Autocollimation optical systems

Abstract

An optical system has a source-detector unit (SDU) and an optical arrangement. The SDU has a detector arrangement and an illumination arrangement that provides a point source that defines an output sub-region of a planar output-input region of the SDU. The optical arrangement is deployed between the SDU and an at least partially reflective surface. The point source outputs illumination from the output sub-region toward the at least partially reflective surface via at least one optical component of the optical arrangement. The detector arrangement forms an image from illumination from the point source that is reflected from the at least partially reflective surface and received at an input sub-region of the output-input region via at least one optical component of the optical arrangement. A component of the optical system is provided with an optical decenter in relation to a datum axis of the optical system.

Description

[0001] APPLICATION FOR PATENT

[0002] TITLE

[0003] Autocollimation Optical Systems

[0004] CROSS-REFERENCE TO RELATED APPLICATIONS

[0005] This application claims priority from US Provisional Patent Application No. 63 / 645,899, filed May 12, 2024, and US Provisional Patent Application No. 63 / 697,524, filed September 22, 2024, both disclosures of which are incorporated by reference in their entireties herein. TECHNICAL FIELD

[0006] The present disclosure relates to optical systems, and, in particular, it concerns optical systems having a source-detector unit.

[0007] BACKGROUND OF THE INVENTION

[0008] Optical systems that use autocollimation for alignment, measuring, calibration and periodical checking of other optical devices have widespread use. The basic configuration of autocollimation devices consists of two channels, a first channel for a projection beam and a second channel for an observation beam. The two-channel configuration is achieved by using a beamsplitter cube. Consequently, autocollimation devices are relatively cumbersome, comprise a large number of components, and require calibration between the two channels during production. Moreover, the use of a beamsplitter is accompanied by drawbacks such as undesired reflections and ghost images on the detector plane, and small angle error of the optical axis. The small angle error stems from imperfect parallelism of faces of the beamsplitter cube, a defect known as an optical wedge angle.

[0009] SUMMARY OF THE INVENTION

[0010] The present disclosed subject matter, also referred to herein as the disclosure, includes various autocollimation optical systems.

[0011] According to the teachings of an embodiment of the present disclosure, there is provided an optical system. The optical system comprises: a source-detector unit having a planar outputinput region and including: a detector arrangement, and an illumination arrangement that provides a point source that defines an output sub-region of the planar output-input region; and an optical arrangement deployed between the source-detector unit and an at least partially reflective surface, the point source outputs illumination from the output sub-region toward the at least partially reflective surface via at least one optical component of the optical arrangement, the detector arrangement is configured to form an image from illumination from the point source that is reflected from the at least partially reflective surface and received at an input sub-region of the output-input region via at least one optical component of the optical arrangement, and a component of the optical system is provided with an optical decenter in relation to a datum axis of the optical system.

[0012] Optionally, the datum axis is defined by the optical arrangement, and the point source is decentered from the datum axis.

[0013] Optionally, the optical arrangement has an optical axis, and the optical arrangement is deployed so that the optical axis is decentered from the datum axis.

[0014] Optionally, the optical arrangement includes a collimating unit having at least one collimating lens, the collimating unit having a focal plane that is coplanar with the planar outputinput region.

[0015] Optionally, the optical arrangement includes: a collimating unit including: a first lens having a focal plane that is coplanar with the planar output-input region, and a second lens having a focal plane that is coplanar with the planar output-input region, and a focusing unit having one or more lenses deployed between the lens arrangement and the at least partially reflective surface, the focusing unit having a focal plane that is coplanar with the at least partially reflective surface.

[0016] Optionally, illumination from the point source that is output from the output-input surface is collimated by the first lens, focused by the focusing unit onto the at least partially reflective surface, reflected from the at least partially reflective surface, transmitted by the focusing unit, and focused by the second lens so as to be focused onto the input sub-region and detected by the detector arrangement.

[0017] Optionally, the source-detector unit includes: an image guide that provide an optical coupling between the input sub-region and detector elements of the detector arrangement, and an illumination optical fiber that provides an optical coupling between the output sub-region and an illumination source of the illumination arrangement.

[0018] Optionally, the source-detector unit includes: a micro reflective element located at a detector plane of the detector arrangement, the micro reflective element defines the output subregion and the detector plane defines the input sub-region, and illumination produced by an illumination source of the illumination arrangement is reflected by the micro reflective element.

[0019] Optionally, the source-detector unit further includes: a substrate having a plurality of surfaces including a first planar surface and a second planar surface parallel to the first planar surface, the micro reflective element is located at the first planar surface, and the detector plane is coplanar with the first planar surface.

[0020] Optionally, the illumination arrangement is deployed to inject illumination into the substrate so that the injected illumination is totally internally reflected from the second planar surface toward the micro reflective element, and reflected out of the substrate by the micro reflective element. Optionally, the plurality of surfaces of the substrate further include a third planar surface oblique to the first and second planar surfaces, the injected illumination is transmitted by the second planar surface and is reflected by the third planar surface prior to being totally internally reflected from the second planar surface.

[0021] Optionally, the plurality of surfaces of the substrate further include a third planar surface oblique to the first and second planar surfaces, the injected illumination is transmitted by the third planar surface prior to being totally internally reflected from the second planar surface.

[0022] Optionally, the plurality of surfaces of the substrate further include a third planar surface oblique to the first and second planar surfaces, and the illumination source is deployed to inject illumination into the substrate through the first planar surface so that the injected illumination is reflected by the third planar surface toward the micro reflective element and reflected out of the substrate by the micro reflective element.

[0023] Optionally, the source-detector unit further includes: a prism having a plurality of surfaces and deployed such that the illumination produced by the illumination source is injected into the prism and reflected by one or more of the surfaces of the prism so as to be coupled out of the prism toward the micro reflective element.

[0024] Optionally, the detector arrangement includes a sensor matrix having a detector plane that defines the input sub-region, the sensor matrix is provided with a through hole that penetrates from a region of the detector plane to a back side of the sensor matrix, the illumination arrangement includes an illumination source coupled to an optical fiber that is accommodated in the through hole such that an output end of the optical fiber is located at the region of the detector plane, the output end of the optical fiber defines the output sub-region.

[0025] Optionally, the detector arrangement includes a first sensor matrix and a second sensor matrix deployed in a side-by-side configuration, the first sensor matrix having a first detector plane and the second sensor matrix having a second detector plane, the first and second detector planes together forming a detector plane of the detector arrangement that defines the input sub-region, the illumination arrangement includes an illumination source coupled to an optical fiber that is accommodated between the first sensor matrix and the second sensor matrix such that an output end of the optical fiber is located at a region of the detector plane of the detector arrangement, the output end of the optical fiber defines the output sub-region.

[0026] Optionally, the illumination arrangement includes: a reflective element mounted to a thin transparent plate, that is attached to a detector plane of the detector arrangement, at a 45-degree angle relative to the detector plane, the reflective element defines the output sub-region and the thin transparent plate defines the input sub-region, and an optical fiber coupled to an illumination source and having an output end deployed adjacent to the reflective element such that illumination from the illumination source that is output from the output end is reflected by the reflective element in a reflection direction that is substantially perpendicular to the detector plane.

[0027] Optionally, the illumination arrangement includes a micro illumination source mounted to a thin transparent plate that is attached to a detector plane of the detector arrangement, the micro illumination source defines the output sub-region and the thin transparent plate defines the input sub-region.

[0028] Optionally, the detector arrangement includes a sensor matrix having a detector plane, a thin transparent plate is attached to the detector plane and defines the input sub-region, the thin transparent plate is provided with a light guiding arrangement coupled to an illumination source of the illumination arrangement and an optical coupling-out surface that defines the output subregion, illumination from the illumination source is coupled into the light guiding arrangement so as to propagate through the light guiding arrangement by total internal reflection and is coupled out of the light guiding arrangement by the optical coupling-out surface in a reflection direction that is substantially perpendicular to the detector plane.

[0029] Optionally, the detector arrangement includes a sensor matrix having a detector plane, a thin transparent plate is attached to the detector plane and defines the input sub-region, the thin transparent plate being polarization-selective so as to transmit illumination that is linearly polarized in a first polarization direction with regards to the thin transparent plate and reflect illumination that is linearly polarized in a second polarization direction, orthogonal to the first polarization direction, with regards to the thin transparent plate, the illumination arrangement is configured to generate illumination that is polarized such that the illumination that is output from the output sub-region is in the second polarization direction with regards to the thin transparent plate, the optical system further comprises an optical retarder deployed between the sourcedetector unit and the optical arrangement that is configured to rotate the polarization state of illumination incident to the optical retarder.

[0030] Optionally, the illumination arrangement includes micro reflective element that provides the point source and that defines the output sub-region.

[0031] Optionally, the micro reflective element includes a micro holographic element.

[0032] Optionally, the micro reflective element includes a micro mirror.

[0033] Optionally, the micro reflective element includes a micro grating.

[0034] Optionally, the micro reflective element is mounted to a thin transparent plate that is attached to a detector plane of the detector arrangement, the detector plane defines the input subregion.

[0035] Optionally, the illumination arrangement includes an optical fiber having an output end that provides the point source. Optionally, the illumination arrangement provides a plurality of point sources that define a plurality of output sub-regions of the planar output-input region.

[0036] Optionally, the illumination arrangement includes a plurality of illumination sources.

[0037] Optionally, the illumination arrangement includes a collimated source.

[0038] Optionally, the detector arrangement includes a sensor matrix having a detector plane that defines the input sub-region.

[0039] Optionally, the at least partially reflective surface is part of the optical system.

[0040] Optionally, when the at least partially reflective surface is perpendicular to the datum axis, the point source and a reflected image of the point source have a symmetric relationship about a mirror axis that is parallel to the datum axis.

[0041] Optionally, the optical system is configured to receive an optical device, having at least one optical element, between the optical arrangement and the at least partially reflective surface, when the at least one optical element is misaligned relative to the datum axis, the symmetric relationship about the mirror axis is broken.

[0042] Optionally, a distance from a sensor matrix of the detector arrangement is equal to a focal length of a collimating unit of the optical arrangement.

[0043] There is also provided according to the teachings of an embodiment of the present disclosure a method for testing alignment of optical devices. The method comprises obtaining an optical system according to an embodiment described in this document; deploying optical device having at least one optical element between the optical arrangement and the at least partially reflective surface; activating the illumination arrangement such that the point source outputs illumination toward the at least partially reflective surface; and determining an amount of misalignment of the at least one optical element relative to the datum axis based on a location of the image on the planar output-input region.

[0044] There is also provided according to the teachings of an embodiment of the present disclosure an optical system. The optical system comprises: a first sensor matrix; a point source; a first collimating unit; a second collimating unit deployed between the point source and a reflective surface, the point source outputs illumination toward the reflective surface via the second collimating unit; a second sensor matrix, the point source lies in a plane of the sensor matrix, and the plane is between first collimating unit and the second collimating unit; a microlens array (MLA) located between the first sensor matrix and the first collimating unit; and a movement mechanism associated with the second sensor matrix and configured to move the second sensor matrix between: a first position in which the point source is adjacent to the second sensor matrix, and a second position in which a gap is formed between the point source and the second sensor matrix, when the second sensor matrix is in the first position, illumination from the point source is reflected from the reflective surface back through the second collimating unit so as to be focused onto the second sensor matrix, and when the second sensor matrix is in the second position, illumination from the point source is reflected from the reflective surface back through the second collimating unit so as to be focused onto a point in the gap and subsequently pass through the first collimating unit and the MLA to the first sensor matrix.

[0045] There is also provided according to the teachings of an embodiment of the present disclosure an optical system. The optical system comprises: a first sensor matrix; a point source; a first collimating unit; a second collimating unit deployed between the point source and a reflective surface, a reference surface located between the second collimating unit and the reflective surface, the point source outputs illumination toward the reflective surface via the second collimating unit and the reference surface; a second sensor matrix, the point source lies in a plane of the sensor matrix, and the plane is between first collimating unit and the second collimating unit; and a movement mechanism associated with the second sensor matrix and configured to move the second sensor matrix between: a first position in which the point source is adjacent to the second sensor matrix, and a second position in which a gap is formed between the point source and the second sensor matrix, when the second sensor matrix is in the first position, illumination from the point source is reflected from the reflective surface back through the reference surface and the second collimating unit so as to be focused onto the second sensor matrix, and when the second sensor matrix is in the second position, illumination from the point source is reflected from the reflective surface back through the reference surface and the second collimating unit so as to be focused onto a point in the gap and subsequently pass through the first collimating unit to the first sensor matrix.

[0046] There is also provided according to the teachings of an embodiment of the present disclosure an optical system. The optical system comprises: a first sensor matrix; a point source; a first collimating unit; a second collimating unit deployed between the point source and a reflective surface, a reference surface located between the second collimating unit and the reflective surface, the point source outputs illumination toward the reflective surface via the second collimating unit and the reference surface; a second sensor matrix, the point source lies in a plane of the sensor matrix, and the plane is between first collimating unit and the second collimating unit; a microlens array (MLA) located between the first sensor matrix and the first collimating unit; a first movement mechanism associated with the second sensor matrix and configured to move the second sensor matrix between: a first position in which the point source is adjacent to the second sensor matrix, and a second position in which a gap is formed between the point source and the second sensor matrix; a second movement mechanism associated with the reference surface and configured to move the reference surface between: a third position in which the reference surface is in a first optical path between the second collimating unit and the reflective surface, and a fourth position in which the reference surface is out of the first optical path; and a third movement mechanism associated with the MLA and configured to move the MLA between: a fifth position in which the MLA is in a second optical path between the first sensor matrix and the second collimating unit, and a sixth position in which the MLA is out of the second optical path, when the second sensor matrix is in the first position and the reference surface is in the fourth position, illumination from the point source is reflected from the reflective surface back through the second collimating unit so as to be focused onto the second sensor matrix, when the second sensor matrix is in the second position and the reference surface is in the third position and the MLA is in the sixth position, illumination from the point source is reflected from the reflective surface back through the reference surface and the second collimating unit so as to be focused onto a point in the gap and subsequently pass through the first collimating unit to the first sensor matrix, and when the second sensor matrix is in the second position and the reference surface is in the fourth position and the MLA is in the fifth position, illumination from the point source is reflected from the reflective surface back through the second collimating unit so as to be focused onto a point in the gap and subsequently pass through the first collimating unit and the MLA to the first sensor matrix.

[0047] Unless otherwise defined herein, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains. Although methods and materials similar or equivalent to those described herein may be used in the practice or testing of embodiments of the disclosure, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0048] BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Some embodiments of the present disclosure are herein described, by way of example only, with reference to the accompanying drawings. With specific reference to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the disclosure. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the disclosure may be practiced.

[0050] Attention is now directed to the drawings, where like reference numerals or characters indicate corresponding or like components. In the drawings:

[0051] FIG. 1 is a schematic representation of an optical system that provides autocollimation function having a collimating unit and a source-detector unit having a point source and a sensor matrix on a common plane, with the point source decentered relative to a datum axis of the optical system and the collimating unit deployed between the source-detector unit and a flat reflective surface, according to an embodiment of the present disclosure;

[0052] FIG. 2 is a schematic representation of an optical system according to an embodiment of the present disclosure that is similar to FIG. 1 , but with the collimating unit decentered relative to the datum axis;

[0053] FIG. 3 is a schematic representation of an optical system that provides autocollimation function having a focusing unit, a collimating unit with a pair of minute lenses, and a sourcedetector unit having a point source and a sensor matrix on a common plane, with the point source decentered relative to a datum axis of the optical system, according to an embodiment of the present disclosure;

[0054] FIG. 4A is a block diagram representing an optical system according to embodiments illustrated in FIGS. 1 and 2;

[0055] FIG. 4B is a block diagram representing an optical system according to embodiments illustrated in FIG. 3;

[0056] FIG. 5 is a schematic representation of a source-detector unit having a sensor matrix that receives illumination via an optical fiber image guide, and an illumination optical fiber having an input end coupled to an illumination source and an output end that provides a point source at an input end of the image guide, according to an embodiment of the present disclosure;

[0057] FIG. 6 is a schematic representation of a source-detector unit having a micro reflective element that provides a point source attached to the detector plane of a sensor matrix via a thin transparent flat plate, according to an embodiment of the present disclosure, showing illumination from an illumination source reaching the micro reflective via injection through a major surface of the thin transparent flat plate;

[0058] FIG. 7 is a schematic representation of a source-detector unit according to an embodiment of the present disclosure that is similar to FIG. 6, but with a different illumination injection configuration;

[0059] FIG. 8 is a schematic representation of a source-detector unit according to an embodiment of the present disclosure that is similar to FIG. 7, but with yet another illumination injection configuration;

[0060] FIG. 9 is a schematic representation of a source-detector unit having a micro reflective element that provides a point source attached directly to the detector plane of a sensor matrix, according to an embodiment of the present disclosure, showing illumination from an illumination source reaching the micro reflective via injection through a prism;

[0061] FIG. 10 is a schematic representation of a source-detector unit having a micro reflective element that provides a point source attached to an external planar surface of a thin transparent flat plate that is attached to the detector plane of a sensor matrix, showing direct illumination of the micro reflective element by an illumination source;

[0062] FIG. 11 is a schematic representation of a source-detector unit according to an embodiment of the present disclosure that is similar to FIG. 10, but with the illumination source illuminating the micro reflective element via an off-axis parabolic mirror;

[0063] FIGS. 12A and 12B are schematic front and isometric views, respectively, illustrating a source-detector unit having an optical fiber accommodated in a through hole of a sensor matrix to provide a point source at the detector plane of the sensor matrix, according to an embodiment of the present disclosure;

[0064] FIGS. 13A and 13B are schematic front and isometric views, respectively, illustrating a source detector unit having a pair of sensor matrixes arranged in a side-by-side configuration and an optical fiber accommodated between the pair of sensor matrixes at the interface between the pair of sensor matrixes to provide a point source at the detector plane, according to an embodiment of the present disclosure;

[0065] FIG. 14A is a schematic representation of a source-detector unit having a thin transparent flat plate attached to the detector plane of a sensor matrix, a reflective element that provides a point source mounted to the thin transparent flat plate, and an optical fiber having an output end adjacent to the reflective element, according to an embodiment of the present disclosure;

[0066] FIG. 14B is a side enlarged view of the region of FIG. 14A designated XIV;

[0067] FIG. 15 is a schematic representation of a source-detector unit having a thin transparent flat plate attached to the detector plane of a sensor matrix, and a micro illumination source mounted to the thin transparent flat plate, according to an embodiment of the present disclosure;

[0068] FIG. 16 is a schematic representation of a source-detector unit having a thin transparent flat plate attached to the detector plane of a sensor matrix and provided with a light guiding arrangement and a coupling-out surface that provides a point source, according to an embodiment of the present disclosure;

[0069] FIG. 17 is a schematic representation of an optical system that is functionally similar to the optical systems of FIGS. 1 and 2, employing a source-detector unit similar to that of FIG. 10 and a polarization management scheme to prevent unwanted illumination from reaching the sensor matrix, according to an embodiment of the preset disclosure;

[0070] FIG. 18A is a schematic representation of an optical system that is similar to the optical system of FIG. 1, where the flat reflective surface is a unit under test;

[0071] FIGS. 18B and 18C are front views of the sensor matrix of the source-detector unit of FIG. 18 A, showing scenarios where the unit under test is aligned relative to the datum axis and titled relative to the datum axis, respectively; FIG. 19 is a schematic representation of a front view of a sensor matrix of a source-detector unit having three point sources, showing the symmetric relationship between locations of the point sources and the reflected images of the point sources when a unit under test is aligned relative to the datum axis;

[0072] FIG. 20 is a schematic representation of an optical system that provides autocollimation function having a collimating unit and a source-detector unit having three point sources and a sensor matrix on a common plane, showing a scenario in which an optical unit that is tested by the optical system is aligned relative to a datum axis of the optical system;

[0073] FIG. 21 is a schematic representation of a front view of a sensor matrix of the sourcedetector unit in the scenario of FIG. 20, showing the locations of the point sources;

[0074] FIG. 22 shows the locations of the reflected images of the point sources on the sensor matrix of the source-detector unit in the scenario of FIG. 20;

[0075] FIG. 23 shows the spot sizes of the reflected images of FIG. 22;

[0076] FIG. 24 is a schematic representation similar to FIG. 20, but showing a scenario in which the optical unit is tilted relative to the datum axis;

[0077] FIG. 25 shows the locations of the reflected images of the point sources on the sensor matrix of the source-detector unit in the scenario of FIG. 24;

[0078] FIG. 26 shows the spot sizes of the reflected images of FIG. 25;

[0079] FIG. 27 is a schematic representation of a pair of optical systems deployed relative to orthogonal surfaces of a hollow cube to provide testing and aligning of optical devices using two sets of beams, according to an embodiment of the present disclosure;

[0080] FIG. 28 is a schematic representation similar to FIG. 27, but with three optical systems deployed to provide testing and aligning of optical devices using three sets of beams, according to an embodiment of the present disclosure ;

[0081] FIG. 29 is a schematic representation of a collimator that is enabled to provide autocollimation function by providing a source-detector unit having a point source and a sensor matrix on a common plane, according to an embodiment of the present disclosure;

[0082] FIG. 30 is a schematic representation of an optical system according to an embodiment of the present disclosure that is similar to FIG. 3, but including polarizers / filters and apertures for reducing or blocking unwanted light, according to an embodiment of the present disclosure;

[0083] FIG. 31 is a schematic representation of an optical system having a source-detector unit deployed relative to a curved reflective surface, according to an embodiment of the present disclosure; FIG. 32 is a schematic representation of an optical system having a source-detector unit combined with optical elements to form a spectrometer configuration, according to an embodiment of the present disclosure;

[0084] FIG. 33 is a schematic representation of an optical system similar to FIG. 1, but integrated with components to form a wavefront sensor device;

[0085] FIG. 34 is a schematic representation of an optical system similar to FIG. 1 , but integrated with components to form an interferometer device;

[0086] FIG. 35 is a schematic representation of an optical system similar to FIG. 34, but further including components that move a sensor matrix to enable the optical system to alternate between functioning as an autocollimator and a wavefront sensor, according to an embodiment of the present disclosure;

[0087] FIGS. 36A and 36B are schematic front views of what a sensor matrix of the sourcedetector unit of FIG. 35 sees when the optical system is in an autocollimator configuration and interferometer configuration, respectively;

[0088] FIG. 37 is a schematic representation of an optical system similar to FIG. 35, but further including components to enable the optical system to alternate between functioning as an autocollimator, a wavefront sensor, and an interferometer, according to an embodiment of the present disclosure;

[0089] FIG. 38 is a schematic representation of an autocollimator optical system having a point source and a sensor matrix with a polarizing beamsplitter cube employing a variant polarization management scheme, according to another embodiment of the present disclosure; and

[0090] FIG. 39 is a schematic representation of an optical system similar to FIG. 38, but further including components that enable the optical system to alternate between functioning as an autocollimator, a wavefront sensor, and an interferometer, according to an embodiment of the present disclosure.

[0091] DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0092] The present disclosure provides autocollimation optical systems.

[0093] The principles and operation of the optical systems according to the present disclosure may be better understood with reference to the drawings accompanying the description.

[0094] Before explaining at least one embodiment of the disclosure in detail, it is to be understood that the disclosure is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or the examples. The disclosure is capable of other embodiments or of being practiced or carried out in various ways. By way of introduction, aspects of the present disclosure include autocollimator optical systems. In certain embodiments, the optical systems include a source-detector unit (SDU), which is a hybrid optical component having an image sensor and a point source provided on the same plane or very close to the same plane. The SDU is of practical use in various applications, including optical testing applications that utilize, for example, autocollimators, wavefront sensors, interferometers, and the like. The non-limiting example embodiments disclosed herein present the SDU in the context of optical systems that are configured to perform, or are configured to be integrated with other optical systems that perform, one or more optical testing functions, such as those which are used in the testing and measurement applications. It will be appreciated, however, the SDU-based optical systems according to the present disclosure may have suitable use in other applications and may be used with other optical systems and configurations beyond those explicitly described herein.

[0095] Bearing the above in mind, and referring now to the drawings, FIGS. 1 and 2 schematically illustrate an exemplary optical system, generally designated 10, according to the teachings of embodiments of the present disclosure. The optical system 10 provides, for example, autocollimator function, and generally includes a source-detector unit (SDU) 22 and an optical arrangement 12, that are deployed in relation to a datum axis 13 of the optical system 10. As is known in the art, the datum axis of an optical system is an axis selected after consideration of specific features of the optical system, and serves as a reference axis for the location of various components of the optical system. The selection of the datum axis may vary depending on the particular configuration of the optical system, as will become apparent in the subsequent sections of the disclosure.

[0096] The optical system 10 also includes a reflective surface 20, that is perpendicular to the datum axis 13 and parallel to a sensor matrix of the SDU 22, and deployed such that the optical arrangement 12 is located between the SDU 22 and the reflective surface 20. It is noted, however, that in certain embodiments the surface 20 is not part of the optical system 10.

[0097] The optical arrangement 12 includes at least one optical component. In the embodiments illustrated in FIGS. 1 and 2, the optical component(s) includes a collimating unit 14 having at least one collimating lens 16.

[0098] The SDU 22 has a planar input-output region 24, which is a physical planar surface that can be, for example, a physical detector plane, a surface of a transparent plate, an input end of an optical fiber bundle, etc. The SDU 22 is positioned so that the focal plane of the collimating unit 14 is on (i.e., coplanar with) the planar region 24. The planar region 24 includes an illumination output sub-region 26, and an illumination input sub-region 28, that is coplanar with the output subregion 26. An illumination arrangement of the SDU 22, having at least one illumination source, is associated with the output sub-region 22. The illumination arrangement provides a point source PS that defines the output sub-region 26. As will be discussed in subsequent sections of the present disclosure, in certain embodiments the point source PS provided by the illumination arrangement is an illumination source itself, such as a micro source, located at the output sub-region 26. In other embodiments, the point source PS is an element or component located at the output sub-region 26 that redirects (via reflection) light or emits light received from an illumination source of the illumination arrangement.

[0099] A detector arrangement of the SDU 22 is associated with the input sub-region 28. The detector arrangement is configured to detect illumination from the point source PS (provide by the illumination arrangement) that is reflected from the reflective surface 20 and received at the input sub-region 28 via at least one optical component of the optical arrangement 12 so as to form an image from the received illumination. The detector arrangement includes an image sensor (also referred to as a “sensor matrix” or “detector”), which is an array of detector elements (pixels) that convey information used to form an image. The sensor matrix includes a detector plane, and the output sub-region 26 is located at or very close to the center of the detector plane (or a plane parallel to the detector plane, that is close to the detector plane). As mentioned, the focal plane of the collimating unit 14 is coplanar with the planar region 24. This implies that the distance from the sensor matrix is equal to a focal length of a collimating unit 14.

[0100] It is noted that the illumination arrangement and the detector arrangement, and their associated components, are not shown in FIGS. 1 and 2, but are illustrated in other drawings.

[0101] The optical system 10 supports autocollimation function for testing other optical devices / systems when such devices / systems are deployed between the optical arrangement 12 and the reflective surface 20. In order to support such autocollimation function, it is a particular feature of the embodiments of the present disclosure to provide a unique deployment configuration of the components of the optical system 10. In particular, the deployment configuration is such that the point source PS, and a reflected image of the point source PS (designated TP) that is formed at the input sub-region 28 from illumination from the point source PS, have a symmetric relationship about a mirror axis MA. This symmetric relationship is present when the reflective surface 20 is perpendicular to the datum axis 13 and parallel to the planar region 24. In certain embodiments, such as the embodiment illustrated in FIG. 1, the mirror axis MA is the datum axis 13. In other embodiments, such as the embodiment illustrated in FIG. 2, the mirror axis MA is parallel to, and laterally offset from, the datum axis 13, and may be, for example the optical axis of an optical component of the optical arrangement 12. More specifically, the location of the point source PS on the planar region 24 and the location of the reflected image on the planar region 24 are mirrored, one with respect to the other, about the mirror axis MA. The symmetry is achieved by providing the optical system with an optical decenter (offset) in relation to the datum axis 13. This decenter may be achieved in various ways by providing a component of the optical system 10 with the optical decenter. In certain embodiments, for example, the embodiment illustrated in FIG. 1, the decenter is provided by deploying the SDU 22 so that the output sub-region 26 (i.e., point source PS) is decentered from the datum axis 13. In this configuration, the datum axis 13 and the optical axis of the collimating unit 14 are one and the same. In other embodiments, for example the embodiment illustrated in FIG. 2, the decenter is provided by deploying the optical arrangement 12 so that at least one optical component (e.g., collimating unit 14) of the optical arrangement 12 is decentered from the datum axis. In this configuration, the datum axis 13 and the optical axis of the collimating unit 14 are different, and the collimating unit 14 is deployed so that its optical axis is parallel to, and laterally offset from, the datum axis 13.

[0102] The illumination arrangement is configured to generate illumination, which is output from the output sub-region 26 (as point source PS) as beam of illumination 37 toward the reflective surface 20 via at least one optical component (e.g., collimating unit 14) of the optical arrangement 12. The illumination 37 reaches the reflective surface 20 as a collimated beam, which reflects at least part of the incident illumination back through at least one optical component (e.g., the collimating unit 14) of the optical arrangement 12 so as to be focused on the input sub-region 28, where the detector arrangement detects the illumination 39 received (focused) at the input subregion 28 and forms a reflected image from the detected illumination.

[0103] Looking in particular at FIG. 1, the datum axis 13 is defined as the optical axis of the collimating unit 14. Since the output sub-region 26 (point source PS) is located on the planar inputoutput region 24 with a lateral offset (decenter) relative to the datum axis 13, the reflected image is focused to a location (designated TP) of the input sub-region 28 that is symmetric to the location of the point source PS in relation to the datum axis 13.

[0104] A similar but slightly different effect is achieved in the configuration of FIG. 2, where the collimating unit 14 is positioned at a decenter from the datum axis 13. The collimating unit 14 is laterally offset from the datum axis 13 in such a way that the optical axis of the collimating unit 14 is shifted (laterally) from the datum axis 13. This lateral offset of the collimation unit 14 enables creating a separation between the illumination emitting channel (output sub-region 26 / point source PS) and the receiving channel (input sub-region 28). More specifically, the offset of the collimating unit 14 is such that the reflected image is focused to a location (designated TP) of the input sub-region 28 that is symmetric to the location of the point source PS in relation to the optical axis of the collimating unit 14. Turning now to FIG. 3, there is illustrated an optical system according to another embodiment of the present disclosure. Here, the optical arrangement 12 includes an optical unit 14-1 having a pair of minute lenses 16a and 16b, and a focusing unit 18 having one or more optical elements 19 (e.g., lenses and the like) that defines the datum axis 13 (i.e., the optical axis of the focusing unit 18 is the datum axis). The focal plane of the focusing unit 18 is on (i.e., coplanar with) the reflective surface 20, and the focal plane of each of the lenses 16a and 16b is on (i.e., coplanar with) the planar region 24. In addition, in the present embodiment the surface 20 is not part of the optical system 10, but instead may be part of the device being tested using the autocollimation function of the optical system.

[0105] In the configuration illustrated in FIG. 3, illumination produced by the illumination arrangement is output from the output sub-region 26 / point source PS (as beam 37), and passes (at a decenter from the datum axis 13) through the lens 16a and through the focusing unit 18, which focuses the illumination on the reflective surface 20. Unlike in FIGS. 1 and 2 where the beam that strikes the reflective surface 20 is collimated, in the present embodiment the beam striking the reflective surface 20 is focused on this surface 20 (at point P). The reflective surface 20 reflects at least part of the incident illumination back through the focusing unit 18 and through the lens 16b. The focusing unit 18 effectively defocuses the reflected illumination (designated 39), and the lens 16b effectively focuses the reflected illumination 39 so as to be focused at location TP on the input sub-region 28, where the detector arrangement detects the illumination 39 received (focused) at the input sub-region 28 and forms an image from the detected illumination.

[0106] Turning now to FIGS. 4A and 4B, there are illustrated block diagrams for SDU-based optical systems supporting collimated beams and focused beams, respectively. The block diagram illustrated in FIG. 4A is representative of an optical system according to embodiments illustrated in FIGS. 1 and 2, showing the SDU 22 with sensor matrix 40 of the detector arrangement and the point source PS provided by the illumination arrangement, and also showing the surface 20 and the optical arrangement 12 having collimating unit 14. The block diagram illustrated in FIG. 4B is representative of an optical system according to embodiments illustrated in FIG. 3, showing the SDU 22 with sensor matrix 40 and point source PS , and also showing the surface 20 and the optical arrangement 12 having optical unit 14-1 (with lenses 16a and 16b) and focusing unit 18 (with lens(es) 19).

[0107] As discussed above, the two sub-regions 26 and 28 are coplanar and are part of common planar region 24. Various SDU 22 architectures are contemplated herein to achieve the coplanarity of the SDU 22 regions. Referring now to FIG. 5, there is schematically illustrated an SDU 22 according to one non-limiting embodiment of the present disclosure, that achieves coplanarity. In the illustrated embodiment, the illumination arrangement and the detector arrangement are shown, and are designated 30 and 38, respectively.

[0108] The illumination arrangement 30 includes an illumination source 32, a relay lens 34, and an optical fiber 36. Illumination produced by the source 32 is relayed to the optical fiber 36 by the lens 34, where the illumination is received at an input end 36a of the optical fiber 36. The optical fiber 36 conveys the received illumination to an output end 36b of the optical fiber 36, located at the output sub-region 26, where the illumination is output from the output end 36b (acting as point source PS) as an output illumination beam 37. Note that in certain embodiments, the illumination source 32 may be directly coupled to the input end 36a.

[0109] The detector arrangement 38 includes the sensor matrix 40, which includes a plurality of detector elements (pixels) 42, and an image guide 44, that includes a bundle of parallel optical fibers having input and output ends 46a and 46b. The image guide 44 provides an optical coupling between the input sub-region 28 and the detector elements 42. The input end 46a of the image guide 44 is located at an input plane which is defined to be the output-input region 24, which coincides with the input sub-region 28. The output end 46b of the image guide 44 is optically coupled to the detector elements 42, such that illumination (reflected from the surface 20) that is received at the input sub-region 28 (first end 46a) is conveyed to the detector elements 42.

[0110] The image guide 44 may contain a slit along part of its length to accommodate the optical fiber 36 so that the output end 36b of the optical fiber 36 and the input end 46a of the image guide 44 can be located at the same plane (i.e., the output-input region 24).

[0111] In the embodiment illustrated in FIG. 5, the plane at which the detector elements 42 are located may be considered as the detector plane 41 of the sensor matrix 40. However, it is noted that the planar region 24 may itself be considered as the detector plane, since the optical fibers of the bundle may be considered as a physical extension of the sensor matrix.

[0112] Turning now to FIGS. 6 - 9, there are schematically illustrated SDUs 22 according to another set of non-limiting embodiments of the present disclosure that employ a micro reflective element (MRE) 50 to implement the point source. In these embodiments, the MRE 50 is mounted to the physical detector plane 41 of the sensor matrix 40, either directly or indirectly. The detector plane 41 defines the input sub-region 28, and the MRE 50 acts as the point source PS and defines the output sub-region 26. The MRE 50 may be implemented in various ways, including, for example, as a micro grating (i.e., micro diffractive optical element), a micro holographic element, a micro mirror, and the like. The MRE 50 is also small-sized (hence “micro”), preferably down to the size of one pixel (detector element) to prevent blocking pixels located behind the MRE 50 from receiving incoming illumination from the input sub-region 28. Looking now at FIG. 6 in detail, the SDU 22 includes a substrate 48, which is a lighttransmitting substrate in the form of a thin transparent flat plate, having a plurality of surfaces including parallel major planar surfaces 49a and 49b. The substrate 48 is attached to the sensor matrix 40, with the surface 49a and the detector plane 41 interfaced together such that the surface 49a and the detector plane 41 are coplanar. The MRE 50 is located at the surface 49a, so as to be on or under the substrate 48, preferably in the vicinity of the center of the substrate 48. The MRE 50 may be attached (e.g., adhesively bonded) to the surface 49a.

[0113] The substrate 48 includes an additional planar surface 49c, oblique to the surfaces 49a and 49b. The surface 49c may be polished and coated with a reflective coating.

[0114] The illumination arrangement 30, which here includes illumination source 33 and focusing lens 35 (and the MRE 50), is deployed with the illumination source 33 in association with the surface 49b so as to inject illumination into the substrate 48. Specifically, the illumination source 33, which may be a collimated source, projects a high-quality collimated beam 31 through the focusing lens 35 perpendicularly to the surface 49b so as to enter the substrate 48. The beam 31 strikes the oblique surface 49c at an angle of incidence so that the beam 31 is reflected back toward the surface 49b. The reflected beam is then totally internally reflected from the surface 49b toward the MRE 50, which acts as point source PS at the output sub-region 26, and reflects the beam out of the substrate 48 as output beam 37. The output beam 37 is a cone of illumination that may vary in shape according to the entrance pupil of the designated application of the optical system.

[0115] The transparency of the substrate 48 enables the sensor matrix 40 to receive incoming illumination (reflected from the surface 20) received at the input sub-region 28. It should be noted that the initial totally internally reflected illumination reaches only the MRE 50 and not any of the active area (pixels) of the sensor matrix 40. Nevertheless, there is a possibility that some of the illumination that reaches the MRE 50 may be totally internally reflected by the MRE 50, resulting in stray (unwanted) rays of illumination, which may exit the substrate 48 at unwanted angles and / or reach the active area of the sensor matrix as stray light. To combat this stray illumination, a light absorbing material can be provided at an additional planar surface 49d of the substrate 48. This surface 49d is also oblique to the surfaces 49a and 49b, and is located at an end the substrate 48 generally opposite the end at which the other oblique surface 49c is located. As a result, totally internally reflected light from the MRE 50 will reach the oblique surface 49c and be absorbed by the light absorbing material.

[0116] Looking now at FIG. 7 in detail, this embodiment is generally similar to the embodiment illustrated in FIG. 6 except here the illumination source 33 is deployed in association with the surface 49c such that the injected illumination 31 is transmitted by the surface 49c prior to being totally internally reflected from the surface 49b. The remaining traversal of the illumination 31 is the same as described with reference to FIG. 6.

[0117] Looking now at FIG. 8 in detail, this embodiment is similar to the embodiments of FIGS. 6 and 7, except here there is no total internal reflection at the surface 49b. Instead, the substrate 48 includes an additional planar surface 49e that is oblique to the surfaces 49a and 49b and which forms a continuation of the surface 49b. The surface 49e may be polished and / or coated with a reflective coating. The illumination source 33 is deployed to inject illumination 31 into the substrate 48 through a portion of the surface 49a so that the injected illumination 31 is reflected by the surface 49e toward the MRE 50. The MRE 50 reflects the illumination 31 out of the substrate 48 as output beam 37.

[0118] Looking now at FIG. 9 in detail, this embodiment employs a prism 52 instead of substrate 48, and the MRE 50 is attached (e.g., adhesively bonded) directly to the detector plane 41. The prism 52, which may be held in place by a mechanical mounting arrangement 54 (such as a bracket or other mechanical holder), has a plurality of surfaces, including surfaces 53a, 53b, and 53c. The illumination source 33 is deployed such that the illumination 31 produced by the source 33 is injected into the prism 52 (via surface 53a) and is reflected by one or more of the surfaces 53b, 53a of the prism so as to be coupled out of the prism (via surface 53c) toward the MRE 50. The MRE 50 reflects the illumination 31 away from the SDU 22 as output beam 37.

[0119] Referring now to FIGS. 10 and 11, there are schematically illustrated SDUs 22 according to another set of non-limiting embodiments of the present disclosure which employ MRE 50. In these embodiments, the MRE 50 is mounted to the sensor matrix 40 via a thin transparent flat plate (i.e., thin window) 56 that has planar surfaces 57a and 57b that are mutually parallel to the detector plane 41. In particular, the MRE 50 is attached (e.g., adhesively bonded) to the external planar surface 57a, and the plate 56 is attached to the sensor matrix 40 at the detector plane 41 via planar surface 57b. As in the embodiments of FIGS. 6 - 9, the MRE 50 defines the output sub-region 26. However, in present embodiment the input sub-region 28 is not defined by the detector plane 41, but rather is defined by the external surface 57a (which also defines the output-input region 24).

[0120] With particular reference to FIG. 10, here the illumination arrangement 30, which includes illumination source 33 and focusing lens 35, is deployed in association with the plate 56 at a preplanned angle relative to the MRE 50 so that the illumination 31 from the illumination arrangement 30 that strikes the MRE 50 is reflected from the MRE 50 (as illumination beam 37) perpendicular to the detector plane 41 (and surface 57a). The transparency of the plate 56 enables the sensor matrix 40 to receive incoming illumination (reflected from the surface 20) received at the input sub-region 28. Looking now at FIG. 11 in detail, this embodiment is similar to the embodiment of FIG. 10, however here an off-axis parabolic mirror 43 is deployed instead of focusing lens, which enables the illumination source 33 to be deployed on the side of the detector 40. The deployment of the illumination source 33 and the parabolic mirror 43 is such that the illumination 31 from the illumination source 33 strikes the parabolic mirror 43 and is reflected toward the plate 56, and more particularly toward the MRE 50. The deployment of the illumination source 33 and the parabolic mirror 43, together with the curvature of the parabolic mirror 43, results in the reflected illumination being focused onto the MRE 50, which reflects the illumination (as illumination beam 37) perpendicular to the detector plane 41 (and surface 57a).

[0121] Turning now to FIGS. 12A and 12B, there is illustrated an SDU 22 according to another embodiment of the present disclosure. Here, the sensor matrix 40 is provided with a through hole 60 that penetrates from a region 62 of the detector plane 41 to a back side 64 of the sensor matrix 40. In certain embodiments, the region 62 may be a central region that is preferably centered or approximately centered on the detector plane 41. The through hole 60 may be a pre-manufactured hole. Optical fiber 36 is accommodated in the through hole 60 such that the output end 36b of the optical fiber 36 is located at the region 62 of the detector plane 41. The output end 36b, which constitutes point source PS, is preferably flush or approximately flush with the detector plane 41, and defines the output sub-region 26. The input end 36a of the optical fiber 36 is coupled to the illumination source (not shown), for example in a manner similar to as shown and described with reference to FIG. 5. Light from the illumination source is projected into the input end 36a and conveyed through the optical fiber to the output end 36b, where it is output as illumination beam 37.

[0122] FIGS. 13A and 13B illustrate another embodiment of SDU 22 that is similar to the embodiment of FIGS. 12A and 12B, except here instead of a through hole, the detector arrangement is formed from a pair of sensor matrixes 40a and 40b deployed in a side-by-side configuration. Each of the sensor matrixes 40a and 40b has a detector plane 41a and 41b, and the two detector planes 41a and 41b together form the detector plane 41 of the detector arrangement (which defines the input sub-region 28). Optical fiber 36 is accommodated between the pair of sensor matrixes 40a and 40b, at the interface 63 between the matrixes 40a and 40b, such that the output end 36b is located at a region 62 of the detector plane 41 that is along the interface 63. The region 62 may be a central region, for example in embodiments where the two sensor matrixes are of the same size and dimensions. It is noted that “side-by-side” refers to any configuration in which the two sensor matrixes are deployed at an abutment to each other, which can include configurations in which one of sensor matrixes is deployed above the other sensor matrix and rotated by 90-degrees with respect to the other sensor matrix. Turning now to FIGS. 14A and 14B, there is illustrated an SDU 22 according to another embodiment of the present disclosure. Here, the SDU 22 is provided with a thin transparent flat plate 70 that is attached to the detector plane 41 (such that the plate 70 and the detector plane 41 are parallel), and a reflective element 72, such as a mirror or a micro reflective element, is mounted to the plate 70 at a 45° relative to the plate 70 (and hence the detector plane 41). The reflective element 72 acts as point source PS and defines the output sub-region 26, and the plate 70 (more particularly external surface 70a of the plate 70) defines the input sub-region 28. Optical fiber 36 is deployed with the output end 36b adjacent to the reflective element 72. The input end 36a of the optical fiber 36 is coupled to the illumination source (not shown), for example in a manner similar to as shown and described with reference o FIG. 5. Light from the illumination source is projected into the input end 36a and conveyed through the optical fiber to the output end 36b. The illumination that is output from the output end 36b is reflected by the reflective element 72, in a reflection direction that is perpendicular to the detector plane 41 (and hence perpendicular to the plate 70), as illumination beam 37.

[0123] Mounting of the reflective element 72 to the plate 70 may be achieved in various ways. In one non-limiting example illustrated in FIG. 14A, the reflective element 72 is attached to another optical fiber segment 74 that is attached to the plate 70. In other embodiments, a thin rod or rodlike element may be used instead of segment 74, or the reflective element 72 may be directly bonded to the plate 70. It is also noted that the optical fiber 36 may be deployed in various ways. In one example, the optical fiber 36 may be accommodated in a through hole that extends through the plate 70. In another example, the optical fiber 36 may be sandwiched between the detector plane 41 and the plate 70.

[0124] The transparency of the plate 70 enables the sensor matrix 40 to receive incoming illumination (reflected from the surface 20) received at the input sub-region 28. However, the configuration of FIGS. 14A and 14B may have certain drawbacks, in particular the optical fiber 36, reflective element 72, and segment 74 (or rod) may block a significant number of pixels of the sensor matrix 41. FIG. 15 illustrates an SDU 22 according to another embodiment of the present disclosure, which achieves reduction (and preferably minimization) of the number of pixel blockages. Here, a micro illumination source 80, preferably down to the size of one pixel, is mounted (e.g., adhesively bonded) to plate 70. The micro illumination source 80 defines the output sub-region 26. Furthermore, the micro illumination source 80 is itself a point source PS and emits output illumination beam 37. The plate 70 (more particularly external surface 70a of the plate 70) defines the input sub-region 28. The back side of the source 80 may be coated with a non-emissive coating in order to prevent light from the source 80 from reaching neighboring pixels of the sensor matrix 40. FIG. 16 illustrates an SDU 22 according to another embodiment of the present disclosure. Similar to the embodiments of FIGS. 14A - 15, the sensor matrix 40 is provided with a thin transparent flat plate 70 that is attached to the detector plane 41 (such that the plate 70 and the detector plane 41 are parallel) so that the plate 70 (more particularly external surface 70a of the plate 70) defines the input sub-region 28. The plate 70 is provided with a light guiding arrangement 90 that is coupled to the illumination source (not shown) of the illumination arrangement and an optical coupling-out surface 92, e.g., a coupling reflector or coupling prism, that defines the output sub-region 26 and acts as point source PS. The light guiding arrangement 90 may be configured as a tunnel or through hole that extends through the plate 70. Alternatively, the light guiding arrangement 90 may be configured as a groove in the external surface 70a. The tunnel or groove may be configured with a refractive index that is higher than the refractive index of the plate 70 (for example via appropriate coating) so that conditions of total internal reflection are achieved when light is injected into the tunnel / groove at appropriate coupling angles. Thus, when illumination from the illumination source is coupled into the light guiding arrangement 90 at appropriate coupling angles, the illumination propagates through the light guiding arrangement 90 by total internal reflection. The propagating illumination encounters the optical coupling-out surface 92, which is angled to couple the illumination out of the light guiding arrangement 90 in a reflection direction that is perpendicular to the detector plane 41 (and hence perpendicular to the plate 70), as illumination beam 37.

[0125] According to certain embodiments of the disclosure, polarization schemes can be utilized in order to prevent unwanted illumination from reaching the sensor matrix while allowing the reflected light (from the surface 20) to form an image on the sensor matrix. An optical system implementing a polarization scheme according to an embodiment of the present disclosure will now be described with reference to FIG. 17. It should be noted that while the embodiment illustrated in FIG. 17 illustrates a configuration that bears a resemblance to that of the embodiment illustrated in FIG. 10, similar polarization schemes are applicable to almost all of the SDU configurations described above.

[0126] As illustrated in FIG. 17, MRE 50 (which acts as point source PS) is mounted to the sensor matrix 40 via thin transparent flat plate 56, similar to as described with reference to FIG. 10. The MRE 50 defines the output sub-region 26, and the external surface 57a defines the input sub-region 28 (and the output-input region 24). The illumination arrangement 30 is configured to output polarized light. This can be accomplished by implementing the illumination source 33 as a polarized source, or by implementing the illumination source 33 as an unpolarized source and deploying a polarizer at the output of the illuminations source 33. The plate 56 is polarization-selective, meaning that the electric field of the plate 56 is polarized in a specific field of polarization. The polarization-selectivity of the plate 56 can be achieved, for example, by applying a polarization-selective coating to the surface 57a.

[0127] The polarization-selectivity of the plate 56 is such that the plate 56 transmits illumination that is linearly polarized in a first linear polarization direction of the electric field propagation (e.g., S -polarization) with regards to the plate 56 and reflects illumination that is linearly polarized in a second linear polarization direction of the electric field propagation (e.g., P-polarization), orthogonal to the first polarization direction, with regards to the plate 56. More specifically, the electric field of the plate 56 is polarized in a field of polarization that is perpendicular to that of illumination emitted by the source 33 or reflected by the MRE 50, thereby blocking : i) illumination from the external light source that is collimated and polarized in the second polarization direction (e.g., P-polarization), and ii) illumination reflected by the MRE in the second polarization direction. In both cases, the illumination that is polarized in the second polarization direction is blocked from reaching the sensor matrix 40 by the polarization-selectivity of the plate 56.

[0128] In order for the reflected illumination (from surface 20) to reach the sensor matrix 40, an optical retarder 95 (implemented as a quarter wave plate) is deployed in the optical path between the SDU 22 and the surface 20, and is configured to rotate the polarization direction (state) of illumination incident to the optical retarder 95. The particular placement of the optical retarder 95 in the optical path depends on the application, and can be anywhere along the datum axis, between the SDU 22 and the surface 20.

[0129] The path of illumination from the illumination source 33 to the sensor matrix 40 will now be described. As mentioned, the illumination arrangement 30 is configured to generate polarized illumination. In particular, the illumination is polarized such that the illumination that is output from the output sub-region 26 (i.e., reflected by the MRE 50) is linearly polarized in the second polarization direction (e.g., P-polarization) with regards to the plate 56. The linearly polarized illumination reflected from the MRE 50 passes through the optical retarder 95 and the collimating unit 14. By passing through the optical retarder 95, the polarization direction of the illumination is rotated to become circularly polarized (in a clockwise rotation). The circularly polarized (and collimated) illumination then strikes the reflective surface 20 so as to be reflected back toward the collimating unit 14 and the optical retarder 95. This reflected illumination remains collimated but is now circularly polarized (in a counterclockwise rotation). The circularly polarized illumination then passes though the collimating unit 14 and the optical retarder 95 retarder. By passing through the optical retarder 95, the polarization direction of the illumination is rotated to become linearly polarized in the first polarization direction (e.g., S -polarization) with regards to the plate 56. The linearly polarized illumination reaches the plate 56, which transmits the received illumination through to the sensor matrix 40.

[0130] It is noted that for each instance where a particular polarized light path has been followed in the examples described above, the polarizations are interchangeable, whereby, for example, on altering the polarization selective properties of the surface 57a, each mention of light having P- polarization could be replaced by light having S -polarization, and vice versa.

[0131] As mentioned above, the embodiments of the optical systems disclosed thus far support autocollimation function for testing other optical devices / systems when such devices / systems are deployed between the optical arrangement 12 and the reflective surface 20. The following sections describe, in greater detail, the functional autocollimator setup of the optical systems according to the present disclosure.

[0132] Referring first to FIG. 18 A, there is shown an optical system that is generally similar to the optical system illustrated in FIG. 1. Thus, the illustrated optical system includes SDU 22, reflective surface 20, and optical arrangement 12 having collimating unit 14 deployed between the SDU 22 and the reflective surface 20. The optical axis of the collimating unit 14 defines the datum axis 13 of the optical system, and the reflective surface 20 is perpendicular to the datum axis 13. The SDU 22 is positioned on the focal plane of the collimating unit 14. Reference is also made to FIG. 18B, which is a front view representation of the detector plane of the sensor matrix 40 of the SDU 22 of the optical system shown in FIG. 18 A. In certain preferred embodiments, the cartesian origin of axes of the datum axis 13 is at the center of the detector plane of the sensor matrix 40 of the SDU 22. However, this may not always be the case, and embodiments permit shifting of the cartesian origin of the axes relative to the center of the detector plane.

[0133] Parenthetically, it is noted that in many embodiments, such as, for example, the embodiment illustrated in FIG. 1 , a tested / measured optical element may function as both a unit under test (UUT) as well as a functional component of the autocollimator and, when such optical element is reflective, may be deployed after the collimating unit (as component 20). A UUT can be a single optical element, a subsystem, or a full optical system, or an optomechanical element or optomechanical system depending on the application. By employing the autocollimation function the UUT can be checked for a wide variety of measuring, testing and optical alignments of the following four common configurations: INFINITE-INFINITE, INFINITE-FINITE, FINITE- INFINITE, FINITE-FINITE while the FINITE conjugate could be equipped with a high-quality concave mirror behind the focus or a convex mirror in front of the focus of the UUT.

[0134] The point source PS, provided by the illumination arrangement (not shown) at the output sub-region 26, is located on the focal plane (the planar region 24) of the collimating unit 14 with a small decenter from the datum axis 13. The reflected image of the point source PS is also on the focal plane of the collimation unit 14, but at a different location TP on the focal plane from the point source PS. Both cartesian origins of axes (of the point source PS and of the reflected image) are on the planar region 24 of the SDU 22 with a small decenter in reference to the datum 13 (thereby providing the mirror symmetry relationship between the point source and its reflected image about the datum 13). Focusing of the reflected image on the planar region 24 of the SDU 22 is facilitated by the fact that, when the point source PS outputs beam 37, the reflected beam 39 (i.e., reflected illumination from the surface 20) passes through the collimating unit 14, which acts as a focusing objective.

[0135] FIG. 18B shows the locations of various points on the detector plane of the sensor matrix when the optical system of FIG. 18 A is in a nominal state. The nominal state occurs when either the surface 20 is the UUT and is deployed perfectly perpendicular to the datum axis 13, or when a UUT is deployed between the optical arrangement 12 and the surface 20 perfectly perpendicular to the datum axis 13. The points illustrated in FIG. 18B include the point source PS, the expected position of the reflected image of the point source PS (designated CR), the actual location of the reflected image of the point source PS (designated TP), and the cartesian origin of axes (designated G) of the datum axis 13. The point source PS, which is located at the focal plane of the collimating unit 14, is decentered from G by some distance A. In the nominal state, the point source PS and its reflected image TP will appear mirror symmetric to each other, at an equal distance A from either side of the datum axis 13 (G, i.e., the point (0, 0, 0), which in the illustrated example is located at the center of the detector plane of the sensor matrix 40). Furthermore, in the nominal state the location of the reflected image TP and its expected location CR are the same.

[0136] Parenthetically, just like with standard digital autocollimators, where the centered reticle (CR) ensures precise alignment and measurement (by keeping a reference crosshairs or other markings centrally positioned in relation to an optical system) the CR of an SDU-based autocollimator functions exactly the same way.

[0137] The equal distances between the point source PS and its reflected image TP do not appear when the UUT is tilted or decentered relative to the datum axis 13. In other words, when the UUT is titled or decentered about the datum axis 13, the symmetric relationship about the mirror axis (which in this configuration is the datum axis 13) between the point source and its image is broken. Therefore, an amount of misalignment (tilt or decenter) of optical element(s) of the UUT relative to the datum axis can be determined based on the location of the reflected image (or locations of the reflected images when there is more than one point source) relative to the location of the point source.

[0138] FIG. 18C shows a scenario in which a UUT, which may be the surface 20 or an optical device, system, etc, that is received by the optical system between the optical arrangement 12 and the surface 20, is presented with some tilt relative to the datum axis 13. Due to this tilt, TP and CR are no longer in the same location. The angular misalignment (tilt or decenter) of the UUT may be calculated using a formula that is based on the locations TP and CR, as well as the effective focal length (EFL) of the collimating unit 14. The specific formula is provided as follows:

[0139] It will immediately be appreciated that the autocollimator setup provided by the optical systems of the present disclosure is completely different from conventional T-shaped autocollimators, in which the light is directed to a collimating unit by reflection from a beamsplitter and, after striking a reflective surface, is reflected in the opposite direction through the same collimating unit and the same beamsplitter cube to form an image on a sensor matrix (or through an eyepiece reticle). Furthermore, the SDU-based configurations of the optical systems of the present disclosure provide significant advantages over conventional autocollimator setups. One advantage is that, by enabling shorter effective focal length (from the collimating unit to the SDU), the optical system provides a much wider field of view than that of conventional autocollimators. Another advantage is that the SDU-based configurations are more compact than conventional beamsplitter-b ased configurations .

[0140] The embodiments of the SDU-based optical systems described thus far have pertained to illumination arrangements that provide a single point source. Such embodiments primarily enable obtaining an angular indication of a tilt of the UUT or a tilt or a decenter of one optical component in a UUT, but lack the ability to measure other misalignment properties such as, for example, astigmatism. According to certain embodiments of the present disclosure the SDU may include an illumination arrangement that provides a plurality of point sources that define a plurality of output sub-regions of the planar output-input region. Such embodiments enable expanded testing and aligning of UUTs.

[0141] Practically, the multiple point sources can be implemented by employing multiple point source elements illustrated and described above with reference to FIGS. 5 - 16, including, for example, multiple optical fibers, multiple MREs, multiple micro illumination sources, multiple, coupling-reflectors with light guiding arrangements, and any combination thereof. Each point source may receive its illumination from its own designated illumination source (or may be a designated illumination source itself in the case of micro illumination sources), or groups of the point sources may share common illumination sources.

[0142] FIG. 19 illustrates a front view representation of the detector plane of the sensor matrix 40 of an SDU 22 when used in a setup similar to FIG. 18A, but showing three point sources, labeled A, B, and C. When the UUT is perfectly aligned, the respective reflected images (on the sensor matrix 40) of each point source appear circular, with a diameter that corresponds to that of their respective point sources and in a mirror symmetry relation about the mirror axis (which in this configuration is the datum axis 13). In the figure, the point sources A, B, and C are marked as dots, and their corresponding reflected images A’, B’, and C’ are marked with an “X” mark.

[0143] It is noted that although three point sources are illustrated in FIG. 19, the number of point sources need not be limited to any particular number.

[0144] The multiple point source SDU enables detecting aberrations caused by incorrect alignment of the optical components under test around its optical axis.

[0145] Parenthetically, it is noted that in embodiments in which the SDU provides a plurality of point sources, the point sources may be configured to output light at different respective wavelengths, including, for example, Visible Range, UV, NIR. SWIR, MWIR, LWIR etc. This may be of particular value when the optical system is used for measuring, aligning, testing, etc., optical devices having smaller-scale components that may, for example, be responsive to illumination with fluorescent emission. In such cases, for example, the point sources of the SDU may provide illumination of different respective wavelengths or different fluorescent excitation. Furthermore, multiple wavelengths can be used simultaneously with multiple point sources on one SDU. It should be also noted that in some embodiments, the MRE may reflect and the SDU sensor matrix may form images in a variety of wavelengths.

[0146] Referring now to FIGS. 20 - 26, the following paragraphs provide a comparison between a nominal state of a UUT (FIGS. 20 - 23) and a state in which at least one of the optical components of the UUT is not properly aligned (FIGS. 24 - 26).

[0147] Looking first at FIG. 20, there is illustrated an optical system similar to the system of FIG. 18A which is used to test the UUT. The UUT is shown as a Galilean telescope 200, deployed between the collimating unit 14 and the reflective surface 20 in the nominal state, with telescope objective 202 aligned perpendicular to the datum axis 13. In this configuration, the SDU includes four point sources that are used to test the alignment or lack of alignment (tilt and decenter) of the objective 202 of the telescope 200. FIG. 21 shows the locations of the point sources, designated a, b, c, and d, on the detector plane of the sensor matrix. One (central) point source (d) is slightly above (in the Y axis direction) the datum axis 13.

[0148] FIG. 22 shows the locations of the reflected images a’, b’, c’, and d’ of the four point sources a, b, c, and d on the detector plane of the sensor matrix in the nominal state of the UUT (telescope 200). The perfect mirror symmetric appearance of the reflected images a’, b’, c’, and d’ in relation to their respective point sources (about the datum axis) is due to the nominal state of the UUT. The reflected image d’ of the central point source d is now below (on the Y axis) the datum axis 13 at an equal distance from the datum axis 13 as the point source d. The other three reflected images a', b’, and c’ are diametrically opposed from their corresponding point sources, on the circumference of a virtual circle, as they should be in the nominal state of the UUT.

[0149] FIG. 23 shows the spot sizes of the reflected images a’, b’, c’, and d’ on the detector plane of the sensor matrix in the nominal state of the UUT (telescope 200).

[0150] Turning now to FIGS. 24, the telescope 200 is shown with its objective 202 at a tilt angle (approximately 2.5°) relative to the datum axis 13. FIG. 25 shows the locations of the reflected images a’, b’, c’, and d’ of the four point sources a, b, c, and d on the detector plane of the sensor matrix when the objective 202 is tilted. In comparison to the locations of the reflected images in the nominal state of the UUT (FIG. 22), the reflected images a’, b’, c’, and d’ are shifted (due to the tilt angle of the objective 202). FIG. 26 shows the spots sizes of the reflected images of FIG. 25 on the detector plane of the sensor matrix. The spots should overlap and be circular and equal in diameter to the circles behind them. However, due to the tilt angle of the objective 202, the spots not only differ in size from the circles behind them, but also in their elongated shapes and directional orientations. These deviations of the spots reveal an astigmatic aberration.

[0151] As discussed, the disclosed SDU-based optical systems may perform autocollimator function, and can replace standard beamsplitter-based autocollimators. The compact form of the SDU-based configurations enables further unique constructions for autocollimation. For example, as illustrated in FIG. 27, a hollow cube 300 may accommodate a pair of SDU-based autocollimator configurations, which enables testing and aligning of complex optical systems with two sets of beams (each set of beams from a separate autocollimator setup). In FIG. 27, two SDU-based autocollimator configurations 10A and 10B are deployed in association with parallel pairs of mutually orthogonal surfaces 302A, 302B and 302C, 302D of cube 300. The surfaces 302A, 302B , 302C, and 302D of the cube 300 are preferably highly reflective, save for transparent windows 303B and 303D in the surfaces 302B and 302D which allows illumination to propagate between the SDUs 22 A and 22B (which are located inside of the cube 300) and the surfaces 20 A and 20B (which are located outside of the cube 300).

[0152] FIG. 28 shows a similar setup, but employing a third autocollimator configuration 10C deployed in association with a third pair of parallel surface 302E, 302F of the cube 300 that is mutually orthogonal to the other two pairs of surfaces 302A, 302B and 302C, 302D. Here too the surfaces 302E and 302F are highly reflective, save for a transparent window (not shown) in the surface 302F which allows illumination to propagate between the SDU 22C (which is located inside of the cube 300) and surface 20C (which is located outside of the cube 300). This configuration enables testing and aligning of complex optical systems with up to three sets of beams. According to another embodiment of the present disclosure, a standalone collimating unit can be enabled to provide autocollimator function by integrating an SDU according to any of the disclosed embodiments with the standalone collimating unit. FIG. 29 illustrates a collimator 14’ (having a set of three lenses 16a’, 16b’, and 16c’) having a focal plane 15. As shown, SDU 22 (with output-input region 24 and point source PS defining output sub-region 26) can be optionally deployed so that the output-input region 24 is coplanar with the focal plane 15 and so that the collimator 14’ is between the SDU 22 and a reflective surface 20’, thereby forming an autocollimator setup. In the illustrated embodiment, the reflective surface 20’ is the unit under test, and is tilted relative to the datum axis 13 by 2.3°. Due to the tilt of the surface 20’ , the location TP of the focused reflected illumination ends up being far away from the point source PS. Deployment of the SDU 22 at the focal plane 15 may be accomplished via a target wheel. As in known in the art, a target wheel having multiple targets may be placed at the focal plane of a collimator, and the wheel may be rotated (e.g., manually, automatically, etc.) to selectively place different targets at the focal plane. In the embodiment of FIG. 29, the SDU 22 may replace one of the targets of the target wheel, so that the target wheel includes the SDU and one or more targets. By doing so, rotation of the target wheel enables alternating the device of FIG. 29 between a collimator configuration and an autocollimator configuration.

[0153] It is noted that in fact, with slight modifications, the use of an SDU according to the embodiments of the present disclosure enables a variety of optical devices to function as autocollimators, for example, a collimator based on an off-Axis parabolic mirror. The following is a non-exhaustive list of optical telescopes that can, when integrated with an SDU (that is, for example, attached to a target wheel), be utilized to function as autocollimators: Apochromatic Refractor Telescopes, Single-mirror Reflecting Telescopes, Parabolic Mirror (Newton Telescope), Two-mirror Reflecting Telescopes, Cassegrain Telescope, Ritchey-Chretien Telescope, Dall-Kirkham Telescope, Gregorian Telescope, Schwarzschild Aplanatic Telescopes, Three-mirror Reflection Telescopes, Paul-Baker Telescope, Two-mirror Schiefspiegler (Oblique Reflector) Telescopes, Herrig Schiefspiegler Telescope, Yolo Telescope, Three-mirror Schiefspiegler Telescopes, Stevick-Paul Schiefspiegler Telescope, Off-axis Anastigmats (TMA) Telescope, Aspherical Maksutov Telescope, Catadioptric Telescopes, and Schupmann Medial Telescope.

[0154] In addition to the use of the SDU in autocollimation applications (where the beam striking a reflective surface is collimated and its rays are parallel) the SDU can also support applications of testing very miniscule, focused, irregularities even on partially reflective surfaces. Referring now to FIG. 30, there is illustrated an optical system that is generally similar to the system illustrated in FIG. 3, but with a few differences. First, the surface against which the beam from the SDU 22 impinges is a partially reflective surface 21, which is the UUT (although the setup can be used to test reflective surfaces as well) In addition, the illustrated optical system may further include an option for a pair of polarizers or filters 76a and 76b, and a pair of apertures 78a and 78b deployed in the optical path between the optical unit 14-1 and the focusing unit 18.

[0155] The lens 16a (which may be implemented as a Gradient-index lens) functions as a collimating lens for the emitted beam 37 and the other lens 16b (which may also be implemented as a Gradient-index lens) functions as a focusing lens for the reflected beam 39. The focal plane of the focusing unit 18 is on (i.e., coplanar with) the partially reflective surface 21. When the illumination arrangement is activated, the point source PS outputs illumination beam 37, which passes, at a decenter (in relation to the datum axis 13), through the lens 16a (which keeps the beam decentered). The beam then passes through the focusing unit 18 (having one or more lenses 19) which focuses the beam on a spot on the partly reflective surface 21. The focused spot can be as miniscule as needed for the desired application. The illumination (even if weakened) of this spot is then reflected back through the focusing unit 18 and the other collimating lens 16b and forms an image (of only the spot under test) on the sensor matrix on the SDU 22.

[0156] Due to the decenter of the output beam 37 in relation to the datum axis 13 and the angle of incidence of the beam 37 when striking the partially reflective (or fully reflective surface) after passing through the focusing unit 18, a separation between the output beam 37 and the reflected beam 39 takes place.

[0157] The optical setup illustrated in FIG. 30 allows measuring of various properties of reflective or partially reflective surfaces (i.e., at least partially reflective surfaces). Furthermore, the quality of the testing / measurement of specific properties of the UUT (surface 21) can be enhanced by employing a light reducing / blocking arrangement in the optical path, for example between the optical unit 14-1 and the focusing unit 18, to reduce or block unwanted environmental light from reaching the detector arrangement. For example, the light reducing / blocking arrangement may include polarizers or filters 76a and 76b associated with the lenses 16a and 16b, and / or a light blocking configuration 78, which can be implemented, for example, as a circular disk with a pair of apertures 78a and 78b on either side of the datum axis 13. Thus, for example, the output beam 37 may pass through the polarizer or filter 76a after passing through the lens 16a, and may then pass through the aperture 78a to reach the focusing unit 18. The reflected beam 39 may pass through the aperture 78b after passing through the focusing unit 18, and may then pass through the polarizer or filter 76b to reach the lens 16b.

[0158] It is to be noted that the optical setup of FIG. 30 illustrates an option for moving (denoted by vertical dashed arrow) and / or rotating (denoted by arcuate arrow) the surface 21, which can enable more thorough examination of the surface 21. Movement / rotation of the surface 21 can be achieved by, for example, placing the surface 21 on a moving or rotating platform.

[0159] Referring now to FIG. 31, there is illustrated optical system according to another embodiment of the present disclosure. Here, the optical system consists primarily of SDU 22, which is deployed relative to a curved reflective surface 82 (e.g., a spherical mirror) that has a center of curvature, and the SDU 22 is positioned at a distance from the center of curvature that is equal to the radius of curvature of the surface 82. This radius of curvature is designated 13’ in FIG. 31 , and is akin to the datum axis in the previously described embodiments. The SDU 22 is deployed such that the point source PS is decentered from the radius of curvature 13’, thereby providing a separation between the output illumination channel (i.e., output beam 37) and the reflective detection channel (i.e., reflected beam 39). Specifically, since the output sub-region 26 is located on the planar input-output region 24 with a lateral offset (decenter) relative to the radius of curvature 13’, the reflected illumination 39 is focused to location TP of the input sub-region that is symmetric to the location of the point source PS in relation to the radius of curvature 13’. It is noted that only when the SDU 22 is deployed at the distance 13’ will the reflected illumination end up being focused on the sensor matrix of the SDU at the location TP. The configuration of FIG. 31 has various applications, including, for example, measuring the radius of curvature, the quality of the surface 82 (peaks and valleys), the tilt and decenter of the surface 82, etc.

[0160] FIG. 32 illustrates an embodiment that utilizes an SDU in order to form a spectrometer based on a Dyson spectrometer configuration. Here, the optical system includes an SDU deployed relative to a structure 120, composed of a solid material (e.g., an optical block, etc.) 119 having a diffractive grating 121 applied to a surface thereof, with a doublet lens 110 deployed between the SDU and the structure 120. The SDU is deployed decentered from the optical axis 13”. The doublet 110 can be designed based on a Dyson configuration and the point source (which may be implemented to advantage as an MRE), for example to support specific wavelengths output by the point source.

[0161] Configurations based on the SDUs according to the embodiments of the present disclosure can be used with optical setups to perform analysis of a test point (TP) image and / or point spread function (PSF), and to obtain information relating to the wavefront of a device being tested (i.e., UUT). Such optical setups make use of the decenter feature and the fact that the focal plane of the collimating unit is on the same plane as the point source. For example, if the SDU is provided with an aperture or opening (e.g., a pinhole) located at the point at which the reflected image of the point source is expected to be received (CR), the reflected illumination can continue further back to another sensing device, such as a Schack-Hartmann Wavefront Sensor, or with small modifications a Fizeau Interferometer, Scatter-Plate, Point Diffraction Interferometer, Ronchi Ruling, Star Test, Relay PSF magnification, MTF.

[0162] FIG. 33 shows an example of implementing a Schack-Hartmann Wavefront Sensing device based on such a configuration. The SDU 22 is provided with a point source PS and an aperture h, and is deployed relative to a UUT with a collimating unit 14 deployed between the SDU 22and the UUT so that there is a decenter relationship with the datum axis 13 (as described in previous embodiments). Another collimating unit 14’ ’ is provided behind the SDU 22 and receives the reflected illumination through the aperture h. The illumination that is collimated by the collimating unit 14’ ’ then reaches a micro lens array (MLA) 17 before reaching a sensor matrix SM. It is noted that the axial location of the MLA 17 is at the focal length of its microlenses from the sensor matrix SM.

[0163] The aperture h can be provided in the SDU 22’ in various ways. In one embodiment, the aperture h can be a through hole provided in the sensor matrix of the SDU, similar to as described above with reference to FIGS. 12A and 12B. In another embodiment, the aperture h can be provided by implementing the detector of the SDU as a pair of sensor matrixes deployed in a side- by-side configuration, similar to as described above with reference to FIGS. 13A and 13B.

[0164] Another option for implementing a Schack-Hartmann Wavefront Sensing device based on the proposed configuration is by shifting the sensor matrix away from the optical path of the reflected beam (either by lateral moving or rotating by 90°) and yet affixing the point source to its original position. Thus, the reflected image will reach the Schack-Hartmann unit directly. In situations where minute geometrical dimensions of some light emitting sources can be used for yet another configuration of a Schack-Hartmann wavefront sensor or other devices, a point source can be attached / bonded to the back side of a mechanical plate and project illumination to the collimating unit 14 through a tiny pinhole. The reflected illumination passes through another pinhole in the SDU toward collimating unit 14’ ’ (behind the SDU) and projects a collimated beam to MLA 17 and from there to the sensor matrix SM.

[0165] FIG. 34 shows an example of implementing a Fizeau-type Interferometer based on an SDU configuration. This setup is similar to the setup illustrated in FIG. 33, but does not include MLA 17, and instead includes a reference unit RU that supports a reference surface RS deployed between the collimating unit 14’ ’ and the UUT. The reference unit RU can take a variety of shapes and configurations, and may be a partially reflective plate. Alternatively, instead of an SDU with a point source and sensor matrix, a planar screen with a pair of apertures can be provided, where one of the apertures acts as the point source and the other aperture is located at the point on the screen at which the reflected image (TP) of the point source (PS) is expected to be received (CR). FIG. 35 illustrates an optical system that can alternate between functioning as an autocollimator and wavefront sensor (and vice-versa). The point source PS is placed at a fixed location, separate from the sensor matrix 40 of the SDU, at a decenter from the datum axis. The sensor matrix 40 is placed next to the point source PS, on the same plane but on the other side of the datum axis. A movement mechanism is deployed to move the sensor matrix 40 in and out of the optical path between the collimating units 14 and 14”. The movement mechanism is indicated in the figure by double-headed arrow, and designated MV1. The sensor matrix 40 is perpendicular to the datum axis.

[0166] Illumination is emitted from the point source PS, for example via projection from an external illumination source SRC (such as an LED or laser) through an optical fiber FBR, toward the collimating unit 14.

[0167] When the movement mechanism MV1 positions the sensor matrix 40 close to the point source PS, the point source PS and sensor matrix 40 resemble the SDU configuration of the previously described autocollimator embodiments (i.e., the point source PS is adjacent (practically abutting) the SDU), and the reflected illumination reaches the sensor matrix 40 and forms an image on it. Thus, the system functions as an autocollimator as described in previous embodiments. Furthermore, in this position, the SDU functions as a screen that blocks the light (the reflected image) from reaching the second collimating unit 14” and the MLA 17 (which are both located behind the SDU).

[0168] When the movement mechanism MV1 positions the sensor matrix 40 away from point source PS a minuscule gap is formed between the sensor matrix 40 and the point source PS for the reflected illumination to continue and eventually reach the sensor matrix SM of the wavefront sensor via collimating lens 14” and MLA 17. Specifically, the reflected illumination from the collimating unit 14 is focused onto a point in the gap, at which an image is formed. The location of the gap through which the reflected illumination passes must be the exact same location of the expected position of the reflected image of the point source PS when the optical system is in the autocollimator configuration. This constraint compels a mode of operation of the optical system in two stages. In the first stage, the operator of the optical system places the optical system in the autocollimator configuration (thereby to ensure that the actual location of the reflected image and the expected position of the reflected image overlap (i.e., the reflected image TP and its expected location CR are the same, as in FIG. 18 A). The operator may then place the optical system in the wavefront sensor configuration by moving the SDU (via the movement mechanism MV1) to provide the aforementioned gap between the sensor matrix 40 and the point source PS.

[0169] FIGS. 36A and 36B are front views of the sensor matrix 40, illustrating what the sensor matrix “sees” when the optical system of FIG. 35 is in the autocollimator configuration and in the wavefront sensor configuration, respectively. When the optical system is in the autocollimator configuration, an image from the reflected illumination is formed on the sensor matrix 40, and thus the sensor matrix “sees” the reflected image. When the optical system is in the wavefront sensor configuration, the sensor matrix 40 does not “see” any reflected illumination because the image from the reflected illumination is formed at the gap between the sensor matrix 40 and the point source PS (i.e., the image is not visible because it is formed in the air). However, the image is still present, and could be made visible to the eye, for example by placing a piece of paper in the gap parallel to the SDU plane.

[0170] FIG. 37 illustrates an optical system similar to the configuration of FIG. 35, but including two additional movement mechanisms MV2 and MV3 that are configured to move reference unit RU and MLA 17, respectively, in and out of respective optical paths. By providing moveability of the SDU, the reference unit RU, and the MLA 17, the optical system of the present embodiment can alternate between functioning as an autocollimator, a wavefront sensor, and interferometer. For example, when both the SDU is positioned (by movement mechanism MV1) out of the optical path between the collimating units 14 and 14” and the reference unit RU is positioned (by movement mechanism MV2) out of the optical path between the collimating unit 14 and the UUT, but the MLA 17 is positioned (by movement mechanism MV3) in the optical path between the collimating unit 14’ ’ and the sensor matrix SM, the optical system functions as a wavefront sensor. When the SDU and the MLA 17 are both positioned out of their respective optical paths (by movement mechanisms MV1 and MV3) but the reference unit RU is positioned (by movement mechanism MV2) in the optical path between the collimating unit 14 and the UUT, the optical system functions as an interferometer. When the reference unit RU and the MLA 17 are both positioned out of their respective optical paths (by movement mechanisms MV2 and MV3) but the SDU is positioned (by movement mechanism MV1) in the optical path between the collimating units 14 and 14” , the optical system functions as an autocollimator.

[0171] Constraints on the location of the gap, and the operation of the optical system in the autocollimator configuration before operating in the wavefront sensor and interferometer configuration are similar to as discussed above with reference to FIG. 35.

[0172] It is noted that embodiments of an optical system that alternates between functioning as an autocollimator and interferometer are also contemplated herein. Such an embodiment can be achieved, for example, by modifying the embodiment illustrated in FIG. 37 by removing the MLA 17 (and the movement mechanism MV3).

[0173] The movement mechanisms MV1, MV2, and MV3 may be implemented in various ways, including, for example, as moveable platforms, mechanical holding arrangement coupled to moveable elements, and the like. Movement of the movement mechanisms MV1, MV2, and MV3 may be controlled by one or more actuator mechanisms, which may be electronically controlled in response to operator input.

[0174] It should be noted that different light sources for the various configurations described above may be used in compatibility with the specific application. Fizeau Interferometery, for example, requires a coherence length of at least tens of centimeters while a LED source is good enough for a Schack-Hartmann sensor and while autocollimators are indifferent to the properties of the light.

[0175] It should be also noted that, if the autocollimator requires a larger area to function, the SDU in FIGS. 36 and 37 may consist of a pair of sensor matrixes deployed in a side-by-side configuration, similar to as described above with reference to FIGS. 13 A and 13B. However, the expected position of the reflected image of the point source PS (i.e., CR) and the circles around it on one of the sensor matrixes should be very close to the edge of the other sensor matrix so as to keep the decenter distance from the datum axis minimal. This is necessary to prevent various optical aberrations (especially astigmatism).

[0176] FIG. 38 shows an optical system that implements a polarization scheme that prevents unwanted illumination from reaching the sensor matrix, according to an embodiment of the present disclosure. As will become apparent, this embodiment shares some similarities with the embodiment illustrated in in FIG. 17, but is fundamentally different from the other embodiments of the present disclosure in that there is no SDU, i.e., the point source and the sensor matrix are not coplanar. In fact, the point source and the sensor matrix are orthogonally deployed. The orthogonal deployment is effectuated by a polarizing beamsplitter (PBS) cube 180. The implementation of preventing unwanted illumination from reaching the sensor matrix is achieved by employing polarization-selectivity at three of the surfaces of the PBS cube 180 while having the propagation of the light from the point source perpendicular to the surface of the PBS cube through which the light enters the PBS cube 180.

[0177] As illustrated, the PBS cube 180 has a plurality of surfaces, including two pairs of parallel surfaces 182, 184 and 186, 188. The surfaces 182, 184 and 186, 188 are mutually orthogonal. A polarizing beamsplitter surface 185 is provided on the diagonal of the PBS cube 180. The surface 182 is associated with a polarization- selective element 190, and is deployed at or close to the detector plane of the sensor matrix 40. The surface 188 is also associated with a polarization- selective element 192. A point source PS is deployed in association with the surface 188 / element 192, in close proximity to the surface 188 preferably almost affixed to the surface 188. Optical retarder 95 (implemented as a quarter wave plate) is deployed in the optical path between the PBS cube 180 and the collimating unit 14, and is associated with the surface 184 (in the figure, optical retarder 95 is shown as being adjacent to surface 184). The PBS 180 cube is constructed from a light-transmitting material that provides very good transmission for light having wavelengths that are used in specific applications and that match the wavelengths of the spectral responsivity of the sensor matrix 40. In certain embodiments, the PBS cube 180 may be constructed from a pair of triangular prisms. For example, the hypotenuse side of at least one of the triangular prisms may be provided with a polarizing beamsplitter coating, and the two triangular prisms may then be bonded together at the hypotenuse sides. The polarization selectivity of the elements 190 and 192 and the retarder 95 can be provided by a coating, lamination, chemical treatment, dyeing polyvinyl alcohol, thin polarizing filters, and the like. In certain embodiments, the elements 190 and 192 can be polarization-selective thin transparent flat plates that are provided with polarization selective properties via one of the aforementioned techniques.

[0178] To illustrate the prevention of unwanted illumination from reaching the sensor matrix, the path of illumination from the point source PS to the sensor matrix 40 will now be described. The illumination that enters the PBS cube 180 from the point source PS is linearly polarized in a first linear polarization direction of the electric field propagation (e.g., P-polarization) with regards to the surface 188. This may be achieved by implementing the point source PS as a polarized source, or by implementing the point source PS as an unpolarized source and deploying a polarizer at the output of the illuminations the point source PS. The element 192 transmits illumination that is linearly polarized in the first linear polarization direction, such that the illumination from the point source PS passes through the surface 188. The illumination then reaches the polarizing beamsplitter surface 185, which reflects illumination that is linearly polarized in the first linear polarization direction (e.g., P-polarized) and transmits illumination that is linearly polarized in a second linear polarization direction (e.g., S-polarized) that is orthogonal to the first direction. Thus, the illumination that enters the PBS cube 180 via the surface 188 is reflected by the polarizing beamsplitter surface 185. The reflected illumination exits the PBS cube 180 via the surface 184, and passes through the optical retarder 95, which rotates the polarization direction of the illumination so that the illumination is circularly polarized (for example in a clockwise direction). The circularly polarized illumination passes through the collimating unit 14 and is reflected by the surface 20 (for example to become circularly polarized in the counter clockwise direction) back through the collimating unit 14 and the optical retarder 95, which rotates the polarization direction of the illumination so that the illumination is linearly polarized in the second linear polarization direction (e.g., S-polarized). The linearly polarized illumination is transmitted by the polarizing beamsplitter surface 185 (which transmits illumination that is linearly polarized in the second linear polarization direction) and reaches the surface 182. The element 190 transmits illumination that is linearly polarized in the second linear polarization direction, such that the illumination passes from the surface 182 through the element 190 so as to be focused onto the sensor matrix 40 at test point TP.

[0179] Preferably, the PBS cube 180 is dimensioned so that the surface 182 covers the entire surface of the sensor matrix 40 and leaves no pixels exposed to light that is not received through the PBS cube 180.

[0180] While the PBS cube 180 and the sensor matrix 40 can be of various dimensions, the distance from the surface 188 to the polarizing beamsplitter surface 185 is equal to the distance from the polarizing beamsplitter surface 185 to the surface 182.

[0181] In certain preferred embodiments, the point source PS is positioned at the center of the surface 188, although this is not a strict requirement. Moreover, in certain embodiments multiple point sources may be employed. Thus, not all of the point sources would be positioned at the center of the surface 182. In certain embodiments, the point source(s) may contain a variety of target shapes, such as crosshair, circle etc.

[0182] The light traversal in this embodiment is similar to that which is common in standard autocollimators, and thus there is no need for a decenter setup nor is there a drawback of overcasting pixels (by an optical fiber for example).

[0183] Although the description of the embodiment illustrated in FIG. 38 has pertained to a PBS cube having a diagonal (internal) polarizing beamsplitter surface and polarization- sensitive elements at three external PBS cube surfaces, variant embodiments of FIG. 38 may still provide prevention of unwanted illumination. In one variant embodiment, surface 185 can be unpolarized, and yet, due to the polarization sensitivity of the other surfaces 182, 184, 188 (or the elements 190, 95, 192 associated therewith), the optical system would function just the same. In another variant embodiment, the surface 185 may be implemented as a polarizing beamsplitter surface, but the surfaces 182 and 188 may be un-polarized (i.e., no polarization selective elements 190 and 192).

[0184] Similar to as described with reference to FIG. 17, for each instance where a particular polarized light path has been followed in the example described above, the polarizations are interchangeable, whereby, for example, on altering the polarization selective properties of a surface or element, each mention of light having P-polarization could be replaced by light having S -polarization, and vice versa.

[0185] FIG. 39 illustrates an optical system according to another embodiment of the present disclosure, which is based on a modified configuration of the optical system illustrated in FIG. 38, which enables the optical system to alternate between functioning as an autocollimator (as in FIG. 38) and one or more additional optical devices, such as a Schack-Hartmann Wavefront Sensor, various interferometers, Scatter-Plate, Point Diffraction Interferometer, Ronchi Ruling, Star Test, Relay PSF magnification, and MTF. The following paragraphs describe the modifications that enable the optical system to perform these functions.

[0186] A quarter wavelength surface 96, such as an optical retarder (implemented as a quarter wave plate) is deployed in association with the surface 186 (in the figure, a quarter wave plate is shown as being adjacent to surface 186, but in principle a quarter wavelength polarizing coating can be applied to the surface 186). The surface 96 facilitates an interferometer reference channel IRC, as will be discussed below.

[0187] A moveable (or removable) opaque plate OPP is deployed in association with the surface 186, either adjacent to the surface 186 or directly attached to the surface 186. The plate OPP, when properly positioned, blocks illumination so as to prevent illumination from passing through the surface 186.

[0188] Three sensor matrixes SMI, SM2, and SM3, are provided. The sensor matrix SMI is akin to sensor matrix 40, placed further back from the PBS cube 180, as compared to the sensor matrix location in FIG. 38. The sensor matrixes SM2 and SM3 are deployed in association with the surface 182, and may be affixed to the element 190. The sensor matrixes SM2 and SM3 are deployed so that a small gap is formed between the two sensor matrixes, (resembling the configuration in FIGS. 13 A and 13B, but without a point source in the gap. Alternatively, a single sensor matrix can be deployed (instead of two sensor matrixes SM2 and SM3). The single sensor matrix has a small hole (resembling the configuration in FIGS. 12A and 12B, but without a point source in the hole).

[0189] An optical arrangement OAR, having one or more optical components, is provided in the interferometer reference channel IRC, preferably in close proximity to the surface 186. This proximity is enabled by the quarter wavelength surface 96 associated with the surface 186 which, in turn, blocks light (from the interferometer reference channel IRC through surface 186) from reaching the surface 182. The optical components optical arrangement OAR can take various forms, such as a combination of a high-quality lens and high-quality mirror, or a concave spherical mirror, or other alternative optical elements. In the non-limiting illustrated example, the optical arrangement OAR of the interferometer reference channel IRC includes a collimating lens CL1 and a flat reflective surface (flat mirror M).

[0190] Positioning of the interferometer reference channel IRC in close proximity to the surface 186 enables the optical system to be compact. Furthermore, the positioning of the optical components of the optical arrangement OAR is pre-defined at a predesignated location. Thus, for example, when the optical arrangement OAR is composed of collimating lens CL1 and mirror M, the distance from the collimating lens CL1 to the point source PS is equal to its focal length. An additional collimating lens CL2 is deployed between the sensor matrix SMI and the two sensor matrixes SM2 and SM3. An MLA unit MLA is provided and is moveable in and out of the optical path between the collimating lens CL2 and the sensor matrix SMI. Movement of the MLA unit MLA may be effectuated by a movement mechanism MV4, such as a moveable platform, a mechanical holding arrangement coupled to moveable elements, etc. The movement mechanism MV4 may be electronically actuated.

[0191] The following paragraphs describe example of beam traversal through the optical system when the optical system assumes various configurations.

[0192] When the optical system functions as an autocollimator, the opaque plate OPP that blocks light from passing through the surface 186 is inserted so as to be in overlapping relation with the surface 186. Insertion of the plate OPP may be effectuated by a movement mechanism (not shown), such as a moveable platform, a mechanical holding arrangement coupled to moveable elements, etc., which may be an electronically actuated mechanism. In this the test point TP image is formed on either the sensor matrix SM2, or the sensor matrix SM3, or in the gap formed between the sensor matrixes SM2 and SM3.

[0193] When the optical system functions as a Schack-Hartmann WFS for example, the opaque plate OPP is inserted so as to be in overlapping relation with the surface 186, and the MLA unit MLA is positioned in the optical path between the collimating lens CL2 and the sensor matrix SMI. The reflected beam (from surface 20) features the same polarizations propagations as that of the embodiment of FIG. 38. After passing through surface 190 and the gap between the sensor matrixes SM2 and SM3, the beam passes through collimating lens CL2 and the MLA unit MLA to form the matrix spots on the sensor matrix SMI.

[0194] When the optical system functions as an interferometer with a reference channel for example, the beam splitter surface 185 should not be polarized, but the other cube surfaces (that are noted in FIG. 38) should be. Furthermore, the quarter wavelength surface 96 is provided to enable transformations of propagations from linear to circular polarizations and vice-vera when the illumination passes through and returns through surface 186 respectively. In this mode, the MLA unit MLA is positioned out of the optical path between the collimating lens CL2 and the sensor matrix SMI. Thus, illumination that passes through the surface 186 turns the linearly polarized propagation (e.g., P-polarization) that crosses the beamsplitter (from the point PS through surface 185) to a circularly polarized propagation (say in a clockwise direction). The illumination travels further on the interferometer reference channel IRC. In FIG. 39 the beam passes through collimating lens CL1 and strikes mirror M. After crossing through the surface 186 (and the quarter wavelength surface 96) the illumination is circularly polarized and passes through the collimating lens CL1. The illumination then strikes the mirror M and is reflected on the interferometer reference channel IRC in a circularly polarized propagation (say in a counterclockwise direction). The illumination then passes through the collimating lens CL1 and the surface 186 and becomes linearly polarized (e.g., S -polarization) when it strikes the beamsplitter surface 185. At the beamsplitter surface 185 the illumination interferes with the illumination that is reflected by the reflective surface 20. The interference occurs inside the PBS cube 180 while the illumination that is reflected from the surface 20 passes through the (unpolarized) beamsplitter. From the interference area, the illumination passes though the surface 182 (and element 190) and through the collimating lens CL2 to form an interference image on the sensor matrix SMI.

[0195] In certain embodiments, an actuator (e.g., a piezoelectric actuator) may be positioned at the back of the interferometer reference channel IRC to effectuate phase shifting. The interferometer reference channel IRC can be oscillated along this axis (toward and away from the cube) in steps that are fractions of microns. With a matching software, the optical system can perform many interferometry images (on sensor matrix SMI) during each time frame and provide accuracy that only high-quality interferometers possess.

[0196] It is noted that beamsplitter cube 180 does not have to be a solid light-transparent material (i.e., solid piece of glass). In certain embodiments, the cube 180 can be formed as a hollow structure (a chassis) supporting four transparent and polarized surfaces as required by the application, with a beamsplitter plate, pellicle, etc., diagonally positioned inside.

[0197] The descriptions of the various embodiments of the present disclosure have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

[0198] As used herein, the singular form, “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.

[0199] The word “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and / or to exclude the incorporation of features from other embodiments.

[0200] It is appreciated that certain features of the 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 disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the disclosure. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. To the extent that the appended claims have been drafted without multiple dependencies, this has been done only to accommodate formal requirements in jurisdictions which do not allow such multiple dependencies. It should be noted that all possible combinations of features which would be implied by rendering the claims multiply dependent are explicitly envisaged and should be considered part of the disclosure. Although the disclosure has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An optical system, comprising: a source-detector unit having a planar output-input region and including: a detector arrangement, and an illumination arrangement that provides a point source that defines an output sub-region of the planar output-input region; and an optical arrangement deployed between the source-detector unit and an at least partially reflective surface, wherein the point source outputs illumination from the output sub-region toward the at least partially reflective surface via at least one optical component of the optical arrangement, wherein the detector arrangement is configured to form an image from illumination from the point source that is reflected from the at least partially reflective surface and received at an input sub-region of the output-input region via at least one optical component of the optical arrangement, and wherein a component of the optical system is provided with an optical decenter in relation to a datum axis of the optical system.

2. The optical system of claim 1, wherein the datum axis is defined by the optical arrangement, and wherein the point source is decentered from the datum axis.

3. The optical system of claim 1, wherein the optical arrangement has an optical axis, and wherein the optical arrangement is deployed so that the optical axis is decentered from the datum axis.

4. The optical system of claim 1, wherein the optical arrangement includes a collimating unit having at least one collimating lens, the collimating unit having a focal plane that is coplanar with the planar output-input region.

5. The optical system of claim 1, wherein the optical arrangement includes: a collimating unit including: a first lens having a focal plane that is coplanar with the planar output-input region, and a second lenshaving a focal plane that is coplanar with the planar output-input region, and a focusing unit having one or more lenses deployed between the lens arrangement and the at least partially reflective surface, the focusing unit having a focal plane that is coplanar with the at least partially reflective surface.

6. The optical system of claim 5, wherein illumination from the point source that is output from the output-input surface is collimated by the first lens, focused by the focusing unit onto the at least partially reflective surface, reflected from the at least partially reflective surface, transmitted by the focusing unit, and focused by the second lens so as to be focused onto the input sub-region and detected by the detector arrangement.

7. The optical system of claim 1, wherein the source-detector unit includes: an image guide that provide an optical coupling between the input subregion and detector elements of the detector arrangement, and an illumination optical fiber that provides an optical coupling between the output sub-region and an illumination source of the illumination arrangement.

8. The optical system of claim 1, wherein the source-detector unit includes: a micro reflective element located at a detector plane of the detector arrangement, wherein the micro reflective element defines the output sub-region and the detector plane defines the input subregion, and wherein illumination produced by an illumination source of the illumination arrangement is reflected by the micro reflective element.

9. The optical system of claim 8, wherein the source-detector unit further includes: a substrate having a plurality of surfaces including a first planar surface and a second planar surface parallel to the first planar surface, wherein the micro reflective element is located at the first planarsurface, and wherein the detector plane is coplanar with the first planar surface.

10. The optical system of claim 9, wherein the illumination arrangement is deployed to inject illumination into the substrate so that the injected illumination is totally internally reflected from the second planar surface toward the micro reflective element, and reflected out of the substrate by the micro reflective element.

11. The optical system of claim 10, wherein the plurality of surfaces of the substrate further include a third planar surface oblique to the first and second planar surfaces, wherein the injected illumination is transmitted by the second planar surface and is reflected by the third planar surface prior to being totally internally reflected from the second planar surface.

12. The optical system of claim 10, wherein the plurality of surfaces of the substrate further include a third planar surface oblique to the first and second planar surfaces, wherein the injected illumination is transmitted by the third planar surface prior to being totally internally reflected from the second planar surface.

13. The optical system of claim 9, wherein the plurality of surfaces of the substrate further include a third planar surface oblique to the first and second planar surfaces, and wherein the illumination source is deployed to inject illumination into the substrate through the first planar surface so that the injected illumination is reflected by the third planar surface toward the micro reflective element and reflected out of the substrate by the micro reflective element.

14. The optical system of claim 8, wherein the source-detector unit further includes: a prism having a plurality of surfaces and deployed such that the illumination produced by the illumination source is injected into the prism and reflected by one or more of the surfaces of the prism so as to be coupled out of the prism toward the micro reflective element.

15. The optical system of claim 1, wherein the detector arrangement includes a sensor matrix having a detector plane that defines the input sub-region, wherein thesensor matrix is provided with a through hole that penetrates from a region of the detector plane to a back side of the sensor matrix, wherein the illumination arrangement includes an illumination source coupled to an optical fiber that is accommodated in the through hole such that an output end of the optical fiber is located at the region of the detector plane, wherein the output end of the optical fiber defines the output sub-region.

16. The optical system of claim 1, wherein the detector arrangement includes a first sensor matrix and a second sensor matrix deployed in a side-by-side configuration, the first sensor matrix having a first detector plane and the second sensor matrix having a second detector plane, the first and second detector planes together forming a detector plane of the detector arrangement that defines the input sub-region, wherein the illumination arrangement includes an illumination source coupled to an optical fiber that is accommodated between the first sensor matrix and the second sensor matrix such that an output end of the optical fiber is located at a region of the detector plane of the detector arrangement, wherein the output end of the optical fiber defines the output subregion.

17. The optical system of claim 1, wherein the illumination arrangement includes: a reflective element mounted to a thin transparent plate, that is attached to a detector plane of the detector arrangement, at a 45-degree angle relative to the detector plane, wherein the reflective element defines the output sub-region and the thin transparent plate defines the input sub -region, and an optical fiber coupled to an illumination source and having an output end deployed adjacent to the reflective element such that illumination from the illumination source that is output from the output end is reflected by the reflective element in a reflection direction that is substantially perpendicular to the detector plane.

18. The optical system of claim 1, wherein the illumination arrangement includes a micro illumination source mounted to a thin transparent plate that is attached to a detector plane of the detector arrangement, wherein the micro illumination source defines the output sub-region and the thin transparent plate defines the input sub-region.

19. The optical system of claim 1, wherein the detector arrangement includes a sensor matrix having a detector plane, wherein a thin transparent plate is attached to the detector plane and defines the input sub-region, wherein the thin transparent plate is provided with a light guiding arrangement coupled to an illumination source of the illumination arrangement and an optical coupling-out surface that defines the output sub-region, wherein illumination from the illumination source is coupled into the light guiding arrangement so as to propagate through the light guiding arrangement by total internal reflection and is coupled out of the light guiding arrangement by the optical coupling-out surface in a reflection direction that is substantially perpendicular to the detector plane.

20. The optical system of claim 1 , wherein the detector arrangement includes a sensor matrix having a detector plane, wherein a thin transparent plate is attached to the detector plane and defines the input sub-region, the thin transparent plate being polarization-selective so as to transmit illumination that is linearly polarized in a first polarization direction with regards to the thin transparent plate and reflect illumination that is linearly polarized in a second polarization direction, orthogonal to the first polarization direction, with regards to the thin transparent plate, wherein the illumination arrangement is configured to generate illumination that is polarized such that the illumination that is output from the output sub-region is in the second polarization direction with regards to the thin transparent plate, wherein the optical system further comprises an optical retarder deployed between the source-detector unit and the optical arrangement that is configured to rotate the polarization state of illumination incident to the optical retarder.

21. The optical system of claim 1, wherein the illumination arrangement includes micro reflective element that provides the point source and that defines the output sub-region.

22. The optical system of claim 21, wherein the micro reflective element includes a micro holographic element.

23. The optical system of claim 21, wherein the micro reflective element includes a micro mirror.

24. The optical system of claim 21, wherein the micro reflective element includes a micro grating.

25. The optical system of claim 21, wherein the micro reflective element is mounted to a thin transparent plate that is attached to a detector plane of the detector arrangement, wherein the detector plane defines the input sub-region.

26. The optical system of claim 21, wherein the illumination arrangement includes an optical fiber having an output end that provides the point source.

27. The optical system of claim 1, wherein the illumination arrangement provides a plurality of point sources that define a plurality of output sub-regions of the planar output-input region.

28. The optical system of claim 1, wherein the illumination arrangement includes a plurality of illumination sources.

29. The optical system of claim 1, wherein the illumination arrangement includes a collimated source.

30. The optical system of claim 1 , wherein the detector arrangement includes a sensor matrix having a detector plane that defines the input sub-region.

31. The optical system of claim 1 , wherein the at least partially reflective surface is part of the optical system.

32. The optical system of claim 1, wherein when the at least partially reflective surface is perpendicular to the datum axis, the point source and a reflected image of the point source have a symmetric relationship about a mirror axis that is parallel to the datum axis.

33. The optical system of claim 31, wherein the optical system is configured to receive an optical device, having at least one optical element, between the optical arrangement and the at least partially reflective surface, wherein when the at least one optical element is misaligned relative to the datum axis, the symmetric relationship about the mirror axis is broken.

34. The optical system of claim 1, wherein a distance from a sensor matrix of the detector arrangement is equal to a focal length of a collimating unit of the optical arrangement.

35. A method for testing alignment of optical devices, the method comprising: obtaining the optical system of claim 1 ; deploying optical device having at least one optical element between the optical arrangement and the at least partially reflective surface; activating the illumination arrangement such that the point source outputs illumination toward the at least partially reflective surface; and determining an amount of misalignment of the at least one optical element relative to the datum axis based on a location of the image on the planar output-input region.

36. An optical system, comprising: a first sensor matrix; a point source; a first collimating unit; a second collimating unit deployed between the point source and a reflective surface, wherein the point source outputs illumination toward the reflective surface via the second collimating unit; a second sensor matrix, wherein the point source lies in a plane of the sensor matrix, and wherein the plane is between first collimating unit and the second collimating unit; a microlens array (MLA) located between the first sensor matrix and the first collimating unit; and a movement mechanism associated with the second sensor matrix and configured to move the second sensor matrix between: a first position in which the point source is adjacent to the second sensor matrix, and a second position in which a gap is formed between the point source and the second sensor matrix, wherein when the second sensor matrix is in the first position, illumination from the point source is reflected from the reflective surface back through thesecond collimating unit so as to be focused onto the second sensor matrix, and wherein when the second sensor matrix is in the second position, illumination from the point source is reflected from the reflective surface back through the second collimating unit so as to be focused onto a point in the gap and subsequently pass through the first collimating unit and the MLA to the first sensor matrix.

37. An optical system, comprising: a first sensor matrix; a point source; a first collimating unit; a second collimating unit deployed between the point source and a reflective surface, a reference surface located between the second collimating unit and the reflective surface, wherein the point source outputs illumination toward the reflective surface via the second collimating unit and the reference surface; a second sensor matrix, wherein the point source lies in a plane of the sensor matrix, and wherein the plane is between first collimating unit and the second collimating unit; and a movement mechanism associated with the second sensor matrix and configured to move the second sensor matrix between: a first position in which the point source is adjacent to the second sensor matrix, and a second position in which a gap is formed between the point source and the second sensor matrix, wherein when the second sensor matrix is in the first position, illumination from the point source is reflected from the reflective surface back through the reference surface and the second collimating unit so as to be focused onto the second sensor matrix, and wherein when the second sensor matrix is in the second position, illumination from the point source is reflected from the reflective surface back through the reference surface and the second collimating unit so as to befocused onto a point in the gap and subsequently pass through the first collimating unit to the first sensor matrix.

38. An optical system, comprising: a first sensor matrix; a point source; a first collimating unit; a second collimating unit deployed between the point source and a reflective surface, a reference surface located between the second collimating unit and the reflective surface, wherein the point source outputs illumination toward the reflective surface via the second collimating unit and the reference surface; a second sensor matrix, wherein the point source lies in a plane of the sensor matrix, and wherein the plane is between first collimating unit and the second collimating unit; a microlens array (MLA) located between the first sensor matrix and the first collimating unit; a first movement mechanism associated with the second sensor matrix and configured to move the second sensor matrix between: a first position in which the point source is adjacent to the second sensor matrix, and a second position in which a gap is formed between the point source and the second sensor matrix; a second movement mechanism associated with the reference surface and configured to move the reference surface between: a third position in which the reference surface is in a first optical path between the second collimating unit and the reflective surface, and a fourth position in which the reference surface is out of the first optical path; and a third movement mechanism associated with the MLA and configured to move the MLA between: a fifth position in which the MLA is in a second optical path between the first sensor matrix and the second collimating unit, and a sixth position in which the MLA is out of the second optical path,wherein when the second sensor matrix is in the first position and the reference surface is in the fourth position, illumination from the point source is reflected from the reflective surface back through the second collimating unit so as to be focused onto the second sensor matrix, wherein when the second sensor matrix is in the second position and the reference surface is in the third position and the MLA is in the sixth position, illumination from the point source is reflected from the reflective surface back through the reference surface and the second collimating unit so as to be focused onto a point in the gap and subsequently pass through the first collimating unit to the first sensor matrix, and wherein when the second sensor matrix is in the second position and the reference surface is in the fourth position and the MLA is in the fifth position, illumination from the point source is reflected from the reflective surface back through the second collimating unit so as to be focused onto a point in the gap and subsequently pass through the first collimating unit and the MLA to the first sensor matrix.

Images