Patent Description:
Current techniques for measuring optics, in particular coatings, are limited to a small range of angles, or a small set of discrete angles, and/or have significant problems due to refraction. Generally, there is a lack of consistency and/or accuracy in the results of measuring.

<CIT> describes an apparatus for optical testing of a sample of optical material, such as a coated glass plate. The apparatus comprises a rotatable assembly and an optical arrangement. The rotatable assembly includes a cylinder, a turntable, and a receptacle. The cylinder has a central hollow sized to receive a core area of the coated glass plate. The receptacle includes the hollow and is sized to receive a portion of the glass plate. The receptacle is sealed for receiving a quantity of index matching fluid, such that the fluid is in contact with the core area and the cylinder. The optical arrangement is aligned with the axis of the cylinder, and includes an optical source and an optical detector. The optical source provides an optical light beam normal to a circumferential surface area at a first side of the cylinder. The optical detector accepts the optical light beam normal to a circumferential surface area at a second side of the cylinder. The turntable rotates the rotatable assembly around the height-axis of the cylinder for testing the sample over a range of angles.

<CIT> discloses a method and a device for three-dimensionally determining the refractive index and, if necessary, the layer thickness of transparent or partially transparent layers in which the layer is irradiated at different angles of incidence with polarised light, and variations in the polarisation of the light are measured and evaluated as the light passes through the layer. The measurement is carried out through an immersion medium.

<CIT> discloses an apparatus for testing transmittance that includes a sample unit to position a material under test. The material under test is disposed between respective flat surfaces of a first mount and a second mount, which are positioned in the sample unit for a test round. The sample unit defines a first volume and a second volume, wherein arc shapes formed by respective surfaces of the first and second volume conform to a circle. During the test round a rotation unit varies an angular position of the material under test relative to a light source. A light detector receives light from the light source which has been transmitted through the first volume, the material under test, and the second volume. A transmittance signature of the material under test for a range of incidence angles is determined based on the received light.

Optical sample characterization facilitates measurement and testing at any angle in a full range of angles of light propagation through an optical sample, such as a coated glass plate, having a higher than air index of refraction. A rotatable assembly includes a cylinder having a hollow, and a receptacle including the hollow. The receptacle also contains a fluid that in some implementations has a refractive index matching the refractive index of the optical sample and/or the cylinder. An optical light beam is input normal to the surface of the cylinder, travels through the cylinder, then via the fluid, to the optical sample, where light beam is transmitted and/or reflected, then exits the cylinder and is collected for analysis. Due at least in part to the fluid surrounding the optical sample, the optical sample can be rotated through a full range of angles (±<NUM>°, etc.) for full range testing of the optical sample.

The invention is directed to an apparatus for optical testing of a sample of optical material as defined in claim <NUM>, and to a method for optical testing of a sample of optical material as defined in claim <NUM>. The apparatus includes an assembly including: an optically transparent general-cylinder having an interior partially filled with a bulk material portion from an interior surface of the general-cylinder toward a center axis of the general-cylinder, and the interior having a hollow portion extending from an opposite interior surface of the general cylinder and including the axis, the hollow sized to receive at least a core area of the sample of optical material, a receptacle including the hollow, the receptacle sized to receive at least a portion of the sample of optical material, and the receptacle sealed for receiving a quantity of fluid, such that the fluid surrounds and is in contact with at least the core area, and is in contact with the general-cylinder and at least a portion of the bulk, and an optical arrangement: aligned with the axis, including an optical source providing an optical light beam normal to a circumferential surface area at a first side of the general-cylinder, and including an optical detector accepting an output signal, the output signal from the optical light beam impinging on the core area and transmitted through or reflected from the sample, the optical detector normal to a circumferential surface area of the general-cylinder.

In an optional embodiment, the assembly is a rotatable assembly, and further including: a turntable aligned with the axis and operable to rotate the rotatable assembly around a height-axis of the general-cylinder.

In another optional embodiment, the bulk fills substantially a semicircular half of the receptacle.

In another optional embodiment, the bulk material is a same optically transparent material as the general-cylinder optically transparent material.

In another optional embodiment, further including: a mounting arrangement for receiving the optical arrangement and adjustable for aligning the optical source and the optical detector.

In another optional embodiment, further including a clamping mechanism securing location of the sample with respect to the receptacle.

In another optional embodiment, further including a motor operationally connected to the rotatable assembly and operable to rotate the rotatable assembly, and an encoder operationally connected to the rotatable assembly and operable to provide position information at least regarding angle of rotation of the rotatable assembly.

In another optional embodiment, wherein the general-cylinder is selected from the group consisting of: a cylinder, and a prism. In another optional embodiment, wherein indexes of refraction of the general-cylinder, the sample, and the fluid are substantially equal. In another optional embodiment, wherein the fluid is an index matching fluid, and indexes of refraction of the sample and the fluid are substantially equal. In another optional embodiment, wherein the general-cylinder and the sample of an optical material are made of the same optically transparent, solid material.

In another optional embodiment, wherein the general-cylinder is substantially symmetric parallel to the height-axis of the general-cylinder. In another optional embodiment, wherein the general-cylinder is positioned according to the group consisting of: stationary, rotatable in a single axis, rotatable in more than one axis, rotatable in a pre-defined range of angles, and
rotatable ±<NUM> degrees from a normal to the sample.

In another optional embodiment, wherein the core area of the sample is a location of the sample where a light beam encounters the sample and testing of the sample is performed.

In another optional embodiment, wherein the receptacle has: a receptacle-width in a direction along a cylinder diameter of the general-cylinder, the receptacle-width being smaller than the cylinder diameter, and a receptacle-thickness non-parallel to the receptacle-width, the receptacle-thickness between a first side and second side of the general-cylinder, and the sample has: a plate-width in a direction along the cylinder diameter, the receptacle-width being greater than the plate-width, and a plate-thickness non-parallel to the plate-width, the receptacle-thickness being greater than the plate-thickness.

In another optional embodiment, the receptacle-width and the plate-width are aligned substantially parallel. In another optional embodiment, the receptacle is configured to contain <NUM> cubic centimeters (cc) to <NUM> cc of fluid.

In another optional embodiment, the sample is selected from the group consisting of: a glass plate, a coated glass plate, a thin film polarizer, a glass polarizer, a plastic polarizer, a beam splitter, a wave plate, a lightguide optical elements (LOE), a structured optical element selected from the group consisting of: a ruled grating, a holographic grating, a holographic volume grating, diffraction optical elements, Fresnel lenses, sub-wavelength photonic structures, and a wire grid.

In another optional embodiment, the optical element is coated with a coating, the coating used to manipulate light incident to the sample.

In another optional embodiment, the optical arrangement includes collimating optics preparing the optical light beam and inputting the optical light beam into the general-cylinder, the collimating optics adjustable with at least two degrees of freedom. In another optional embodiment, an optical path of the optical light beam is through the general-cylinder and the fluid, and a majority of the optical path is through the general-cylinder.

In an optional embodiment, there is provided a controller operationally connected to the apparatus of claim <NUM> or claim <NUM>, the controller configured to initiate inputting an optical light beam normal to a surface area of a first side of the general-cylinder; position the general-cylinder so a light beam path traverses via a first side of the general-cylinder until reaching the hollow, then traverses from the first side into the fluid in the hollow on a first side of the sample, through the sample, through the fluid on an other side of the sample, into a second side of the general-cylinder, traverses the second side and exits normal to a surface area of the second side of the general-cylinder as an output signal; and activate capturing the output signal by the optical detector. In another optional embodiment, the controller is further configured to: after positioning the general-cylinder at a first angle of the sample relative to the light beam path, rotate the general-cylinder such that the sample is at a second angle relative to the light beam path, and repeat the capturing and the rotating.

The method according to the invention includes the steps of: providing the apparatus according to claim <NUM>, inputting an optical light beam normal to a circumferential surface area of a first side of the general-cylinder; positioning the general-cylinder so that the light beam path traverses via a first side of the general-cylinder until reaching the hollow, then traverses from the first side into the fluid in the hollow on a first side of the sample, through the sample, through the fluid on an other side of the sample, into a second side of the general-cylinder, traverses the second side and exits normal to a circumferential surface area of the second side of the general-cylinder as an output signal; and capturing the output signal by the optical detector.

In another optional embodiment, further including the steps of: after the positioning at a first angle of the sample relative to the light beam path, rotating the general-cylinder such that the sample is at a second angle relative to the light beam path, and repeating the capturing and the rotating. In another optional embodiment, further including the step of: processing data collected by the capturing to calculate results of the optical testing.

The embodiment is herein described, by way of example only, with reference to the accompanying drawings, wherein:.

The principles and operation of the apparatus and method according to a present embodiment may be better understood with reference to the drawings and the accompanying description. The present invention is an apparatus and method for optical sample characterization as defined by the appended claims. The invention facilitates measurement and testing of a full range of angles of light propagation through an optical sample, such as a coated glass plate, having a higher than air index of refraction.

In general, an innovative rotatable assembly includes a glass cylinder having a hollow. The hollow is a portion of a receptacle in the rotatable assembly. The receptacle is sized for variable-size coated glass plates. The receptacle is also sealed for receiving a quantity of fluid with a certain, given, refractive index. A light beam propagates from a test source via collimating optics, entering normal (<NUM> degrees) to the surface of the cylinder, through the cylinder, then via the fluid through the coating, the (coated) glass plate, the fluid, the other side of the cylinder, and is collected for analysis. Due at least in part to the fluid surrounding the coated plate, the plate can be rotated through a full range of angles (±<NUM>°, etc.) for any particular angle in the full range testing of the coating. Preferably, the cylinder and the plate are made of the same material, thus having matching indexes of refraction. An exemplary typical material is BK7 glass, however, this example is not limiting, and other glasses and other materials besides glass can be tested. This apparatus and method can also be used to measure directly the reflectance of the coated plate.

Current devices and methods are not adequate for characterizing the current and foreseen coatings over a full range of incident angles in glass. Conventional techniques are inadequate for meeting existing requirements. A technique is required to implement maximal, preferably full range angular measurement of coatings. In the context of this document, the term "full range" generally refers to a range of <NUM>°, or ±<NUM>°, with respect to normal to the coated plate being tested. The full range may be other than ±<NUM>° for specific implementations. In contrast, conventional measurement techniques typically measure a range of discrete angles only in air. For example, <NUM>° transmission in air and <NUM>° reflection in air with optional specialized modules added to standard single or double beam spectrophotometers. For measurement in glass, the conventional method is to assemble the coating in a prism assembly and then measure the performance in a range of up to ±<NUM>°. The measurement angle is restricted to the angle of the prisms in the assembly (±<NUM>°).

Snell's law, regarding total internal reflection (TIR) and dependency of the path of light travelling through the materials, limits the angle of incidence of the plate being measured. For example, consider a ray of light moving from an example glass to air. The critical angle θct is the value of incident angle in the glass, θ<NUM>, for which the exit angle in air, θ<NUM>, equals <NUM>°, i.e. the refractive indices of example glass n<NUM> and air n<NUM>, are respectively approximately <NUM> and <NUM> giving the value of -<NUM>°, using Snell's law for light traversing from one optical medium to another. Therefore, a measurement in air cannot replicate measurement of angles above ∼<NUM>° in glass.

For simplicity in this description, the term "coated plate" may also be referred to as a "plate" or "coating", as will be obvious from context. Current typical plate sizes include 70x70 mm (millimeters) and 60x30 mm. In the context of this document, the term "coated plate" generally refers to a plate having an optical coating on a surface of the plate. Coatings are typically multilayer thin films. A coated glass plate is generally used in this description, but is not limiting, and other samples, of other materials and shapes may be used. In general, the plate can be an arbitrary, non-air, shape which allows free, non-scattering, optical path between the light source and the light detector. The testing apparatus may measure any sample of an optical material (sample, optical element), such as thin film, glass, or plastic polarizers, wave plates, beam splitters, dichroic reflectors, Lightguide Optical Elements (LOEs), a structured optical element like a grating or wire grid, and more. Optical filters (coatings) are used to manipulate incident light (incident to the coated plate) to designated reflectance, transmittance, absorption, polarization, etc. To test (probe and measure) the coating and/or compare the actual performance of the coating versus the designated required performance of the coating, optical measurement is used.

Similarly, for simplicity in this description, the term "glass cylinder" is used, but is not limiting. For example, the materials of the cylinder (cylinder, cylinder ring, sphere, bulk, half bulk, etc.) can also be a polymer (one non-limiting example is an optical non-birefringent polymer).

Embodiments of the apparatus and method of the current description can be used for characterization, measurement, and testing. The apparatus can be implemented for a variety of functions, including acceptance measurements for coating devices and processes (coating materials such as glass plates). For simplicity in this document, the term "testing" is used, but should not be considered limiting.

Referring now to the drawings <FIG>, is a sketch of an apparatus for full-range optical sample characterization (testing) and <FIG> is a sketch of a sectional view of the apparatus. The testing apparatus <NUM> is generally referred to in the context of this document as a "jig". The testing apparatus <NUM> holds the plate being tested, support structure, and guides the elements, providing repeatability, accuracy, and interchangeability in the testing. The testing apparatus <NUM> includes a base <NUM> to which various other elements are mounted. The exemplary optical material being tested is a coated plate <NUM> seated in a receptacle <NUM> in a rotatable assembly. The rotatable assembly includes a cylinder <NUM> and a turntable. The cylinder <NUM> includes a hollow <NUM>. The turntable can be implemented by the bottom portion <NUM> having a motor attachment area 408B with a motor 408A connected. The receptacle <NUM> is filled with a fluid <NUM>, in some implementations being a refractive index matching fluid. Position pins <NUM> can be used to clamp the cylinder <NUM> between a top portion <NUM> and a bottom portion <NUM>. An exemplary side containment for fluid <NUM> is shown as rib <NUM>. An input test light source <NUM> provides an optical input signal via optional input cable 6F to collimating optics <NUM>. The collimating optics <NUM> prepares the input signal for input into rotatable cylinder <NUM>. The prepared light beam provides parallel illumination for testing. Output optics <NUM> feed an optional output cable 104F to an output light collector (light detector) <NUM>.

For convenience of reference, the rotatable cylinder <NUM> is referred to in the context of this document as the cylinder <NUM>. The rotatable cylinder <NUM> is typically a solid material, an optical material, transparent to an optical light beam. The rotatable cylinder <NUM> interior is substantially filled with a solid material, at least a majority of the interior filled with a solid material other than the fluid <NUM>. The shape of the cylinder <NUM> can be, in general, what is known by some authors in the field of mathematics as a "general-cylinder". A general-cylinder is defined as a category of solids which include prisms as a form of cylinder. As the receptacle <NUM> can be formed within both cylinders and prisms, we use the term "general-cylinder" to include embodiments using either a cylinder or prism. Thus, the rotatable cylinder <NUM> can have the shape of a cylinder or polygonal prism. For example, the round surface of a cylinder allows any angle of rotation to be used for the cylinder (and hence for measuring the coated plate <NUM>) while maintaining the optical input and output substantially normal to the surface of the cylinder <NUM>. If one were to only need, for example, <NUM> or <NUM> discrete measurements, a <NUM> or <NUM>-sided a polygonal circumference can be used and the motor confined to step by <NUM> or <NUM> degrees. Even more generally, the shape of the cylinder <NUM> can be an arbitrary, non-air, shape which allows free, non-scattering, optical path from the optical light source <NUM> to the optical detector <NUM>. Based on this description, one skilled in the art will be able to design the other apparatus and system components accordingly.

The cylinder <NUM> can be stationary, rotate in a single axis, or rotate in one or more axes to move the plate <NUM> for testing of various incident angles and areas of the plate. The current description and figures are only of the cylinder <NUM> being rotated around a fixed axis (the height-axis of the cylinder). Based on this description, one skilled in the art will be able to design and implement one of more directions of movement and testing of the plate <NUM>.

For convenience of reference, the input signal is shown entering the cylinder <NUM> from a left side of the figures and the corresponding labeled first side is a left side of the cylinder <NUM>. A labeled second side is a right side of the cylinder 100R adjacent to output optics <NUM> that feed an optional output cable 104F to an output light collector <NUM>. It will be obvious to one skilled in the art that the cylinder <NUM> is generally substantially symmetric. The cylinder <NUM> can be rotated horizontally, and the left side <NUM> and right side 100R of the cylinder can be interchanged. In a non-limiting example, the cylinder <NUM> can be implemented as a single piece (of glass), with a hollow <NUM> in the middle for the receptacle <NUM>. In this case, the left side of the cylinder <NUM> and the right side of the cylinder 100R are opposite sides of the same piece. The hollow <NUM> may extend the entire height of the cylinder (top to bottom), or be partial, for example, forming a pocket in the cylinder. In another non-limiting example, the cylinder <NUM> can be created from two pieces, a first piece being the first, left side of the cylinder <NUM> and a second piece being the second, right side of the cylinder 100R.

The collimating optics <NUM> and the output optics <NUM> are preferably adjustable with at least two degrees of freedom to allow adjustment of the light beam, initial, and subsequent calibration. For example, the collimating optics <NUM> and the output optics <NUM> may be adjusted ±<NUM> along the x-axis and y-axis of the light beam path.

In some implementations, the fluid <NUM> is an index matching fluid. For convenience of reference, refractive index matching fluid <NUM> is referred to in the context of this document as "fluid <NUM>". In some implementations, the fluid <NUM> has a refractive index matching the refraction index of (the material / glass of) the cylinder <NUM>. In some implementations, the fluid <NUM> has a refractive index matching the refraction index of the plate <NUM>. In some implementations, the cylinder <NUM> and the plate <NUM> are made of the same material (so the respective indices of refraction match). Similarly, one or more of the refractive indexes of the fluid <NUM>, the plate <NUM>, and the cylinder <NUM> can differ from each other. Regarding specific matching of indexes and ranges of difference between element's refractive indexes, one skilled in the art will be aware of the allowable tolerances.

The input cable 6F and the output cable 104F are typically optical fibers, but can be any suitable transmission medium depending on the specifics of the implementation.

The testing apparatus <NUM> typically includes the top portion <NUM> and the bottom portion <NUM> for supporting and mounting various cylinders <NUM>. Position pins <NUM> can be used to attach the top portion <NUM> to the bottom portion <NUM>, clamping the cylinder <NUM> between the top and bottom portions, facilitating alternative cylinders <NUM>, top <NUM>, and bottom <NUM> portions being used. For example, the top portion <NUM> can be changed to a second top portion including a different size and/or configuration of receptacle to test a different plate. Or for example, a cylinder composed of a first material having a first index of refraction for testing a plate having a first index of refraction can be replaced with a cylinder composed of a second material having a second index of refraction for testing a plate having a second index of refraction. In another example, the cylinder, top, and bottom portions are all replaced with alternative elements having (creating) a wider/thicker receptacle for testing a thicker plate, or for creating a different shaped receptacle for testing a different shape of optical sample, for example round.

The cylinder <NUM> can be rotated by a variety of means. In the current figures, exemplary motor attachment area 408B is provided at the bottom of the bottom portion <NUM>, and also shown with a motor 408A connected. The motor 408A, in this case in a typical combination with the bottom portion <NUM>, functions as a general turntable for rotating the cylinder <NUM> around a height-axis of the cylinder <NUM>. The cylinder <NUM> and turntable form the rotatable assembly. Rotating the rotatable assembly rotates the cylinder <NUM>, thereby rotating the receptacle <NUM> and sample (coated plate <NUM>). A controller <NUM> is operationally connected to the motor 408A in the current figure, and for clarity is not shown in all figures. Not shown in the figures is an encoder operationally connected to the rotatable assembly. The encoder provides position information at least regarding angle of rotation of the rotatable assembly so the position of the coated plate <NUM> is known with respect to an axis of the cylinder <NUM> and to angle with regard to a normal to the coated plate <NUM> (the optical sample being tested). As is known in the art, the position encoder may be part of the motor 408A or a separate component.

For reflectance measurements, the output optics <NUM> are typically placed at a different angle than shown in the drawings, to collect a beam reflected from the plate <NUM> under test.

The base <NUM> provides a mounting arrangement for various jig components, depending on specific testing configurations, such as the motor 408A, motor attachment area 408B, bottom portion <NUM>, and for receiving, adjusting and aligning the optical arrangement (optical test light source <NUM>, input cable 6F, collimating optics <NUM>, output optics <NUM>, output cable 104F, and output light collector <NUM>).

Referring now to the drawings, <FIG> is a sketch of a top view of cylinder <NUM>. Optional input cable 6F and optional output cable 104F are not shown in the current figure. The test light source <NUM> provides an optical input signal to collimating optics <NUM>. Similarly, the output optics <NUM> feed the output light collector <NUM>. Optionally, optical input signal is input via a polarizer and a <NUM>° ±<NUM>° rotating apparatus after or before fixed lenses. The coated plate <NUM> is mounted in the receptacle <NUM> and surrounded by the fluid <NUM>. In the current top view, side containment for the fluid <NUM> is not shown. Based on the current description, one skilled in the art will be able to design and implement appropriate containment for the fluid, for example, by using the top portion <NUM> extended around the cylinder <NUM>. The controller <NUM> is typically operationally connected at least to the test light source <NUM> and the output light collector <NUM>.

The plate <NUM> has a first dimension horizontally (up-down on the page of the current figure, along an axis of the cylinder <NUM>) as plate-width 102W and a second dimension shown as plate-thickness 102T (left-right on the page of the current figure). Similarly, and correspondingly, the receptacle <NUM> has a first dimension shown as receptacle-width 110W (up-down on the page of the current figure, along an axis of the cylinder <NUM>) and a second dimension shown as receptacle-thickness 110T (left-right on the page of the current figure). The receptacle-width 110W can be slightly smaller than the diameter 100W of the cylinder <NUM>, depending on the size of implementation of side containment for the fluid <NUM>. As noted above, in the current figure the side containment is not shown, and the receptacle width 110W is shown as the same size as the diameter 100W of the cylinder <NUM>. The receptacle-thickness 110T is a distance between the left side of the cylinder <NUM> and the right side of the cylinder 100R. Alternatively, the receptacle-width 110W can be a different size from the cylinder diameter 100W, for example the receptacle-width 110W being smaller than the cylinder diameter 100W.

Typically, the plate <NUM> and the receptacle <NUM> are substantially parallel, that is, the widths of the plate (plate-width 100W) and receptacle (receptacle-width 110W) are aligned. The sides of the receptacle <NUM> (the edges of the receptacle, distant from the area of the receptacle <NUM> used to perform the measurement of the plate <NUM>) are typically parallel, but not required to be parallel. Depending on the specific measurement required, a distance between the sides of the receptacle at the edges of the receptacle can be closer or preferably farther apart than a distance between the sides of the receptacle in a core area 110C where the measurement is performed. The core area 110C, also known as the "critical area" is a location where the coating is tested, that is, the location where the light beam encounters the coated plate <NUM>. Typically, the core area 110C is small, and the remaining area of the receptacle <NUM> can be designed primarily to support the sample test plate <NUM>. A typical core area 110C includes a minimum defined cylinder measuring zone of ± <NUM>.

A feature of the current embodiment of the testing apparatus <NUM> is that the receptacle <NUM> is small compared to the bath <NUM> of the bath-jig <NUM>. An alternative embodiment using a fluid bath is described below in reference to the bath-jig <NUM> of <FIG>. The bath <NUM> typically holds <NUM> cc (cubic centimeters) to <NUM> cc of fluid. Conventional baths require minimum of <NUM> cc of fluid, otherwise the level of the fluid is lower than the light source input and output, and the measurement will be in air (not fluid). Typically, volume of the bath is about <NUM> - <NUM> cc.

In contrast, the receptacle <NUM> typically holds <NUM> cc to <NUM> cc of fluid. The receptacle <NUM> can be adjustable in one or more dimensions to accommodate various sizes of plates <NUM>. Another feature of the current embodiment of the testing apparatus <NUM> is that the cylinder <NUM> is rotated (as part of the rotatable assembly, thus, the sample to be tested, coated plate <NUM>, is stationary with respect to the fluid <NUM> and receptacle <NUM>. In contrast, in the bath-jig <NUM> the sample (coated plate <NUM>) is rotated within the fluid, that is, within the bath <NUM>. Due to high viscosity of the fluid <NUM> the rotation of the plate <NUM> in the fluid <NUM> in a bath-jig <NUM> causes disturbance in the fluid <NUM> and in turn this affects the measured spectra. This problem is solved at least in part by the use of the cylinder <NUM>.

Referring now to the drawings, <FIG> is a sketch of a sectional side view of the cylinder <NUM> and bottom portion <NUM>. The plate <NUM> has a third dimension shown vertically (up-down on the page of the current figure, along a height-axis of the cylinder <NUM>) as plate-height <NUM>. Similarly, and correspondingly, the receptacle <NUM> has a third dimension shown as receptacle-height <NUM>. The receptacle-height <NUM> can be the same size as cylinder height <NUM> of the cylinder <NUM>. Alternatively, the receptacle-height <NUM> can be a different size from the cylinder height <NUM>. For example, the receptacle-height <NUM> can be smaller than the cylinder height <NUM> to account for a fluid containment implementation (sealing) at the bottom of the hollow <NUM>, in the hollow <NUM> between the left side <NUM> and the right side 100R of the cylinder. Or for example, the receptacle height <NUM> can be greater than the cylinder height <NUM> (as shown in the current figure) and the bottom portion <NUM> provides sealing at the bottom (below) of the hollow of the receptacle <NUM>.

Referring now to the drawings, <FIG> is a sketch of a top view of the cylinder <NUM> with the coated plate <NUM> rotated during testing. In this non-limiting example, the coated plate <NUM> has been rotated clockwise almost <NUM>° from the starting position shown in the above figures.

As can be seen in the current figure, a light beam <NUM>, in this case optical light (as a test signal), is provided 420A by the test light source <NUM> (optional input cable 6F is not shown). The provided 420A light beam is prepared and collimated by the collimating optics <NUM>, and then is input 420B normal to a surface area of the rotatable cylinder <NUM>. The precision of the shape of the cylinder <NUM> can be determined by the required precision of measurement of the coating on the plate <NUM>. The light beam travels 420C via the left side of the cylinder <NUM> until reaching the receptacle <NUM>. The light beam traverses (420D - 420E) from the left side of the cylinder <NUM> into the fluid <NUM> in the receptacle <NUM>, through the coated glass plate <NUM> (note, the coating on the glass plate is not shown), through the fluid <NUM> on the other side of the plate <NUM> and into 420E the right side of the cylinder 100R.

Then the signal traverses 420F the right side of the cylinder 100R and exits <NUM> normal to the surface of the rotatable cylinder <NUM>. Output optics <NUM> passes an output light beam as an output signal <NUM> to the output light collector <NUM> (optional output cable 104F is not shown in the current figures).

As a cylinder only has one circumferential surface, references to inputting the optical light beam and exiting/outputting the optical light beam are to different areas or regions of the surface. Correspondingly, first and second sides of the cylinder are directional references, as can be seen in the figures as shown on the pages.

Referring now to the drawings <FIG>, is a sketch of a bath-jig apparatus for testing transmittance of an optical sample and <FIG> is a sketch of a sectional view of the bath-jig apparatus. The testing bath-jig apparatus <NUM> is generally referred to in the context of this document as a "bath-jig" <NUM>. Similar to the testing apparatus (jig) <NUM>, the bath-jig <NUM> holds the plate being tested, support structure, and guides the elements. The bath-jig <NUM> includes a base <NUM> to which various other elements are mounted. The coated plate <NUM> being tested is seated in a plate-mount <NUM> in a bath <NUM>. The bath <NUM> is an area of the bath-jig <NUM> built to contain fluid. The bath <NUM> is an internal, hollow space of the bath-jig <NUM>, designed as a fluid containment area. The bath <NUM> is filled with the fluid <NUM> (not shown in the current figures). A test light source <NUM> provides an optical input signal via optional input cable 6F (not shown) to collimating optics <NUM>. The collimating optics <NUM> (prepare and focus) collimates the input signal into the bath <NUM>.

The plate-mount <NUM> can be rotated by a variety of means. In the current figures, exemplary motor attachment area 5408B is provided at the top of the bath-jig <NUM>, and also shown with a motor 5408A connected.

As can be seen in the <FIG>, a light beam <NUM>, in this case optical light, is provided 5420A by the test light source <NUM>. The provided 5420A light beam is prepared and expanded by the collimating optics <NUM> and traverses into the fluid <NUM> in the bath <NUM>. The light beam then travels 5420C through the fluid <NUM> in the bath <NUM>, through the coated glass plate <NUM> (note, the coating on the glass plate is not shown), through 5420F the fluid <NUM> on the other side (of the plate <NUM>). As the bath <NUM> is filled with the fluid <NUM>, this traversal of the light beam through the bath-jig <NUM> is substantially without refraction. Then the signal exits 5420E from the fluid <NUM> to output optics <NUM> that feed <NUM> the output signal to the output light collector <NUM>.

The bath-jig <NUM> is shown with an optional front window 5130F and back window 5130B that allow the internal bath <NUM>, plate-mount <NUM>, coated plate <NUM>, and other components to be viewed.

Both the testing apparatus (jig) <NUM> and the bath-jig <NUM> can include optional, additional, and alternative configurations. In one alternative, the jigs can be adapted to include vacuum, such as a vacuum bell, to extract dissolved air from the fluid <NUM>. In another alternative, mechanical and/or other enhancements can be used to handle and prevent wobbling in the jigs. Hard fixation (rigid routing) can be used on the optical fibers. The receptacle <NUM> and plate-mount <NUM> can be adjustable to accommodate variable size plates <NUM>. As described above regarding the position pins <NUM>, the jigs, top <NUM> and bottom <NUM> portions can be detachable (removably attached) to facilitate replacement with a different refractive index cylinder and ease of operation (for example, sample placement and cleanup).

Additional alternatives for the jigs can include a dark (light opaque) box to cover the entire jig, a dynamic receptacle for the test plate to avoid scratching the plate <NUM>, rotating stages including engine and drivers, an inner clean option, air bubbles extraction (a stagnation area), and sample plate squeezers.

Referring now to <FIG> is a flowchart of a method for optical sample characterization. The current method can be used with the testing apparatus (jig) <NUM> and the bath-jig <NUM>, as well as with the below-described MPL testing apparatus <NUM>, as described below in a testing sequence. A method of testing <NUM> for optical sample characterization starts in step <NUM>, the light beam <NUM> is provided normal to the cylinder <NUM>. The light beam is typically an optical light beam, referred to as the "input light", or simply as "light", as will be clear to one skilled in the art from the context of this description. Providing the light at a constant normal to the cylinder <NUM> facilitates the majority of the light coupling into the cylinder <NUM>, so that no light, or minimal light is lost when entering the cylinder. Exemplary coatings include filters that transmit a part of the visible spectrum and reflect another part, a polarizing filter that transmit one polarization state and reflects another polarization state, or an absorbing coating that absorbs part of the visible light.

In step <NUM>, optional configurations are used, as described below.

In step <NUM>, the output light is collected after traversing the cylinder <NUM>, the receptacle <NUM>, and the plate <NUM>, as described above. The output light can be collected, for example, with a spectrometer.

In step <NUM>, the plate <NUM> is rotated. To what degree the plate is rotated depends on the specific requirements of the test being performed and the measurements desired. Exemplary rotations include <NUM>° and <NUM>° steps. After rotating the plate, output light can again be collected (step <NUM>) at the new, known angle. This cycle of rotating and collecting can be repeated as necessary to gather data on the desired range of angles to be tested (step <NUM> returns to step <NUM>).

Note that a feature of the current embodiment is that the plate <NUM> is rotated by rotating the entire cylinder <NUM>, in contrast to conventional implementations that rotate a test sample inside a testing apparatus, for example, in a bath of fluid inside a testing chamber. In step <NUM>, optional calculations (processing, signal processing) can be performed on the collected signals to determine a figure of merit for transmittance and/or reflectance of the coating and/or plate <NUM>. The data from the collected output light <NUM> is processed to calculate results of the optical testing.

In step <NUM>, optionally the results of the collection and processing can be displayed (output, transferred, stored, etc.).

Referring now to <FIG>, shown is a plot of transmittance (y-axis) vs. angle (x-axis), and <FIG>, showing a close-up (zoom in) of the transmittance plot of <FIG>. In general, a successful coating is shown by the plot being horizontally oriented, indicating that over a range of angles the coating had consistent transmittance. The transmittance (amount of light provided minus the amount of light collected) can be of the s or p polarization.

<FIG> is a high-level partial block diagram of an exemplary controller <NUM> configured to implement the method for optical sample characterization <NUM> of the present invention. Controller (processing system) <NUM> includes a processor <NUM> (one or more) and four exemplary memory devices: a random-access memory (RAM) <NUM>, a boot read only memory (ROM) <NUM>, a mass storage device (hard disk) <NUM>, and a flash memory <NUM>, all communicating via a common bus <NUM>. As is known in the art, processing and memory can include any computer readable medium storing software and/or firmware and/or any hardware element(s) including but not limited to field programmable logic array (FPLA) element(s), hard-wired logic element(s), field programmable gate array (FPGA) element(s), and application-specific integrated circuit (ASIC) element(s). Any instruction set architecture may be used in processor <NUM> including but not limited to reduced instruction set computer (RISC) architecture and/or complex instruction set computer (CISC) architecture. A module (processing module) <NUM> is shown on mass storage <NUM>, but as will be obvious to one skilled in the art, could be located on any of the memory devices.

Mass storage device <NUM> is a non-limiting example of a non-transitory computer-readable storage medium bearing computer-readable code for implementing the testing methodology described herein. Other examples of such computer-readable storage media include read-only memories such as CDs bearing such code.

Controller <NUM> may have an operating system stored on the memory devices, the ROM may include boot code for the system, and the processor may be configured for executing the boot code to load the operating system to RAM <NUM>, executing the operating system to copy computer-readable code to RAM <NUM> and execute the code.

Network connection <NUM> provides communications to and from controller <NUM>. Typically, a single network connection provides one or more links, including virtual connections, to other devices on local and/or remote networks. Alternatively, controller <NUM> can include more than one network connection (not shown), each network connection providing one or more links to other devices and/or networks.

Controller <NUM> can be implemented as a server or client respectively connected through a network to a client or server.

Referring now to the drawings <FIG>, is a sketch of an apparatus for full-range optical sample characterization (testing) and <FIG> is a sketch of an exploded view of the apparatus. The variable position testing apparatus <NUM> is also referred to in the context of this document as an "MPL apparatus" or "MPL". The term "MPL" refers to "mounting a plate in liquid" which is a typical non-limiting use for the testing apparatus <NUM>. The core MPL apparatus can be configured similarly to the above-described testing apparatus <NUM>, and not shown in the current figures are a support structure, base, and related elements, as will be obvious to one skilled in the art.

The MPL apparatus <NUM> can be configured inside a spectrophotometer measuring configuration (tool) to create a fuller MPL testing system. The MPL testing system provides an apparatus and method for testing and measurements including, but not limited to, reflection, transmittance, and chromaticity of a coating between a substrate material and the incident material for different angles relative to the coating on a plate.

A cover <NUM> is attached to an MPL cylinder top portion <NUM>. A test MPL cylinder <NUM> is between the MPL cylinder top (top portion) <NUM> and an MPL cylinder bottom (bottom portion) <NUM>. Gaskets <NUM> are a non-limiting example of parts used to assist in operationally configuring the MPL testing apparatus <NUM>, in this case designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at interfaces between elements of the apparatus.

Similar, and corresponding to the above-described testing apparatus <NUM>, the exemplary optical material (sample of optical material) being tested is a coated plate <NUM> seated in the MPL testing apparatus <NUM>. The MPL cylinder <NUM> includes an MPL hollow <NUM> in at least a portion of the interior of the MPL cylinder <NUM>. Typically, the MPL hollow <NUM> is a central hollow on an axis of the MPL cylinder <NUM>. The MPL hollow <NUM> is sized to receive at least a core area of the sample of optical material (coated plate <NUM>). The MPL hollow <NUM> is an interior part of an MPL receptacle <NUM>. The MPL receptacle <NUM> is sealed for receiving a quantity of fluid <NUM>, such that the fluid <NUM> surrounds and is in contact with at least the core area of coated plate <NUM>, and the fluid <NUM> is in contact with the MPL cylinder <NUM>. As will be obvious to one skilled in the art, references in this description to the fluid <NUM> in the MPL hollow <NUM> can also be to the fluid <NUM> in the MPL receptacle <NUM>. In some implementations, the refraction index of the glass of the MPL cylinder <NUM> matches the refractive index of the fluid <NUM>. In some implementations, the MPL cylinder <NUM> and the plate <NUM> are made of the same material (so the respective indices of refraction match). Regarding specific matching of indexes and ranges of difference between element's refractive indexes, one skilled in the art will be aware of the allowable tolerances.

A feature of the current embodiment is to mount a coated plate <NUM> in a cylinder, the MPL cylinder <NUM>, having circular symmetry. This enables measurement of light reflected by the plate <NUM> at different angles, in particular large angles with respect to a normal to the surface of the plate <NUM>.

Referring now to the drawings <FIG>, is a sketch of a sectional view of the MPL testing apparatus, and <FIG> is a rotated sectional view. As can be seen in the current figure, the plate <NUM> is preferably positioned (mounted) with the plate's diagonal on the equator (see below <FIG>, the equator 1100E), so as to increase area of inspection (core area), and enable larger angle of inspection (AOI) with no vignetting.

Referring now to the drawings <FIG>, is a sketch of the MPL testing apparatus including a variable positioning mechanism. The MPL testing apparatus <NUM> can be varied in position, in particular optionally and preferably varying all six degrees of mechanical positioning. Positioning includes stationary, rotate in a single axis, rotate in one or more axes, raising, and lowering, to move the plate <NUM> for testing of various incident angles and areas of the plate. A non-limiting exemplary implementation for varying the position of the apparatus is using a variable positioning mechanism 1408A, for example, mechanical actuators for accurate positioning. The variable positioning mechanism 1408A is appropriately operationally attached to the MPL cylinder bottom portion <NUM> and normally to a base (not shown, similar to the testing apparatus <NUM> base <NUM>). An exemplary implementation is the variable positioning mechanism 1408A being a turntable, implemented by the MPL cylinder bottom portion <NUM> having a motor attachment area with a motor connected. The variable positioning mechanism 1408A varies the position of the MPL testing apparatus <NUM>, thus varying the position of the plate <NUM>.

Preferably, the MPL cylinder <NUM> should be mounted (configured) to minimize obstacles surrounding the MPL cylinder <NUM>. This enables measurements at a maximum range of angles (substantially <NUM>°) around the MPL cylinder <NUM>, and hence enabling direct-view of the plate <NUM> within the MPL cylinder <NUM>. Position pins <NUM> can be used to clamp the MPL cylinder <NUM> between the MPL cylinder top portion <NUM> and the MPL cylinder bottom portion <NUM>. In the current figure, two exemplary position pins <NUM> are shown. When used, these position pins <NUM> should be placed in consideration of the desired measurement angles, so as to minimize obstruction by the pins in the desired range of testing angles.

The MPL cylinder top portion <NUM> and the MPL cylinder bottom portion <NUM> can be used for supporting and mounting various implementations of the MPL cylinder <NUM>. For example, the MPL cylinder <NUM> can be clamped between the top and bottom portions, facilitating alternative MPL cylinders <NUM>, top <NUM>, and bottom <NUM> portions being used. For example, the top portion <NUM> can be changed to a second top portion including a different size and/or configuration of receptacle to test a different plate. Or for example, a cylinder composed of a first material having a first index of refraction for testing a plate having a first index of refraction can be replaced with a cylinder composed of a second material having a second index of refraction for testing a plate having a second index of refraction. In another example, the cylinder, top, and bottom portions are all replaced with alternative elements having (creating) a wider/thicker receptacle for testing a thicker plate, or for creating a different shaped receptacle for testing a different shape of optical sample, for example round.

A controller <NUM> is connected to the variable positioning mechanism 1408A and functions similar to the operation of the controller <NUM> with the testing apparatus <NUM> and the motor 408A. For clarity, the controller <NUM> is not shown in all figures. Optionally, positioning items <NUM> (for example, pins) can provide the dynamic freedom to replaceably remove and return accurately the MPL testing apparatus <NUM> to a given position.

Referring now to the drawings <FIG>, is a sketch of cross section of the MPL cylinder for testing of a plate. The plate <NUM> is mounted inside the MPL cylinder <NUM>. The plate <NUM> has a first side, referred to in the context of this document as a "target reflecting surface" <NUM>, "target surface", "coated surface", or "front surface". The target surface <NUM> is typically the surface of interest to be tested, and may be coated with one or more coatings. Alternatively, the target surface <NUM> may be uncoated. The plate <NUM> has a second side, opposite the first side, referred to in the context of this document as the "back surface" 102R. The back surface 102R is typically uncoated, but may be coated with one or more coatings. For simplicity, the coatings are not shown in the figures. For convenience of reference in the figures, the target surface <NUM> is a first surface typically drawn facing left on the page, the "left side" of the MPL cylinder <NUM> and the plate <NUM>. Correspondingly, the back surface 102R is a second surface drawn facing the right on the page, the "right side" of the MPL cylinder <NUM> and the plate <NUM>. As described above (see <FIG>) the plate <NUM> can be mounted such that the target reflecting surface <NUM> is at the center of the diameter of the MPL cylinder <NUM>. The MPL cylinder <NUM> has an MPL cylinder diameter 1100D from an exterior outside surface 1100U to an opposite outside surface and an MPL cylinder thickness 1100T from an outside surface 1100U to an inside surface 1100N of a ring of the circumference.

Similar to the optical arrangement used for testing the above-described testing apparatus <NUM>, a light beam <NUM> is provided 420A by an input test light source <NUM> as an optical input signal. The provided 420A light beam is optionally prepared and collimated by collimating optics <NUM>, and then is input 420B normal to a surface area of the MPL cylinder <NUM>. The light beam travels 1420C (via the "left side") toward the target surface <NUM> of the plate <NUM>, impinging on the (coated) target surface <NUM>. In the current figure, the hollow <NUM> is an entire interior portion of the MPL cylinder <NUM>, the fluid112 fills the hollow <NUM> and surrounds the plate <NUM>, in contact with both the target surface <NUM> and the back surface 102R. In this case, the light beam travels 1420C via the left side, through the fluid <NUM>, toward the target surface <NUM> of the plate <NUM>.

A normal line 1115N is defined normal to the surface of the plate <NUM>, at the core area, at a location where the light beam 1420C impinges the target surface <NUM> of the plate <NUM>. A test angle θ (theta, <NUM>) is defined between the line of the light beam 1420C and the normal line 1115N. The target surface <NUM> of the plate <NUM> is closer, on the side toward the test light source <NUM> as compared to the back surface 102R of the of the plate <NUM> that is farther away, on the side of the plate <NUM> opposite the test light source <NUM>.

After the light beam <NUM> impinges on the target surface <NUM>, a portion of the beam may reflect from the surface of the plate <NUM>, shown as reflected output beam 1420F. A portion of the beam may enter and traverse the plate <NUM> (not shown in the current figure, similar to the above description, for example, of the testing apparatus <NUM> and <FIG>). The portions of the beam that reflect from, and enter into the plate <NUM> are determined by the specifics of implementation, such as the index of refraction of the fluid <NUM> in the hollow <NUM> and in the receptacle <NUM>, the angle of incidence (test angle θ <NUM>) between the input signal (the light beam 1420C) and the plate <NUM>, the index of refraction and properties of any coatings, and the index of refraction of the plate <NUM>.

In the current reflectance test, the output beam 1420F travels via the "left side" away from the target surface <NUM> of the plate <NUM>. The output beam 1420F travels away from the plate <NUM> via the same side of the plate <NUM> as the incoming light beam 1420C travelled toward the plate <NUM>. In the current case of the fluid <NUM> filling the hollow <NUM> and surrounding the plate <NUM>, the output beam 1420F travels from the target surface <NUM>, through the fluid <NUM>, toward an interior surface of the MPL cylinder <NUM>. The output beam 1420F exits <NUM> normal to both an interior surface area (interior curved surface) and exterior curved surface of the MPL cylinder <NUM>. The output beam 1420F is optionally prepared by the output optics <NUM> and passes as output signal <NUM> to the output light collector <NUM>. Optional input cable 6F, output cable 104F, and other supporting elements are not shown in the current figure. As described above, the collimating optics <NUM> and the output optics <NUM> are preferably adjustable with at least two degrees of freedom to allow adjustment of the light beam, initial, and subsequent calibration.

A feature of the current embodiment is that the location of the output light collector <NUM> is adjustable, in particular rotatably adjustable with respect to the location of the test light source <NUM>, configured to receive a reflected signal from the plate <NUM> under test. The location of the output light collector <NUM> can be calculated, or otherwise determined (such as experimentally) based on the specifics of implementation (described above, such as the location of the test light source <NUM>, indexes of refraction, etc.). In one implementation, during rotation of the plate <NUM>, the output light collector <NUM> is synchronized and rotated at twice the angle of the rotation of the plate <NUM>, relative to the same axis. For example, if the plate <NUM> is rotated <NUM> (two) degrees on the vertical axis of the MPL cylinder <NUM>, then the output light collector <NUM> will be rotated around the exterior of the MPL cylinder <NUM> <NUM> (four) degrees. In alternative implementations, the output light collector <NUM> can be positioned by manual inspection of the location of the output light beam <NUM>, or by measuring at the output light collector <NUM> the strength of the output signal <NUM> and positioning the output light collector <NUM> to maximize the strength of the received output signal <NUM>. Typically, the plate <NUM> is vertical, aligned parallel to the height axis of the MPL testing apparatus <NUM>. The light source <NUM> and light collector <NUM> are correspondingly in a horizontal plane, aligned with the diameter of the MPL cylinder <NUM>, and aligned with the normal line 1115N to the surface of the plate <NUM>. In other words, the output light collector <NUM> can be configured in a plane defined by the light source <NUM> and the normal line 1115N.

Measurement of transmittance of the light beam <NUM> via the plate <NUM> has been described above with respect to the testing apparatus <NUM> and cylinder <NUM>. One skilled in the art will be able to apply the above description to the current embodiment of MPL testing apparatus <NUM> with MPL cylinder <NUM> and, will not be described here in detail.

Referring now to the drawings <FIG>, is a sketch of a cross section and <FIG> is a sketch of a sectional view of an implementation of an alternative implementation of the MPL cylinder. In <FIG> the MPL cylinder <NUM>, and correspondingly the plate <NUM>, are oriented and the light collector <NUM> positioned for a transmittance test. In <FIG> the MPL cylinder <NUM>, and correspondingly the plate <NUM>, are oriented and the light collector <NUM> positioned for a reflectance test. The target reflecting surface <NUM> is parallel and aligned with an equator 1100E of the MPL cylinder <NUM>. The equator 1100E is a diameter of the cylinder. Also shown in this figure is an MPL cylinder height <NUM> from a top side of the MPL cylinder <NUM> for contact with the MPL cylinder top portion <NUM> to a bottom side of the MPL cylinder <NUM> for contact with the MPL cylinder bottom portion <NUM>.

In the exemplary transmittance test implementation of <FIG>, the plate <NUM> is normal to the input test light beam <NUM>, the test angle θ (<NUM>) is <NUM>° (zero degrees, shown in the figure for reference), and the output light collector <NUM> is located on the second side ("right side") 102R of the MPL cylinder <NUM>. Note that the normal line 1115N in this figure is drawn offset slightly from the light beam <NUM> so the that the normal line 1115N can be seen. A bulk material 1100B is shown. The bulk material 1100B is referred to in the context of this document as "bulk", and described below.

Referring now also to the drawings <FIG>, is a sketch of the MPL cylinder of <FIG> as viewed from above at an angle. For clarity, the plate <NUM> is not shown in the current figure. In the current figure, unlike in <FIG>, the test light source <NUM> and the output light collector <NUM> are configured for a reflectance test of the plate <NUM>. The input test light beam <NUM> and the output signal <NUM> are at oblique angles to the target reflecting surface <NUM>.

Referring now to the drawings <FIG>, is a sketch of a cross section view of an alternative implementation of the MPL cylinder. In the above-described <FIG> the majority of the path of the test light beam (the light beam <NUM> and the output signal <NUM>) traversed the MPL cylinder <NUM> via the fluid <NUM>. In the current figure, the majority of the path of the test light beam (<NUM>, <NUM>) traverses the MPL cylinder <NUM> via the bulk 1100B and then via a small amount of the fluid <NUM> (small relative to the length of the light path through the bulk 110B or the size of the fluid <NUM> in the hollow <NUM> of the half-cylinder MPL cylinder <NUM>. In the current figure, the MPL cylinder <NUM>, and correspondingly the plate <NUM>, are oriented for a reflectance test, as are the light source <NUM> and the light collector <NUM> positioned for a reflectance test. The target reflecting surface <NUM> is parallel and aligned with the equator 1100E of the MPL cylinder <NUM>. In the case of a reflectance test, the light beam <NUM> is at a test angle θ (<NUM>) relative to the normal line 1115N to the plate <NUM> (or equivalently, normal to the equator 1100E), and the output light collector <NUM> is located on the same side ("left side", the target reflecting surface side) <NUM> of the MPL cylinder <NUM> as the light source <NUM>A bulk material 1100B is shown.

When performing a reflectance test, reducing or eliminating reflections from surfaces other than the surface under test is desirable. For example, when testing the front, target reflecting surface <NUM>, and/or a coating on the front surface <NUM>, a portion of the input light beam <NUM> may refract into the plate <NUM> via the front surface <NUM> and then reflect from the back surface 102R and refract out of the front surface <NUM> resulting in a portion of unwanted light impinging on the output light collector <NUM>, and interfering with testing. Unwanted reflections can also be generated, for example, from the fluid <NUM> in the hollow <NUM> and the bulk 1100B on the right/back side of the MPL test cylinder <NUM>. Methods of reducing or eliminating reflections from the back surface <NUM> include configuring a non-reflecting material in the hollow <NUM>. Alternatively, or in addition, the back surface 102R can be roughed. Alternatively, or in addition, the back surface 102R can be slanted non-parallel to the front surface <NUM>.

A feature of the current embodiment is that the circular MPL cylinder <NUM> can be filled at least partially with a bulk material 1100B. Correspondingly, a portion of the interior of the MPL cylinder <NUM> forms the MPL receptacle <NUM> (that includes the MPL hollow <NUM>), in this case, the portion (the MPL hollow <NUM><NUM><NUM>) being less than an entirety of the interior of the MPL cylinder <NUM>. In an exemplary implementation, the bulk 1100B is typically the same solid material as the MPL cylinder <NUM>, optically transparent to the light beam <NUM>. The MPL cylinder may be constructed at the same time as the bulk, as a single piece of the same material, thus simplifying construction as compared to other implementations. Using a bulk 1100B material interior to the cylinder reduces the amount of fluid <NUM> required to fill the receptacle <NUM>, thus reducing problems with relatively larger amounts of fluids in conventional bath implementations.

In a basic MPL cylinder <NUM>, such as shown in <FIG>, the cylinder has circular symmetry, with material only around the circumference, with a circular interior chamber creating the MPL receptacle <NUM> and the MPL hollow <NUM> in the interior of the MPL cylinder <NUM>. However, this configuration is not limiting. In the current figure, the material creating the circumference of the MPL cylinder <NUM> also partially fills the right side, substantially almost entirely filling the right-side half of the circular interior, and forming the bulk 1100B portion. The bulk 1100B typically fills substantially half of the interior of the MPL cylinder <NUM> (receptacle <NUM>). The bulk is substantially semicircular, and the corresponding receptacle <NUM> (hollow <NUM>) is substantially semicircular. In a typical transmittance test, such as shown in <FIG>, substantially half of the path of a light beam traverses the bulk material 1100B. In a typical reflectance test, such as shown in <FIG>, the majority path of the light beam will be through the fluid <NUM>. In a typical reflectance test, such as shown in <FIG>, the majority path of the light beam will be through the bulk 1100B, which allows the majority of the path to be through a solid material, and avoid known problems with test light propagating via a fluid. As is known in the art, the fluid <NUM> surrounding the optical element to be tested (plate <NUM>) can affect the measurement accuracy due to fluid dynamics. In particular, the larger the amount of fluid, the more difficulties with measurement accuracy. Hence, a desire to reduce the amount of fluid <NUM> used in the apparatus. Including a bulk 1100B portion with the MPL cylinder <NUM> reduces the amount of fluid <NUM> required to fill the MPL receptacle <NUM>, and thus reducing the amount of fluid <NUM> required to fill the MPL hollow <NUM>. Using a similar concept of filling areas interior to the MPL testing apparatus <NUM> to minimize the amount of fluid <NUM> in the MPL cylinder <NUM>, the MPL cylinder top portion <NUM> and the MPL cylinder bottom portion <NUM> (not shown in the current figure) can include solid portions at the respective bottom and top of each portion. In addition, the height of the cylinder (MPL cylinder height <NUM> of the MPL cylinder <NUM>) can be optimized to reduce the height to a minimal height required for the desired measurements, thus reducing the size of the MPL receptacle <NUM>. The plate <NUM> can be placed in a minimal sized receptacle in the top and bottom portions, thus minimizing the amount of fluid required.

As described above, in particular with reference to the rotatable cylinder <NUM>, the cylinder and bulk can be made of glass, or another suitable material. Alternatively, the bulk can be filled with any solid object that will have no reflection to the same direction of the coating, for example, opaque, very diffusive, or deflecting in different directions.

The MPL cylinder <NUM> and the fluid <NUM> can have the same refractive indices. Alternatively, the MPL cylinder <NUM> and the fluid <NUM> can have different refractive indices. For example, the MPL cylinder <NUM> can have a first refractive index and the fluid <NUM> and the plate can have a same second refractive index. Thus, a single apparatus can operate with a variety of plates <NUM>.

Typically, the outside surface 1100U of the MPL cylinder <NUM> is polished to facilitate the input test light beam 420A normal input 420B to the cylinder. The inside surface 1100N of the MPL cylinder <NUM> can be polished or unpolished. The precision (for example of the outside surface 1100U smoothness), size, and shape of the MPL cylinder <NUM> can be determined by the required precision of measurement of the coating on the plate <NUM>.

Referring now to <FIG>, is a sketch of an alternative embodiment of the MPL cylinder. The vertical cross section of the MPL testing apparatus <NUM> may be round, as shown in the previous figures (test MPL cylinder <NUM>), or can be an alternative shape such as a full or sliced part of a hollow ball 1100X, as shown in the current figure. Alternatively, the shape can be a wedge not shown).

Embodiments can include the above-described testing apparatus (jig) <NUM>, and the MPL testing apparatus <NUM>, mounted in a Universal Measurement Accessory (UMA). In these cases, the UMA typically provides the input test light source <NUM>. The UMA also provides a rotating mount holding the apparatus and rotating the apparatus, and thus rotating the optical sample. For example, the turntable implemented by the motor 408A, to which the bottom portion <NUM> motor attachment area 408B or the positioning items <NUM> are connected, thus rotating the apparatus (<NUM>, <NUM>). Typically, the rotating is around the center of the sample, in particular around a height-axis of the apparatus. The UMA also typically provides a detector, for example the output light collector <NUM>. The detector can be implemented on a leverage (arm) that rotates around the optical sample, substantially with the same axis of rotation as the axis of rotation of the apparatus.

Using this UMA configuration, the reflected light (input test light) can be aimed (deflected) to the detector for a range of angles by changing the angular rotation of the apparatus (<NUM>, <NUM>) and the detector. In general, the testing apparatus (<NUM>, <NUM>) and the output light collector <NUM> are configured as two elements with a substantially common axis, each rotating around the common axis, the apparatus configured on the axis and the collector rotating around the apparatus.

Refer again to <FIG>, the flowchart for a method for optical sample characterization, described above regarding the testing apparatus <NUM>, can be applied to the MPL testing apparatus <NUM>.

The method of testing <NUM> starts in step <NUM> with the light beam <NUM> provided normal to the MPL cylinder <NUM>.

In step <NUM>, optional configurations are used, as described above.

In step <NUM>, the output light is collected after traversing the MPL cylinder <NUM>, the receptacle <NUM>, and being reflected from the plate <NUM>, as described above.

In step <NUM>, the plate <NUM> is rotated, as described above. After rotating the plate, output light can again be collected (step <NUM>) at the new, known angle. This cycle of rotating and collecting can be repeated as necessary to gather data on the desired range of angles to be tested (step <NUM> returns to step <NUM>).

In step <NUM>, optional calculations (processing, signal processing) can be performed on the collected signals, the data from the collected output light <NUM> can be processed to calculate results of the optical testing to determine a figure of merit for transmittance and/or reflectance of the coating and/or plate <NUM> of the optical sample under test.

In step <NUM>, optionally the results of the collection and processing can be output, displayed, stored, and/or transferred.

Note that the above-described examples, numbers used, and exemplary calculations are to assist in the description of this embodiment. Inadvertent typographical errors, mathematical errors, and/or the use of simplified calculations do not detract from the utility and basic advantages of the invention.

Claim 1:
An apparatus for optical testing of a sample (<NUM>) of optical material, the apparatus comprising:
(a) an assembly comprising:
(i) an optically transparent general-cylinder (<NUM>) having an interior partially filled with a bulk material (1100B) portion from an interior surface of said general-cylinder (<NUM>) toward a center axis of said general-cylinder (<NUM>), and said interior having a hollow (<NUM>) portion extending from an opposite interior surface of said general cylinder (<NUM>) and including said axis, said hollow (<NUM>) sized to receive at least a core area of the sample (<NUM>) of optical material,
(ii) a receptacle (<NUM>) including said hollow (<NUM>), said receptacle (<NUM>) sized to receive at least a portion of the sample (<NUM>) of optical material, and said receptacle (<NUM>) sealed for receiving a quantity of fluid (<NUM>), such that said fluid (<NUM>) surrounds and is in contact with at least said core area, and is in contact with said general-cylinder (<NUM>) and at least a portion of said bulk (1100B), and
(b) an optical arrangement:
(i) aligned with said axis,
(ii) including an optical source (<NUM>) providing an optical light beam (<NUM>) normal to a circumferential surface area at a first side of said general-cylinder (<NUM>), and
(iii) including an optical detector (<NUM>) accepting an output signal (<NUM>), said output signal (<NUM>) from said optical light beam (<NUM>) impinging on said core area and transmitted through or reflected from the sample (<NUM>), said optical detector (<NUM>) normal to a circumferential surface area of said general-cylinder (<NUM>).