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EP-4542285-B1 - OPTICAL-BASED VALIDATION OF ORIENTATIONS OF INTERNAL FACETS

EP4542285B1EP 4542285 B1EP4542285 B1EP 4542285B1EP-4542285-B1

Inventors

  • EISENBERG, Ido

Dates

Publication Date
20260513
Application Date
20211118

Claims (15)

  1. An optical-based system (100, 200) for validating an orientation of an internal facet (14) of a sample (10) relative to an external, flat first surface (12a) of the sample, the system comprising: a light guiding arrangement, LGA (102, 202) comprising a light folding component, LFC (122, 222) and a coupling prism, CP, (132, 232) configured to redirect light, which is incident on the LFC, into or onto the sample, such that light, transmitted thereby into the sample, impinges on the internal facet of the sample nominally normally to the internal facet, wherein the CP, comprising an external, flat CP first surface (138a, 238a), an external, flat CP second surface (138b, 238b), nominally inclined at the nominal angle relative to the CP first surface, and an external CP third surface (138c, 238c), opposite the CP second surface, wherein the CP is disposed such that the CP first surface is parallel to the first surface (12a) of the sample, and is further disposed such that the light, folded by the LFC, nominally normally impinges on the CP second surface (138b, 238b); and an illumination and collection arrangement, ICA (104, 204) comprising: one or more light sources (112) and optical equipment (118) configured to (a) project a first incident light beam (LB) (105a, 205a) on the first surface (12a), so as to generate a first returned LB (133a, 233a) by reflection off the first surface, (b) project a second incident LB (105b, 205b) on the LFC (122, 222), in parallel to the first incident LB, so as to generate a second returned LB (133b, 233b), by redirection by the LFC of the second incident LB nominally normally on the CP second surface (138b, 238b) and into or onto the sample (10), such that light, transmitted thereby into the sample, nominally normally impinges on the internal facet (14), and (c) project an additional incident LB (205s) normally on CP first surface (238a) so as to obtain an additional returned LB (233s) by the reflection of the additional incident LB off CP first surface; wherein the ICA further comprises at least three blocking elements (256a, 256b, 256s) configured to block one or more of the first, second and additional incident LBs, and/or one or more spectral filters configured to at least facilitate distinguishing between respective returned LBs; and at least one sensor (114).
  2. The optical-based system of claim 1, wherein the sensor (114) is configured to: measure a first angular deviation of the second returned LB (133b, 233b) relative to the first returned LB (133a, 233a), and/or an eyepiece assembly configured to enable manually measuring the first angular deviation, wherein the measured first angular deviation is indicative of an actual inclination angle of the internal facet (14) relative to the first surface (12a); and/or measure a second angular deviation of the additional returned LB (233s) obtained by the reflection of the additional incident LB (205s) off CP first surface (138a, 238a), relative to first returned LB (133a, 233a).
  3. The optical-based system of claim 1, wherein the first, second and/or third blocking elements comprise a shutter and/or a filter (256a, 256b, 256s).
  4. The optical-based system of claim 1, wherein the at least one sensor comprises one or more light sensors and/or one or more image sensors (114); and wherein the one or more light sources is configured to generate a single LB (201), and wherein the optical equipment is configured to collimate the single LB (201) and preferably further comprising one or more autocollimators (250), the one or more autocollimators comprising the one or more light sources (112, 212), the at least one sensor (114), and a collimating lens or collimating lens assembly.
  5. The optical-based system of claim 4, wherein the first incident LB (105a, 205a), the second incident LB (105b, 205b) and the incident additional LB (205s) are complementary portions of the collimated LB (201).
  6. The optical-based system of claim 1, wherein the sample is a prism or a waveguide (10).
  7. The optical-based system of claim 1, wherein the LFC is or comprises a prism, one or more mirrors, and/or a diffraction grating and preferably wherein the light folding angle of the LFC is insensitive to variations in a pitch of the LFC, and preferably wherein the LFC is or comprises a pentaprism or a prism comprising an even number of internally reflecting surfaces (328a, 328b), or a pair of mirrors set at an angle relative to one another (like-function mirrors).
  8. The optical-based system of claim 1, wherein the LGA further comprises a shape conforming interface (134, 234), which is disposed between the CP third surface (138c, 238c) and the sample (10), wherein the shape conforming interface has a same refractive index as the first part of the sample or a refractive index close thereto.
  9. The optical-based system of claim 8, wherein the shape-conforming interface (134, 234) is or comprises a liquid and/or a gel.
  10. The optical-based system of claim 8, wherein the system further comprises orienting infrastructure (140, 240) configured to orient the sample (10) such that the first incident LB (105a, 205a) normally impinges on the first surface (12a), and/or a folded LB, obtained by folding of the second incident LB (105b, 205b) by the LFC (122, 222), nominally normally impinges on the CP second surface (138b, 238b) and/or the additional incident LB (205s) is oriented nominally normally to the CP first surface (138a, 238a).
  11. The optical-based system of claim 1, further comprises one or more processors (530) configured to compute the actual one or more inclination angle, based at least on the measured first angular deviation and preferably wherein the sample further comprises an external, flat third surface (12c), which is parallel to the first surface (12a), wherein the one or more processors (530) are configured to compute the actual inclination angle additionally taking into account a measured second angular deviation of a fourth returned LB (533b') relative to a third returned LB (533a'), obtained by, with the sample flipped, such that the first surface and the third surface are inverted, (a') projecting a third incident light beam on the third surface of the sample (505a'), so as to generate the third returned LB (533a') by reflection off the third surface (12c), and (b') projecting a fourth incident LB (505b') on the LFC (522), in parallel to the third incident LB, so as generate the fourth returned LB (533b'), by redirection by the LGA (502) of the fourth incident LB into or onto the sample, reflection thereof off the internal facet (54), and inverse redirection by the LGA.
  12. The optical-based system of claim 11, wherein the processor (530) is configured to compute the orientation of CP first surface (538a) relative to first surface (12a).
  13. The optical-based system of claim 1, wherein the CP further comprises an external, flat CP fourth surface (138d), which is parallel to the CP first surface (138a), wherein the CP is mechanically flippable, such that the CP first surface and the CP fourth surface are invertible, while maintaining a nominal orientation of the CP second surface (138b) relative to the sample (10) and preferably wherein the measured second angular deviation is obtained with the CP flipped, such that the CP first surface (138a) and the CP fourth surface (138d) are inverted and the nominal orientation of the CP second surface (138b) relative to the sample is maintained.
  14. The optical-based system of claim 1, wherein the one or more light sources and optical equipment comprise: (a) a first light source (112a) and first optical equipment (118a) configured to project the first incident light beam (LB) (105a) on the first surface (12a), so as to generate the first returned LB (133a) by reflection off the first surface, (b) a second light source (112b) and second optical equipment (118b) configured to project the second incident LB (105b) on the LFC (122), in parallel to the first incident LB, so as generate the second returned LB (133b), by redirection by the LFC of the second incident LB nominally normally on the CP second surface (138b) and into or onto the sample (10), such that light, transmitted thereby into the sample, nominally normally impinges on the internal facet (14), and (c) a third light source (112c) and third optical equipment (118c) configured to project the additional incident LB (205s) normally on CP first surface (138a) so as to obtain the additional returned LB (233s) by the reflection of the additional incident LB off CP first surface, wherein the first, second and third light sources and respective optical equipment are configured to provide and/or block one or more of the first, second and additional incident LBs so as to at least facilitate distinguishing between respective returned LBs.
  15. The optical-based system of claim 14, further comprising a first, second and third autocollimators, the first, second and third autocollimators comprising the first, second and third light sources (112a, 112b, 112c), the at least one sensor (114), and collimating lenses or collimating lens assemblies, respectively.

Description

TECHNICAL FIELD The present disclosure relates generally to methods and systems for metrology of samples including internal facets. BACKGROUND Some transparent optical elements, such as glass prisms and waveguides, may include reflective, internal facets. In order to validate to high precision the orientation of such a facet relative to one or more external surfaces of the optical element, current state-of-the-art techniques require high-end optical components and implementation of complex alignment and calibration procedures. There is thus an unmet need in the art for simple and easily implementable metrology techniques, which avoid the use of high-end optical components, thereby addressing mass production demands. Examples of prior art optical element inspection devices can be found e.g. in US2003063293A1 and WO2019131277A1. SUMMARY The object of the present invention is an optical-based system for validating an orientation of an internal facet of a sample relative to an external, flat first surface of the sample, in accordance with the appended claims. Aspects of the disclosure, according to some embodiments thereof, relate to methods and systems for metrology of samples including one or more internal facets. More specifically, but not exclusively, aspects of the disclosure, according to some embodiments thereof, relate to optical-based methods and systems for metrology of samples including one or more internal facets. Advantageously, the present application discloses fast, simple, and precise methods and systems for validating 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, flat surfaces of the sample. Thus, according to an aspect of some embodiments, there is provided an optical-based method for validating an orientation of one or more internal facets of a sample relative to an external, flat surface thereof. The method includes: Providing a sample including an external, flat first surface and an internal facet nominally inclined (intended by design and fabrication to be inclined) at a nominal inclination angle µ relative to the first surface.Providing a light guiding arrangement (LGA) configured to redirect light, which is incident on the LGA in a direction perpendicular to the first surface, into or onto the sample, such that light, transmitted thereby into the sample, impinges on the internal facet nominally normally to the internal facet.Generating a first incident light beam (LB), directed at the first surface normally thereto, and a second incident LB, parallel to the first incident LB and directed at the LGA.Obtaining a first returned LB by reflection of the first incident LB off the first surface.Obtaining a second returned LB by redirection by the LGA of the second incident LB into or onto the sample, reflection thereof off the internal facet, and inverse redirection by the LGA.Measuring a first angular deviation of the second returned LB relative to the first returned LB.Deducing an actual inclination angle µ' of the internal facet relative to the first surface, based at least on the measured first angular deviation. According to some embodiments of the method, the sample includes a first part and a second part, between which the internal facet extends. The first part is positioned between an external second surface of the sample and the internal facet. A transmitted LB, which constituting a portion of the second incident LB, is directly or indirectly transmitted into the sample, and enters into the sample via the second surface. According to some embodiments of the method, the LGA includes a light folding component (LFC) nominally configured to fold light, at least when projected thereon in a direction perpendicular to the first surface, at a light folding angle equal to the nominal inclination angle. According to some embodiments of the method, the LFC is or includes a prism, one or more mirrors, and/or a diffraction grating. According to some embodiments of the method, the light folding angle is insensitive to variations in a pitch of the LFC. According to some embodiments of the method, the LFC is or includes a pentaprism or a like-function prism, or a pair of mirrors set at an angle relative to one another, or a like-function mirror arrangement. According to some embodiments of the method, the LGA further includes a coupling infrastructure configured to guide the light, folded by LFC, onto or into to the sample, such that light, transmitted thereby into the sample, nominally normally impinges on the internal facet. 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 inclined at the nominal angle relative to the CP first surface, and an external CP third surface, opposite the CP second surface. The CP has a same refractive index as the fir