Optical verification of surface orientation

Abstract

Disclosed herein is an optical method for verifying the angle between outer flat surfaces of a sample. The method includes: (i) providing a sample including a first outer flat surface and a second outer flat surface nominally tilted at a nominal angle relative to the first surface; (ii) generating a first incident light beam (LB) directed at the first surface and a second incident LB parallel to the first incident LB; (iii) obtaining a first return LB by reflecting the first incident LB from the first surface; (iv) obtaining a second return LB by bending the second incident LB at the nominal angle, reflecting the bent LB from the second surface, and bending the reflected LB at the nominal angle; (v) measuring a first angular deviation between the return LB; and (vi) estimating an actual tilt angle between the first and second surfaces based at least on the measured first angular deviation.

Description

[Technical Field]

[0001] The present disclosure generally relates to methods and systems for surface metrology of a sample. [Background technology]

[0002] Optical elements, such as glass prisms, are increasingly required to exhibit higher tolerances for the angles between their surfaces. Meeting the required angular tolerances requires highly accurate metrology to verify the angles between the surfaces, which in turn requires the use of high-end optics and complex alignment and calibration procedures. Thus, there is an unmet need in the art for simple, easily implementable metrology techniques that avoid the use of high-end optics, thereby meeting the demands of mass production. Summary of the Invention

[0003] Aspects of the present disclosure, according to some embodiments thereof, relate to methods and systems for surface metrology of a sample. More particularly, but not exclusively, according to some embodiments of the present disclosure, aspects of the present disclosure relate to optical methods and systems for metrology of an external surface of a sample.

[0004] The present application discloses a fast, simple, and accurate method and system for measuring the tilt of an outer flat surface of a sample relative to one or more other outer flat surfaces of the sample. To achieve this, two parallel-oriented light beams (LBs) can be used. A first LB impinges on a first outer flat surface of the sample. A second LB is redirected to nominally impinge on a second outer flat surface of the sample, and its tilt angle relative to the first surface is verified at the same angle of incidence as the first LB. The second reflected LB is then redirected again, and the angular deviation between the reflected LBs is measured. Advantageously, according to some embodiments of the disclosed technology, a collimated light source, a light sensor (or image sensor), a light bending component for redirecting the second LB, and an orientation infrastructure for orienting the sample are sufficient to verify the tilt of an outer flat surface.

[0005] Thus, according to an aspect of some embodiments there is provided an optical method for verifying an angle between outer flat surfaces of a sample, the method comprising: - Providing a sample that includes an outer flat first surface and an outer flat second surface that is nominally inclined (intended to be inclined by design and fabrication) at a nominal inclination angle relative to the first surface. - generating a first incident light beam (LB) directed at the first surface and a second incident LB that is parallel to the first incident LB; Obtaining a first return LB by reflection from a first surface of the first incident LB. - Bending the second incident LB at an optical bending angle nominally equal to the nominal tilt angle, reflecting the bent LB from a second surface, and obtaining a second return LB by bending the reflected LB at the optical bending angle. - Measuring a first angular deviation of the second return LB relative to the first return LB. - estimating an actual tilt angle of the second surface relative to the first surface based at least on the measured first angular deviation.

[0006] According to some embodiments of the method, the estimated actual tilt angle is equal to or approximately equal to α+δ / 2 (e.g., the estimated actual tilt angle is α+0.475 δ to α+0.525 δ, α+0.45 δ to α+0.55 δ, or even α+0.4 δ to α+0.6 δ, each possibility corresponding to a separate embodiment), where α is the nominal tilt angle, and δ is a measure of the first angular deviation.

[0007] According to some embodiments of the method, the first incident light LB is directed towards the first surface perpendicular to the first surface.

[0008] According to some embodiments of the method, the bending is performed using a light bending component (LFC), which is or includes a prism, one or more mirrors, and / or a diffraction grating.

[0009] According to some embodiments of the method, the light bending angle is insensitive to variations in the pitch of the LFC.

[0010] According to some embodiments of the method, the LFC is or includes a pentaprism or a similarly functional prism, or a pair of mirrors set at an angle relative to each other, or a similarly functional mirror device.

[0011] According to some embodiments of the method, the sample is or comprises glass, polymer, metal, crystal, and / or combinations thereof.

[0012] According to some embodiments of the method, the sample is a prism.

[0013] According to some embodiments of the method, the second surface does not share a common edge with the first surface.

[0014] According to some embodiments of the method, the first incident light LB and the second incident light LB are complementary parts of a single collimated light LB.

[0015] According to some embodiments of the method, the first incident light LB and the second incident light LB are prepared by blocking one or more portions of a single collimated light LB.

[0016] According to some embodiments of the method, the single collimated LB is polychromatic.

[0017] According to some embodiments of the method, the single collimated LB is a laser beam.

[0018] According to some embodiments of the method, the first angular deviation is measured using an autocollimator.

[0019] According to some embodiments of the method, the first angular deviation between the return beams LB is equal to or approximately equal to Δu / f, where Δu is the difference between the coordinates of the first spot and the corresponding coordinates of the second spot on the photosensitive surface of the autocollimator, and f is the focal length of the collimating lens of the autocollimator. The first spot is formed by the first return beam LB, and the second spot is formed by the second return beam LB.

[0020] According to some embodiments of the method, the method further comprises an initial calibration stage in which an absolute reference sample is utilized to calibrate the system.

[0021] According to some embodiments of the method, the nominal tilt angle is an obtuse angle.

[0022] According to some embodiments of the method, the nominal tilt angle is an acute angle.

[0023] According to some embodiments of the method, the nominal tilt angle is 90° and the sample has an outer flat third surface that is parallel to the first surface, and the method further includes, following measurement of the first angular deviation: - Inverting the sample to reverse the first and third surfaces while maintaining the nominal orientation of the second surface relative to the LFC. Preparing a third incident LB directed towards a third surface and a fourth incident LB directed parallel to the third incident LB. Obtaining a third return LB by reflection of the third incident LB from a third surface. - Bending the fourth incident LB at an optical bending angle nominally equal to the nominal tilt angle, reflecting the bent fourth incident LB from the second surface, and obtaining a fourth return LB by bending the fourth incident LB reflected at the optical bending angle. - Measuring the second angular deviation of the fourth return LB relative to the third return LB.

[0024] In estimating the actual tilt angle, the actual tilt angle is estimated by additionally taking into account the measured second angular deviation.

[0025] According to some embodiments of the method, the uncertainty in the parallelism of the first and third surfaces is less than the required measurement accuracy of the actual tilt angle.

[0026] According to some embodiments of the method, the estimated actual tilt angle is equal to x+(δ1-δ2) / 4 or approximately equal to %+(δ1-δ2) / 4 (e.g., the estimated actual tilt angle is %+0.235·(δ1-δ2) to %+0.265·(δ1-δ2), %+0.225·(δ1-δ2) to %+0.275·(δ1-δ2), or even %+0.2·(δ1-δ2) to %+0.3·(δ1-δ2), each possibility corresponding to a separate embodiment). x is the nominal tilt angle. δ1 is the measured first angular deviation, and δ2 is the measured second angular deviation.

[0027] According to some embodiments of the method, the method further comprises suppressing internal reflections from the fourth surface, provided that the sample includes an outer flat fourth surface that is nominally parallel to the second surface.

[0028] According to an aspect of some embodiments there is provided an optical system for verifying an angle between outer flat surfaces of a sample, the system including: - A light bending component (LFC) nominally configured to bend light incident at its top at a nominal tilt angle defined by an outer flat first surface and an outer flat second surface of the sample. -Illumination and Collection Apparatus (ICA), including: ■A light generating assembly for (a) projecting a first incident light beam (LB) onto a first surface to generate a first return LB by reflection from the first surface, and (b) projecting a second incident LB onto the LFC parallel to the first incident LB to generate a second return LB by reflection from a second surface and back through the LFC. ■At least one sensor configured to measure a first angular deviation between the first return LB and the second return LB, and / or an eyepiece assembly configured to enable manual measurement of the first angular deviation.

[0029] The measured first angular deviation indicates the actual tilt angle of the second surface relative to the first surface.

[0030] According to some embodiments of the system, the light generation assembly includes a light source and an optical instrument.

[0031] According to some embodiments of the system, the system further includes an orientation infrastructure configured to orient the sample so that the first incident LB strikes the first surface normal (i.e., perpendicular) and / or so that the bent LB obtained by bending the second incident LB by the LFC strikes the second surface nominally normal.

[0032] According to some embodiments of the system, the system comprises at least one sensor, and the system further comprises a calculation module configured to calculate an actual tilt angle of the second surface relative to the first surface based on at least the measured first angular deviation.

[0033] According to some embodiments of the system, the system includes at least one sensor and the ICA is or includes an autocollimator, the autocollimator including a light source and at least one sensor.

[0034] According to some embodiments of the system, the ICA further includes a pair of blocking elements configured to enable selective blocking of each of the first and second incident beams LB, According to some such embodiments, the blocking elements are shutters that completely block the light beam incident thereon.

[0035] According to some embodiments of the system, the LFC includes a prism, one or more mirrors, and / or a diffraction grating.

[0036] According to some embodiments of the system, the light bending angle of the LFC is not affected by variations in the pitch of the LFC.

[0037] According to some embodiments of the system, the LFC is or includes a pentaprism or a prism with similar functionality, or a pair of mirrors placed at an angle to each other, or a mirror device with similar functionality.

[0038] According to some embodiments of the system, the system is configured to facilitate sample inversion.

[0039] According to some embodiments of the system, the system includes at least one sensor and a calculation module. The nominal tilt angle is 90°, and the sample further includes an outer, flat, third surface parallel to the first surface. The calculation module is configured to calculate the actual tilt angle by additionally taking into account the measured second angular deviation of the fourth return light beam relative to the third return light beam. When the sample is inverted, the first and third surfaces are reversed, and the nominal orientation of the second surface relative to the LFC is maintained. (a') The third return light beam LB is obtained by projecting a third incident light beam onto the third surface of the sample to generate the third return light beam LB by reflection from the third surface, and (b') the fourth return light beam LB is obtained by projecting the fourth incident light beam LB onto the LFC parallel to the third incident light beam LB to generate the fourth return light beam LB by its bending due to the LFC, reflection from the second surface, and back through the LFC.

[0040] According to some embodiments of the system, the calculation module is further configured to calculate the uncertainty in the obtained value of the actual tilt angle, taking into account at least manufacturing tolerances and imperfections of the LFC and the ICA.

[0041] According to some embodiments of the system, the system includes an orientation infrastructure, and the calculation module is configured to calculate the uncertainty in the calculated value of the actual tilt angle by additionally taking into account manufacturing tolerances and imperfections of the orientation infrastructure.

[0042] According to some embodiments of the system, the light-generating assembly includes a light source and an optics: the light source is configured to generate a single LB; and the optics is configured to collimate the single LB.

[0043] According to some embodiments of the system, the first incident light LB and the second incident light LB are complementary portions of a collimated light LB.

[0044] According to some embodiments of the system, the light source is a polychromatic light source.

[0045] According to some embodiments of the system, the light source is a monochromatic light source.

[0046] According to some embodiments of the system, the light source is configured to generate a laser beam.

[0047] According to some embodiments of the system, the at least one sensor includes an optical sensor and / or an image sensor (eg, a camera).

[0048] According to an aspect of some embodiments there is provided a method for manufacturing a sample having a pair of outer flat surfaces set at a nominal angle relative to one another, the method comprising the steps of: - Providing a raw sample. - processing the raw sample to obtain a processed sample comprising a first outer flat surface and a second outer flat surface set at a test angle relative to the first surface. - measuring the test angle using the optical method described above. - subjecting the processed sample to further processing if the test angle differs from the nominal angle by more than a predetermined difference to obtain a reprocessed sample. - measuring the difference between the test angle of the reprocessed sample and the nominal angle until it is below a predetermined difference, and repeating the reprocessing step as necessary.

[0049] Particular embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the drawings, specification, and claims included in this application. Furthermore, while specific advantages are listed above, various embodiments may include all, some, or none of the listed advantages.

[0050] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In case of conflict, the present patent specification, including definitions, will control. As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more," unless the context clearly dictates otherwise.

[0051] Unless otherwise specified, it will be understood from this disclosure that, according to some embodiments, terms such as "processing," "calculating," "operating," "determining," "estimating," "evaluating," or "measuring" may refer to acts and / or processes of a computer or computing system, or similar electronic computing device, that manipulate and / or transform data represented as physical (e.g., electronic) quantities in the registers and / or memory of the computing system into other data that is similarly represented as physical quantities in the memory, registers, or other such information storage, transmission, or display device of the computing system.

[0052] Embodiments of the present disclosure may include apparatuses for performing the operations herein. The apparatus may be specially constructed for the desired purposes, or may comprise a general-purpose computer that is selectively differentiated or reconfigured by a computer program stored in the computer. Such a computer program may be stored on a computer-readable storage medium, such as, but not limited to, 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 programmable read-only memory (EEPROM), a magnetic or optical card, or any other type of medium suitable for storing electronic instructions and capable of being coupled to a computer system bus.

[0053] The processes and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may be convenient to construct more specialized apparatus to perform the desired method. The desired structure for a variety of these systems will appear from the following description. Additionally, descriptions of embodiments of the present disclosure do not refer to any particular programming language. It will be understood that a variety of programming languages ​​may be used to implement the teachings of the present disclosure as described herein.

[0054] Aspects of the disclosure may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The disclosed embodiments may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media, including memory storage devices. [Brief explanation of the drawings]

[0055] Some embodiments of the present disclosure will be described with reference to the accompanying drawings. The description, together with the drawings, will make apparent to those skilled in the art how some embodiments may be implemented. The drawings are for illustrative purposes and do not attempt to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the present disclosure. For clarity, some objects depicted in the drawings have not been drawn to scale. Furthermore, two different objects in the same drawing may be drawn to different scales. In particular, the scale of some objects may be greatly exaggerated compared to other objects in the same drawing.

[0056] In the figure,

[0057] [Figure 1A] 1 illustrates a schematic diagram of an optical system for metrology of an outer flat surface of a sample during testing of the sample, according to some embodiments. [Figure 1B] 1B shows a schematic perspective view of the sample of FIG. 1A during testing of the sample, according to some embodiments. [Figure 1C] 1B illustrates a schematic diagram of spots on a photosensitive surface of a sensor of the system of FIG. 1A, according to some embodiments. [Figure 2A] 1B shows a schematic diagram of an optical system for verifying the perpendicularity of one outer flat surface of a sample relative to two other parallel outer flat surfaces of the sample during testing of the sample, the system corresponding to a specific embodiment of the system of FIG. 1A. [Figure 2B] 1B shows a schematic diagram of an optical system for verifying the perpendicularity of one outer flat surface of a sample relative to two other parallel outer flat surfaces of the sample during testing of the sample, the system corresponding to a specific embodiment of the system of FIG. 1A. [Figure 2C] 2C illustrates a schematic diagram of a spot on a photosensitive surface of a sensor of the system of FIGS. 2A and 2B, according to some embodiments. [Figure 2D] 2C illustrates a schematic diagram of a spot on a photosensitive surface of a sensor of the system of FIGS. 2A and 2B, according to some embodiments. [Figure 3] 1A shows a schematic diagram of an optical system for measuring the outer flat surface of a sample during testing of the sample, the system corresponding to the specific embodiment of the system of FIG. 1A, in which the system light bending component is a prism. [Figure 4] 1B shows a schematic diagram of an optical system for measuring the outer flat surface of a sample during testing of the sample, the system corresponding to the specific embodiment of the system of FIG. 1A, in which the system optical bending component is a mirror. [Figure 5] 1 shows a flowchart of an optical method for external flat surface metrology of a sample, according to some embodiments. [Figure 6] 1 shows a flowchart of an optical system for verifying the perpendicularity of one outer flat surface of a sample relative to two other parallel outer flat surfaces of the sample, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0058] The principles, uses, and implementations of the teachings disclosed in the present application may be better understood by reference to the accompanying specification and drawings. Those skilled in the art, having reviewed the specification and drawings of the present application, will be able to practice the teachings herein without undue effort or experimentation. In the drawings, like reference numerals refer to like parts throughout.

[0059] In the specification and claims of this application, the words "comprise" and "have" and their forms are not limited to the elements in a list with which they may be associated.

[0060] As used in this application, the term "about" may be used to specify the value of a quantity or parameter (e.g., the length of an element) within a continuous range of values ​​near (and including) a given (recited) value. According to some embodiments, "about" may specify the value of the parameter to be between 80% and 120% of the given value. For example, stating that "the length of the element is equal to about 1 meter" is equivalent to stating that "the length of the element is between 0.8 meters and 1.2 meters." According to some embodiments, "about" may specify the value of the parameter to be between 90% and 110% of the given value. According to some embodiments, "about" may specify the value of the parameter to be between 95% and 105% of the given value.

[0061] As used herein, according to some embodiments, the terms "substantially" and "about" may be synonymous.

[0062] For ease of illustration, a three-dimensional Cartesian coordinate system is introduced in some of the drawings. Note that the orientation of the coordinate system relative to the depicted object may vary from one drawing to another. Also, the symbols

number

number

[0063] In the figures, optional elements and optional steps (in the flow charts) are depicted with dashed lines.

[0064] system According to some aspects of embodiments, an optical method for metrology of a sample's outer flat surfaces is provided. FIG. 1A schematically depicts such a system, an optical-based system 100, according to some embodiments. The optical system 100 is configured to verify the angle between two outer flat surfaces of a sample. FIG. 1A provides a side view of the system 100 and a sample 10, according to some embodiments. (It should be understood that the sample 10 does not constitute a part of the system 100.) The sample 10 is shown as being inspected by the system 100. The sample 10 can be any opaque or partially transparent element having two or more reflective flat (external) surfaces, which are set at a (non-zero) angle relative to each other. According to some embodiments, the sample 10 can be made of glass, polymer, metal, crystal, and / or combinations thereof. According to some embodiments, the sample 10 can be an optical element such as a prism, a waveguide, or a beam splitter. According to some embodiments, the prism can be shaped as a polyhedron. According to some embodiments, and as illustrated in FIG. 1A, a cross section of the sample 10 taken parallel to the zx plane may define a polygon.

[0065] The sample 10 includes an outer flat first surface 12a (i.e., a first flat outer surface) and an outer flat second surface 12b (i.e., a second flat outer surface). The sample 10 is manufactured to exhibit a nominal tilt angle α between the first surface 12a and the second surface 12b. However, due to imperfections in fabrication, the actual tilt angle between the first surface 12a and the second surface 12b, labeled α' in FIG. 1A, will generally differ from the nominal tilt angle α. In FIG. 1A, a dashed line L is shown intersecting the second surface 12b, which is tilted at the nominal tilt angle α relative to the first surface 12a. The dashed line L indicates the intended tilt of the second surface 12b. 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°.

[0066] 1A also shows a (straight) dashed line H extending parallel to the first surface 12a and intersecting the second surface 12b. A complementary angle to the nominal tilt angle α is labeled as β (i.e., β=180°−α) and spans between the second surface 12b and the dashed line H.

[0067] According to some embodiments, system 100 includes a light bending component (LFC) 102 and an illumination and collection apparatus (or assembly, ICA) 104. System 100 may further include a controller 108 operatively associated with ICA 104 and configured to control its operation. According to some embodiments, and as illustrated in FIG. 1A , ICA 104 includes a light source 112 (or multiple light sources) and a sensor 114 (or multiple sensors), and optionally, optics 118. According to some embodiments, sensor 114 is an optical sensor or an image sensor (alternatively, the multiple sensors include one or more optical sensors and / or one or more image sensors, e.g., cameras). According to some alternative embodiments not depicted in FIG. 1A , ICA 104 includes an eyepiece assembly in place of sensor 114, thereby configuring for visual determination (i.e., by eye) of the actual tilt angle. Light source 112 and optics 118 are collectively referred to as a “light generation assembly.”

[0068] As described in detail below, the ICA 104 is configured to output a pair of parallel light beams (LBs): a first LB 105a (also referred to as a "first incident LB" and shown in FIG. 1A by a pair of parallel light rays) and a second LB 105b (also referred to as a "second incident LB" and shown in FIG. 1A by a pair of parallel light rays). According to some such embodiments, the optical device 118 may be configured to collimate the light generated by the light source 112, thereby generating the (parallel) incident LBs 105a and 105b. According to such embodiments, the optical device 118 may include a collimating lens or a collimating lens assembly (not shown). According to some embodiments, the incident LBs 105a and 105b may form complementary portions of a collimated light beam (focused by the collimating lens or collimating lens assembly). Alternatively, according to some embodiments, the incident LBs 105a and 105b may be spaced apart (and parallel). According to some such embodiments, the optical device 118 may further 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 mirrors (not shown) configured to prepare a pair of spaced-apart parallel LBs from the collimated LB.

[0069] According to some embodiments, the optical device 118 may include a plurality of blocking elements (such as the pair of blocking elements illustrated in FIGS. 2A and 2B ) configured to enable selective blocking of each of the incident LBs 105, thereby enabling individual sensing of each of the return LBs induced by the first incident LB 105 a and the second incident LB 105 b, respectively. As used herein, the term “blocking element,” with respect to an optical element, is broadly interpreted to encompass both an opaque element (such as a shutter) that can be controllably opened or closed and configured to block (when closed) an incident light beam, and a filtering element (such as a spectral filter) configured to completely or partially block one or more portions of the light spectrum (e.g., the visible spectrum).

[0070] According to some embodiments, the light source 112 may be configured to generate polychromatic light. According to some such embodiments, the spectrum of the light may be controllable. According to some embodiments, the light source 112 may be configured to generate monochromatic light. In this regard, it should be noted that when the LFC 102 is a prism and the second incident LB 105b is generated to impinge non-perpendicularly on the prism (e.g., when the first incident LB 105a is generated to impinge non-perpendicularly on the first surface 12a), it may be preferable to use monochromatic light.

[0071] According to some embodiments, the ICA 104 is or includes an autocollimator (i.e., some or all of the light source 112, the sensor 114, and the optics 118 constitute components of an autocollimator). According to some embodiments, the incident LB 105 constitutes adjacent partial beams of a single collimated wide-area LB produced by the autocollimator. According to such embodiments, the optics 118 may include an optical filter configured to transmit two partial beams of the collimated LB (such as the incident LB 105) prepared by the autocollimator and incident on the optical filter (the parallelism of the two partial beams is maintained upon exiting the optical filter).

[0072] According to some embodiments, the light source 112 may be configured to generate a collimated laser beam. According to some such embodiments, the optics 118 may include a beam expander (not shown) configured to increase the laser beam diameter, such that the expanded laser beam may simultaneously impinge on both the sample 10 and the LFC 102. In such embodiments, the first incident light LB 105a and the second incident light LB 105b may constitute complementary portions of the laser beam. Alternatively, the optics 118 may include a beam splitter and optical components configured to split the laser beam into a pair of parallel (spaced) sub-beams, i.e., the first and second sub-beams constituting the first incident light LB 105a and the second incident light 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 each sub-beam is redirected onto a single optical sensor (i.e., the sensor 114 according to some such embodiments) and focused (e.g., using a lens or lens arrangement) onto the photosensitive surface of the optical sensor. Ideally, if the second sub-beam impinges perpendicularly on the internal facet 14 (after redirection by the LFC 122 and transmission through the sample 10), the recombined sub-beams will form a collimated (second) laser beam, and the two spots formed on the optical sensor by the return sub-beams will overlap. According to some other embodiments, two optical sensors may be used—such that the distance between and relative orientation between them is known. In such embodiments, each of the return partial beams may be directed to a different one of the two optical sensors.

[0073] According to some embodiments, the ICA 104 may be configured for interferometry. The light source 112, some or all of the optics 118, and the sensor 114 constitute components of an interferometric apparatus, as described below. In such embodiments, the light source 112 may be configured to generate a coherent, planar wavefront. The optics 118 may be configured to split the generated wavefront into two wavefronts: a first (coherent, planar) incident wavefront and a second (coherent, planar) incident wavefront, which constitute the first incident LB 105a and the second incident LB 105b, respectively.

[0074] According to some embodiments, the LFC 102 is or includes a prism, one or more mirrors, and / or a diffraction grating. According to some embodiments, the LFC 102 is a pentaprism or similarly functional prism that is insensitive to pitch variations (in the sense that when the pitch of the LFC is slightly changed, i.e., when the LFC 102 is slightly rotated about the y-axis, its light bending angle remains unchanged).

[0075] According to some embodiments, system 100 may further include an orienting infrastructure 120 for orienting sample 10 relative to ICA 104. By way of non-limiting example, orienting infrastructure 120 may be in the form of a stage 122 mounted on a base 124. Stage 122 is configured to mount a sample thereon, such as sample 10. Base 124 is configured to orient and, optionally, translate stage 122. According to some embodiments, the base 124 may be configured to provide manipulation of the sample 10 in each of six degrees of freedom (i.e., translation in any direction, and rotation about the yaw axis, and rotation about (at least limited) pitch and roll axes). In particular, the orienting infrastructure 120 may be configured to orient the sample 10 so that a first incident LB 105a impinges perpendicularly on the first surface 12a, and a bending LB 113b obtained by impinging a second incident LB 105b on the LFC 102 impinges nominally perpendicularly on the second surface 12b. According to some embodiments, the orienting infrastructure 120 may be functionally associated with and configured to be controlled by the controller 108.

[0076] As used herein, according to some embodiments, the terms "nominal" and "ideally" may be synonymous. When an object is intended, through design and fabrication, to exhibit (i.e., be characterized by) a certain intrinsic property (such as the tilt angle between the flat surfaces of a sample), the object may be said to "nominal" exhibit that property, but in reality, due to manufacturing tolerances, the object may actually exhibit that property imperfectly. This also applies to extrinsic properties of an object, such as the light propagation direction of a light beam. In this case, it should be understood that although the object has been intentionally prepared or otherwise manipulated to ideally exhibit that property, in reality, the object may actually exhibit that property imperfectly due, for example, to inherent imperfections in the apparatus used for its preparation.

[0077] In operation, a first incident LB 105a is directed at the sample 10, and a second incident LB 105b is directed at the LFC 102. According to some embodiments, and as illustrated in FIG. 1A, the first incident LB 105a is incident on the first surface 12a perpendicularly thereto. The first incident LB 105a (or at least a portion thereof) is reflected from the first surface 12a and sensed by the sensor 114, as shown by the first return LB 125a.

[0078] The second incident light LB 105b is directed at the LFC 102. The LFC 102 is nominally configured to bend the second incident light LB 105b at a nominal tilt angle α. More precisely, the LFC 102 is configured to "bend" (i.e., redirect) the second incident light LB 105b, so that the bend LB 113b (obtained by bending the second incident light LB 105b) is nominally directed at a nominal tilt angle α relative to the second incident light LB 105b and nominally perpendicular to the second surface 12b. In practice, due to manufacturing imperfections, the actual light bending angle α" of the LFC 102 may deviate slightly from the nominal tilt angle α. If the uncertainty in the light bending angle of the LFC 102 (due to manufacturing tolerances) is significantly lower than the precision with which the actual tilt angle of the second surface 12b is determined, then the uncertainty in the light bending angle can be ignored (i.e., the LFC 102 can be considered to bend the second incident LB 105a at the exact nominal tilt angle α). Otherwise, the uncertainty in the light bending angle will contribute (non-negligibly) to the overall uncertainty in the measured value of the actual tilt angle unless the nominal tilt angle is equal to 90°, in which case the deviation in the actual bending angle can be discounted through performing additional measurements with the sample inverted, as detailed below in the description of Figures 2A and 2B and in the description of Figure 6.

[0079] To avoid cluttering the figures, typically only two rays of each light beam are shown. Also, it should be understood that the depiction of the light beams is schematic, and the depicted light beams may be wider or narrower than depicted. Thus, for example, according to some embodiments, the first incident LB 105a may impinge across the entire first surface 12a and / or the second incident LB 105b may impinge across the entire light-receiving surface of the LFC 102.

[0080] The bent LB 113b impinges on the second surface 12b at an incident angle θ. The angle is measured clockwise from the perspective of the reader viewing the figure. Angles greater than 180° are set to negative values ​​by subtracting 360°. Thus, in FIG. 1A, as a non-limiting example intended to facilitate explanation by providing more specificity, the incident angle θ is negative, and the return angle (i.e., the angle of reflection) is positive. More precisely, the incident angle θ is shown for ray 113b1 (one of the two rays representing the bent LB 113b in FIG. 1A) as extending counterclockwise from dashed line B, which represents the normal to the second surface 12b. The tilt angles α and α' are measured clockwise from the first surface 12a (in FIG. 1A, as a non-limiting example intended to facilitate explanation, α' is shown as being greater than α). The nominal tilt angle α extends clockwise from the first surface 12a to dashed line L. The actual tilt angle α' extends clockwise from the first surface 12a to the second surface 12b.

[0081] The incident angle θ depends on the deviation Δα'=α-α' (i.e., the deviation of the tilt of the second surface 12b from the nominal tilt) and the deviation Δα''=α-α'' (i.e., the deviation of the actual light bending angle of the LFC 102 from α). If there are no imperfections in the system 100 (i.e., α''=α), the incident angle θ will be equal to Δα'. In other words, the incident angle θ is equivalent to Δα', to an accuracy that depends on the uncertainty in the actual light bending angle α'' and any other relevant uncertainties in the parameters of the LFC 102, the ICA 104, and the orientation infrastructure 120. In particular, the system 100 is configured to output the LB 113b that strikes nominally normal (i.e., perpendicular) on the second surface 12b when Δα'=0. The magnitude of Δα' (i.e.,

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[0082] The bent LB 113b (or at least a portion thereof) is reflected from the second surface 12b in a specular manner (i.e., at a return angle θ equal to the negative angle of incidence θ), as shown by the reflected LB 117b. R (by) is reflected.

[0083] The reflected light LB 117b returns towards the LFC 102 and is bent by the LFC 102 at an actual light bending angle α''. More precisely, the reflected light LB 117b is redirected by the LFC 102 towards the ICA 104, as shown by a second return light LB 125b. The second return light LB 125b is sensed by the sensor 114.

[0084] Typically, due to manufacturing imperfections in both the sample 10 and the LFC 102, the second return LB 125b will not be parallel to the first return LB 125a. The angle δ (also called the "angular deviation") between the first return LB 125a and the second return LB 125b is 2·θ Rand is therefore dependent on Δα′. The angle δ is shown extending clockwise from ray 105b1 (one of the two rays representing the second incident LB 105b in FIG. 1A) to ray 125b1 (one of the two rays representing the second returning LB 125b in FIG. 1A), and is therefore positive in FIG. 1A.

[0085] 1B, which shows a schematic perspective view of sample 10 during sample inspection by system 100. Also shown in FIG. 1B are first incident LB 105a, first return LB 133a, bent LB 113b (which should be understood as impinging nominally normal on second surface 12b), and reflected LB 117b.

[0086] 1C schematically illustrates the first spot 133a and the second spot 133b formed by the first return LB 125a and the second return LB 125b, respectively, on the photosensitive surface 134 of the sensor 114, according to some embodiments, where u1 and u2 are the horizontal coordinates (i.e., as measured along the x-axis) of the first spot 133a and the second spot 133b, respectively. (The coordinate system depicted in FIG. 1C is assumed to coincide with the coordinate system depicted in FIG. 1A, up to a possible translation of the origin. Thus, the x-axis in FIG. 1C 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 the difference Δu=u2-u1. As a non-limiting example, if the measurement is based on an autocollimator (i.e., in embodiments where the ICA 104 is or includes an autocollimator), then δ=Δu / f, and so Δα′=−Δu / (2·f), where f is the focal length of the autocollimator's collimating lens. (More precisely, Δα′ is equal to −Δu / (2·f), with the accuracy depending on the uncertainty in the actual light bending angle α″ and any other relevant uncertainties in the parameters of the LFC 102, the ICA 104, and the orientation infrastructure 120.)

[0087] 1C, the vertical coordinates (i.e., as measured along the y-axis) of the first spot 133a and the second spot 133b may differ slightly from one another due to, for example, misalignment of the LFC 102 and the sample 10 relative to their respective yaw angles (i.e., about the z-axis). Such potential misalignment can be minimized during calibration of the system 100, for example, using an autocollimator.

[0088] Alternatively, according to some embodiments in which the ICA 104 is or includes an interferometric device, the angle δ can be estimated from an interference pattern formed by the first return LB 125a and the second return LB 125b. More specifically, in such embodiments, the first return LB 125a constitutes a first return wavefront obtained from reflection of the first incident wavefront from the first surface 12a, and the second return LB 125b constitutes a second return wavefront obtained by bending the second incident wavefront by the LFC 102, reflecting from the second surface 12b, and bending it again by the LFC 102. The returning wavefronts are recombined, and their interference pattern is measured by the sensor 114. If the first and second wavefronts impinge on their respective surfaces (i.e., the first surface 12a or the second surface 12b, respectively) at right angles, 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 inferred from the periodicity of the pattern.

[0089] According to some embodiments, the controller 108 may be communicatively associated with the computation module 130. The computation module 130 may include a processor and volatile and / or non-volatile memory components. The processor may be configured to receive from the controller 130, sensor 114 data (i.e., values ​​of u1 and u2) and calculate Δα′ based thereon. Optionally, according to some embodiments, the processor may be further configured to calculate the uncertainty in the (calculated value of) Δα′, taking into account manufacturing tolerances and imperfections of the LFC 102 (including uncertainty in the actual light bending angle), the ICA 104, and the orienting infrastructure 120. According to some embodiments, the computation module 130 may be included in the system 100.

[0090] According to some embodiments, the system 100 may further include two shutters (positioned similarly to the blocking elements of Figures 2A and 2B) configured to enable selective blocking of each of the first return LB 125a and the second return LB 125b, so that each of the return LBs 125 may be sensed separately (thereby facilitating attributing each of the spots 133 to the return LB that induced the spot).

[0091] According to some embodiments, the first surface 12a and the second surface 12b may be coated or temporarily coated with a reflective coating material so that light incident on the surface is maximally reflected or at least increased in reflection from the surface. According to some embodiments in which the light source 112 is configured to generate polychromatic light, the first surface 12a may be coated with a first coating material configured to reflect light within a first spectrum, and the second surface 12b (or LFC 102) may be coated with a second coating material configured to reflect light within a second spectrum, the second spectrum not overlapping or substantially not overlapping with the first spectrum. In such embodiments, selective blocking of the first return LB 125a and the second return LB 125b may be implemented using a spectral filter or spectral filtering device (optionally instead of a shutter) configured to allow each of the return LBs 125 to impinge on a coating material and selectively block or at least partially block light of the second spectrum and the first spectrum, respectively.

[0092] According to some alternative embodiments, a first (passive) spectral filter can be used to filter the first incident LB 105a into a first spectrum, and a second (passive) spectral filter can be used to filter the second incident LB 105b into a second spectrum. In such embodiments, to enable separate sensing of each of the return LBs 125, an additional spectral filter can be used positioned between the spectral filter and the sensor 114 and that enables selective filtering of light passing either into the first spectrum or the second spectrum.

[0093] It should be noted that a spectral filter or spectral filtering device can be used to reduce the signal associated with stray light and associated with any one incident LB 105 reaching the sensor 114 .

[0094] 1A, first surface 12a and second surface 12b are shown as sharing a common edge, it should be understood that the scope of the present disclosure is not limited to measuring samples so shaped. In particular, any sample including an outer flat first surface and an outer flat second surface that is inclined relative to the first surface but does not share a common edge with that surface can also be measured using system 100, as described above.

[0095] 2A and 2B schematically illustrate an optical system 200 for verifying the perpendicularity of one outer flat surface of a sample relative to at least two other outer flat surfaces of the sample, where the surfaces are parallel to one another, according to some embodiments. System 200 corresponds to a specific embodiment of system 100. More specifically, FIG. 2A provides a side view of system 200 and sample 20 being inspected by system 200, according to some embodiments. Sample 20 may be an optical element such as a prism, a waveguide, or a beam splitter. According to some embodiments, the prism may be shaped as a polyhedron. According to some embodiments, and as illustrated in FIGS. 2A and 2B, a cross section of sample 20 may be taken parallel to the zx plane and define a polygon.

[0096] Sample 20 includes an outer planar first surface 22a, an outer planar second surface 22b, and an outer planar third surface 22c. First surface 22a and third surface 22c are nominally parallel by design. Furthermore, sample 20 is fabricated to exhibit a nominal tilt angle between first surface 22a and second surface 22b of 90°. However, due to imperfections in fabrication, the actual tilt angle of second surface 22b relative to first surface 22a, labeled as χ' in FIGS. 2A and 2B, will generally differ from 90°.

[0097] It should be noted that, when using state-of-the-art manufacturing techniques, the (manufacturing) tolerance of the actual angle between surfaces that are fabricated to be parallel is much smaller than the tolerance of the actual angle between surfaces that are fabricated to be non-parallel. Thus, because first surface 22a and third surface 22c are fabricated to be parallel, the deviation of their planes from parallelism 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 second surface 22b and third surface 22c is 180°-χ ’ , i.e., the actual tilt angle χ ’ (The nominal value of the actual supplementary angle ψ' is 90°.)

[0098] System 200 includes an LFC 202 and an ICA 204. LFC 202 corresponds to a specific embodiment of LFC 102 and is configured to nominally bend light by 90°. According to some embodiments, LFC 202 is a prism, one or more mirrors, or a diffraction grating that is nominally configured to bend light incident on its top portion by 90° in a direction perpendicular to first surface 22a. According to some embodiments, LFC 202 is a pentaprism or a prism of similar functionality (i.e., it is not sensitive to pitch variations).

[0099] The ICA 204 corresponds to a specific embodiment of the ICA 104 and includes a light source (not shown), a sensor (not shown), and, optionally, optics (not shown) corresponding to specific embodiments of the light source 112, the sensor 114, and the optics 118, respectively. According to some embodiments, the ICA 204 includes an autocollimator 240. The autocollimator 240 may be configured to generate a collimated LB 201. The first incident LB 205 a and the second incident LB 205 b form sub-beams of the LB 201. According to some embodiments, and as illustrated in FIGS. 2A and 2B , the ICA 204 may further include a pair of blocking elements 246 a and 246 b, which allow selective blocking of each of the first incident LB 205 a and the second incident LB 205 b. According to some embodiments, each of the blocking elements 246 a and 246 b may be a shutter (e.g., controllable by the controller 208).

[0100] A first incident LB 205a is directed at the sample 20, and a second incident LB 205b is directed at the LFC 202. According to some embodiments, and as illustrated in FIG. 2A, the ICA 204 and the sample 20 are positioned and oriented so that the first incident LB 205a is incident on the first surface 22a normal to that surface. The first incident LB 205a (or at least a portion thereof) is reflected from the first surface 22a, as shown by the first return LB 225. The first return LB 225a is sensed by the autocollimator 240.

[0101] The LFC 202 is configured to bend the second incident LB 205b nominally by 90°. More precisely, the LFC 202 is configured to bend the second incident LB 205b so that the (first) bend LB 213b (obtained by bending the second incident LB 205b) is nominally oriented at 90° with respect to the second incident LB 205b and (nominally) perpendicular to the second surface 12b. In practice, due to manufacturing imperfections in embodiments where the LFC 202 is susceptible to pitch variations and imprecision in alignment, the actual light bending angle χ'' of the LFC 202 may deviate slightly from 90°. As described in more detail below, the effects of manufacturing imperfections in the LFC 202 can be offset or substantially offset by inverting the sample 20 so that the first surface 22a and the third surface 22c are reversed (while maintaining the nominal orientation of the second surface 22b relative to the LFC 202) and repeating the measurements described in the description of Figure 2B.

[0102] The bent LB 213b impinges on the second surface 22b at a first angle of incidence η1, which depends on the deviation Δχ′=90°−χ′ (i.e., the deviation of the tilt of the second surface 22b from the nominal tilt) as well as the deviation Δχ″=90°−χ″ (i.e., the deviation of the actual light bending angle of the LFC 202 from 90°). The normal to the second surface 22b is shown in FIG. 2A by the (straight) dashed line C1.

[0103] The bent light LB213b (or at least a portion thereof) is specularly reflected from the second surface 22b (i.e., at a return angle ζ1 equal to the negative of the first angle of incidence η1), as shown by a (first) reflection LB217b. The reflection LB217b returns towards the LFC 202 and is bent by the LFC 202 at an actual light bending angle χ'', resulting in a second return light LB225b. The second return light LB225b is sensed by the sensor 214.

[0104] The angle δ1 (also referred to as the "first angular deviation") between the second return LB 225b and the first return LB 225a is equal to 2·ζ1. Therefore, the angle δ1 depends on Δχ'. FIG. 2C schematically shows the first spot 233a and the second spot 233b formed by the first return LB 225a and the second return LB 225b, respectively, on the photosensitive surface 234 of the autocollimator 240 according to some embodiments, where w1 and w2 are the horizontal coordinates (i.e., as measured along the axis) of the first spot 233a and the second spot 233b, respectively. The angle δ1 can be directly inferred from the difference Δw=w2-w1.

[0105] Referring to FIG. 2B, compared to FIG. 2A, sample 20 has been inverted to reverse first surface 22a and third surface 22c (while maintaining the nominal orientation of second surface 22b relative to LFC 202).

[0106] A third incident LB 205a' is directed at the sample 20 perpendicular thereto, and a fourth incident LB 205b' is directed at the LFC 202. The third incident LB 205a' (or at least a portion thereof) is reflected from the third surface 22c, as shown by the third return LB 225a'. The third return LB 225b' is sensed by the sensor 214.

[0107] The fourth incident LB 205b′ strikes the LFC 202, resulting in a second bent LB 213b′. The second bent LB 213b′ has a second incident angle η 2 The second incident angle η2 is a deviation

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[0108] As shown by the second reflection LB217b', the fourth incident light LB205b' is (at least partially) specularly reflected from the second surface 22b (i.e., at a return angle ζ2 equal to the negative of the second incident angle η2). The second reflection LB217b' returns towards the LFA 202 and is bent by the LFA 202 at an actual light bending angle χ', as shown by the fourth return light LB225b'. The fourth return light LB225b' is sensed by the sensor 214.

[0109] The angle δ2 (also referred to as the "second angular deviation") between the fourth return LB 225b' and the third return LB 225a' is equal to 2·ζ2. Therefore, the angle δ2 depends on Δψ' and thereby on Δχ' (since χ'+φ'=180°, therefore Δψ'=-Δχ'). FIG. 2D schematically illustrates the third spot 233a' and the fourth spot 233b' formed by the third return LB 225a' and the fourth return LB 225b', respectively, on the photosensitive surface 234 of the sensor 214 according to some embodiments, where w1' and w2' are the horizontal coordinates of the third spot 233a' and the fourth spot 233b', respectively. The angle δ2 can be directly estimated from the difference Δw'=w2'-w1'.

[0110] Although Δw and Δw′ are shown in FIGS. 2C and 2D as both negative (so that δ1 and δ2 are both negative), it will be understood that in general, Δw and Δw′ can have opposite signs (so that δ1 and δ2 have opposite signs) or can both be positive (so that δ1 and δ2 are both positive).

[0111] Each of the measured angles δ1 and δ2 can be used to provide a respective estimate of the deviation angle Δχ'. If the system 200 were perfect, η2 would be equal to -η1 and δ1 would be equal to -δ2. However, in practice, the two estimates will generally differ due to deviations of the actual light bending angle from its nominal value. Because δ1 and δ2 have the same or substantially the same dependence as the actual light bending angle (if the LFC is not affected by pitch variations) (i.e., both δ1 and δ2 increase with increasing χ'' and decrease with decreasing χ''), deviations in the light bending angle can be canceled or substantially canceled out by averaging over the two estimates of the deviation angle Δχ'. That is, <Δχ'> is equal to or substantially equal to −(δ−δ / 4. In particular, in embodiments in which ICA 204 is or includes an autocollimator, <Δχ'> is equal to or substantially equal to −(Δw−Δw') / (2·f), where f is the focal length of the collimating lens of the autocollimator.

[0112] According to some embodiments, the first surface 22 a, the second surface 22 b, and the third surface 22 c may be coated or temporarily coated with a reflective coating material so that light incident on the reflective coating material is maximized or at least increased in reflection therefrom. According to some embodiments in which the autocollimator 240 is configured to generate a polychromatic LB, the first surface 12 a and the third surface 12 c may be coated with a first coating material configured to reflect light within a first spectrum, and the second surface 12 b may be coated with a second coating material configured to reflect light within a second spectrum, the second spectrum being different from the first spectrum. In such embodiments, the autocollimator 240 may include a spectral filter configured to selectively filter light within the first spectrum or the second spectrum, thereby facilitating separate sensing of each of the return LBs 225.

[0113] According to some embodiments, blocking elements 246a and 246b may be spectral filters (as a specific example, dichroic filters) configured to block light in the second spectrum and the first spectrum. In such embodiments, to enable separate sensing of each of the return LBs 225, an additional spectral filter positioned between blocking element 246 and autocollimator 240 or included within autocollimator 240 and configured to enable selective filtering of light in the first spectrum or the second spectrum may be used.

[0114] 2A and 2B, second surface 22b is shown as extending from first surface 22a to third surface 22c, it should be understood that the scope of the present disclosure is not limited to measurements of samples so shaped. In particular, any sample including an outer flat first surface, an outer flat second surface that is inclined relative to the first surface, and an outer flat third surface that is parallel to the first surface, such that the second surface does not share a common edge with the first surface and / or does not share a common edge with the third surface, can also be measured using system 200, as described above.

[0115] 2A and 2B, light source 212 and optics 218 may be configured to generate an expanded (collimated) laser beam or a pair of parallel and spaced (collimated) laser beams, essentially as described above in the description of system 100. According to still other embodiments, ICA 204 may be or include an interferometric device, as described above in the description of system 100.

[0116] FIG. 3 schematically illustrates an optical system 300 for verifying the angle between two outer flat surfaces of a sample, according to some embodiments. System 300 corresponds to a specific embodiment of system 100 in which the LFC is or includes a prism. More specifically, FIG. 3 provides a side view of system 300 and sample 10 inspected by system 300, according to some embodiments. System 300 includes prism 302, ICA 304 (parts of which are not shown), and orientation infrastructure 320. According to some embodiments, and as illustrated in FIG. 3 , system 300 further includes controller 308 and, optionally, computation module 330. Prism 302, ICA 304, orientation infrastructure 320, controller 308, and computation module 330 correspond to specific embodiments of LFC 102, ICA 104, orientation infrastructure 120, controller 108, and computation module 130, respectively.

[0117] According to some embodiments, prism 302 may be immune to pitch variations—i.e., rotation about the y-axis—at least over a continuous range of pitch angles. According to some such embodiments, as depicted in FIG. 3 , prism 302 may be a pentaprism or a prism with similar functionality, such as a prism including an even number of internally reflective surfaces. According to some alternative embodiments not shown in FIG. 3 , instead of prism 322, system 300 may include two mirrors set at the same angle relative to each other as the two surfaces of prism 302 (pentaprism first surface 328a and pentaprism second surface 328b) are set, which internally reflect the transmitted portion of second incident LB 305b.

[0118] 3 shows first incident LB 305a, first return LB 325a, second incident LB 305b, bending LB 313b, reflection LB 317b, and second return LB 325b, which correspond to specific embodiments of first incident LB 105a, first return LB 125a, second incident LB 105b, bending LB 113b, reflection LB 117b, and second return LB 125b, respectively. Also shown are the trajectories of second incident LB 305b and reflection LB 317b within prism 302 after entering the prism. The transmitted portions of second incident LB 305b after entering prism 302, after reflecting therein, and after two reflections therein are numbered 309b1, 309b2, and 309b3, respectively. The transmitted portions of reflected LB 317b after refraction into, reflection within, and two reflections within prism 302 are numbered 321b1, 321b2, and 321b3, respectively.

[0119] The angle of incidence of the bent LB 313b on the second surface 12b is labeled as 63. The angular deviation of the second return LB 325b from the first return LB 325a is labeled as 83.

[0120] FIG. 4 schematically illustrates an optical system 400 for verifying the angle between two outer flat surfaces of a sample, according to some embodiments. System 400 corresponds to a specific embodiment of system 100, in which the LFC is or includes a mirror. More specifically, FIG. 4 provides a side view of system 400 and sample 10 being inspected by system 400, according to some embodiments. System 400 includes a mirror 402, an ICA 404 (parts of which are not shown), and an orientation infrastructure 420. According to some embodiments, and as illustrated in FIG. 4, system 400 further includes a controller 408 and, optionally, a computation module 430.

[0121] Mirror 402, ICA 404, orienting infrastructure 420, controller 408, and computing module 430 correspond to particular embodiments of LFC 102, ICA 104, orienting infrastructure 120, controller 108, and computing module 130, respectively.

[0122] According to some embodiments, and as illustrated in FIG. 4, mirror 402 may be a flat mirror.

[0123] FIG. 4 shows a first incident LB405a, a first return LB425a, a second incident LB405b, a bending LB413b, a reflection LB417b, and a second return LB425b, which correspond to specific embodiments of the first incident LB105a, the first return LB125a, the second incident LB105b, the bending LB113b, the reflection LB117b, and the second return LB125b, respectively.

[0124] The angle of incidence of the bent LB 413b on the second surface 12b is labeled as θ4. The angular deviation of the second return LB 425b from the first return LB 425a is labeled as δ4.

[0125] method According to aspects of some embodiments, an optical method for metrology of an outer flat surface of a sample is provided. The method can be used to verify the orientation of one outer flat surface of a sample relative to another outer flat surface of the sample. Figure 5 presents a flowchart of such a method, i.e., optical method 500, according to some embodiments. Method 500 can include the following steps: An optional step 505 in which the system used to implement the method (eg, system 100) is calibrated. A sample to be tested (e.g., sample 10) is provided, step 510. The sample includes an outer flat first surface (e.g., first surface 12a) and an outer flat second surface (e.g., second surface 12b) nominally inclined at a nominal inclination angle (e.g., nominal inclination angle α) relative to the first surface. - Step 520, in which a first incident light LB (e.g., first incident light LB 105a) directed at a first surface and a second incident light LB (e.g., second incident light LB 105b) parallel to the first incident light LB are generated (e.g., by the light source 112 and the optical device 118). - Step 530, in which a first return LB (for example the first return LB 125a) is obtained by reflecting the first incident LB from the first surface. - Step 540, in which a second return LB (e.g., second return LB 125b) is obtained by nominally bending the second incident LB at an optical bending angle equal to the nominal tilt angle, reflecting the bent LB (e.g., bent LB 113b) from the second surface, and nominally bending the reflected LB (e.g., reflected LB 117b) at the optical bending angle. - Step 550, in which the angular deviation of the second return LB relative to the first return LB is measured (for example using the sensor 114 or the autocollimator 240). - step 560, in which the actual tilt angle of the second surface relative to the first surface is estimated based at least on the measured angular deviation.

[0126] As used herein, the term "obtaining" may be used in both an active and passive sense. Thus, for example, obtaining a first return LB in step 540 may result from the generation of a first incident LB in step 520, rather than from an action implemented in step 540. In general, a step may represent an active action performed by a user or by a system used to implement the method, and / or the result or effect of one or more actions performed in one or more previous steps.

[0127] Method 500 can be implemented using any one of optical systems, such as optical systems 100, 300, and 400, or similar optical systems, as described above in their respective descriptions. In particular, according to some embodiments, method 500 can be based on an autocollimator, based on measuring the distance between laser beams, or based on interferometry, as detailed in the descriptions of various embodiments of system 100. In step 540, a bent LB can be obtained from the second incident LB using any one of LFC 102, prism 302, and mirror 402, or similarly functional LFCs. Similarly, a second returned LB can be obtained from the reflected LB using any one of LFC 102, prism 302, and mirror 402, or similarly functional LFCs.

[0128] According to some embodiments, in step 520, the first incident LB may be projected on the first surface at a right angle (i.e., perpendicular) to the first surface. Thus, in such embodiments, the bent LB (obtained from the bending of the second incident LB) will strike the second surface at a nominally right angle. According to some embodiments, in step 505, a “Absolute Reference” (GS) sample may be used as part of a calibration of the system used to perform method 500. More specifically, given a sample to be inspected, a corresponding GS sample (i.e., a known sample that represents the required geometry with high precision) may be used in calibrating the system. In particular, the GS sample may be used to align the orientable stage (e.g., stage 122) and the LFC on which the sample is mounted, so that the bent LB strikes the second surface (similar to second surface 12b) of the GS sample at a right angle (to the precision provided by the GS sample). The GS sample can also be used to orient the stage so that the first incident LB strikes perpendicularly on a first surface (similar to first surface 12a) of the GS sample. Whether or not a portion of the ICA (e.g., ICA 104) of the system is included in the system, an autocollimator can be used to perform alignment and verify the squareness of the first incident LB.

[0129] According to some embodiments, once a sample to be tested has been provided, e.g., placed on an orientable stage, a calibration or further calibration may be performed after step 510. The further calibration may include, for example, orienting or reorienting the stage (e.g., using an autocollimator) so that the first incident light LB falls perpendicularly on the first surface (of the sample to be inspected).

[0130] According to some embodiments, in step 520, an autocollimator (e.g., autocollimator 240) can be used to generate a single incident light LB, with the first incident light LB and the second incident light LB constituting sub-beams within the single incident light LB. Alternatively, an expanded (collimated) laser beam can be generated, with the first incident light LB and the second incident light LB constituting sub-beams within the laser beam. In still other embodiments, a pair of parallel, spaced apart laser beams can be generated, with the first incident light LB and the second incident light LB corresponding thereto, respectively.

[0131] According to some embodiments, in steps 530 and 540, an autocollimator (e.g., autocollimator 240, or more generally, the same autocollimator in embodiments in which an autocollimator is used to prepare the incident LB) may be used to sense the return LB. According to some embodiments, a shutter and / or a spectral filter may be used to selectively block or partially block the first or second return LB, essentially as described above in the description of FIG. 1A and FIGS. 2A and 2B. In addition to facilitating attributing each of a pair of spots (spots on the photosensor surface of an optical or image sensor (e.g., sensor 114) utilized to sense the return LB) to the return LB that formed the spot, blocking one return LB may serve to increase measurement accuracy by attenuating signals associated with stray light while sensing the other return LB.

[0132] According to some embodiments, particularly those in which steps 520, 530, and 540 are performed using an autocollimator (such as autocollimator 240), in step 550, the angular deviation of the second return LB relative to the first return LB is calculated.

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[0133] In step 560, the actual tilt angle

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[0134] 6 shows a flowchart of an optical method 600 for metrology of an outer flat surface of a sample, according to some embodiments. Method 600 corresponds to a specific embodiment of method 500, and can be used to verify the perpendicularity of an outer flat surface of a sample relative to at least two other outer flat surfaces of the sample, which surfaces are parallel to one another. Method 600 can include the following steps: A sample to be tested (e.g., sample 20) is provided, step 605. The sample includes an outer flat first surface (e.g., first surface 22a), an outer flat second surface (e.g., second surface 22b) nominally inclined at a nominal inclination angle relative to the first surface, and an outer flat third surface (e.g., third surface 22c) that is parallel to the first surface. - Step 610, in which a first incident light LB (e.g., first incident light LB 205a) directed perpendicular to the first surface and a second incident light LB (e.g., second incident light LB 205b) parallel to the first incident light LB are generated (e.g., by an autocollimator 240). - Step 615, in which a first return LB (for example the first return LB 225a) is obtained from the reflection of the first incident LB from the first surface. - Step 620, in which a second return LB (e.g., second return LB225b) is obtained by nominally bending the second incident LB at an optical bending angle equal to the nominal tilt angle, reflecting the bent LB (e.g., first bent LB213b) from the second surface, and nominally bending the reflected LB (e.g., first reflected LB217b) at the optical bending angle. - step 625, in which a first angular deviation of the second return LB relative to the first return LB is measured. - Step 630, in which the sample is inverted, thereby reversing the first and third surfaces while maintaining the nominal orientation of the second surface. - Step 635, in which a third incident light LB (e.g., third incident light LB 205a') directed perpendicular to the third surface and a fourth incident light LB (e.g., fourth incident light LB 205b') parallel to the third incident light LB are generated (e.g., by autocollimator 240). - Step 640, in which a third return LB (for example the third return LB 225a') is obtained from the reflection of the third incident LB from a third surface. - Step 645, in which a fourth return LB (e.g., fourth return LB225b') is obtained by nominally bending the fourth incident LB at an optical bending angle, reflecting the bent LB (e.g., second bent LB213b') from the second surface, and nominally bending the reflected LB (e.g., second reflected LB217b') at an optical bending angle. - step 650, in which a second angular deviation between the fourth return LB and the third return LB is measured. - step 655, in which the actual tilt angle of the second surface relative to the first surface is estimated based on the measured first and second angular deviations.

[0135] Method 600 can be implemented using an optical system, such as optical system 200 or a similar optical system, as described above in the description of FIGS. 2A-2D . In particular, according to some embodiments, method 600 can be an autocollimator based on distance measurement between laser beams or based on interferometry. In step 620, a first bent LB and a second returned LB can be obtained from the second incident LB and the first reflected LB, respectively, using LFC 202 or a similarly functional LFC. The LFC can be or include a prism (e.g., a pentaprism), a mirror, or a diffraction grating nominally configured to bend light incident on the top by 90° toward a direction perpendicular to first surface 22a. Similarly, in step 645, a second bent LB and a fourth returned LB can be obtained from the fourth incident LB and the second reflected LB, respectively, using LFC 202 or a similarly functional LFC.

[0136] According to some embodiments, method 600 may include an optional calibration step (not shown in FIG. 6) similar to step 505 of method 500.

[0137] According to some embodiments, an autocollimator (e.g., an autocollimator) may be used to generate multiple pairs of parallel incident LBs in steps 610 and 635. According to some embodiments, an autocollimator (e.g., an autocollimator used in preparing the incident LBs) may be used to sense the return LBs in steps 615, 620, 640, and 645. According to some embodiments, a shutter and / or a spectral filter may be used to selectively block or partially block one of the second and first return LBs, and one of the fourth and third return LBs, essentially as described above in the description of Figures 2A and 2B.

[0138] According to some embodiments, particularly those in which steps 610, 615, 620, 635, 640, and 645 are performed using an autocollimator (such as autocollimator 240), step 625 determines a first angular deviation of the second return LB relative to the first return LB.

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[0139] In step 655, the actual tilt angle value

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[0140] It should be understood that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately, in any suitable subcombination, or in any manner suitable with 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 expressly stated otherwise.

[0141] Although steps of methods according to some embodiments may be described in a particular order, methods of the present disclosure may include some or all of the described steps performed in a different order. Methods of the present disclosure may include some of the described steps or all of the described steps. No particular step of a disclosed method should be considered essential to the method unless specifically stated.

[0142] While the present disclosure has been described in conjunction with specific embodiments thereof, it is evident that numerous alternatives, modifications, and variations apparent to those skilled in the art may exist. Accordingly, the present disclosure embraces all such alternatives, modifications, and variations that fall within the scope of the appended claims. It is to be understood that the present disclosure is not necessarily limited in its application to the details of construction and arrangement of components and / or methods described herein. Other embodiments may be implemented and the embodiments may be carried out in various ways.

[0143] The phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. Citation or identification of any reference in this application should not be construed as an admission that such reference is available as prior art to the present disclosure. The section headings used herein are for ease of understanding the specification and should not be construed as necessarily limiting.

Claims

1. 1. An optical method for verifying angles between outer flat surfaces of a sample, said method comprising: providing a sample including a first outer flat surface and a second outer flat surface nominally inclined at a nominal inclination angle relative to the first surface; generating a first incident light beam (LB) directed at the first surface and a second incident LB parallel to the first incident LB; Obtaining a first return light beam LB by reflecting the first incident light beam LB from the first surface, bending the second incident light beam LB at an optical bending angle nominally equal to the nominal tilt angle, reflecting the bent light beam LB from the second surface, and bending the reflected light beam LB at the optical bending angle, thereby obtaining a second return light beam LB; Measuring a first angular deviation of the second return LB relative to the first return LB; and estimating an actual tilt angle of the second surface relative to the first surface based at least on the measured first angular deviation; the nominal tilt angle is 90° and the sample includes an outer flat third surface that is parallel to the first surface, the first incident light LB is directed at the first surface normal to the first surface, and the method, following the measuring of the first angular deviation, comprises: inverting the sample to reverse the first and third surfaces while maintaining the nominal orientation of the second surface relative to the LFC; Preparing a third incident light LB directed at the third surface perpendicular to the third surface and a fourth incident light LB parallel to the third incident light LB; Obtaining a third return light LB by reflecting the third incident light LB from the third surface; bending the fourth incident light LB at an optical bending angle nominally equal to the nominal tilt angle; reflecting the bent fourth incident light LB from the second surface; and obtaining a fourth return light LB by bending the reflected fourth incident light LB at the optical bending angle; measuring a second angular deviation of the fourth return LB relative to the third return LB; An optical method, wherein in estimating the actual tilt angle, the actual tilt angle is estimated by additionally taking into account the measured second angular deviation.

2. The optical method of claim 1 , wherein the first incident light LB is directed at the first surface perpendicular to the first surface.

3. 3. The optical method of claim 2, wherein the bending is performed using a light bending component (LFC), the light bending component being or including a prism, one or more mirrors, and / or a diffraction grating.

4. The optical method of claim 3 , wherein the light bending angle is insensitive to variations in the pitch of the LFC.

5. 5. The optical method of claim 4, wherein the LFC is or includes a pentaprism or similarly functional prism, or a pair of mirrors set at an angle to each other or a similarly functional mirror device.

6. The optical method of any one of claims 1 to 3, wherein the sample is or comprises glass, a polymer, a metal, a crystal, and / or combinations thereof.

7. The optical method of claim 1 , wherein the sample is a prism or a waveguide.

8. The optical method of claim 1 , wherein the second surface shares no common edges with the first surface.

9. The optical method of claim 1 , wherein the first incident light beam LB and the second incident light beam LB are complementary portions of a single collimated light beam LB.

10. The optical method of claim 1 , wherein the first incident LB and the second incident LB are prepared by blocking one or more portions of a single collimated LB.

11. The optical method of claim 9 , wherein the single collimated LB is polychromatic.

12. The optical method of claim 10 , wherein the single collimated LB is a laser beam.

13. The optical method of claim 1 , wherein the first angular deviation is measured using an autocollimator.

14. 14. The optical method of claim 13, wherein the measured first angular deviation between the return beams L and B is equal to or approximately equal to Δu / f, where Δu is the difference between coordinates of a first spot and corresponding coordinates of a second spot on a photosensitive surface of the autocollimator, f is the focal length of a collimating lens of the autocollimator, and the first spot is formed by the first return beam L and the second spot is formed by the second return beam L.

15. 10. The optical method of claim 1, further comprising an initial calibration stage, in which an absolute reference sample is utilized to calibrate the system.

16. 2. The optical method of claim 1, wherein the uncertainty in the parallelism of the first surface and the third surface is less than the required measurement accuracy of the actual tilt angle.

17. 10. The optical method of claim 1, further comprising suppressing internal reflections from an outer flat fourth surface, provided that the sample includes an outer flat fourth surface that is nominally parallel to the second surface.

18. 1. An optical system for verifying an angle between outer flat surfaces of a sample, said system comprising: a light bending component (LFC) nominally configured to bend light incident thereon at a nominal tilt angle defined by an outer planar first surface and an outer planar second surface of the sample; An illumination and collection apparatus (ICA), comprising: a light generation assembly configured to (a) project a first incident light beam (LB) onto the first surface to generate a first return light beam (LB) by reflection from the first surface, and (b) project a second incident light beam (LB) onto the LFC parallel to the first incident light beam (LB) to generate a second return light beam (LB) by bending from the LFC, the second surface, and back through the LFC; an illumination and collection arrangement including 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 allow manual measurement of the first angular deviation, wherein the measured first angular deviation indicates an actual tilt angle of the second surface relative to the first surface; a calculation module comprising the at least one sensor and configured to calculate the actual tilt angle of the second surface relative to the first surface based at least on the measured first angular deviation; an optical system in which the nominal tilt angle is 90° and the sample further includes an outer flat third surface parallel to the first surface, and the calculation module is configured to calculate the actual tilt angle by additionally taking into account a measured second angular deviation of a fourth return light beam (LB) relative to a third return light beam (LB), and the actual tilt angle is obtained by: (a') projecting a third incident light beam onto the third surface of the sample to generate the third return light beam (LB) by reflection from the third surface, and (b') projecting a fourth incident light beam (LB) onto the LFC parallel to the third incident light beam (LB) to generate a fourth return light beam (LB) by its bending due to the LFC, reflection from the second surface, and back through the LFC.

19. 20. The optical system of claim 18, configured such that the first incident light LB strikes the first surface normally.

20. 20. The optical system of claim 19, further comprising an orientation infrastructure configured to orient the sample so that the first incident LB strikes the first surface perpendicularly and / or so that a bent LB obtained by bending the second incident LB by the LFC strikes the second surface nominally perpendicularly.

21. 20. The optical system of claim 18, wherein the ICA is or includes an autocollimator, the autocollimator including a light source and the at least one sensor.

22. 22. The optical system of claim 21, further comprising a pair of blocking elements configured to enable the ICA to selectively block each of the first incident LB and the second incident LB.

23. The optical system of claim 18 , wherein the LFC comprises a prism, a plane mirror, and / or a diffraction grating.

24. 20. The optical system of claim 18, wherein the light bending angle of the LFC is insensitive to variations in pitch of the LFC.

25. An optical system as described in claim 24, wherein the prism is a pentaprism or a prism of similar function, or a pair of mirrors set at an angle to each other or a mirror device of similar function.

26. 20. The optical system of claim 18, wherein the light generation assembly includes a light source and an optical instrument, the light source configured to generate a single LB, and the optical instrument configured to collimate the single LB.

27. 27. The optical system of claim 26, wherein the first incident light LB and the second incident light LB are complementary portions of the collimated light LB.

28. 27. The optical system of claim 26, wherein the light source is a polychromatic light source.

29. 27. The optical system of claim 26, wherein the light source is configured to generate a laser beam.

30. The optical system of claim 18 , wherein the at least one sensor comprises an optical sensor and / or an image sensor.

31. 20. The optical system of claim 18, wherein 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 imperfections of the LFC and the ICA.

32. 32. The optical system of claim 31 , further comprising an orientation infrastructure, wherein the calculation module is configured to calculate the uncertainty in the calculated value of the actual tilt angle by additionally taking into account manufacturing tolerances and imperfections of the orientation infrastructure.

33. 1. A method for producing a sample having a pair of outer flat surfaces set at a nominal angle relative to one another, the method comprising: providing a raw sample; processing the raw sample to obtain a processed sample including a first outer flat surface and a second outer flat surface set at a test angle relative to the first surface; measuring the test angle using an optical method according to any one of claims 1 to 17; subjecting the processed sample to further processing if the test angle differs from the nominal angle by more than a predetermined difference to obtain a reprocessed sample; and repeating the step of measuring and reprocessing, as necessary, until the difference between the test angle of the reprocessed sample and the nominal angle is below the predetermined difference.

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