optically-based method for verifying the perpendicularity of an internal facet of a sample relative to two parallel external planar surfaces of the sample, according to some embodiments;

[0107] Fig. 9 schematically depicts an optical-based system for internal facet metrology of a sample during sample inspection, according to some embodiments; and

[0108] Fig.10 Schematically depicted is an optical-based system for internal facet metrology of a sample during sample inspection, according to some embodiments. DETAILED DESCRIPTION

[0109] The principles, uses and implementations of the teachings herein may be better understood with reference to the attached description and drawings. After perusing the description and drawings presented herein, those skilled in the art will be able to implement the teachings herein without undue effort or experimentation. In the accompanying drawings, the same reference numerals always represent the same components.

[0110] In the description and claims of this application, the words "including", "having" and forms thereof are not limited to the members of the list with which the words can be associated.

[0111] As used herein, the term "about" can be used to specify that the value of a quantity or parameter (e.g., the length of an element) is within a continuous range of values ​​around (and including) a given (described) value. According to some embodiments, "about" can specify that the value of a parameter is between 80% and 120% of the given value. For example, the statement "the length of the element is equal to about 1 m" is equivalent to the statement "the length of the element is between 0.8 m and 1.2 m." According to some embodiments, "about" can specify that the value of a parameter is between 90% and 110% of the given value. According to some embodiments, "about" can specify that the value of a parameter is between 95% and 105% of the given value.

[0112] As used herein, the terms "substantially" and "about" may be interchangeable according to some embodiments.

[0113] For ease of description, in some of the figures, a three-dimensional Cartesian coordinate system is introduced. Note that the orientation of the coordinate system relative to the objects depicted may vary from one figure to another. In addition, the symbol ⊙ may be used to indicate an axis pointing "out of the page", while the symbol Can be used to represent axes that point "inside the page".

[0114] In the drawings, optional elements and optional stages (in the flow diagrams) are depicted by dashed lines.

[0115] Throughout the specification, an internal planar surface of a three-dimensional element (eg, a planar boundary between two parts of a three-dimensional element or an internal planar layer of material incorporated into a three-dimensional element) is referred to as an "internal facet".

[0116] system

[0117] According to an aspect of some embodiments, an optical-based system for internal facet metrology of a sample is provided. Figure 1A Such a system, an optical-based system 100, according to some embodiments is schematically depicted. The optical-based system 100 is configured to verify the angle between an internal facet of a sample and an external flat surface of the sample. Figure 1A A cross-sectional side view of a system 100 and a sample 10 is presented according to some embodiments. (It should be understood that the sample 10 does not form part of the system 100 .) The sample 10 is shown being inspected by the system 100 .

[0118] The sample 10 includes an outer first surface 12a (i.e., a first outer surface), an outer second surface 12b (i.e., a second outer surface), and an inner facet 14. The first surface 12a is flat. The remaining outer surfaces of the sample 10 can be of any shape, such as curved, as long as their shape does not hinder the positioning and orientation of the sample 10, as described in detail below. As a non-limiting example, the second surface 12b is depicted as convex, but it should be understood that the second surface 12b can also be flat, concave, or even wavy or rough (e.g., unpolished), or include multiple non-parallel flat surfaces. According to some embodiments, Figure 1A Not shown in FIG. 1 , the sample 10 may be shaped as a polyhedron.

[0119] The sample 10 includes at least a first portion 16a and a second portion 16b. According to some embodiments, the first portion 16a and the second portion 16b share a common boundary that is flat and is constituted by an internal facet 14. In such an embodiment, the first portion 16a and the second portion 16b are characterized by different refractive indices, respectively (i.e., the refractive index of the first portion 16a is different from the refractive index of the second portion 16b). As a non-limiting example, according to some such embodiments, the sample can be an element including two glass portions, which are characterized by two different refractive indices, respectively. Alternatively, according to some embodiments, the first portion 16a and the second portion 16b can be separated by a thin and flat layer of material or a layer of several materials formed by the internal facet 14. The layer is characterized by a different refractive index than at least one of the first portion 16a and the second portion 16b (whose refractive index may be the same or different). In accordance with some such embodiments, the first portion 16a and the second portion 16b can be made of the same material, for example, in embodiments in which the sample 10 is a prism or waveguide and a flat layer (layer) of material having a refractive index different from that of the first portion 16a and / or the second portion 16b is incorporated into the sample 10 between the first portion 16a and the second portion 16b.

[0120] The sample 10 was manufactured to exhibit a (nominal) tilt angle α between the first surface 12a and the inner facet 14 (at Figure 1A However, due to manufacturing imperfections, the actual tilt angle α′ between the first surface 12a and the inner facet 14 is usually different from the nominal tilt angle α. Figure 1A A straight (first) dashed line L intersecting the inner facet 14 is shown in FIG. 1 and is tilted at a nominal tilt angle α relative to the first surface 12a. The dashed line L indicates the intended tilt of the inner facet 14. The nominal tilt angle α may be an acute angle (i.e., α < 90°), an obtuse angle (i.e., α > 90°), or equal to 90°. Figure 1BThe complementary angle of the actual tilt angle α′ is shown in , marked as β′ (ie β′=180°-α′).

[0121] The orientation of the internal facets 14 is in principle unrestricted, other than being nominally tilted at a tilt angle α relative to at least one external planar surface of the sample 10. Several different orientations of the internal facets (the internal facet (actual) tilt angles can be measured using the system 100) within samples sharing the same external geometry are described below. 4A to 4D Described in the description.

[0122] According to some embodiments, the first part 16a may be made of a transparent or translucent material, while the second part 16b may be made of a transparent material or a translucent material or even an opaque material. According to some embodiments, the first part 16a may be made of glass or crystal (or even a transparent or translucent polymer or metal), while the second part 16b may in principle be made of any material (including an opaque material). According to some embodiments, where the first part 16a and the second part 16b share a common border, the first part 16a and the second part 16b may be glued and / or fused (e.g., laser fused) to each other along their common border.

[0123] According to some embodiments, the system 100 includes a light guiding arrangement (LGA) 102 and an illumination and collection arrangement (or assembly; ICA) 104. The system 100 may also include a controller 108, which is functionally associated with the ICA 104 and is configured to control its operation. According to some embodiments, and as Figure 1A As shown, ICA 104 includes a light source 112 (or multiple light sources) and a sensor 114 (or multiple sensors). Figure 1A In an alternative embodiment depicted in FIG, ICA 104 includes an eyepiece assembly in place of sensor 114, thereby being configured for visual determination (ie, by eye) of the actual tilt angle.

[0124] As described in detail below, the ICA 104 is configured to output at least two parallel light beams (LB), including a first LB 105a (also referred to as a "first incident LB"; Figure 1A ) and a second LB 105b (also referred to as a "second incident LB"; Figure 1A indicated by a pair of parallel rays).

[0125] According to some embodiments, the optical device 118 may be configured to collimate the light generated by the light source 112, and thereby generate (parallel) incident LB 105a and 105b. According to some such embodiments, the optical device 118 may include a collimating lens or a collimating lens assembly (not shown). According to some embodiments, the incident LB 105a and the incident LB 105b may form complementary parts of a collimated light beam (which has been focused by the collimating lens or the collimating lens assembly). Alternatively, according to some embodiments, the incident LB 105a and the incident LB 105b may be spaced apart (and parallel). According to some such embodiments, the optical device 118 may also include one or more optical filters (e.g., light absorbing filters or opaque plates), and / or one or more beam splitters, and optionally, one or more reflectors (not shown), which are configured to prepare a pair of spaced apart and parallel light beams from the collimated light beam.

[0126] According to some embodiments, the optical device 118 may also include a plurality of blocking elements (such as Figure 2 ), which is configured to allow selective blocking of each of the incident LB 105 or at least facilitate differentiation between a first return LB 133a caused by a first incident LB 105 and a second return LB 133b caused by a second incident LB 105b. As used herein, the term "blocking element" with respect to an optical element is broadly interpreted to include both a controllably openable and closable opaque element (such as a shutter) configured to (when closed) block a light beam incident thereon and a filtering element (such as a spectral filter) configured to completely or partially block one or more portions of a light spectrum (e.g., a visible light spectrum).

[0127] According to some embodiments, light source 112 may be configured to generate or allow generation of polychromatic light. According to some such embodiments, the spectrum of the light may be controllable. According to some embodiments, light source 112 may be configured to generate or allow generation of monochromatic light.

[0128] According to some embodiments, ICA 104 is or includes an autocollimator (i.e., light source 112, sensor 114, and some or all of optical device 118 constitute components of an autocollimator). According to some embodiments, incident LB 105 constitutes adjacent sub-beams of a single, wide, collimated LB generated by the autocollimator. According to such embodiments, optical device 118 may include a filter configured to transmit two sub-beams (e.g., incident LB 105) of a collimated LB prepared by the autocollimator and incident on the filter (maintaining parallelism of the two sub-beams upon exiting the filter).

[0129] According to some embodiments, and as Figure 1AAs depicted in , LGA 102 includes a light folding component 122 (lightfolding component, LFC) and a coupling infrastructure 124, which can be arranged between LFC 122 and sample 10. LFC 122 is nominally configured to fold light projected on LFC 122 in a direction perpendicular to first surface 12a at a light folding angle α" equal to the nominal tilt angle α. (That is, ideally, the light folding angle α" will be equal to the nominal tilt angle). According to some embodiments, LFC 122 can be or include a prism, one or more mirrors, or a diffraction grating. According to some embodiments, LFC 122 can be a pentaprism (such as Figure 3 According to some embodiments, LFC 122 may be a pair of mirrors arranged at an angle relative to each other, or a similarly functional arrangement of mirrors (i.e., insensitive to changes in pitch).

[0130] In embodiments where the internal facet 14 is not parallel to the second surface 12b (by design), additional infrastructure may be required to allow light projected (outside the sample 10) on the second surface 12b in a direction perpendicular to the internal facet 14 to maintain its propagation direction after entering the sample 10. This may also apply to the case when the internal facet 14 and the second surface 12b are nominally parallel, because even if the second surface 12b is sufficiently smooth, the actual inclination of the second surface 12b will typically be slightly different from the nominal inclination due to manufacturing tolerances. As described below, a coupling infrastructure 124 is configured for this purpose.

[0131] According to some embodiments, and as Figure 1A , the coupling infrastructure 124 may include a coupling prism (CP) 132 and a shape-complaint interface 134. The CP 132 includes an outer flat (CP) first surface 138a, an outer flat (CP) second surface 138b, and an outer (CP) third surface 138c (which may be flat or uneven). The CP second surface 138b is nominally tilted relative to the CP first surface 138a at a nominal tilt angle α, as shown by a second dashed line L′ parallel to the first dashed line L. The CP third surface 138c may be positioned opposite the CP first surface 138a.

[0132] According to some embodiments, the shape-compliant interface 134 may be confined between the second surface 12b (of the sample 10) and the CP third surface 138c adjacent to each of the second surface 12b and the CP third surface 138c. The shape-compliant interface 134 may be a liquid, gel, or paste characterized by surface tension and / or adhesive properties to maintain its integrity and arrangement when confined in a narrow space. According to some embodiments, the shape-compliant interface 134 may be a ductile material. According to some embodiments and as Figure 1B As depicted, the refractive index of CP 132 and shape-compliant interface 134 are each equal to or close to the refractive index of sample 10 (e.g., within 0.001%, 0.01%, or even 0.1% of the refractive index of sample 10, each possibility corresponding to a separate embodiment). According to some embodiments, the values ​​of the refractive index of CP 132 and shape-compliant interface 134 are sufficiently small that the overall uncertainty in the measurement of the actual tilt angle α′ does not exceed the required measurement accuracy. Therefore, a light beam propagating through CP 132, shape-compliant interface 134, and sample 10 will maintain its propagation direction when transitioning from CP 132 to shape-compliant interface 134 and when transitioning from shape-compliant interface 134 to sample 10.

[0133] According to some embodiments, the system 100 may also include an orientation infrastructure 140 for orienting the sample 10 relative to the ICA 104. As a non-limiting example, the orientation infrastructure 140 may include an orientable (first) stage 142 (i.e., a first stage that can be oriented) configured for movement in six degrees of freedom. The stage 142 is configured for mounting a sample thereon, such as the sample 10. In particular, the orientation infrastructure 140 may be configured for orienting the sample 10 so that the first incident LB 105a will be vertically projected onto the first surface 12a. According to some embodiments, the orientation infrastructure 140 may be functionally associated with the controller 108 and configured to be controlled thereby.

[0134] According to some embodiments, the orientation infrastructure 140 may also be configured to orient the CP 132 relative to the LGA 102, the ICA 104, and the sample 10. According to some such embodiments, the orientation infrastructure 140 may include an orientable second stage 144 configured to place the CP 132 thereon and rotate the CP 132 along each of three non-parallel axes, and optionally translate the CP 132.

[0135] As used herein, the terms "nominal" and "ideally" may be interchangeable according to some embodiments. When an object is intended by design and manufacture to exhibit an intrinsic property (e.g., the tilt angle between planar surfaces of a sample), but in reality the object may only imperfectly exhibit the property due to manufacturing tolerances, the object may be said to "nominally" exhibit (i.e., be characterized as) the property. The same applies to non-intrinsic properties of an object, such as the direction of light propagation of a light beam. In this case, it should be understood that the object is intentionally prepared or otherwise manipulated to ideally exhibit the property, but, in reality, the object may only imperfectly exhibit the property due to, for example, inherent defects in the equipment used for preparation.

[0136] In operation, a first incident LB 105a is projected on sample 10 normal to first surface 12a, and a second incident LB 105b is projected on LFC 122. First incident LB 105a (or at least a portion thereof) is reflected from first surface 12a - as indicated by first return LB 133a - and sensed by sensor 114.

[0137] The second incident LB 105b is folded by the LFC 122 at a light folding angle α”, as shown by the fold LB 113b. The light folding angle α” is nominally equal to the nominal tilt angle α. However, in practice, due to manufacturing defects, the light folding angle α” of the LFC 122 may slightly deviate from the nominal tilt angle α. When the uncertainty of the light folding angle of the LFC 122 (due to manufacturing tolerances) is lower or significantly lower than the accuracy with which the actual tilt angle of the internal facet 14 is to be determined, the uncertainty of the light folding angle can be ignored (i.e., it can be assumed that the LFC 122 accurately folds the second incident LB 105b at the nominal tilt angle α). Otherwise, the uncertainty of the light folding angle may (non-negligibly) be one of the causes of the overall uncertainty of the measured value of the actual tilt angle.

[0138] In order to keep the graphics uncomplicated, generally only two rays of each beam are indicated. Furthermore, the depiction of the beams is schematic, and it should be understood that the depicted beams may be wider or narrower than what is drawn. Thus, for example, according to some embodiments, the first incident LB 105a may impinge on the entirety of the first surface 12a, and / or the second incident LB 105b may impinge on the entirety of the light receiving surface of the LFC 122.

[0139] Also refer to Figure 1B, fold LB 113B travels onto CP 132. Transmission LB 117b indicates a portion of fold LB 113b that is transmitted into CP 132 via CP second surface 138b (the portion of fold LB 113b that is reflected from CP second surface 138b is not shown and may be negligible). Transmission LB 117b propagates from CP second surface 138b through CP 132 to CP third surface 138c, then from CP third surface 138c through shape compliant interface 134 to second surface 12b of sample 10, and finally propagates through first portion 16a toward inner facet 14.

[0140] Reflection LB 121b indicates the portion of transmission LB 117b that is reflected back by the internal facet 14 toward the shape-conforming interface 134 (the portion of transmission LB 117b that is transmitted from the first portion 16a to the second portion 16b (if any) is not shown). Reflection LB 121b propagates through the first portion 16a toward the second surface 12b, then propagates from the second surface 12b through the shape-conforming interface 134 to the CP third surface 138c, and finally propagates from the CP third surface 138c through the CP 132 to the CP second surface 138b. Exit LB 125b indicates a portion of reflection LB 121b that leaves the CP 132 via the CP second surface 138b (the portion of reflection LB 121b that is reflected inwardly by the CP second surface 138b is not shown). The outgoing LB 125b propagates toward the LFC 122 and is folded by the LFC 122 at a light folding angle α″ as shown by the second return LB 133b. More precisely, the outgoing LB 125b is redirected by the LFC 122 toward the ICA 104 (as shown by the second return LB 133b). The second return LB 133b is sensed by the sensor 114.

[0141] Transmission LB 117b impinges on interior facet 14 at an angle of incidence θ. Angles are measured clockwise relative to the viewpoint of a reader reading the drawing. Angle values ​​greater than 180° are set to negative values ​​by subtracting 360°. Thus, as a non-limiting example intended to facilitate description by making it more specific, Figure 1B In the case of R More precisely, the incident angle θ is shown as spanning counterclockwise from the dashed line B (which indicates the normal to the inner facet 14) to the ray 117b1 (one of the two rays indicates the transmission LB 117b). The tilt angles α and α′ are measured clockwise from the first surface 12a (as a non-limiting example to facilitate the description, in Figure 1A, α′ is shown as being greater than α). The nominal tilt angle α spans clockwise from the first surface 12 a to the dashed line L. The actual tilt angle α′ spans clockwise from the first surface 12 a to the inner facet 14 .

[0142] The angle of incidence θ depends on each of the deviation Δα′=α-α′ (i.e., the deviation of the inclination of the internal facet 14 from the nominal inclination), the deviation Δα″=α-α″ (i.e., the deviation of the (actual) light folding angle of the LFC 122 from α), and the deviation Δα″′=α-α″′ (i.e., the deviation of the inclination of the CP second surface 138b from the nominal inclination). In the absence of any defects in the system 100 (i.e., α″′=α″=α), and in the case where the CP first surface 138a is oriented parallel to the first surface 12a, the angle of incidence θ will be equal to Δα′. In other words, the angle of incidence θ is equal to Δα′, and its accuracy depends on the uncertainties in the light folding angle α″ and the actual inclination angle α″′, as well as any other relevant uncertainties in the parameters of the LGA 102, ICA 104, and the orientation infrastructure 140 (i.e., the accuracy of their orientation). In particular, the system 100 is nominally configured so that when Δα′=0, the transmission LB 117b strikes the interior facet 14 normally (ie, perpendicularly). The normal to the interior facet 14 is at Figure 1B Indicated by the (straight) dashed line B.

[0143] Typically, due to manufacturing defects in both sample 10 and LGA 102, the second return LB 133b will not be parallel to the first return LB 133a. The angle δ (also called "angle deviation") between the first return LB 133a and the second return LB 133b depends on the deviations Δα′, Δα″ and Δα″′ and the refractive index n of the first portion 16a (which is equal to or close to the refractive index of the CP 132 and the shape-compliant interface 134). The angle δ is shown as spanning clockwise from ray 105b1 (one of the two rays indicating the second incident LB 105b) to ray 133b1 (one of the two rays indicating the second return LB 133b) and is therefore Figure 1A The middle is positive.

[0144] Using the laws of geometric optics, in particular Snell's law (and taking into account the actual light folding angle of LFC 122, the actual tilt angle of CP second surface 138b relative to CP first surface 138a, and the refractive index n), angle δ can be related to Δα′. In other words, Δα′ depends on Δα″, Δα″′, the measured value of angle δ, and the refractive index n.

[0145] Also refer to Figure 1C , Figure 1CSchematically depicts a first point 147a and a second point 147b formed on a photosensitive surface 148 of a sensor 114 by a first return LB 133a and a second return LB 133b, respectively, according to some embodiments. u1 and u2 are horizontal coordinates (i.e., measured along the x-axis) of the first point 147a and the second point 147b, respectively. (Assuming Figure 1C The coordinate system described in Figure 1A The coordinate system described in is consistent with that described in , up to a possible translation of the origin. Therefore, Figure 1C The x-axis in extends parallel to the first surface 12a from the second incident LB 105b to the first incident LB 105a). The angle δ can be directly inferred from Δu=u2-u1. As a non-limiting example, when the measurement is based on an autocollimator (i.e., in an embodiment where the ICA 104 is or includes an autocollimator), δ=Δu / f.

[0146] According to some embodiments, the controller 108 may be communicatively associated with the computing module 130. The computing module 130 may include a processor and volatile and / or non-volatile memory components. The processor may be configured to receive sensor 114 data (i.e., the values ​​of u1 and u2) from the controller 108 and calculate Δα′ based on the data. Optionally, according to some embodiments, the processor may also be configured to calculate the uncertainty of (the calculated value of) Δα′ taking into account manufacturing tolerances and calibration limitations of the LGA 102 (including the uncertainty of the actual light folding angle), the ICA 104, and the directional infrastructure 140. According to some embodiments, the computing module 130 may be included in the system 100.

[0147] According to some embodiments, the light source 112 may be configured to generate a collimated (first) laser beam. According to some such embodiments, the optical device 118 may include a beam expander (not shown) configured to increase the diameter of the laser beam so that the expanded laser beam can be simultaneously projected on both the sample 10 and the LFC 122. In such embodiments, the first incident LB 105a and the second incident LB 105b may constitute complementary parts of the laser beam. Alternatively, the optical device 118 may include a beam splitter and an optical device configured to split the laser beam into a pair of parallel (spaced apart) sub-beams: a first sub-beam and a second sub-beam, the first sub-beam and the second sub-beam constituting the first incident LB 105a and the second incident LB 105b, respectively. According to some such embodiments, the optical device 118 may be configured to recombine the return sub-beams (i.e., the first return LB 133a and the second return LB 133b) so that the sub-beams are redirected onto a single light sensor (i.e., the sensor 114 according to some embodiments thereof). Ideally, if the second beamlet (after being redirected by LFC 122 and transmitted into sample 10) strikes the internal facet 14 perpendicularly, the recombined beamlets will form a collimated (second) laser beam, and the two points formed by the recombined beamlets on the light sensor will overlap. According to some other embodiments, two light sensors may be employed such that the distance and relative orientation between the two light sensors is known. In such embodiments, each of the returning beamlets may be directed to a different light sensor from the two light sensors.

[0148] According to some alternative embodiments, ICA104 can be configured for interferometry. That is, the light source 112, some or all of the optical device 118, and the sensor 114 can constitute components of an interferometric measurement device, as described below. In such an embodiment, the light source 112 can be configured to generate a coherent plane wavefront. The optical device 118 can be configured to split the generated wavefront into two wavefronts: a first (coherent, plane) incident wavefront and a second (coherent, plane) incident wavefront, which respectively constitute the first incident LB 105a and the second incident LB 105b. In such an embodiment, the angle δ can be derived from the interference pattern formed by the first return LB 133a and the second return LB 133b. More specifically, in such an embodiment, the first return LB 133a constitutes a first return wavefront obtained by reflecting the first incident wavefront from the first surface 12a, and the second return LB 133b constitutes a second incident wavefront obtained by folding the second incident wavefront by the LFC 122, reflecting from the internal facet 14, and folding again by the LFC 122. The return wavefronts are recombined and their interference pattern is measured by the sensor 114. If the first wavefront and the second wavefront are perpendicularly incident on the corresponding surface (i.e., the first surface 12a or the internal facet 14, respectively), the recombined wavefront will form a uniform pattern on the sensor 114. If the second surface 12b deviates from the nominal tilt, the recombined wavefront will form a periodic pattern on the sensor 114. The deviation Δα′ can be derived from the periodicity of the pattern.

[0149] According to some embodiments, the system 100 may further include two shutters configured to allow selective blocking of each of the first return LB 133a and the second return LB 133b so that each return LB 133 can be sensed separately (thereby facilitating attribution of each point 147 to the return LB that caused the point).

[0150] According to some embodiments, the first surface 12a can be coated or temporarily coated with a reflective coating such that light incident on the first surface 12a is maximally reflected or reflection from it is at least increased. According to some embodiments, the CP second surface 138b can be coated with an anti-reflective coating such that external light incident on the CP second surface 138b is maximally transmitted into the CP 132, and internal light incident on the CP second surface 138b is maximally transmitted out of the CP 132. According to some embodiments, where the light source 112 is configured to generate polychromatic light, the first surface 12a can be coated with a first coating configured to reflect light in a first spectrum, and the CP second surface 138b (or LFC 122 or internal facet 14) can be coated with a second coating configured to reflect light in a second spectrum that does not overlap or does not substantially overlap with the first spectrum. In such an embodiment, selective blocking of the first return LB 133a and the second return LB 133b can be achieved using a spectral filter or a spectral filter device (optionally, in place of a shutter), wherein the spectral filter or spectral filter device is positioned so that each return LB 133 is incident thereon and is configured to allow selective blocking or at least partial blocking of light in the second spectrum and the first spectrum, respectively.

[0151] According to some alternative embodiments, a first (passive) spectral filter may be employed to filter the first incident LB 105a into the first spectrum, and a second (passive) spectral filter may be employed to filter the second incident LB 105b into the second spectrum. In such an embodiment, in order to allow each return LB 133 to be sensed individually, an additional spectral filter may be employed, which is located between the spectral filter and the sensor 114 and is configured to allow selective filtering of light in the first spectrum or the second spectrum passing therethrough.

[0152] Note that a spectral filter or spectral filter arrangement may be used to reduce the signal associated with stray light reaching sensor 114 associated with any of the incident LBs 105 .

[0153] Although in Figure 1A , the internal facet 14 is shown as sectioning (i.e., dividing into two parts) the sample 10, and in particular extending to the first surface 12a, but it should be understood that the scope of the present disclosure is not limited to the measurement of samples formed in this way: any sample including an external flat surface and an internal facet may also undergo internal facet measurement using system 100 as described above, wherein the internal facet is inclined relative to the external flat surface but does not extend to the external flat surface.

[0154] Figure 2Schematically depicts an optical-based system 200 for verifying the angle between an internal facet of a sample and an external flat surface of the sample according to some embodiments. System 200 corresponds to a specific embodiment of system 100. More specifically, Figure 2 A side view of a system 200 and a sample 10 inspected by the system 200 is provided according to some embodiments. The system 200 includes an LGA 202 and an ICA 204, which correspond to specific embodiments of the LGA 102 and the ICA 104. According to some embodiments, and as Figure 2 , system 200 may also include an orientation infrastructure 240, a controller 208, and an optional computing module 230. Orientation infrastructure 240, controller 208, and computing module 230 may correspond to specific implementations of orientation infrastructure 140, controller 108, and computing module 130, respectively. Orientation infrastructure 240 may include a first station 242 and a second station 244, which may correspond to specific implementations of first station 142 and second station 144, respectively.

[0155] According to some embodiments, ICA204 includes an autocollimator 250. The autocollimator 250 can be configured to generate a collimated wide LB 201 in a direction perpendicular to the first surface 12a of the sample 10. The first incident LB 205a and the second incident LB 205b constitute the first sub-beam and the second sub-beam of LB 201, respectively. The first incident LB 205a and the second incident LB 205b correspond to specific embodiments of the first incident LB 105a and the second incident LB 105b, respectively. A folding LB 213b and an exit LB 225b are also indicated, and the folding LB 213b and the exit LB 225b correspond to specific embodiments of the folding LB 113b and the exit LB 125b, respectively.

[0156] LGA 202 includes LFC 222 and coupling infrastructure 224, which correspond to specific implementations of LFC 122 and coupling infrastructure 124, respectively. According to some implementations, and as Figure 2 As depicted, the coupling infrastructure 224 includes a CP 232 and a shape compliant interface 234, which correspond to specific implementations of the CP 132 and the shape compliant interface 134, respectively. The CP 232 includes a CP first surface 238a, a CP second surface 238b, and a CP third surface 238c, which correspond to specific implementations of the CP first surface 138a, the CP second surface 138b, and the CP third surface 238c of the CP 132, respectively.

[0157] The additional incident LB 205s can be used to orient the CP second surface 238b parallel to the internal facet 14 (nominal). More specifically, the additional incident LB 205s can be used to ensure the parallelism of the CP first surface 238a of the CP 232 and the first surface 12a of the sample 10 (on which the first incident LB 205a is incident normally), because when the CP first surface 238a is oriented parallel to the first surface 12a, the additional incident LB 205s will be incident normally on the CP first surface 238a. Therefore, by measuring the angular deviation of the additional return LB 233s (obtained by reflection of the additional incident LB 205s from the CP first surface 238a) relative to the first return LB 233a, the orientation of the CP first surface 238a can be adjusted (by rotating the second stage 244 and / or the first stage 242) until its parallelism relative to the first surface 12a is obtained. In the case where the CP first surface 238a is arranged parallel to the first surface 12a, the (nominal) parallelism of the CP second surface 238b and the internal facet 14 can be achieved by rotating the CP 232 about an axis parallel to the z-axis.

[0158] According to some embodiments, and as Figure 2 As depicted, the optical device of ICA204 may include a pair of blocking elements 256a and 256b, thereby allowing each of the first incident LB 205a and the second incident LB 205b to be selectively blocked, or at least facilitating the differentiation between the first return LB 233a and the second return LB 233b. According to some such embodiments, and wherein the ICA204 is also configured to generate an additional incident LB 205s, the optical device may also include a third blocking element 256s, which is configured to allow the additional incident LB 205s to be selectively blocked or at least facilitate the differentiation between the additional return LB 233s and the first return LB 233a and the second return LB 233b.

[0159] According to some embodiments, each of blocking elements 256a and 256b, and blocking element 256s (when included), may be a shutter.

[0160] According to some embodiments, the first surface 12a may be coated or temporarily coated with a reflective coating so that light incident on the first surface 12a is maximally reflected or the reflection therefrom is at least increased. According to some embodiments, the CP second surface 238b may be coated with an anti-reflective coating so that light incident on the CP second surface 238b is maximally transmitted into the CP 232 or the transmission thereto is at least increased. According to some embodiments, the CP first surface 238a may be coated with a reflective coating so that light incident on the CP first surface 238a is maximally reflected or the reflection therefrom is at least increased.

[0161] According to some embodiments (wherein the autocollimator 250 is configured to produce polychromatic light), the first surface 12a can be coated with a first coating configured to reflect light in a first spectrum, and the CP second surface 238b can be coated with a coating configured to transmit light in a second spectrum different from the first spectrum into the CP 232 to facilitate distinguishing the first return LB 233a from the second return LB 233b, and / or the internal facet 14 can be configured to reflect light in the second spectrum (and at least partially transmit light in the first spectrum). According to some such embodiments, a spectral filter or spectral filter device (e.g., included in the autocollimator 250) configured to allow controllable filtering of light in the first spectrum or the second spectrum passing therethrough can be employed to facilitate separate sensing of each return LB 233.

[0162] According to some embodiments, where the ICA 204 is also configured to generate additional incident LB205s, the CP first surface 238a can be coated with a third coating configured to reflect light in a third spectrum that is different from each of the first spectrum and the second spectrum, so as to distinguish the additional return LB 233s from each of the first return LB 233a and the second return LB 233b. In such an embodiment, the spectral filter or spectral filter device (e.g., included in the autocollimator 250) can also be configured to allow controllable filtering of light in the third spectrum passing therethrough.

[0163] According to some embodiments, the blocking elements 256a and 256b may be (passive) spectral filters (specific examples are dichroic filters) configured to filter light passing therethrough in the first spectrum and the second spectrum, respectively. In such embodiments, in order to allow each return LB 233 to be sensed separately, an additional spectral filter may be employed, which is located between the blocking element 256 and the autocollimator 250 or included in the autocollimator 250 and is configured to allow selective filtering of light passing therethrough in the first spectrum or the second spectrum.

[0164] Figure 3 Schematically depicts an optical-based system 300 for verifying the angle between an internal facet of a sample and an external flat surface of the sample according to some embodiments. System 300 corresponds to a specific embodiment of system 100, wherein the LFC is or includes a prism. More specifically, Figure 3A side view of a system 300 and a sample 10 inspected by the system 300 is provided. The system 300 includes an LGA 302 and an ICA 304 (components of which are not shown), which correspond to specific implementations of the LGA 102 and the ICA 104. According to some implementations, and as Figure 3 As depicted in , system 300 may also include controller 308, orientation infrastructure 340, and optionally computing module 330. Orientation infrastructure 340, controller 308, and computing module 330 correspond to specific implementations of orientation infrastructure 140, controller 108, and computing module 130, respectively.

[0165] LGA 302 includes prism 322 and coupling infrastructure 324, which includes CP 332 and form compliant interface 334. Prism 322 corresponds to a specific implementation of LFC 122. CP 332 and form compliant interface 334 correspond to a specific implementation of CP 332 and form compliant interface 134.

[0166] According to some embodiments, prism 322 may be insensitive to pitch changes (i.e., rotation about the y-axis) at least over a continuous range of pitch angles. According to some such embodiments, and as Figure 3 As depicted in FIG. 1 , prism 322 may be a pentaprism or a similarly functional prism, such as a prism including an even number of internal reflective surfaces. Figure 3 In some alternative embodiments not shown, in place of the prism 322, the LGA 302 may include two mirrors that are nominally disposed relative to each other at the same angle as the two surfaces of the prism 322 (the pentaprism first surface 328a and the pentaprism second surface 328b) at which the two surfaces of the prism 322 internally reflect the transmitted portion of the second incident LB 305b.

[0167] Figure 3 The first incident LB 305a, the first return LB 333a, the second incident LB 305b, the folding LB 313b, the transmission LB 317b, the reflection LB 321b, the output LB 325b and the second return LB 333b are shown in the figure. The first incident LB 305a, the first return LB 333a, the second incident LB 305b, the folding LB 313b, the transmission LB 317b, the reflection LB 321b, the output LB 325b and the second return LB 333b correspond to the specific implementation methods of the first incident LB 105a, the first return LB 333a, the second incident LB 105b, the folding LB 113b, the transmission LB 117b, the reflection LB 121b, the output LB 125b and the second return LB 133b respectively. Figure 3Also shown are the trajectories of the second incident LB 305b and the outgoing LB 325b in the prism 322 after entering the prism 322. The penetrating portions of the second incident LB 305b are numbered 309b1, 309b2, and 309b3 after being transmitted into the prism 322, after being reflected therein, and after being reflected twice therein, respectively. The penetrating portions of the outgoing LB 325b are numbered 329b1, 329b2, and 329b3 after being refracted into the prism 322, after being reflected therein, and after being reflected twice therein, respectively.

[0168] Figures 4A to 4D An example of an orientation of an internal facet within a sample according to some embodiments is presented. The sample depicted is non-limiting and is intended to illustrate by way of a specific example that the capabilities of the system 100 are not limited in principle as long as the sample includes: (i) an external (first) surface that is flat; (ii) an internal facet disposed at an angle relative to the first surface; and (iii) a first portion located between an external second surface of the sample and the internal facet that is characterized by a uniform refractive index and provides a continuous straight path for a light beam transmitted into the sample via the second surface so as to impinge normally on the internal facet.

[0169] Reference Figure 4A , according to some embodiments, a sample 40 is depicted. Sample 40 includes an outer planar first surface 42a, an outer second surface 42b, and an inner facet 44. Second surface 42b is positioned opposite inner facet 44. A first portion 46a of sample 40 is characterized by a uniform refractive index and is partially bounded by second surface 42b and inner facet 44. Inner facet 44 is nominally inclined 90° relative to first surface 42a. According to some embodiments, and as Figure 4A As depicted, second surface 42b may be flat, nominally oriented parallel to interior facet 44. Sample 40 also includes an exterior third surface 42c positioned opposite first surface 42a.

[0170] Also shown is a CP432 of a system for measuring the internal facets of a sample (only CP432 of the system is shown), which corresponds to a specific embodiment of system 100. In particular, CP 432 corresponds to a specific embodiment of CP 132. CP 432 includes an external and flat CP first surface 438a, an external and flat CP second surface 438b, and an external CP third surface (not numbered). The CP second surface 438b is nominally inclined relative to the CP first surface 438a at a nominal tilt angle. CP432 is oriented so that the CP first surface 438a is parallel to the first surface 42a, and the CP second surface 438b is nominally parallel to the internal facet 44. A shape-compliant interface (not shown) can be arranged between the CP third surface and the second surface 42b.

[0171] When sample 40 is subjected to inspection, incident LB is folded by LFC in accordance with the teachings disclosed herein so as to incident nominally normally on CP second surface 438b, as described in the description of system 100.

[0172] According to some embodiments, wherein Figure 4A As depicted, the third surface 42c is flat and parallel to the first surface 42a, and the uncertainty of the parallelism of the third surface 42c and the first surface 42a is less than the required measurement accuracy of the tilt angle, Figure 5A and 5B The depicted system can be used to measure the (actual) tilt angle.

[0173] Reference Figure 4B , according to some embodiments, a sample 40′ is depicted. Sample 40′ includes an outer flat first surface 42a′, an outer second surface 42b′, and an inner facet 44′. A first portion 46a′ of sample 40′ characterized by a uniform refractive index is partially bounded by the second surface 42b′ and the inner facet 44′. Sample 40′ has the same outer geometry as sample 40, but differs therefrom in the inclination angle of the inner facet 44′ (relative to the first surface 42a′), which is an obtuse angle. More specifically, the inclination of the inner facet 44′ differs from the inclination of the inner facet 44 by rotating about an axis parallel to the y-axis.

[0174] Also shown is a CP 432′ of a system for measuring internal facets of a sample (of which only CP 432′ is shown), which corresponds to a specific embodiment of system 100. In particular, CP 432′ corresponds to a specific embodiment of CP 132. CP 432′ includes an external and flat CP first surface 438a′, an external and flat CP second surface 438b′, and an external CP third surface (not numbered). The CP second surface 438b′ is nominally inclined relative to the CP first surface 438a′ at a nominal inclination angle. CP 432′ is oriented so that the CP first surface 438a′ is parallel to the first surface 42a′, and the CP second surface 438b′ is nominally parallel to the internal facet 44′. A shape-compliant interface (not shown) can be arranged between the CP third surface and the second surface 42b′.

[0175] When sample 40 ′ undergoes inspection, incident LB is folded by LFC in accordance with the teachings disclosed herein so as to impinge nominally normally on CP second surface 438 b ′, as described in the description of system 100 .

[0176] Reference Figure 4C, according to some embodiments, a sample 40" is depicted. The sample 40" includes an outer flat first surface 42a", an outer second surface 42b", an outer third surface 42c", an outer fourth surface 42d", and an inner facet 44" nominally inclined at 90° relative to the first surface 42a. A first portion 46a" of the sample 40" characterized by a uniform refractive index is partially bounded by the second surface 42b" and the inner facet 44". The third surface 42c" is positioned opposite the first surface 42a". The fourth surface 42d" extends between the first surface 42a and the second surface 42b, and shares an edge with the second surface 42b". According to some embodiments and as Figure 4C As depicted, fourth surface 42d" is flat. Sample 40" has the same external geometry as sample 40, but differs therefrom in the orientation of internal facets 44". More specifically, the orientation of internal facets 44" differs from the orientation of internal facets 44 by being rotated about an axis parallel to the z-axis.

[0177] Also shown is a system CP 432" (of which only CP 432" is shown) for measuring internal facets of a sample, the system corresponding to a specific embodiment of system 100. In particular, CP 432" corresponds to a specific embodiment of CP 132. CP432" includes an external and flat CP first surface 438a", an external and flat CP second surface 438b", and an external CP third surface (unnumbered). The CP second surface 438b" is nominally inclined at a nominal inclination angle relative to the CP first surface 438a". CP 432" is oriented so that the CP first surface 438a" is parallel to the first surface 42a", and the CP second surface 438b" is nominally parallel to the internal facet 44". A shape-compliant interface (not shown) can be arranged between the CP third surface and the second surface 42b".

[0178] When sample 40 ″ undergoes inspection, in accordance with the teachings disclosed herein, incident LB is folded by LFC so as to impinge nominally normally on CP second surface 438 b ″, as described in the description of system 100 .

[0179] According to some embodiments, wherein Figure 4C As depicted, the third surface 42C" is flat and parallel to the first surface 42a, and the uncertainty of the parallelism of the third surface 42C" and the first surface 42A" is less than the required measurement accuracy of the tilt angle, Figure 5A and Figure 5B The depicted system can be used to measure the (actual) tilt angle.

[0180] Reference Figure 4D, according to some embodiments, a sample 40'' is depicted. The sample 40'' includes an outer flat first surface 42a'', an outer second surface 42b'', and an inner facet 44''. A first portion 46a'' of the sample 40w'' characterized by a uniform refractive index is partially bounded by the second surface 42b'' and the inner facet 44''. The sample 40w'' has the same outer geometry as the sample 40, but differs therefrom in the tilt angle γ (relative to the first surface 42a''), which is an obtuse angle, and in the orientation relative to the second surface 42b''. More specifically, the tilt of the inner facet 44'' is determined by rotating the inner facet 44'' around an axis parallel to the axis s (at Figure 4C 4. The first axis s of the rotation of the inner facet 44 is different from the inclination of the inner facet 44, and the axis s is located approximately midway between the positive y-axis and the positive z-axis in the yz plane.

[0181] The top edge 48a''' of the inner facet 44''' extends along the first surface 42a'''. Also indicated are: (i) a straight and imaginary first line T1, which extends along the inner facet 44''' and is perpendicular to the top edge 48a''', (ii) a second straight and imaginary second line T2, which is perpendicular to the first surface 42a''' and intersects the first line T1 at the top edge 48a''', and (iii) a straight and imaginary third line T3, which extends parallel to the first surface 42''' from the first line T1 to the second line T2 (and is therefore perpendicular to the second line T2). Finally, the tilt angle γ is indicated.

[0182] Also shown is a CP 432'" of a system for measuring internal facets of a sample (of which only CP 432'" is shown), which corresponds to a specific embodiment of system 100. In particular, CP 432'" corresponds to a specific embodiment of CP 132. CP 432'" includes an external and flat CP first surface 438a'"', an external and flat CP second surface 438b'"', and an external CP third surface (unnumbered). The CP second surface 438b'"' is nominally inclined relative to the CP first surface 438a'"' at a nominal inclination angle. CP 432'" is oriented such that the CP first surface 438a'"' is parallel to the first surface 42a'"', and the CP second surface 438b'"' is nominally parallel to the internal facet 44'"'. A shape-compliant interface (not shown) may be arranged between the CP third surface and the second surface 42b'"'

[0183] When sample 40 ′″ undergoes inspection, incident LB is folded by LFC in accordance with the teachings disclosed herein so as to impinge nominally normally on CP second surface 438 b ′″, as described in the description of system 100 .

[0184] Figure 5A and Figure 5BSchematically depicts an optical-based system 500 for verifying the perpendicularity of an internal facet of a sample relative to at least two other external and flat surfaces of the sample, the at least two other external and flat surfaces being parallel to each other, according to some embodiments. System 500 corresponds to a specific embodiment of system 100. More specifically, Figure 5A and Figure 5B Each of presents a corresponding cross-sectional side view of a system 500 and a sample 50 being inspected by the system 500 according to some embodiments.

[0185] The sample 50 includes an outer and flat first surface 52a, an outer second surface 52b, an outer and flat third surface 52c, and an inner facet 54. Similar to the inner facet 14 (which constitutes a boundary between the first portion 16a and the second portion 16b of the sample 10, or forms a thin flat layer disposed between the first portion 16a and the second portion 16b of the sample 10), the inner facet 54 constitutes a boundary between the first portion 56a and the second portion 56b of the sample 50, or forms a thin flat layer 25 disposed between the first portion 56a and the second portion 56b of the sample 50. The first surface 52a and the third surface 52c are designed to be parallel. In addition, the sample 50 is manufactured to present a (nominal) inclination angle of 90° of the inner facet 54 relative to the first surface 52a (and the third surface 52c). However, due to manufacturing defects, the actual inclination angle of the inner facet 52b relative to the first surface 52a is 90°. Figure 5A and Figure 5B This angle is marked as χ′ and will usually be different from 90°.

[0186] Note that, using prior art manufacturing techniques, the (manufacturing) tolerance of the actual angle between the outer flat surfaces manufactured to be parallel is significantly smaller than the tolerance of the actual angle between the inner facet and the outer flat surface. Therefore, due to being manufactured to be parallel, the deviation from the parallelism of the first surface 52a and the third surface 52c is expected to be negligible compared to the deviation of the actual tilt angle χ' from 90°. Therefore, the actual angle ψ' (also called the "actual supplementary angle") between the inner facet 54 and the first surface 52a can be taken to be equal to 180°-χ', that is, to be supplementary to the actual tilt angle χ'. (The nominal value of the actual supplementary angle ψ' is 90°).

[0187] System 500 includes LGA 502 and ICA 504. LGA 502 corresponds to a specific implementation of LGA 102, and includes LFC 522 and coupling infrastructure 524, which correspond to specific implementations of LFC 122 and coupling infrastructure 124, respectively. LFC 522 is nominally configured to fold light incident thereon by 90° in a direction perpendicular to the nominal tilt of internal facet 54. According to some embodiments, LFC 522 can be a prism, one or more mirrors, or a diffraction grating. According to some embodiments, LFC 522 can be a pentaprism or a similarly functional prism (i.e., insensitive to changes in pitch) that is configured to fold light incident thereon by 90°. According to some embodiments, LFC 522 can be a pair of mirrors set at an angle, or a similarly functional device of mirrors (i.e., insensitive to changes in pitch) that is configured to fold light incident thereon by 90°.

[0188] According to some embodiments, and as Figure 5A and Figure 5B As depicted, coupling infrastructure 524 may include CP 532 and shape compliant interface 534, CP 532 and shape compliant interface 534 corresponding to specific embodiments of CP 132 and shape compliant interface 134, respectively. CP 532 includes CP first surface 538a, CP second surface 538b, CP third surface 538c, CP first surface 538a, CP second surface 538b, CP third surface 538c corresponding to specific embodiments of CP first surface 138a, CP second surface 138b, and CP third surface 138c, respectively. CP second surface 538b is nominally perpendicular to CP first surface 538a. CP 532 also includes CP fourth surface 538d, CP fourth surface 538d is positioned opposite to CP first surface 538a. According to some embodiments, and as Figure 5A and Figure 5B As depicted, the CP fourth surface 538d can be parallel to the CP first surface 538a.

[0189] According to some embodiments, system 500 may further include an orientation infrastructure 540, which corresponds to a specific embodiment of orientation infrastructure 140. Orientation infrastructure 540 includes an orientable first stage 542 and an orientable second stage 544, which are configured to place sample 50 and CP 532 thereon and orient sample 50 and CP 532, respectively, substantially as described with respect to first stage 142 and second stage 144 in the description of system 100.

[0190] According to some embodiments, and as Figure 5A and Figure 5BAs depicted, system 500 may also include controller 508 and optionally computing module 530 , which may correspond to specific implementations of controller 108 and computing module 130 , respectively.

[0191] ICA 504 corresponds to a specific implementation of ICA 104 and includes a light source 512, a sensor 514, and optionally an optical device 518, which correspond to specific implementations of light source 112, sensor 114, and optical device 118, respectively. According to some implementations, light source 512, sensor 514, and some or all of optical device 518 may constitute components of an autocollimator, which may be similar to autocollimator 250. According to some implementations, optical device 518 may include a blocking element (not shown), which may be similar to blocking element 256.

[0192] The ICA 504 is configured to output a first incident LB 505a directed to the sample 50 and a second incident LB 505b directed to the LFC 522. The ICA 204 and the sample 50 are positioned and oriented so that the first incident LB 505a is incident on the first surface 52a perpendicular to the first surface 52a. In operation, the first incident LB 505a (or at least a portion thereof) is reflected from the first surface 52a, as shown by the first return LB 533a. The first return LB 533a is sensed by the sensor 514.

[0193] LFC 522 is configured to nominally fold the second incident LB 505b by 90°. More specifically, LFC 522 is configured and oriented to fold the second incident LB 505b so that the (first) folded LB 513b (obtained by folding the second incident LB 505b) is nominally oriented at 90° relative to the second incident LB 505b and is (nominal) perpendicular to the CP second surface 538b. In practice, due to manufacturing imperfections (and alignment inaccuracies in embodiments in which LFC 522 is sensitive to pitch variations), the actual light folding angle χ" of LFC 522 may deviate slightly from 90°. As described in detail below, the effects of manufacturing imperfections of LFC 522 can be offset or substantially offset by flipping sample 50 so as to invert first surface 52a and third surface 52c, and by flipping CP 532 so as to invert CP first surface 538a and CP fourth surface 538d, and then repeating the measurements described in the next two paragraphs.

[0194] In operation, fold LB 513b or at least a portion thereof is transmitted into CP 532 via CP second surface 538b, as shown by (first) transmission LB 517b. Transmission LB 517b propagates through CP 532, through shape-conforming interface 534 and first portion 56a, and strikes interior facet 54 at a (first) incident angle η1, substantially as described above with respect to Figure 1B As described in the description of transmission LB117b. The incident angle η1 depends on each of the deviation Δχ′=90°-χ′ (i.e., the deviation of the inclination of the internal facet 54 relative to the first surface 52a from 90°), the deviation Δχ″=90°-χ″ (i.e., the deviation of the (actual) light folding angle of the LFC 522 from 90°), and the deviation Δχ″′=90°-χ″′ (i.e., the deviation of the inclination of the CP second surface 538b relative to the CP first surface 538a from 90°). In particular, the system 500 is nominally configured so that when Δχ′=0, the transmission LB 517b is incident normally on the internal facet 54. Figure 5A , the normal to the inner facet 54 is represented by the (straight) dashed line C1.

[0195] The transmitted LB 517b (or at least a portion thereof) is specularly reflected from the internal facet 54 (i.e., reflected at a return angle ζ1 that is equal to the negative first incident angle η1), as shown by the (first) reflected LB 521b. The reflected LB 521b propagates back toward the LFC 522 via the first portion 56a, the shape-conforming interface 534, and the CP 532. The (first) exit LB 525b indicates the (first) portion of the reflected LB 521b that is refracted outside the CP 532 via the CP second surface 538b (unless exactly perpendicularly incident on the CP second surface 538, in which case the first portion will maintain its propagation direction; the second portion of the reflected LB 521b that is specularly reflected inside the CP 532 by the CP second surface 538b is not shown). The exit LB 525b is folded by the LFC 522 at a light folding angle χ″, as shown by the second return LB 533b. The second return LB 533b is sensed by the sensor 514.

[0196] The angle δ1 between the second return LB 533b and the first return LB 533a - also called the "first angular deviation" - depends on the deviations Δχ′, Δχ″ and Δχ″′ and the refractive index n′ of the first portion 56a (which is equal to or close to the refractive index of CP 532 and the shape-conforming interface 534). Figure 5CSchematically depicts a first point 547a and a second point 547b formed on a photosensitive surface 548 of a sensor 514 by a first return LB 533a and a second return LB 533b, respectively, according to some embodiments. w1 and w2 are the horizontal coordinates (i.e., as measured along the x-axis) of the first point 547a and the second point 547b, respectively. Angle δ1 can be directly inferred from the difference Δw=w2-w1.

[0197] Reference Figure 5B ,and Figure 5A In comparison, sample 50 has been flipped so that first surface 52a and third surface 52c are inverted (while maintaining the nominal orientation of internal facet 54 relative to LGA 502), and CP 532 has been flipped so that CP first surface 538a and CP fourth surface 538d are inverted (while maintaining the nominal orientation of CP second surface 538b relative to sample 50).

[0198] In operation, the third incident LB 505a' is directed perpendicularly to the sample 50, and the fourth incident LB 505b' is directed toward the LFC 522. The third incident LB 505a' (or at least a portion thereof) is reflected from the third surface 52c - as shown by the third return LB 533a'. The third return LB 533a' is sensed by the sensor 514.

[0199] The fourth incident LB 505b' impinges on the LFC 522, resulting in a second fold LB 513b', which in turn impinges on the CP second surface 538b, resulting in a second transmission LB 517b', which propagates through the CP 532, through the shape-conforming interface 534, and into the first portion 56a of the sample 50. The second transmission LB 517b' impinges on the internal facet 54 at a second incident angle η2. The second incident angle η2 depends on each of the deviation Δψ'=90°-ψ' (i.e., the deviation of the inclination of the internal facet 54 relative to the third surface 52c from 90°), the deviation Δχ"=90°-χ" and the deviation Δχ"'=90°-χ"' (implicitly assuming that the uncertainty in the parallelism of the CP first surface 538a and the CP fourth surface 538d is less than the required measurement accuracy of the actual inclination angle χ'). The normal of the internal facet 54 is at Figure 5B Indicated by the (straight) dashed line C2.

[0200] The second transmission LB 517b′ is (at least partially) specularly reflected from the internal facet 54 (i.e., reflected at a return angle ζ2 equal to the negative second incident angle η2), as shown by the second reflection LB 521b′. The second reflection LB 521b′ propagates back toward the LFC522 via the first portion 56a, the shape-conforming interface 534 and the CP 532. The second exit LB 525b′ indicates a portion of the second reflection LB521b′ that leaves the CP 532 via the CP second surface 538b (the portion of the second reflection LB 521b′ that is reflected internally by the CP second surface 538b is not shown). The second exit LB 525b′ is folded by the LFC 522 at a light folding angle χ″, as shown by the fourth return LB 533b′. The fourth return LB 533b′ is sensed by the sensor 514.

[0201] The angle δ2 between the fourth return LB 533b′ and the third return LB 533a′ - also called the "second angle deviation" - depends on the deviations Δχ′, Δχ″ and Δχ″′ and the refractive index n′. More specifically, as the correlation shown by the angle δ1 on the deviations Δχ′, Δχ″ and Δχ″′ and the refractive index n′, the angle δ2 shows the same correlation on Δχ′=180°-Δχ′, Δχ″, Δψ″′=180°-Δχ″′ and the refractive index n′. Figure 5D Schematically depicting the third point 547a' and the fourth point 547b' formed by the third return LB 533a' and the fourth return LB 533b' on the photosensitive surface 548 according to an embodiment. w1' and w2' are the horizontal coordinates of the third point 547a' and the fourth point 547b', respectively. The angle δ2 can be directly inferred from the difference Δw'=w2'-w1'.

[0202] Although in Figure 5C and Figure 5D In the figure, both Δw and Δw′ are shown as negative (so that both δ1 and δ2 are negative), but it should be understood that in general Δw and Δw′ can have opposite signs (so that δ1 and δ2 will have opposite signs), or both can be positive (so that both δ1 and δ2 are positive).

[0203] Each measured angle δ1 and δ2 can be used to provide a corresponding estimate of the offset angle Δχ'. In the absence of any defects in the system 500, η2 will be equal to -η1, and δ1 will be equal to -δ2. However, in practice, these two estimates are usually different because the actual light folding angle deviates from 90° and the actual tilt angle of the CP second surface 538b deviates from 90°. Because δ1 and δ2 have the same (when LFC is insensitive to pitch changes) or substantially the same correlation with the deviation Δχ″ (i.e., both δ1 and δ2 increase with increasing χ″ and decrease with decreasing χ″), by averaging the two estimates of the deviation angle Δχ′, the deviation of the (actual) light folding angle from 90° can be offset or substantially offset. By representing such an averaged estimate of the actual inclination of the internal facet 54 by <χ′>, and representing the averaged estimate of the deviation of the actual inclination angle from 90° by <Δχ′> (i.e., <χ′>=90°-<Δχ′>), <χ′> can be shown to be equal to 90°+(δ1-δ2) / (4n′)+Δχ″′·(n′-1) / n′. More generally, <χ′> can be between 90°+0.95·[(δ1-δ2) / (4n)+Δχ″′·(n-1) / n)] and 90°+1.05·[( δ1-δ2) / (4n)+Δχ″′·(n-1) / n)], between 90°+0.9·[(δ1-δ2) / (4n)+Δχ″′·(n-1) / n)] and 90°+1.1·[(δ1-δ2) / (4n)+Δχ″′·(n-1) / n)], or even between 90°+0.8·[(δ1-δ 2) / (4n)+Δχ″′·(n-1) / n)] and 90°+1.2·[(δ1-δ2) / (4n)+Δχ″′·(n-1) / n)]. Each possibility corresponds to a separate embodiment. In particular, in embodiments where the ICA 504 is or includes an autocollimator, <χ′> can be shown to be equal to or equal to approximately 90°+(Δw-Δw′) / (2·f0·n′)+Δχ″′·(n′-1) / n′, where f0 is the focal length of the collimating lens of the autocollimator.

[0204] According to some Figure 5A and Figure 5B , light source 512 and optical device 518 can be configured to produce an expanded (collimated) laser beam or a pair of parallel and spaced apart (collimated) laser beams, substantially as described above in the description of system 100. According to still other embodiments, ICA 504 can be or include an interferometric measurement device, as described above in the description of system 100.

[0205] Although in Figure 1A , Figure 1B , Figure 2 , Figure 3, Figure 5A and Figure 5B In each of the examples, the samples are shown as including a single internal facet (e.g., internal facet 14 in sample 10 and internal facet 54 in sample 50), but the disclosed system can also be used to obtain information about multiple internal facets that are nominally parallel. According to some embodiments, the information can be aggregate information, and can specify an average (mean) actual tilt angle of the internal facets, or a weighted average of the actual tilt angles, as described below.

[0206] Reference Fig. 6A , Fig. 6A Such a sample, sample 60, is depicted according to some embodiments. To aid in the description, sample 60 is shown as including two nominally parallel internal facets by making it more specific, but those skilled in the art will readily appreciate that Fig. 6A and Figure 6B The teaching of is applied to samples including three or more nominally parallel internal facets. Sample 60 includes an outer flat first surface 62a, an outer second surface 62b, a first internal facet 64a, and a second internal facet 64b. The second surface 62b is set at an angle relative to the first surface 62a (and can be flat or uneven). The first internal facet 64a is flat and nominally tilted relative to the first surface 62a at a nominal tilt angle (not shown). The second internal facet 64b is flat and nominally parallel to the first internal facet 64a. The first internal facet 64a is located between the second surface 62b and the second internal facet 64b. The first portion 66a of sample 60 is partially bounded by the second surface 62b and the first internal facet 64a. The second portion 66b of sample 60 is partially bounded by the first internal facet 64a and the second internal facet 64b. The second internal facet 64b extends between the second portion 66b and the third portion 66c of sample 60. The first portion 66a and the second portion 66b have the same refractive index (or a close refractive index). The first interior facet 64a constitutes a thin layer of material characterized by a refractive index that is different from the refractive index of the first portion 66a and the second portion 66b.

[0207] Information about the actual tilt angles of the first interior facet 64a and the second interior facet 64b relative to the first surface 62a can be obtained using any of the systems 100, 200, or 300, substantially as described above in the corresponding descriptions, with additions / adjustments as specified below. In embodiments where the nominal tilt angle is 90° and the sample 60 includes an exterior flat third surface 62c parallel to the first surface 62a, information about the actual tilt angle can be obtained using the system 500, substantially as described above in the corresponding descriptions, with additions / adjustments as specified below.

[0208] For ease of description and to make the discussion more specific, it is assumed that a system ( Fig. 6A 62a). A first incident LB 605a (only a single ray of which is shown) is shown, which is projected on the first surface 62a perpendicularly. A first return LB 633a is obtained from the reflection of the first incident LB 605a from the first surface 62a. Also shown is a transmission LB 617b (only a single ray of which is shown), which can be obtained by nominally folding (using the LFC (not shown) of the system used to perform the inspection) the second incident LB at a nominal tilt angle, and then transmitting it into the CP of the system, oriented so that the folded LB is nominally perpendicularly incident on the outer flat surface of the CP, which is nominally parallel to the inner facet 64. The transmission LB 617b leaves the CP and enters the shape-compliant interface located between the CP and the sample 60. Each of the CP and the shape-compliant interface is characterized by a refractive index that is equal to or at least close to the refractive index of the first portion 66a and the second portion 66b of the sample 60.

[0209] Transmission LB 617b enters sample 60 via second surface 62b. Transmission LB 617b nominally strikes first internal facet 64a perpendicularly. Reflection LB 621b corresponds to the portion of transmission LB 617b that is specularly reflected from first internal facet 64a. (First) transmission portion 637b corresponds to the portion of transmission LB 617b that is transmitted to second portion 66b. Transmission portion 637b nominally strikes second internal facet 64b perpendicularly. Reflection portion 641b corresponds to the portion of transmission portion 637b that is specularly reflected from second facet 64b. Second transmission portion 645b indicates the portion of reflection portion 641b that is transmitted back into first portion 66a via first internal facet 64a.

[0210] Figure 6BA first point 647a and a pair of points 647b, including a second point 647b1 and a third point 647b2, on a photosensitive surface 648 of a sensor 614 of a system for inspecting a sample 60 according to some embodiments are schematically depicted. The first point 647a is formed by the first return LB 633a. The second point 647b1 and the third point 647b2 are formed by the return LB caused by the reflection LB 621b and the second transmission portion 645b (i.e., by reflection from the first internal facet 64a and the second internal facet 64b, respectively). The first return LB 633a can be distinguished from the return LB (not shown) caused by the reflection LB 621b and the second transmission portion 645b using a blocking element and blocking / filtering techniques. If the second point 647b1 (and the third point 647b2) cannot be attributed to one of the two return LBs caused by the reflection LB 621b and the second transmission portion 645b, then only the collective information about the first inner facet 64a and the second inner facet 64b (e.g., the average actual tilt) can be extracted based on the positions of the second point 647b1 and the third point 647b2 (based on the average value of the deviation angles of the return LBs associated with the reflection LB 621b and the second transmission portion 645b relative to the first return LB 633a).

[0211] According to some embodiments, the intensity of the return LB associated with the reflection LB 621b can be significantly greater than the intensity of the return LB associated with the second transmission portion 645b. Therefore, depending on whether the brightness of the first point 647b1 is greater or less than the brightness of the second point 647b2, the first point 647b1 can be attributed to the reflection LB 621b or the second transmission portion 645b (the opposite applies to the second point 647b2).

[0212] According to some embodiments, the first internal facet 64a is configured to reflect a first spectrum of light, and the second internal facet 64b is configured to reflect a second spectrum of light. The second spectrum is sufficiently different from the first spectrum to allow the return LB caused by reflection from the first internal facet 64a to be distinguished from the return LB caused by reflection from the second internal facet 64b. This distinction can be achieved using a spectral filter that is configured to selectively filter light from either the first spectrum or the second spectrum passing therethrough, as described above in Figure 1A and Figure 2 The distinction between the first return LB 633a and the return LB caused by reflection from the internal facet 64 can be similarly achieved.

[0213] According to some embodiments, where the sample 60 includes a third surface 62c opposite the first surface 62a, by flipping the sample 60 so that the first surface 62a and the third surface 62c are reversed, and maintaining the orientation of the second surface 62b used to perform the measurement relative to the LGA, and repeating the measurement, additional collective or individual information about the actual tilt angle of the internal facet 64 can be obtained, substantially as described above in the description of the system 500 and below in Fig. 8A and Figure 8B As taught in the description of the method.

[0214] method

[0215] According to an aspect of some embodiments, an optically based method for metrology of internal facets of a sample is provided. The method can be used to verify the orientation of one or more internal facets of a sample relative to an external and flat surface of the sample. Figure 7 A flow chart of such a method (i.e., optical-based method 700) according to some embodiments is presented. Method 700 may include:

[0216] - Optional stage 705, in which a system (eg, system 100) for implementing the method is calibrated.

[0217] - Stage 710, wherein a sample to be tested is provided (e.g., sample 10). The sample comprises an outer planar first surface (a first outer surface, which is planar; e.g., first surface 12a) and an inner facet (e.g., inner facet 14) nominally inclined at a nominal inclination angle (e.g., nominal inclination angle α) relative to the first surface.

[0218] - Stage 720, in which a pair of parallel light beams (LB) are generated (e.g., by light source 112 and optical device 118 or by autocollimator 250): a first incident LB (e.g., first incident LB 105a) is projected on the first surface of the sample perpendicular to the first surface of the sample. A second incident LB (e.g., second incident LB 105b) is projected on a light guide device (LGA; e.g., LGA 102) parallel to the first incident LB.

[0219] - Phase 730, in which a first return LB (eg first return LB 133a) is obtained by reflection of the first incident LB from the first surface of the sample.

[0220] - Stage 740, wherein a second return LB (eg, second return LB 133b) is obtained by redirecting a second incident LB by the LGA into or onto the sample, reflecting from the internal facet after striking nominally normally on the internal facet, and redirecting it back by the LGA.

[0221] - Phase 750, in which the angular deviation of the second return LB relative to the first return LB is measured by sensing the first return LB and the second return LB (eg by the sensor 114 or the autocollimator 250).

[0222] - A stage 760 of deriving an actual inclination angle of the inner facet relative to the first surface (for example said actual inclination angle α′) at least based on the measured angular deviation.

[0223] As used herein, the term obtain may be used in both active and passive senses. Thus, for example, in stage 730, the first return LB may be obtained not as a result of any operation implemented in stage 730, but as a result of the generation of the first incident LB in stage 720. In general, a stage may describe an active operation performed by a user or by a system for implementing the method, and / or the result or effect of one or more operations performed in one or more earlier stages.

[0224] The method 700 may be implemented using an optical-based system, such as any of the optical-based systems 100, 200, and 300 or optical-based systems similar thereto, as described above in their respective descriptions. In particular, according to some embodiments, the method 700 may be based on an autocollimator based on the measurement of the distance between the laser beams, or may be based on interferometry, as detailed in the description of the various embodiments of the system 100. In stage 730, the second incident LB may be nominally folded at a nominal tilt angle using any of the LFC 122, the LFC 222, and the prism 322, or similar functional LFCs. Similarly, the second return LB may be obtained using any of the LFC 122, the LFC 222, and the prism 322, or similar functional LFCs.

[0225] According to some embodiments, the internal facet may define a flat boundary between a first portion (e.g., first portion 16a) and a second portion (e.g., second portion 16b) of the sample, the first portion and the second portion of the sample having different refractive indices. Alternatively, according to some embodiments, the internal facet may constitute a thin and flat layer between the first portion and the second portion of the sample, having a different refractive index than each of the first portion and the second portion (the refractive indices of the first portion and the second portion may be the same or may be different). The first portion may extend between the internal facet and an external flat second surface (e.g., second surface 12b) of the sample. In stage 740, a transmission LB (e.g., transmission LB 117b) constituting a portion of a second incident LB transmitted into the sample may enter the sample via the second surface.

[0226] According to some embodiments, in stage 720, a collimated light beam, such as LB 201, may be generated, wherein the first sub-beam and the second sub-beam constitute the first incident LB and the second incident LB, respectively. According to some embodiments, the first incident LB and the second incident LB may be adjacent. According to some embodiments, the first incident LB and the second incident LB may form complementary parts of the collimated light beam. Alternatively, according to some embodiments, the first incident LB and the second incident LB may be spaced apart, wherein a portion of the collimated light beam that has been positioned between the first incident LB and the second incident LB is removed (e.g., blocked using a light absorbing filter or an opaque plate). According to some embodiments, a collimated light beam may be generated using an autocollimator such as autocollimator 250.

[0227] According to some embodiments, the LFC may be configured such that its light folding angle is independent of the pitch angle to which the LFC is set (such that the second incident LB is nominally folded at a nominal tilt angle α, regardless of the pitch angle). According to some such embodiments, the LFC may be a pentaprism or similar functional prism, or a pair of plane mirrors set at an angle relative to each other, or a similar functional mirror device, as described above in the system section in the description of systems 100 and 300.

[0228] According to some embodiments, in addition to the LFC, the LGA can include a coupling infrastructure, such as coupling infrastructure 124. The coupling infrastructure is configured to direct light nominally folded by the LFC (e.g., fold LB 113b) at a nominal tilt angle into or onto the sample such that transmitted light (e.g., transmission LB 117b) strikes the internal facet nominally normally.

[0229] According to some embodiments, the coupling infrastructure may include a coupling prism (CP), such as CP 132, and a shape-compliant interface, such as shape-compliant interface 134. Each of the CP and the shape-compliant interface may be characterized by a refractive index that is equal to or nearly equal to the refractive index of the sample, or equal to or nearly equal to the refractive index of at least the first portion of the sample in an embodiment in which the first portion and the second portion of the sample do not have the same refractive index. The CP includes an outer and flat first surface (referred to as "CP first surface"), an outer and flat second surface (referred to as "CP second surface"), and an outer third surface (referred to as "CP third surface"), such as CP first surface 138a, CP second surface 138b, and CP third surface 138c, respectively. In particular, the CP second surface is nominally tilted relative to the CP first surface at a nominal tilt angle α.

[0230] A shape-compliant interface is disposed between the CP and the first portion of the sample adjacent to each of the CP and the first portion of the sample so as to define a continuum of material having an equal or nearly equal refractive index. More specifically, the shape-compliant interface is disposed between the CP third surface and the second surface of the sample, wherein the CP and the sample are aligned with each other such that the CP second surface and an internal facet of the sample are nominally parallel.

[0231] Forming a continuum of materials having the same or close refractive index helps ensure that, in stage 740, (i) the propagation direction of the light beam transmitted into the CP (e.g., transmission LB 117b) is maintained when traversing from the CP to the shape-compliant interface and then maintained when traversing from the shape-compliant interface to the first portion of the sample, and (ii) the propagation direction of the light beam reflected from the internal facet (e.g., reflection LB 121b) is maintained when traversing from the first portion of the sample into the shape-compliant interface and then maintained when traversing from the shape-compliant interface into the CP. Advantageously, this helps ensure that the transmitted portion of the light beam (e.g., fold LB 113b) that is normally incident on the second surface of the CP will nominally impinge normally on the internal facet of the sample.

[0232] Thus, in an embodiment including a CP and a shape-compliant interface, a folded LB (e.g., folded LB 113b) obtained by folding a second incident LB by an LFC is incident on the CP second surface nominally perpendicular to the CP second surface and is (at least partially) transmitted into the CP. A transmitted LB (e.g., transmitted LB 117b) continuously travels through the CP, through the shape-compliant interface, and the first portion of the sample. The transmitted LB is nominally incident normally on the internal facet and is (at least partially) reflected from the internal facet. A reflected LB (e.g., reflected LB 121b) propagates back through the first portion, the shape-compliant interface, and the CP. At least a portion of the reflected LB (e.g., exit LB 125b) exits from the CP in the direction of the LFC. The LFC nominally folds the exit LB at a nominal tilt angle, thereby obtaining a second returned LB.

[0233] According to some embodiments, an additional incident LB (e.g., additional incident LB 205s) may be projected nominally perpendicular to the CP first surface in stage 705. The additional incident LB may be used to verify that the CP first surface is aligned with the first surface of the sample, for example, by measuring an angular deviation between an additional return LB (e.g., additional return LB 233s) obtained by reflection of the additional incident LB from the CP first surface and the first return LB.

[0234] According to some embodiments, in stage 705, a "gold standard" (GS) sample can be employed as part of the calibration of the system for implementing method 700. More specifically, given a sample to be tested, a corresponding GS sample (i.e., a sample known to exhibit the necessary geometry to a high degree of accuracy and having the same refractive index as the sample to be tested) can be used when calibrating the system. The GS sample can be used to calibrate the directional infrastructure (e.g., directional infrastructure 140, directional infrastructure 240) and the LGA so that (i) the first incident light will be incident normally on the first surface of the GS sample (similar to the first surface 12a), and (ii) the transmitted LB will be incident perpendicularly on the internal facet of the GS sample (similar to the internal facet 14) (i.e., to the accuracy provided by the GS sample and the LGA).

[0235] According to some embodiments, a (first) orientable stage (e.g., stage 142) on which the sample can be mounted can be used to orient the GS sample relative to each of the LGA (as a whole or relative to its individual components (e.g., CP)) and the ICA. Additionally or alternatively, a second orientable stage (e.g., second stage 144) can be used to orient the CP relative to the GS sample and the LFC. Whether as part of the ICA (in embodiments in which the system includes an autocollimator) or not included in the system, the autocollimator can be used to verify the verticality of the transmission LB.

[0236] According to some embodiments, calibration or additional calibration may be performed after stage 710, when a sample to be tested has been provided and the sample is set on, for example, an orientable stage. The additional calibration may include, for example, orienting or reorienting the orientable stage on which the sample to be tested is mounted so that the first incident LB is perpendicularly incident on the first surface of the sample to be tested. According to some embodiments, in stage 750, an autocollimator (e.g., autocollimator 250, and more generally, the same autocollimator in embodiments in which an autocollimator is used to prepare the incident LB) may be used to sense the first return LB and the second return LB (e.g., their impact positions on the photosensitive surface of the sensor of the autocollimator), and thereby measure the angular deviation. According to some embodiments, substantially as described above in the description of systems 100 and 200, a blocking element such as a shutter and / or a spectral filter may be used to selectively block (or at least partially block) each return LB. In addition to facilitating attribution of each of a pair of points (on the photosensitive surface of a light sensor or image sensor (e.g., sensor 114) used to sense return LB) to the return LB that formed that point, blocking one return LB while sensing another return LB can be used to improve measurement accuracy by attenuating signals associated with stray light.

[0237] According to some embodiments, particularly those in which stages 710, 720, and 730 are implemented using an autocollimator such as autocollimator 250, in stage 740, the angular deviation of the second return LB relative to the first return LB is Can be through calculate. and are the horizontal coordinates of a first point (eg, first point 247a) and a second point (eg, second point 247b) formed on the photosensitive surface (eg, photosensitive surface 248) of the autocollimator by the first return LB and the second return LB, respectively. is the focal length of the collimating lens of the autocollimator.

[0238] In stage 750, the actual tilt angle can be calculated using the laws of geometric optics, in particular Snell's law (and taking into account the actual light folding angle of the LFC, the actual tilt angle of the CP second surface relative to the CP first surface, and the value of the refractive index of the first portion of the sample)

[0239] According to some embodiments, wherein the sample (e.g., sample 60) includes a plurality of internal facets (e.g., internal facets 64) that are nominally perpendicular to the first surface, and in addition to the internal facets, the sample is characterized by a uniform or near-uniform refractive index, in stage 740, a plurality of return LBs are obtained by redirecting a second incident LB into or onto the sample by the LGA, reflecting the second incident LB from each of the internal facets, and reversely redirecting the second incident LB by the LGA, substantially as described above. Fig. 6A and Figure 6B As described in the description of . In stage 750, multiple angular deviations of each of the multiple return LBs relative to the first return LB are measured by sensing the first return LB and each of the multiple return LBs. According to some such embodiments, in stage 760, the actual tilt angle of each of the multiple internal facets relative to the first surface can be derived based at least on the multiple measured angular deviations. According to some embodiments, each of the points formed by the multiple return LBs on the photosensitive surface of the sensor (e.g., sensor 614) can be attributed to a corresponding one of the multiple return LBs based on the relative brightness of the points and / or using a spectral filter in an embodiment in which each internal facet is configured to reflect light of a corresponding different spectrum. Additionally or alternatively, according to some embodiments, collective information about the actual tilt angle (e.g., an average actual tilt angle) is derived based at least on the multiple measured angular deviations.

[0240] Fig. 8A and Figure 8BA flow chart of an optically based method 800 for metrology of internal facets of a sample according to some embodiments is presented. Method 800 corresponds to a specific embodiment of method 700 and can be used to verify the perpendicularity of one or more internal facets of a sample relative to at least two external planar surfaces of the sample that are parallel to each other. Method 800 can include:

[0241] - Stage 805, in which a sample to be tested is provided (e.g., sample 50). The sample comprises an outer planar first surface (i.e., a first outer surface, which is planar; e.g., first surface 52a), an outer second surface (i.e., a second outer surface, which may be planar or non-planar; e.g., second surface 52b), an outer planar third surface parallel to the first surface (i.e., a third outer surface, which is planar; e.g., third surface 52c), and an inner facet nominally inclined at 90° relative to the first surface.

[0242] - Stage 810, wherein a first pair of parallel LBs is generated (e.g., by light source 512, and optionally optical device 518): a first incident LB (e.g., first incident LB 505a) is projected on the first surface of the sample perpendicular to the first surface of the sample. A second incident LB (e.g., second incident LB 505b) is projected on the LGA (parallel to the first incident LB).

[0243] - Stage 815, in which a first return LB (eg first return LB 533a) is obtained by reflection of the first incident LB from the first surface.

[0244] - Stage 820, wherein a second return LB (e.g., second return LB 533b) is obtained by redirecting a second incident LB into or onto the sample by the LGA, reflecting the second incident LB from the internal facet after nominally impinging normally on the internal facet, and reversely redirecting it by the LGA.

[0245] - Phase 825, in which a (first) angular deviation of the second return LB relative to the first return LB is measured by sensing the first return LB and the second return LB (eg by sensor 514).

[0246] - Stage 830, in which the sample is flipped so as to invert the first and third surfaces (while maintaining the nominal orientation of the internal facets relative to the LGA).

[0247] - Stage 835, in which a second pair of parallel LBs is generated (e.g., by light source 512 and optionally optical device 518): a third incident LB (e.g., third incident LB 505a') is projected perpendicularly to the third surface of the sample onto the third surface of the sample. A fourth incident LB (e.g., fourth incident LB 505b') is projected onto the LGA (parallel to the third incident LB).

[0248] - Phase 840, in which a third return LB (eg third return LB 533a') is obtained by reflection of the third incident LB from the third surface.

[0249] - Stage 845, wherein a fourth return LB (e.g., fourth return LB 533b′) is obtained by redirecting a fourth incident LB into or onto the sample by the LGA, reflecting the fourth incident LB from the internal facet after nominally impinging normally on the internal facet, and redirecting it in the opposite direction by the LGA.

[0250] - Phase 850, in which a (second) angular deviation of the fourth return LB relative to the third return LB is measured by sensing the third return LB and the fourth return LB (eg by sensor 514).

[0251] - A stage 855 of deducing the actual inclination angle of the internal facet relative to the first surface based on the measured angular deviation.

[0252] Method 800 may be implemented using an optical-based system (e.g., optical-based system 500 or an optical-based system similar thereto), as described above. FIG. 5A to FIG. 5D as described in the description.

[0253] In particular, according to some embodiments, method 800 may be based on an autocollimator based on a measurement of the distance between the laser beams or based on interferometry. In stage 820, a first folded LB and a second returned LB may be obtained from a second incident LB and a first reflected LB, respectively, using an LFC, such as LFC 522 or a similarly functional LFC, which is configured to symmetrically fold the light incident thereon by 90°. According to some embodiments, the LFC may be or include a prism (e.g., a pentaprism) configured to fold the light by 90°, or one or more mirrors (collectively) configured to fold the light by 90°. Similarly, in stage 845, a second folded LB and a fourth returned LB may be obtained from a fourth incident LB and a second reflected LB, respectively, using LFC 522 or a similarly functional LFC.

[0254] According to some embodiments, in addition to the LFC, the LGA may also include a coupling infrastructure, such as coupling infrastructure 524. The coupling infrastructure is configured to direct light folded by the LFC (e.g., fold LB 513b) into or onto the sample such that transmitted light (e.g., transmission LB 517b) nominally strikes the internal facet normally.

[0255] According to some embodiments, the coupling infrastructure may include a coupling prism (CP), such as CP532, and a shape-compliant interface, such as shape-compliant interface 534. Each of the CP and the shape-compliant interface is characterized by a corresponding refractive index that is equal to or close to the refractive index of the sample or, in an embodiment in which the first and second portions of the sample do not have the same refractive index, is equal to or close to the refractive index of at least the first portion of the sample. The CP includes an external and flat first surface (referred to as "CP first surface"), an external and flat second surface (referred to as "CP second surface"), and an external third surface (referred to as "CP third surface"), such as CP first surface 538a, CP second surface 538b, and CP third surface 538c, respectively. In particular, the CP second surface is nominally inclined vertically relative to the CP first surface. The CP and the shape-compliant interface can be used substantially as described above in the description of method 700, and optionally, additionally as described below.

[0256] According to some embodiments, the CP includes an outer and flat fourth surface (referred to as "CP fourth surface"), such as CP fourth surface 538d. The CP fourth surface is opposite and parallel to the CP first surface. In such an embodiment, in stage 830, the CP can also be flipped so that the CP first surface and the CP fourth surface are reversed, wherein the nominal orientation of the CP second surface (through which the light folded by the LFC enters the CP) relative to the internal facet is maintained.

[0257] According to some embodiments, in stages 810 and 835, a pair of parallel incident LBs may be generated using an autocollimator (e.g., an autocollimator used to prepare the incident LBs). According to some embodiments, in stages 815, 820, 840, and 845, an autocollimator (e.g., an autocollimator used to prepare the incident LBs) may be employed to sense the return LBs. According to some embodiments, a shutter and / or a spectral filter may be employed to selectively block (or at least partially block) one of the second return LB and the first return LB and one of the fourth return LB and the third return LB, substantially as described above in Figure 5A and Figure 5B as described in the description.

[0258] According to some embodiments, method 800 may include an optional calibration phase similar to phase 705 of method 700 ( Fig. 8A and 8B 855), and the optional calibration stage is repeated (in part) after flipping the sample in stage 830 (and performed before stages 835 to 855). More specifically, in stage 830, after flipping the sample, the orientation of the sample can be redirected so that light transmitted into the sample is incident on the internal facet nominally perpendicular to the internal facet. In embodiments where the CP is also flipped, the CP can also be redirected so that light folded by the LFC (e.g., second fold LB 513b') will incident on the CP second surface nominally perpendicularly.

[0259] According to some embodiments, particularly embodiments in which stages 810, 815, 820, 835, 840, and 845 are implemented using an autocollimator (e.g., autocollimator 250), at stage 825, via Obtain a first angle deviation of the second return LB relative to the first return LB and are the horizontal coordinates of the first point and the second point (eg, the first point 547a and the second point 547b) formed on the photosensitive surface (eg, the photosensitive surface 548) of the autocollimator by the first return LB and the second return LB, respectively. is the focal length of the collimating lens of the autocollimator. Similarly, in stage 850, Obtain a second angle deviation of the fourth return LB relative to the third return LB and are the horizontal coordinates of the third point and the fourth point (eg, the third point 547a' and the fourth point 547b') formed on the photosensitive surface of the autocollimator by the third return LB and the fourth return LB, respectively.

[0260] In stage 855, the actual tilt angle The value of (or more precisely, the average obtained by averaging the two obtained estimates) can be obtained via the relation Deviation from angle and (measured value) obtained. is the refractive index of the first part of the sample (and of the CP and the shape compliant interface or at least close to their corresponding refractive indices).

[0261] According to some embodiments, wherein the sample (e.g., sample 60) includes a plurality of internal facets (e.g., internal facets 64) that are nominally perpendicular to the first surface, and in addition to the internal facets, the sample is characterized by a uniform or near-uniform refractive index, in stage 820, a first plurality of returned LBs are obtained by redirecting a second incident LB into or onto the sample by the LGA, reflecting the second incident LB from each of the internal facets, and redirecting the second incident LB back by the LGA, substantially as described above. Fig. 6A and 6B As described in the description of. In stage 825, a first plurality of angular deviations of each of the first plurality of return LBs relative to the first return LB are measured by sensing each of the first plurality of return LBs and the first return LB. Similarly, in stage 845, a second plurality of return LBs are obtained by redirecting a fourth incident LB into or onto a sample by the LGA, reflecting the fourth incident LB from each internal facet, and redirecting it in reverse by the LGA. In stage 850, a second plurality of angular deviations of each of the second plurality of return LBs relative to the third return LB are measured by sensing each of the second plurality of return LBs and the third return LB. According to some such embodiments, in stage 855, an actual tilt angle of each of the plurality of internal facets relative to the first surface can be derived based on the first plurality of measured angular deviations and the second plurality of measured angular deviations. According to some embodiments, each of the points formed by the plurality of return LBs can be attributed to a corresponding one of the plurality of return LBs based on the relative brightness of the points and / or using a spectral filter in an embodiment in which each of the internal facets is configured to reflect light of a corresponding different spectrum. Additionally or alternatively, according to some embodiments, aggregate information about the actual tilt angle (eg an average actual tilt angle) is derived based on the first plurality of measured angle deviations and the second plurality of measured angle deviations.

[0262] According to some embodiments, where the sample is flipped such that the first and third surfaces thereof are inverted and such that the orientation of the internal facet relative to the LGA is maintained and additionally the internal facet remains nominally parallel to the CP second surface (when the CP is not flipped), then method 800 may alternatively additionally include four measurements: a first measurement where neither the sample nor the CP is flipped, a second measurement where the sample is not flipped and the CP is flipped, a third measurement where both the sample and the CP are flipped, and a fourth measurement where the sample is flipped and the CP is not flipped. The four measurements may be made by effectively canceling right According to some specific embodiments of the present invention, a non-limiting example of such a sample is Figure 4AThe sample 40 in FIG. 1 further comprises an outer and flat surface opposite to the first surface 42 a.

[0263] Additional systems

[0264] Fig. 9 Schematically depicted is an optically based system 900 for metrology of internal facets of sample 30, according to some embodiments, system 900 is similar to system 100, but unlike some embodiments of system 100, does not include any coupling infrastructure (e.g., coupling infrastructure 124). System 900 is configured for use with a sample comprising at least two exterior and planar surfaces and an interior facet that is tilted at a nominal tilt angle relative to a first of the two surfaces. According to some embodiments, such a sample, sample 90, is Fig. 9 . Sample 90 includes an outer planar first surface 92a and an outer planar second surface 92b and an inner facet 94. The inner facet 94 is nominally tilted relative to the first surface 92a at a nominal tilt angle ω. Sample 90 is shown as being inspected by system 900.

[0265] System 900 includes ICA 904 and LFC 922, which may correspond to specific implementations of ICA 104 and LFC 122, respectively. ICA 904 may include a light source, at least one sensor, and optionally an optical device (all not shown), which may correspond to specific implementations of light source 112, at least one sensor 114, and optical device 118, respectively. System 900 may also include a controller, an orientable stage, and a computing module (all not shown), which may correspond to specific implementations of controller 108, first stage 142, and computing module 130. The controller may be functionally associated with ICA 904 components, the stage, and the computing module in a similar manner that controller 108 is functionally associated with ICA 104 components, first stage 142, and computing module 130, respectively.

[0266] In operation, the ICA 904 generates a pair of incident LBs: a first incident LB 905a and a second incident LB 905b parallel to the first incident LB 905a. The first incident LB 905a is nominally projected perpendicular to the first surface 92a. The first return LB 933a is obtained by reflection of the first incident LB 905a from the first surface 92a and is sensed by a sensor (not shown) of the ICA 904.

[0267] Second incident LB 905b is folded by LFC 922, as shown by fold LB 913b. Fold LB 913b impinges on second surface 92b. Transmission LB 917b indicates a portion of fold LB 913b that is transmitted into sample 90. Transmission LB 917b nominally impinges normally on interior facet 94. That is, the nominal fold angle of LFC 922 and the orientation of sample 90 relative to LFC 922 are selected so that transmission LB 917b nominally impinges normally on interior facet 94.

[0268] Reflection LB 921b indicates a portion of transmission LB 917b that is specularly reflected from the internal facet 94. Exit LB 925b indicates a portion of reflection LB 921b that leaves the sample 90 by refraction of the second surface 92b. A second return LB 933b is obtained by folding the exit LB 925b by the LFC 922. The second return LB 933b is sensed by the sensor of the ICA 904.

[0269] According to some embodiments, the angular deviation of the second return LB 933b relative to the first return LB 933a can be obtained based on the horizontal distance between the second point and the first point formed by the second return LB 933b and the first return LB 933a on the photosensitive surface of the sensor, respectively, as described above in the description of the system 100 and the method 700. Based on the measured value of the angular deviation, the deviation of the (actual) inclination of the internal facet from its nominal inclination can be derived, basically as described in the description of the system 100 and the method 700.

[0270] Fig.10 Schematically depicts an optical-based system 1100 for internal facet metrology of a sample according to some embodiments, the system 1100 being configured for use with a sample comprising an external and planar surface and an internal facet nominally tilted relative to the surface at a nominal tilt angle. According to some embodiments, such a sample, sample 1010, is Fig.10 10. The sample 1010 includes an outer flat (first) surface 1012a and an inner facet 1014. The inner facet 1014 is nominally tilted relative to the first surface 1012a at a nominal tilt angle ω′. The sample 1010 is shown as being inspected by the system 1100.

[0271] System 1100 includes ICA 1104 and LFC 1122, which may be similar to ICA 104 and LFC 122, respectively, but differ therefrom as described below. ICA 1104 may include a light source, at least one sensor, and optionally an optical device (all not shown), which may be similar to light source 112, at least one sensor 114, and optical device 118, respectively. System 1100 may also include a controller and a computing module (all not shown), which may correspond to a specific implementation of controller 108 and computing module 130. The controller may be functionally associated with ICA 1104 components and computing module 130 in the same manner that controller 108 is functionally associated with ICA 104 components and computing module 130, respectively. System 1100 may also include an orientable stage (not shown), which may be similar to first stage 142 and may be controlled by the controller.

[0272] In operation, ICA1104 generates a pair of incident LBs: a first incident LB 1105a and a second incident LB 1105b parallel to the first incident LB 1105a. The first incident LB 1105a is nominally projected perpendicular to the first surface 1012a. The first return LB 1133a is obtained by reflection of the first incident LB 1105a from the first surface 1012a and is sensed by a sensor (not shown) of ICA1104.

[0273] The second incident LB 1105b is folded by the LFC 1122 as shown by the fold LB 1113b. The fold LB 1113b impinges on the first surface 1012a. The transmission LB 1117b indicates a portion of the fold LB 1113b that is refracted in the sample 1000. The transmission LB 1117b nominally impinges normally on the internal facet 1014. That is, the nominal fold angle of the LFC 1122 and the orientation of the sample 1000 relative to the LFC 1122 are selected so that the transmission LB 1117b will nominally impinge normally on the internal facet 1014.

[0274] Reflection LB 1121b indicates a portion of transmission LB 1117b that is specularly reflected from the internal facet 1014. Exit LB 1125b indicates a portion of reflection LB 1121b that leaves the sample 1000 by refraction of the first surface 1012a. The second return LB 1133b is obtained by folding the exit LB 1125b by the LFC 1122. The second return LB 1133b is sensed by the sensor of the ICA 1104.

[0275] According to some embodiments, the angular deviation of the second return LB 1133b relative to the first return LB 1133a can be obtained based on the horizontal distance between the second point and the first point formed on the photosensitive surface of the sensor by the second return LB 1133b and the first return LB 1133a, respectively, as described above in the description of the system 100 and the method 700. From the measured value of the angular deviation, the deviation of the (actual) inclination of the inner facet 1014 from its nominal inclination can be derived in a manner similar to the deriving of the actual inclination angle α′ from the angular deviation δ (described above in the description of the system 100 and the method 700).

[0276] According to some embodiments, the nominal fold angle of LFC 1122 may be selected to maximize the strength of second return LB 1133b.

[0277] Regarding the implementation methods including the above embodiments, the following technical solutions are also disclosed:

[0278] Scheme 1. An optically based method for verifying the orientation of one or more internal facets of a sample relative to an external planar surface of the sample, the method comprising:

[0279] providing a sample comprising an outer planar first surface and an inner facet, the inner facet being nominally tilted at a nominal tilt angle μ relative to the first surface;

[0280] providing a light guide arrangement (LGA) configured to redirect light incident on the LGA in a direction perpendicular to the first surface into or onto the sample such that light transmitted into the sample by the sample impinges on the internal facet symmetrically perpendicular to the internal facet;

[0281] Generate a first incident light beam (LB) and a second incident LB, wherein the first incident LB is directed to the first surface in a normal manner to the first surface, and the second incident LB is parallel to the first incident light beam and directed to the LGA;

[0282] obtaining a first return LB by reflecting the first incident LB from the first surface;

[0283] obtaining a second return LB by redirecting the second incident LB by the LGA into or onto the sample, reflecting the second incident LB from the internal facet, and back-redirecting by the LGA;

[0284] measuring a first angular deviation of the second return LB relative to the first return LB; and

[0285] An actual inclination angle μ′ of the inner facet relative to the first surface is derived based at least on the measured first angular deviation.

[0286] Option 2. An optical-based method according to Option 1, wherein the sample includes a first portion and a second portion, the internal facet extends between the first portion and the second portion, wherein the first portion is located between an external second surface of the sample and the internal facet, and wherein a transmitted LB that constitutes a portion of the second incident LB and is directly or indirectly transmitted into the sample enters the sample via the second surface.

[0287] Option 3. An optical-based method according to Option 2, wherein the LGA includes a light folding component (LFC), and the LFC is nominally configured to fold the light at a light folding angle equal to the nominal tilt angle at least when the light is projected onto the LFC in a direction perpendicular to the first surface.

[0288] Option 4. An optical-based method according to Option 3, wherein the LFC is or includes a prism, one or more mirrors and / or a diffraction grating.

[0289] Option 5. An optical-based method according to Option 4, wherein the light folding angle is insensitive to changes in the pitch of the LFC.

[0290] Option 6. An optical-based method according to Option 5, wherein the LFC is or includes a pentaprism or a similar functional prism, or a pair of mirrors set at an angle relative to each other, or a similar functional mirror device.

[0291] Option 7. An optical-based method according to Option 3, wherein the LGA also includes a coupling infrastructure, which is configured to guide the light folded by the LFC onto or into the sample, so that the light transmitted from the sample into the sample is projected normally onto the internal small plane.

[0292] Option 8. The optical-based method of Option 7, wherein the coupling infrastructure comprises a coupling prism (CP), the CP comprising an outer flat CP first surface, an outer flat CP second surface nominally tilted at the nominal angle relative to the CP first surface, and an outer CP third surface opposite the CP second surface;

[0293] wherein the CP has a refractive index that is the same as the refractive index of the first portion of the sample, or a refractive index that is close to the refractive index of the first portion of the sample; and

[0294] Wherein, the CP is arranged so that the CP first surface is parallel to the first surface of the sample, and the CP is also oriented so that the light folded by the LFC is incident normally on the CP second surface.

[0295] Option 9. An optical-based method according to Option 8, wherein the coupling infrastructure also includes a shape-compliant interface, which is arranged between the CP third surface and the sample and is made to present a shape such that the CP first surface is parallel to the first surface of the sample.

[0296] Option 10. An optical-based method according to Option 9, wherein the shape-conforming interface has a refractive index that is the same as the refractive index of the first portion of the sample, or a refractive index that is close to the refractive index of the first portion of the sample.

[0297] Option 11. An optical-based method according to Option 9, wherein the shape-conforming interface is or includes liquid and / or gel.

[0298] Option 12. An optical-based method according to Option 2, wherein the sample is a prism, a waveguide or a beam splitter.

[0299] Option 13. An optical-based method according to Option 1, wherein the first incident LB and the second incident LB constitute complementary parts of a single collimated light beam, or are prepared by blocking one or more parts of the single collimated light beam.

[0300] Option 14. An optical-based method according to Option 13, wherein the single collimated LB is polychromatic, wherein the single collimated LB is a laser beam.

[0301] Option 15. According to Option 8, the optical-based method also includes an initial calibration stage, wherein a gold standard sample is used to calibrate the LFC, the CP and / or the orientation of the sample.

[0302] Option 16. According to Option 8, the optical-based method also includes generating an additional incident LB, which is directed to the first surface of the CP and parallel to the first incident LB, and wherein, during the measurement of the first angular deviation, the orientation of the CP is (a) calibrated and / or (b) tested by measuring the additional angular deviation of the additional return LB relative to the first return LB to obtain the correct orientation, and the additional return LB is obtained by reflecting the additional incident LB from the first CP surface.

[0303] Option 17. An optical-based method according to Option 1, wherein the first angular deviation is obtained based on measured coordinates of a first point and a second point formed on a photosensitive surface of a light sensor or an image sensor by the first return LB and the second return LB, respectively.

[0304] Option 18. An optical-based method according to Option 1, wherein the first angular deviation is measured using an autocollimator.

[0305] Option 19. An optical-based method according to Option 18, wherein the measured first angular deviation is equal to Δu / f, wherein Δu is the difference between the coordinates of a first point on the photosensitive surface of the autocollimator and the corresponding coordinates of a second point, and f is the focal length of the collimating lens of the autocollimator, and wherein the first point is formed by the first return LB and the second point is formed by the second return LB.

[0306] Option 20. An optical-based method according to Option 8, including the CP, and wherein the actual inclination angle of the internal facet relative to the first surface is obtained based on the measured first angular deviation and taking into account the value of the actual inclination angle of the CP second surface relative to the CP first surface and the refractive index of the first part of the sample and optionally taking into account the actual light folding angle of the LFC.

[0307] Embodiment 21. An optical-based method according to any one of embodiments 2 to 20, wherein the sample includes the first portion and the second portion, wherein the nominal tilt angle is 90° and the sample includes an outer third surface, the outer third surface is flat and parallel to the first surface of the sample, and wherein the method further comprises performing the following operations after measuring the first angular deviation:

[0308] flipping the sample to invert the first surface and the third surface while maintaining a nominal orientation of the interior facet relative to the LGA;

[0309] Generate a third incident LB and a fourth incident LB, wherein the third incident LB is directed to the third surface in a manner perpendicular to the third surface, and the fourth incident LB is parallel to the third incident LB and directed to the LGA;

[0310] obtaining a third return LB by reflecting the third incident LB from the second surface;

[0311] obtaining a fourth return LB by redirecting the second incident LB by the LGA into or onto the sample, reflecting the second incident LB from the internal facet, and back-redirecting by the LGA;

[0312] measuring a second angular deviation of the fourth return LB relative to the third return LB; and

[0313] An actual tilt angle between the first exterior surface and the interior facet is derived based on the measured first angular deviation and the measured second angular deviation.

[0314] Option 22. According to Option 21, the optical-based method includes the CP, wherein the CP also includes a CP fourth surface opposite to and parallel to the CP first surface, and wherein flipping of the sample is accompanied by flipping of the CP, so that the CP first surface and the CP fourth surface are reversed while maintaining the nominal orientation of the CP second surface relative to the sample.

[0315] Option 23. An optical-based method according to Option 21, wherein the uncertainty of the parallelism of the first surface of the sample and the third surface of the sample is significantly smaller than the required measurement accuracy of the actual tilt angle.

[0316] Option 24. An optical-based method according to Option 21, including the CP, and wherein the actual inclination angle of the internal facet relative to the first surface is obtained based on the measured first angular deviation and the value of the actual inclination angle of the CP second surface relative to the CP first surface and the refractive index of the first part of the sample.

[0317] Option 25. According to Option 21, the optical-based method also includes measuring the actual inclination of the CP second surface relative to the CP first surface.

[0318] Embodiment 26. The optical-based method of any one of embodiments 1 to 15, wherein the sample comprises k ≥ 1 additional internal facets nominally parallel to the internal facet;

[0319] wherein, when obtaining the second return LB, k additional return LBs are obtained by respectively reflecting k LBs from each of the k additional internal facets, and the k LBs together constitute a portion of the second incident LB that is transmitted into the sample and is also transmitted via the internal facets;

[0320] Wherein, when measuring the first angular deviation, k additional angular deviations of the k additional return LBs relative to the first return LB are measured; and

[0321] Wherein, when deriving the actual inclination angle μ′ of the internal small facet, (i) k additional actual inclination angles of each of the k additional internal small facets are further derived, and / or (ii) an average actual inclination angle is derived, the average actual inclination angle being equal to or approximately equal to the average of the actual inclination angles of the internal small facet and the k additional internal small facets, the average actual inclination angle indicating the actual inclination angle μ′ of the internal small facet.

[0322] Option 27. An optical-based method according to Option 26, wherein k≥2, wherein a first internal facet among the additional internal facets is located between the internal facet and a second internal facet among the additional internal facets, and wherein, for each m such that 2≤m≤k-1, the mth internal facet among the k additional internal facets is located between the (m-1)th internal facet and the (m+1)th internal facet among the k additional internal facets.

[0323] Option 28. An optical-based method according to Option 26, wherein the internal facet and each of the k additional internal facets are configured to reflect a corresponding spectrum of light, each spectrum being different from the other spectra to allow differentiation between the second return LB and each of the k additional return LBs.

[0324] 29. An optically based system for verifying the orientation of an internal facet of a sample relative to an external planar surface of the sample, the system comprising:

[0325] a light guiding arrangement (LGA) configured to redirect light incident on the LGA in a direction perpendicular to an exterior and planar first surface of a sample into or onto the sample such that light transmitted into the sample by the sample impinges on the interior facet of the sample symmetrically perpendicular to the interior facet;

[0326] An illumination and collection arrangement (ICA), the ICA comprising:

[0327] a light generating assembly configured to (a) project a first incident light beam (LB) onto the first surface to generate a first return LB by reflection from the first surface, and (b) project a second incident LB onto the LGA parallel to the first incident LB to generate a second return LB by redirecting the second incident LB by the LGA into or onto the sample, reflecting the second incident LB from the internal facet, and redirecting it back by the LGA; and

[0328] at least one sensor configured to measure a first angular deviation of the second return LB relative to the first return LB, and / or an eyepiece assembly configured to enable manual measurement of the first angular deviation;

[0329] The measured first angular deviation indicates an actual inclination angle of the inner facet relative to the first surface.

[0330] Option 30. An optical-based system according to Option 29, wherein the sample includes a first portion and a second portion, the internal facet extends between the first portion and the second portion, wherein the first portion is located between an external second surface of the sample and the internal facet, and wherein the LGA is configured to redirect the LGA into or onto the first portion via the second surface.

[0331] Option 31. An optical-based system according to Option 30, wherein the LGA includes a light folding component (LFC), and the LFC is nominally configured to fold the light at a light folding angle equal to the nominal tilt angle at least when the light is projected onto the LFC in a direction perpendicular to the first surface.

[0332] Option 32. An optical-based system according to Option 31, wherein the LFC is or includes a prism, one or more mirrors and / or a diffraction grating.

[0333] Option 33. An optical-based system according to Option 32, wherein the light folding angle of the LFC is insensitive to the pitch change of the LFC.

[0334] Option 34. An optical-based system according to Option 34, wherein the LFC is or includes a pentaprism or a similar functional prism, or a pair of mirrors or a similar functional mirror device set at an angle relative to each other.

[0335] Option 35. An optical-based system according to Option 32, wherein the LGA also includes a coupling infrastructure, which is configured to guide light folded by the LFC onto or into the sample so that the light transmitted from the sample into the sample is incident normally on the internal facet.

[0336] Embodiment 36. An optical-based system according to embodiment 35, wherein the coupling infrastructure includes a coupling prism (CP), the CP including an outer flat CP first surface, an outer flat CP second surface nominally inclined at the nominal angle relative to the CP first surface, and an outer CP third surface opposite the CP second surface;

[0337] wherein the CP has a refractive index that is the same as the refractive index of the first portion of the sample, or a refractive index that is close to the refractive index of the first portion of the sample; and

[0338] Wherein, the CP is arranged so that the CP first surface is parallel to the first surface of the sample, and is also arranged so that the light folded by the LFC is symmetrically incident on the CP second surface normally.

[0339] Option 37. An optical-based system according to Option 36, wherein the coupling infrastructure also includes a shape-compliant interface, which is arranged between the CP third surface and the sample so that the CP first surface is parallel to the first surface of the sample, wherein the shape-compliant interface has a refractive index that is the same as the refractive index of the first portion of the sample, or a refractive index that is close to the refractive index of the first portion of the sample.

[0340] Option 38. An optical-based system according to Option 37, wherein the shape-conforming interface is or includes liquid and / or gel.

[0341] Option 39. An optical-based system according to Option 30, wherein the sample is a prism or a waveguide.

[0342] Option 40. An optical-based system according to Option 37, wherein the system also includes an oriented base structure, which is configured to orient the sample so that the first incident LB is normally incident on the first surface and / or the folded LB obtained by folding the second incident LB by the LFC is nominally normally incident on the CP second surface.

[0343] Option 41. An optical-based system according to any one of Option 29 to Option 40, comprising the at least one sensor, wherein the at least one sensor comprises one or more light sensors and / or one or more image sensors.

[0344] Option 42. An optical-based system according to Option 41, wherein the light generating component includes a light source and an optical device, wherein the light source is configured to generate a single LB, and wherein the optical device is configured to collimate the single LB.

[0345] Option 43. An optical-based system according to Option 42, wherein the first incident LB and the second incident LB 25 are complementary parts of the collimating LB.

[0346] Option 44. An optical-based system according to any one of Option 43, wherein the light source is a polychromatic light source, or wherein the light source is configured to generate a laser beam.

[0347] Option 45. According to Option 42, the optical-based system also includes an autocollimator, which includes a light source, the at least one sensor, and a collimating lens or a collimating lens assembly.

[0348] Option 46. An optical-based system according to Option 29, wherein the ICA further includes: at least two shutters, the at least two shutters being configured to selectively block each of the incident LBs; and / or one or more spectral filters, the one or more spectral filters being configured to at least facilitate distinguishing the return LBs.

[0349] Option 47. An optically-based system according to Option 40, comprising the at least one sensor, and wherein the system further comprises a computing module configured to calculate the actual tilt angle based at least on the measured first angular deviation.

[0350] Option 48. An optical-based system according to Option 47, wherein the sample also includes an external flat third surface parallel to the first surface, wherein the computing module is configured to additionally consider a measured second angular deviation of the fourth return LB relative to the third return LB to calculate the actual tilt angle, and the third return LB and the fourth return LB are obtained by flipping the sample so that the first surface and the third surface are reversed by the following operations: (a′) projecting a third incident light beam onto the third surface of the sample to generate the third return LB by reflection from the third surface, and (b′) projecting a fourth incident LB onto the LFC parallel to the third incident LB to generate the fourth return LB by redirecting the fourth incident LB into or onto the sample by the LGA, reflecting the fourth incident LB from the internal facet and redirecting it in the opposite direction by the LGA.

[0351] Option 49. An optical-based system according to Option 48, wherein the CP also includes an external flat CP fourth surface, which is parallel to the CP first surface, and wherein the CP is mechanically capable of flipping so that the CP first surface and the CP fourth surface are capable of being reversed while maintaining the nominal orientation of the CP second surface relative to the sample.

[0352] Option 50. An optical-based system according to Option 49, wherein the measured second angular deviation is obtained when: the CP is flipped so that the CP first surface and the CP fourth surface are reversed and the nominal orientation of the CP second surface relative to the sample is maintained.

[0353] It should be understood that certain features of the present disclosure described in the context of separate embodiments for the sake of clarity may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure described in the context of a single embodiment for the sake of brevity may also be provided individually or in any suitable subcombination or as appropriate in any other described embodiment of the present disclosure. Features described in the context of an embodiment should not be considered essential features of that embodiment unless explicitly specified as such.

[0354] Although the stages of the method according to some embodiments may be described in a particular order, the method of the present disclosure may include some or all of the described stages that are performed and / or occur in a different order. The method of the present disclosure may include several of the described stages or all of the described stages. No specific stage in the disclosed method should be considered as a necessary stage of the method unless explicitly specified in this way.

[0355] Although the present disclosure is described in conjunction with specific embodiments of the present disclosure, it is apparent that there may be many alternatives, modifications, and variations that are apparent to those skilled in the art. Therefore, the present disclosure encompasses all such alternatives, modifications, and variations that fall within the scope of the appended claims. It should be understood that the present disclosure and its application are not necessarily limited to the details of the construction and arrangement of the components and / or methods set forth herein. Other embodiments may be practiced, and embodiments may be implemented in various ways.

[0356] The words and terms used herein are for descriptive purposes and should not be considered limiting. The reference or identification of any reference in this application should not be construed as an admission that such reference can be used as prior art for the present disclosure. Section headings are used herein to facilitate understanding of the specification and should not be construed as necessarily limiting.

Claims

1. An optically based method for verifying the orientation of one or more internal facets of a sample relative to an external planar surface of the sample, the method comprising: providing a sample comprising an outer planar first surface and an inner facet, the inner facet being nominally tilted at a nominal tilt angle μ relative to the first surface; providing a light guide device LGA, the LGA being configured to redirect light incident on the LGA in a direction perpendicular to the first surface into or onto the sample so that light transmitted by the sample into the sample impinges on the inner facet symmetrically perpendicular to the inner facet; Generate a first incident light beam LB and a second incident light beam LB, wherein the first incident light beam LB is directed to the first surface in a normal direction to the first surface, and the second incident light beam LB is parallel to the first incident light beam and directed to the LGA; obtaining a first return LB by reflecting the first incident LB from the first surface; obtaining a second return LB by redirecting the second incident LB by the LGA into or onto the sample, reflecting the second incident LB from the internal facet, and back-redirecting by the LGA; measuring a first angular deviation of the second return LB relative to the first return LB; as well as An actual inclination angle μ' of the inner facet relative to the first surface is derived based at least on the measured first angular deviation.

2. The optical-based method of claim 1, wherein: The sample comprises a first portion and a second portion, the internal facet extending between the first portion and the second portion, wherein the first portion is located between an external second surface of the sample and the internal facet, and wherein a transmission LB constituting a portion of the second incident LB that is directly or indirectly transmitted into the sample enters the sample via the second surface.

3. The optical-based method of claim 2, wherein: The LGA comprises a light folding component LFC, the LFC being nominally configured to fold light at a light folding angle equal to the nominal tilt angle at least when light is projected onto the LFC in a direction perpendicular to the first surface.

4. The optical-based method of claim 3, wherein: The LFC is or comprises a prism, one or more mirrors and / or a diffraction grating.

5. The optical-based method of claim 4, wherein: The light folding angle is insensitive to changes in the pitch of the LFC.

6. The optical-based method of claim 5, wherein: The LFC is or includes a pentaprism or similar functional prism, or a pair of mirrors arranged at an angle relative to each other, or a similar functional mirror arrangement.

7. The optical-based method of claim 3, wherein: The LGA also includes a coupling infrastructure configured to direct light folded by the LFC onto or into the sample such that light transmitted by the sample into the sample impinges nominally normally on the interior facet.

8. The optical-based method of claim 7, wherein: The coupling infrastructure comprises a coupling prism CP, the CP comprising an outer planar CP first surface, an outer planar CP second surface nominally tilted at the nominal tilt angle relative to the CP first surface, and an outer CP third surface opposite the CP second surface; wherein the CP has a refractive index that is the same as the refractive index of the first portion of the sample, or a refractive index that is close to the refractive index of the first portion of the sample; and Wherein, the CP is arranged so that the CP first surface is parallel to the first surface of the sample, and the CP is also oriented so that the light folded by the LFC is incident normally on the CP second surface.

9. The optical-based method of claim 8, wherein: The coupling infrastructure also includes a shape-compliant interface disposed between the CP third surface and the sample and formed to present a shape such that the CP first surface is parallel to the first surface of the sample.

10. The optical-based method of claim 9, wherein: The shape compliant interface has a refractive index that is the same as, or close to, a refractive index of the first portion of the sample.

11. The optical-based method of claim 9, wherein: The shape compliant interface is or includes a liquid and / or a gel.

12. The optical-based method of claim 2, wherein: The sample is a prism, a waveguide or a beam splitter.

13. The optical-based method of claim 1, wherein: The first incident LB and the second incident LB constitute complementary parts of a single collimating LB, or are prepared by blocking one or more parts of a single collimating LB.

14. The optical-based method of claim 13, wherein: The single collimation LB is polychromatic, or wherein the single collimation LB is a laser beam.

15. The optical-based method of claim 8, further comprising an initial calibration phase, wherein: A gold standard sample is used to calibrate the LFC, the CP and / or the orientation of the sample.

16. The optical-based method according to claim 8, further comprising generating an additional incident LB directed to the CP first surface and parallel to the first incident LB, and wherein, During measurement of the first angular deviation, the orientation of the CP is (a) calibrated and / or (b) tested to obtain a correct orientation by measuring an additional angular deviation of an additional return LB relative to the first return LB, wherein the additional return LB is obtained by reflection of the additional incident LB from the first CP surface.

17. The optical-based method of claim 1, wherein: The first angular deviation is obtained according to measured coordinates of a first point and a second point formed on a photosensitive surface of a light sensor or an image sensor by the first return LB and the second return LB, respectively.

18. The optical-based method of claim 1, wherein: The first angular deviation is measured using an autocollimator.

19. The optical-based method of claim 18, wherein: The measured first angular deviation is equal to Δu / f, where Δu is the difference between the coordinates of a first point on the photosensitive surface of the autocollimator and the corresponding coordinates of a second point, and f is the focal length of the collimating lens of the autocollimator, and where the first point is formed by the first return LB and the second point is formed by the second return LB.

20. The optical-based method of claim 8, comprising the CP, and wherein, The actual tilt angle of the internal facet relative to the first surface is obtained based on the measured first angular deviation and taking into account the value of the actual tilt angle of the CP second surface relative to the CP first surface and the refractive index of the first part of the sample and optionally taking into account the actual light folding angle of the LFC.

21. An optical-based method according to any one of claims 2 to 20, wherein: The sample comprises the first portion and the second portion, wherein the nominal tilt angle is 90° and the sample comprises an outer third surface, the outer third surface being flat and parallel to the first surface of the sample, and wherein the method further comprises, after measuring the first angular deviation, performing the following operations: flipping the sample to invert the first surface and the third surface while maintaining a nominal orientation of the interior facet relative to the LGA; Generate a third incident LB and a fourth incident LB, wherein the third incident LB is directed to the third surface in a manner perpendicular to the third surface, and the fourth incident LB is parallel to the third incident LB and directed to the LGA; obtaining a third return LB by reflecting the third incident LB from the second surface; obtaining a fourth return LB by redirecting the second incident LB by the LGA into or onto the sample, reflecting the second incident LB from the internal facet, and back-redirecting by the LGA; measuring a second angular deviation of the fourth return LB relative to the third return LB; and An actual tilt angle between the first exterior surface and the interior facet is derived based on the measured first angular deviation and the measured second angular deviation.

22. The optical-based method of claim 21, comprising the CP, wherein: The CP also includes a CP fourth surface opposite to and parallel to the CP first surface, and wherein flipping of the sample is accompanied by flipping of the CP, so that the CP first surface and the CP fourth surface are reversed while maintaining the nominal orientation of the CP second surface relative to the sample.

23. The optical-based method of claim 21, wherein: The uncertainty of the parallelism of the first surface of the sample and the third surface of the sample is significantly smaller than the required measurement accuracy of the actual tilt angle.

24. The optical-based method of claim 21, comprising the CP, and wherein, The actual tilt angle of the inner facet relative to the first surface is obtained according to the measured first angular deviation and the value of the actual tilt angle of the CP second surface relative to the CP first surface and the refractive index of the first portion of the sample.

25. The optical-based method of claim 21, further comprising measuring an actual tilt angle of the CP second surface relative to the CP first surface.

26. An optical-based method according to any one of claims 1 to 15, wherein: The sample includes k ≥ 1 additional internal facets nominally parallel to the internal facet; wherein, when obtaining the second return LB, k additional return LBs are obtained by respectively reflecting k LBs from each of the k additional internal facets, and the k LBs together constitute a portion of the second incident LB that is transmitted into the sample and is also transmitted via the internal facets; Wherein, when measuring the first angular deviation, k additional angular deviations of the k additional return LBs relative to the first return LB are measured; and Wherein, when deriving the actual inclination angle μ′ of the internal small facet, (i) k additional actual inclination angles of each of the k additional internal small facets are further derived, and / or (ii) an average actual inclination angle is derived, the average actual inclination angle being equal to or approximately equal to the average of the actual inclination angles of the internal small facet and the k additional internal small facets, the average actual inclination angle indicating the actual inclination angle μ′ of the internal small facet.

27. The optical-based method of claim 26, wherein: k≥2, wherein a first internal facet among the additional internal facets is located between the internal facet and a second internal facet among the additional internal facets, and wherein, for each m such that 2≤m≤k-1, an mth internal facet among the k additional internal facets is located between an m-1th internal facet and an m+1th internal facet among the k additional internal facets.

28. The optical-based method of claim 26, wherein: The interior facet and each of the k additional interior facets are configured to reflect a corresponding spectrum of light, each spectrum being different from the other spectrums to allow differentiation between the second return LB and each of the k additional return LBs.

29. An optically based system for verifying the orientation of an internal facet of a sample relative to an external planar first surface of the sample, the system comprising: a light guiding arrangement LGA, the LGA comprising a light folding component LFC and a coupling prism CP, the LGA being configured to redirect light incident on the LFC into or onto the sample such that light transmitted by the sample into the sample impinges on the inner facet of the sample nominally perpendicularly to the inner facet, wherein the CP comprises an outer flat CP first surface, an outer flat CP second surface nominally inclined at a nominal angle relative to the CP first surface, and an outer CP third surface opposite the CP second surface, wherein the CP is arranged such that the CP first surface is parallel to the first surface of the sample, and the CP is further arranged such that light folded by the LFC impinges on the CP second surface nominally normally; and An illumination and collection device ICA, the ICA comprising: one or more light sources and optical devices, the one or more light sources and optical devices being configured to: (a) project a first incident light beam LB onto the first surface to generate a first return LB by reflection from the first surface, (b) project a second incident LB onto the LFC parallel to the first incident LB to generate a second return LB by redirecting the second incident LB nominally normally onto the CP second surface and into or onto the sample by the LFC, so that the light transmitted into the sample by the sample nominally strikes the inner facet normally, and (c) project an additional incident LB normally onto the CP first surface to obtain an additional return LB by reflection of the additional incident LB from the CP first surface, wherein the ICA further comprises at least three blocking elements and / or one or more spectral filters, the at least three blocking elements being configured to block one or more of the first incident LB, the second incident LB and the additional incident LB, the one or more spectral filters being configured to at least help distinguish between corresponding return LBs; and At least one sensor.

30. The optically based system of claim 29, wherein: The sensor is configured to: measuring a first angular deviation of the second return LB relative to the first return LB, and / or an eyepiece assembly configured to enable manual measurement of the first angular deviation, wherein the measured first angular deviation indicates an actual inclination angle of the inner facet relative to the first surface; and / or A second angular deviation of the additional return LB obtained by reflection of the additional incident LB from the CP first surface relative to the first return LB is measured.

31. The optically based system of claim 29, wherein: The first blocking element, the second blocking element and / or the third blocking element include a shutter and / or a filter.

32. The optically based system of claim 29, wherein: The at least one sensor comprises one or more light sensors and / or one or more image sensors; and wherein the one or more light sources are configured to generate a single LB, and wherein the optical device is configured to collimate the single LB.

33. The optical-based system of claim 32, further comprising one or more autocollimators comprising the one or more light sources, the at least one sensor, and a collimating lens or collimating lens assembly.

34. The optically based system of claim 32, wherein: The first incident LB, the second incident LB and the additional incident LB are complementary parts of the collimating LB.

35. The optically based system of claim 29, wherein: The sample is a prism or a waveguide.

36. The optically based system of claim 29, wherein: The LFC is or comprises a prism, one or more mirrors and / or a diffraction grating.

37. The optically based system of claim 36, wherein: The light folding angle of the LFC is insensitive to the pitch variation of the LFC.

38. The optically based system of claim 37, wherein: The LFC is either comprised of a pentaprism or a prism comprising an even number of internal reflective surfaces, or a pair of mirrors disposed at an angle relative to each other.

39. The optical-based system of claim 29, wherein: The LGA further comprises a shape-compliant interface disposed between the CP third surface and the sample, wherein the shape-compliant interface has a refractive index that is the same as or close to a refractive index of a first portion of the sample.

40. The optically based system of claim 39, wherein: The shape compliant interface is or includes a liquid and / or a gel.

41. The optically based system of claim 39, wherein: The system also includes an orienting infrastructure configured to orient the sample so that the first incident LB is incident normally on the first surface, and / or the folded LB obtained by folding the second incident LB by the LFC is incident nominally normally on the CP second surface, and / or the additional incident LB is oriented nominally perpendicular to the CP first surface.

42. The optical-based system of claim 29, further comprising one or more processors configured to calculate one or more actual tilt angles based at least on the measured first angular deviation.

43. The optically based system of claim 42, wherein: The sample also includes an external flat third surface parallel to the first surface, wherein the one or more processors are configured to additionally consider a measured second angular deviation of the fourth return LB relative to the third return LB to calculate the actual tilt angle, and the third return LB and the fourth return LB are obtained by the following operations when the sample is flipped so that the first surface and the third surface are reversed: (a') projecting a third incident LB onto the third surface of the sample to generate the third return LB by reflection from the third surface, and (b') projecting a fourth incident LB onto the LFC parallel to the third incident LB to generate the fourth return LB by redirecting the fourth incident LB into or onto the sample by the LGA, reflecting the fourth incident LB from the internal facet and redirecting it in the opposite direction by the LGA.

44. The optically based system of claim 42, wherein: The processor is configured to calculate an orientation of the CP first surface relative to the first surface.

45. The optically based system of claim 29, wherein: The CP also includes an external flat CP fourth surface, which is parallel to the CP first surface, wherein the CP is mechanically capable of flipping so that the CP first surface and the CP fourth surface are capable of being reversed while maintaining the nominal orientation of the CP second surface relative to the sample.

46. ​​The optically based system of claim 45, wherein: The measured second angular deviation is obtained by flipping the CP such that the CP first surface and the CP fourth surface are reversed and the nominal orientation of the CP second surface relative to the sample is maintained.

47. An optically based system for verifying the orientation of an internal facet of a sample relative to an external planar first surface of the sample, the system comprising: a light guiding arrangement LGA, the LGA comprising a light folding component LFC and a coupling prism CP, the LGA being configured to redirect light incident on the LFC into or onto the sample such that light transmitted by the sample into the sample impinges on the inner facet of the sample nominally perpendicularly to the inner facet, wherein the CP comprises an outer flat CP first surface, an outer flat CP second surface nominally inclined at a nominal angle relative to the CP first surface, and an outer CP third surface opposite the CP second surface, wherein the CP is arranged such that the CP first surface is parallel to the first surface of the sample, and the CP is further arranged such that light folded by the LFC impinges on the CP second surface nominally normally; and An illumination and collection device ICA, the ICA comprising: (a) a first light source and an optical device, which are configured to project a first incident light beam LB onto the first surface to generate a first return LB by reflection from the first surface, (b) a second light source and an optical device, which are configured to project a second incident LB onto the LFC in parallel with the first incident LB to generate a second return LB by redirecting the second incident LB nominally normally onto the CP second surface and into or onto the sample by the LFC, so that the light transmitted into the sample by the sample nominally strikes the inner facet normally, and (c) a third light source and an optical device, which are configured to project an additional incident LB normally onto the CP first surface to obtain an additional return LB by reflection of the additional incident LB from the CP first surface, wherein the first light source, the second light source and the third light source and the corresponding optical device are configured to provide and / or block one or more of the first incident LB, the second incident LB and the additional incident LB so as to at least help distinguish between the corresponding return LBs; and At least one sensor.

48. The optical-based system of claim 47, further comprising a first autocollimator, a second autocollimator, and a third autocollimator, wherein the first autocollimator, the second autocollimator, and the third autocollimator respectively comprise the first light source, the second light source, and the third light source, the at least one sensor, and a collimating lens or a collimating lens assembly.

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