SUPERCONTINUUM LASER BASED WEB GAUGING SYSTEM

A web gauging system and methods of using the web gauging system are described. The web gauging system includes a supercontinuum Laser providing a light beam. A beam expander is configured to expand the light beam and provide an expanded beam to a sample illumination area. A detector unit configured to detect a sample light from the illumination area. A moving web can be placed in the illumination area, where the web gauging system measures parameters of the web.

FIELD OF THE INVENTION

This invention is directed to a supercontinuum Laser based web gauging system. For example, the system can be used to measure properties of a web in a continuous web making process.

BACKGROUND OF THE INVENTION

Web gauging systems are measurement and control systems used for materials manufactured in a continuous web process. They are typically non-contact scanners utilizing beta, x-ray, or infrared spectroscopy to measure the basis weight, composition, or thickness of flat sheets of plastic, rubber, packaging, building materials, or textiles. Typical continuous web manufacturing processes produce webs that range from 1 to 10 meters wide and move on conveyor systems at linear speeds of up to 600 meters per minute.

Web gauging systems help manufactures reduce costs and improve quality by providing real time, closed loop feedback on-line during the “Web Processing” or “Roll-to-Roll Processing” technologies.FIG.1shows a typical web gauging system100. The web gauging system100utilizes infrared absorption or transmission spectroscopy to actively monitor the thickness of a moving web102as it passes through the sensor104. The web102is fed through the web gauging system100typically using rollers that keep the web at the correct tension and position in the web gauging system100. The web gauging system100consists of a light source, typically a broad spectrum infrared source such as a tungsten coil, which can be mounted on a first head106, an infrared array detector integrated with a linear variable filter capable of detecting infrared radiation from about 1.4 to 3.7 microns in wavelength, collimating optics, and a frame108that acts as gantry to hold the sensor104in position relative to the web and scan the sensor104across the web102as the web102is moving relative to the sensor104. The first head106is mounted facing a first side110of the web102, and a second head112can be mounted facing a second, opposite side114of the web102. For example, in a transmission mode, the first head106can provide IR light to the first side110of the web102, and the second head112can input/direct IR light transmitted through the web102to a detector. In a reflection mode, the IR light is provided to the same side where reflected IR light is input/directed to a detector, i.e., first side110provides IR light, and reflected IR light is detected from the first side110. The resulting infrared transmission or reflection spectrum provides real time feedback about the thickness and composition of the web to the manufacturer.

While existing web gauging systems such as100are very robust and useful systems, they are unable to achieve 100% web inspection. A typical the sensor104has a spot size of roughly 10 mm×35 mm or 350 mm2and a measurement time of 18 milliseconds. As described above, the sensor104is held on the gantry108that translates the sensor104back and forth across the moving web102in a cross-web direction or sensor direction120. At the same time, the web102is moving perpendicular to the sensor direction120at speeds of up to 600 meters/min in what is referred to herein as a web direction130. Inherently, the sensor104is only capable of measuring a few % of the total area of the moving web102, and in many cases less than 1% of the total area is measured. This leaves most of the area of the web not actively monitored and forces manufacturers to make process control adjustments that affect the entire web based on a small sample size.

One solution to increase the area of measured web is to simply measure and scan faster. There are two factors however that contribute to scan time that make it difficult to do so. The first is the rate at which the gantry can translate the sensor104in the cross-web direction120. As scan speeds increase, it can introduce vibrations and oscillations that affect the accuracy and reproducibility of the optical measurement. In addition, the sensor weight is not insignificant and turn-around time must be taken into consideration when changing the scan direction. The gantry108can be made more robust, but this comes with added cost and one quickly reaches the point of diminishing returns. The second factor limiting the scan speed is the data acquisition rate of the sensor itself. Acquisition rates are driven by the sensitivity and response time of the detector, the optical power emitted by the light source, and the ability of the system to focus the optical energy onto the detector. Without changing the detector or source, increasing the data acquisition rate of the existing systems will result in reduced signal to noise, which in turn affects the accuracy and reproducibility of the optical measurement.

A corollary to the above flawed solution is to slow the web translation speed in the web direction130. This is usually not an optimal solution as it would introduce a time bottleneck in established web-making processes. Additionally, in some optimized web-making processes, such a blown film extrusion process, the web/film may be cooling while being translated and the process cannot be slowed down without changing the film properties.

Another solution to increase the area of the measured web would be to add additional sensors104to the gantry108or using more gantries, enabling increased coverage of the moving web102. While viable, these options increase the cost of the system with each additional sensor head and gantry installed.

Accordingly, there remains a need for improved web gauging systems. Systems that can scan a larger portion/area of a moving web while maintaining a high throughput are highly desirable.

SUMMARY

Systems, methods, and products to address these and other needs are described herein with respect to illustrative, non-limiting, implementations. Various alternatives, modifications and equivalents are possible.

In accordance with a first aspect, a web gauging system includes a supercontinuum (SC) Laser providing a light beam; a beam expander configured to expand the light beam and provide an expanded beam to a sample illumination area; and a detector unit configured to detect a sample light from the illumination area.

In accordance with a second aspect, a method of measuring a web parameter includes positioning a web in a sample illumination area of the web gauging system according to the first aspect; illuminating a first portion of the web with the light beam and producing a first sample light; detecting the first sample light with the detector unit, wherein the first sample light is indicative of a web parameter of the first portion of the web. Optionally, the method includes moving the web to illuminate a second portion of the web and detecting a second sample light with the detector unit, wherein the second sample light is indicative of the web parameter of the second portion of the web.

The web gauging systems described herein can scan a large portion/area of a moving web while maintaining a high throughput.

The figures referred to above are not drawn necessarily to scale, should be understood to provide a representation of particular embodiments, and are merely conceptual in nature and illustrative of the principals involved. The same reference numbers are used in the drawings for similar or identical components and features shown in various alternative embodiments.

DETAILED DESCRIPTION

In the description of the invention herein, it is understood that a word appearing in the singular encompasses its plural counterpart, and a word appearing in the plural encompasses its singular counterpart, unless implicitly or explicitly understood or stated otherwise. Furthermore, it is understood that for any given component or embodiment described herein, any of the possible candidates or alternatives listed for that component may generally be used individually or in combination with one another, unless implicitly or explicitly understood or stated otherwise. Moreover, it is to be appreciated that the figures, as shown herein, are not necessarily drawn to scale, wherein some of the elements may be drawn merely for clarity of the invention. Also, reference numerals may be repeated among the various figures to show corresponding or analogous elements. Additionally, it will be understood that any list of such candidates or alternatives is merely illustrative, not limiting, unless implicitly or explicitly understood or stated otherwise. In addition, unless otherwise indicated, numbers expressing quantities of ingredients, constituents, reaction conditions and so forth used in the specification and claims are to be understood as being modified by the term “about.”

Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the subject matter presented herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the subject matter presented herein are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

As used herein “supercontinuum” or “SC” Laser light refers to light that has high spatial coherence and low temporal coherence. This means that the light has the same phase across the beam, and different phases after long propagation times. As used herein “across” the beam is a direction perpendicular to the direction of the light propagation. Similarly, a “cross-wise” area of the beam is an area of illumination perpendicular to the beam. Monochromatic Laser light differs from SC Laser light in that monochromatic Laser light has high spatial and high temporal coherence. That is, monochromatic Laser light has the same phase across the beam and maintains the same phase after long propagation times. Both SC Laser beams and monochromatic Laser beams have “low divergence,” meaning they can be effectively directed (collimated) for relatively long distances as a collimated beam (e.g., more than 1 meter). This contrasts with light from a filament or globar source, which produces light having low spatial and temporal coherence and where the light, even if collimated will spread out at relatively short distances (e.g., less than 1 mm).

Although monochromatic Lasers can provide a highly collimated beam that can be focused to a spot or area of high brightness, they only provide a very narrow spectral band of light. This narrow spectral band is of limited use for effectively exciting diverse energy transitions, such as IR stretching bands for different chemical species. Traditional filament or globar light sources are “broadband” sources, meaning they can provide a wide diversity of excitation energies/frequencies, but are not amenable to production of bright illumination over a large area. SC Lasers combine some of the properties of conventional broadband light sources with the properties of monochromatic Lasers, including having a broad spectral output while being amenable to collimation and focusing to a large area with a high brightness.

By using the unique optical characteristics of SC Lasers, a new web gauging system as described herein overcomes the drawbacks of traditional web gauging systems such as100(FIG.1). With its low divergence, a SC Laser source can be fixed and no longer needs to be scanned along with the sensor over the web. In addition, due to the high brightness of the SC Laser, the light can be multiplexed across the web, illuminating up to 100% of the width of the web in the cross-web direction120. In some implementations infrared light is used in the systems described herein. For example, Mid-IR light having wavelengths between about 1 μm and 5 μm can be used. These wavelengths include energies that are absorbed by a large amount of chemical species of interest such as C—H, O—H, and N—H stretching which is relevant to analysis of organic resins and films, graphene oxide, metal oxides, and silica. Advantageously, mid-IR supercontinuum lasers, which emit high brightness, low noise, mid-infrared light and which were previously only found in research laboratories, are becoming increasingly available for industrial applications. One such example is the ThorLabs SC4500 which emits SC Laser light in the range of 1.3 to 4.5 microns.

FIG.2is a block diagram showing components of a web gauging system200, according to some implementations. The web gauging system200includes a SC Laser202, a beam expander204, a sample illumination area206and a detector unit208. The SC Laser202provides a light beam that is expanded by the beam expander204. The expanded beam is then provided to the sample illumination area206, where the light from the expanded beam can interact with a sample (e.g., a web). Light from the sample illumination area206, such as light that passes through the sample illumination area206, or light that is reflected from the sample illumination area206, is referred to herein as a sample light. The sample light from the sample illumination area206can be detected by the detector208.

As used herein “expanded” refers to an increase in the cross-wise area of the light beam after the beam is directed to/through the beam expander204. In some implementations, the beam expander204expands the beam substantially evenly: that is there is a one to one correspondence in the light flux in the cross-wise area before the beam is expanded and in the light flux in the cross-wise area after the beam is expanded. Otherwise described, the beam expander204increase the diameter of a collimated input beam to a larger collimated output beam.

The beam expander204can be a transmissive element or a reflective element. For example, transmissive lenses can be appropriate for visible light expansion, e.g., silica-based glasses, transparent salts, or plastics such as polycarbonate. In some implementations, the lenses can be appropriate for infrared light, such as ZnSe or KBr transmissive lenses. In some implementations, the beam expander is a reflective element, which can be used for visible or infrared light. Without limitation, and by way of example, the beam expander can include a curved mirror or a cylindrical mirror. In some implementations, the beam expander204expands the beam by sweeping an input beam over a sweeping angle. For example, a rotating or pivoting lens or mirror that sequentially fans out the input beam. These implementations are described in more detail in the forgoing with reference toFIGS.5A-8, and after a detailed description of detectors.

The detector unit208can be any detector unit that inputs and detects the sample light.FIG.3illustrate an implementation of the detector unit208which is configured to include a spectrophotometer300. The spectrophotometer300includes an entrance slit302, which inputs the sample light303from the sample illumination area206of the web102. The entrance slit302controls the spectral resolution of the optical system. The spectrophotometer300also includes a collimating optic304, a dispersive flat grating306, and a focusing optic308that focuses the dispersed light of different wavelengths (e.g., λ1, λ2, λ3) onto the detector316.

In some implementations the spectrophotometer300is a small (e.g. about 5 cm3), Czerny Turner design, optimized for the mid-IR region of 1-5 μm. In such implementations, the detector316can be any infrared array detector with sensitivity over the wavelength range of 1 to 5 microns such as a PbS or PbSe array, a Mercury-Cadmium-Telluride (MCT) array, an InAsSb array, or a Lead-Zirconate-Titanate (PZT) based array.

In some other implementations, the detector unit208is configured as a hyperspectral imaging system400, illustrated byFIG.4. The hyperspectral imaging system400can be used to monitor about 100% of the web102(FIG.1) as it moves in the web direction130while being illuminated by the SC laser202(FIG.2). In this implementation, the beam expander204, is used to disperse light from the SC Laser202across the width of the web102. On the other side of the web102, an image capture optic401with a large enough field of view to simultaneously capture all of the sample light303, across the entire width of the web102, directs the sample light303to the entrance slit302. The image capture optics can include collimating, relay and focusing optics. Within the hyperspectral imaging system400, a dispersive element (grating)402and an array detector404enable the capture of both spatial and spectral information of the web simultaneously across the entire frame of view (FOV) of the hyperspectral imaging system400. For example, the figure shows a single image captures three different areas and three different frequencies for each area (λ1a, λ1b, λ1c, λ2a, λ2b, λ2c, λ3a, λ3b, λ3c). In this configuration, spatial resolution is defined by height of the entrance slit302and the pixel size/pitch of the array detector404. Generally, an MCT, InSb, or InAsSb focal plane array of more than 1000×1000 pixels is used to achieve the desired spatial and spectral range.

The hyperspectral imaging system can be implemented in a push broom configuration or in a whisk broom configuration, and can be as described in the art. For example, as described in: “Mid-Infrared Compressive Hyperspectral Imaging,” S. Yang et al.,Remote Sens.2021, 13, 741, available atwww.mdpi.com/2072-4292/13/4/741 accessed Oct. 8, 2021; “Near-infrared hyperspectral single-pixel imaging system,” P. Gattinger, Thesis, Technische Universtitat Wien, available at www.repositum.tuwien.at/handle/20.500.12708/6517 accessed Oct. 8, 2021; S. Kraft et al.,Fluorescence imaging spectrometer concepts for the Earth, available at www.researchgate.net/publication/25924097 Fluorescence Imaging Spectrometer concepts for_the_Earth_Explorer_Mission_Candidate_FLEX, accessed Nov. 29, 2021; and Ryan Gosselin et al. “Potential of Hyperspectral Imaging for Quality Control of Polymer Blend Films, Ind. Eng. Chem. Res. 2009, 48, 3033-3042.

FIG.5Aillustrates an implementation, of the web gauging system200(FIG.2). The SC Laser202provides a collimated SC Laser beam502. The collimated SC Laser beam502is directed to the beam expander204(FIG.2), which is configured as a combination of two mirrors; a cylindrical mirror504of relatively short focal length (beam expanding), and a concave mirror506of relatively long focal length (beam collimating). This combination of mirrors504and506, with short and long focal lengths respectively, expands and collimates the collimated SC laser beam502to an expanded beam507, approximately having the width of the web102in the cross-web direction120. A series of pre-sample mirrors510are then used to multiplex the expanded beam507into discrete channels512, one channel per pre-sample mirror510, which is directed to the sample illumination area206. The path of light through three channels512a,512band512cis indicated. For legibility, not all channels are shown.

The web102is positioned in the sample illumination area206. InFIG.5A, the web direction130(FIG.1) is perpendicular to the page and the cross-web direction120is horizontal to the page, as indicated by the double headed arrow. Light from the pre-sample mirrors510, which is partitioned from expanded beam507into the channels512, is directed simultaneously to the first side110of the web102across the web102. In this implementation, the detector unit208includes the flipper mirrors514, re-focusing optics516, and the spectrophotometer300. The flipper mirrors514are positioned facing the second side114of the web102and include a hinge515on one side. By rotation about the hinge515, the flipper mirrors514are used to direct the light from each of the channels512, one at a time, to the re-focusing optics516. For example, the flipper mirror514at the channel512acan be positioned in an orientation as shown (“on” or “active”) directing sample light303towards the re-focusing optics516, while the mirrors at the channels512band512care rotated out of the path of sample303(“off” or “inactive”). This arrangement passes sample light303from each channel512sequentially into the spectrophotometer300where an optical measurement is made. As used herein “sequentially” denotes a specific order that can be repeated to cycle through all or a portion of the expanded beam507that produces sample light303. Any order can be used in the sequence to send sample light303from the channels512to the re-focusing optics516. In some implementation, a subset of the channels512are used, for example where only a portion of the web102is analyzed, or the coverage of the web by the channels512is larger than the web102in the cross-web120direction. This can be used to advantageously select only areas of interest for analysis where monitoring may be more important (e.g., outer edges of web102or the center areas of the web102), or to minimize data processing.

In some implementations, the flipper mirrors514are mirrors mounted to a stepper motor, where the axel is perpendicular to the page and is located at hinge515. In some other implementations, the flipper mirrors are a MEMS device such as a digital micromirror device (DMD). In such devices, each mirror can be individually rotated to the on (active) or off (inactive) state.

As noted earlier, the web102cross-web diameters can be between about 1 and 10 meters. A person of skill in the art understands how to select ratios of the focal lengths for mirrors504and506to illuminate a desired cross-wise width of the web102. The number and dimensions of the pre-sample mirrors510and the flipper mirrors514can also be selected by choice of the person of skill in the art depending on how many channels are desired and the cross-wise width of the web102. In some implementations, there is a one to one correspondence between the pre-sample mirrors510and the flipper mirrors514. In some other implementations, there is not a one to one correspondence, for example, where two or more pre-sample mirrors510reflect light to fewer flipper mirrors514, or one pre-sample mirror510reflects light to two or more flipper mirrors514.

In some implementations, one or more of the pre-sample mirrors510are flat mirrors. In some other implementations, one or more of the pre-sample mirrors510are concave mirrors which focus the expanded beam507into a spot size illuminating the web102that is smaller than the pre-sample mirror510width. In yet other implementations, one or more of the mirrors510can be convex mirrors to expand the light to a larger spot size.

FIG.5Bshows a top view of the web102positioned in the web gauging system200ofFIG.5A. The web102is held in place and conveyed in the web direction130through the sample illumination area206by rollers520. In some implementations, multiple rollers can be used, for example to press or pinch the web102and hold the web102in the sample illumination area206.

The sample illumination area206has a substantially rectangular boundary having a long dimension524approximately parallel to the cross-web direction120, and a short dimension526approximately parallel to the web direction130. The rectangular boundary524,526defines a maximum of the sample illumination area206, or the maximum area of web102illuminated by the expanded beam507(FIG.5A). The shape of the pre-sample mirrors510will change the sample illumination area206shape. For example, if the pre-sample mirrors510are circular, these will provide an array of circular illumination spots, illustrated as dashed circles corresponding to the channels512such as512a,512band512c. This array of channels512define the sample illumination area206, which is bounded by the rectangular boundary524,526. A person of skill in the art recognizes that boundary shapes other than the rectangular boundary524,526can be implemented and is determined by the arrangement of the optics such as the pre-sample mirrors510.

In some implementations, the short dimension526is between about 1 mm and 10 cm. In some implementations, the long dimension524is at least about 10% of a width528of the web102in the cross-web direction120, and the sample illumination area206illuminates at least about 10% of the moving web102as the web102moves through the rectangular boundary524,526. In some implementations, the long dimension524is not more than about 110% of the width528. In some implementations, the sample illumination area206illuminates between about 90% and 110% of the moving web102as the web102moves through the rectangular boundary524,526. As previously described, in some implementations only some of the channels512are used, for example only the channels512aand512care used to analyze the outer edges of web102, where the sample illumination area206is discontinuous. As an alternative example, only channel the512bis used to analyze a center area of the web102.

The amount of the web102that can be analyzed is not more than what is illuminated in the rectangular boundary524,526as the web102moves through the sample illumination area206. In addition, time to collect data is limited by the frame rate, which in turn depends on the Detectivity (D*). For example, some D* values for detectors are listed in Table 1.

For example, in an implementation with three channels512and a PZT detector having a frame rate of 250 Hz (4 ms) to obtain 50 co-additions of the collected spectra it take 200 ms to collect the desired amount of spectral data. Using less co-additions will shorten the time at the expense of a good signal to noise ratio. Choosing a PbS detector increases the speed for collecting the same amount of spectral data by a factor of about 285 to less than 1 ms.

For the current systems depicted inFIG.1, the scan rate is 25 ms with 50 co-additions when using a PbS detector. The current systems cover about 1% of the moving web. The increase in implementing the gauging system200as depicted inFIG.5A,5Btranslates to an increase in the coverage to at least 25%. Accordingly, in some implementations, more than 1% of the moving web102provides sample light303(FIG.2) that is analyzed by the detector unit208(e.g., more than 5%, more than about 10%, more than about 25%).

Another factor to consider is that the amount of the web102that can be analyzed is limited by the speed at which the flipper mirrors514can move from the active state, shown in channel the512a, to the inactive state shown in the channels512band512c(FIG.5A). In some implementations, the rate of switching between active/inactive states for each of the channels512is selected between about 1 ms (1000 Hz) and about 100 ms (10 Hz).

FIG.5Cillustrates an implementation of the web gauging system200using the hyperspectral imaging system400. In this implementation, similar elements as described forFIG.5Aare used for illuminating the web. Specifically, the SC Laser202provides the SC Laser beam502which is expanded by cylindrical mirror504, concave mirror506, and pre-sample mirrors510. The detector unit208includes the image capture optic401which is positioned far enough from the web102, and has a large enough field of view, to capture all the sample light303simultaneously. The sample light is focused and sent to the entrance slit of the hyperspectral imaging systems and is positioned to image the second side114of web102.

FIG.6illustrates another implementation of the web gauging system200. In this implementation, the pre-sample mirror510′ is not multiplexed. That is, only one pre-sample mirror510′ is used to direct light from the concave mirror506. In this implementation, the channels512(e.g.,512a,512band512c) are created by the flipper mirrors514, as each sequentially directs light to the re-focusing optics516. Other features, such as the SC Laser202, the cylindrical mirror504, the sample illumination area206, the web102, the detector unit208, the re-focusing optics516, and the spectrophotometer300are as previously described.

In yet another implementation as shown inFIG.7, no pre sample mirror510or510′ is used. The expanded light507from the concave mirror506is sent directly to the sample illumination area206. Other elements such as the SC Laser202, the cylindrical mirror504, the web102, the flipper mirrors514, the channels512, the detector unit208, the refocusing optics516, and the spectrophotometer300are as previously described.

FIG.8shows an implementation of the web gauging system200with an alternative beam expander204(FIG.2) configuration. The beam expander204includes a rotating mirror802that reflects the collimated SC Laser beam502sequentially over a sweeping angle α (between the dash-dot-dot lines) towards pre-sample mirrors510″, which redirect the light towards the sample illumination area206. In some implementations, a is between about 10° and 170°. In some implementations, the pre-sample mirrors510″ are concave.

InFIG.8, solid lines indicate light ray paths at one instance in time where the rotating mirror802is in the one rotational position of angle α. Dashed lines indicate other light paths that can occur when the rotating mirror802rotates to other possible rotational positions of angle α. The solid and dashed lines also show how expanded beam507′ is directed towards the sample illumination area206as discrete channels512, and through the web102. In the figure, an instant in time is shown when the rotating mirror802has activated the channel512c, where the channels512aand512bare not activated.

A reflective surface or mirror806is positioned facing the second side114of the web102. The expanded light507′ passes through the first side110of the web102, is reflected by the reflective surface806, and the expanded light507′ then passes again through the web102from the second side114. Light emerges from the first side110of the web102in the opposite direction of expanded light507′ as sample light303. Sample light303follows the same path as the expanded beam507, except in the reverse direction.

The detector unit208shown inFIG.8includes a beam splitter706. The beam splitter706diverts the sample light303to the re-focusing optic516and the spectrophotometer300. In some implementations, linear variable filters808or a filter array are used. In such implementations, a single element detector is used instead of the spectrophotometer300. It is understood that the linear variable filters808can optionally be implemented in any of the previously described implementations.

In some implementations, a purge box810is used. The purge box810can create a controlled environment for the light paths, such as expanded beam507′ and sample light303, to avoid unwanted absorption from gases such as water vapor or scattering from liquid droplets/aerosols or particulates such as dust. The purge box810can be purged with any useful gas such as dry air, nitrogen, argon, or helium. In some implementations, a pressure higher than atmospheric pressure is maintained within the purge box810. In some other implementations, a pressure lower than atmospheric pressure is maintained within the purge box. A window815that is transparent to the light of interest (e.g., IR light with 1 μm≤λ≤5 μm) allows the collimated SC Laser beam502into the purge box810. Transparent window(s) are also positioned facing the first side of web110to allow expanded beam507′ out of the purge box810, and to allow sample light303into the purge box810. Other configurations of the purge box810can be used as would be understood by a person of skill to minimize unwanted absorption of light. The purge box810is also optionally implemented in all of the web gauging systems200described herein.

Re-directing mirror812and focusing mirror814are also show. These can be implemented as needed to provide or direct the collimated SC Laser beam502to the rotating mirror802. In some implementation, addition focusing, re-directing or collimating mirrors can be used.

In some implementations, the reflective surface806contacts the web102, or is part of the web. For example, in some implementations the web102slides on the reflective surface, or the reflective surface moves/conveys the web102, such as with a moving conveyor belt including the reflective surface806facing the second side114of the web102. As another example, the web102can include the reflective surface806as a layer e.g., on the bottom, such as an aluminum foil or a copper.

FIGS.5-8show implementations of the web gauging system200for transmission of light through the web102. That is, light from the expanded beam507or507′ passes through the sample illumination area206providing the sample light303. A person of skill in the art would understand how to make modifications to convert these to detection reflected or scattered light from the web102. In the implementation shown byFIG.8, this can be accomplished by removing/not including the reflective surface806, where the sample light303would be created by scattering and reflecting off web the102.

The web gauging system200(FIG.2) also includes a central control system CCS to control and synchronize the various elements such as the flipper mirrors514(FIGS.5A,6and7), the rotating mirror802(FIG.8), the SC Laser202, the spectrophotometer300(FIG.3), and the hyperspectral imaging system400(FIG.4). The CCS includes at least a CPU, memory (volatile and non-volatile), and a power source. Sensors (e.g., cameras, temperature, tension, electrical resistance), alarms and microcontrollers can also be connected to the CCS, for example to monitor the state of the various components of the web gauging system200(e.g., overheating, out of specification) or of the web102(e.g., detection of the presence of the web in the illumination area206), and provide a record to the memory or an alarm to alert operators of a specific condition. The detector unit208includes or is connected to a digital signal processor (DSP) which can be controlled by the CCS. The DSP can include a memory and CPU configured to store and execute algorithms for analysis of the signals detected by the detector unit208. The CCS can be partially or entirely provided remotely at a central server or in the cloud. For example, the CCS is connected by WiFI, Zigbee, or Bluetooth to the sensors, microcontrollers, or DSP. The CCS can also be connected to one or more user interfaces such as a monitor, and input devices such as a keyboard.

FIG.9is a flow diagram showing a method900for measuring a web parameter. The method can be implemented using the web gauging system200(FIGS.5-8). In step902, the web102is positioned in the sample illumination area206. In step904, a first portion of the web is illuminated by the expanded light beam507,507′ and a first sample light303is produced. The first sample light303is detected by the detector unit208in step906. For a continuous web system, the steps908,910, and912are used to measure the moving web. The web102is moved to a second position in step908, for example by translating in the web direction130. A second portion of the web102is illuminated in step910, and a second sample light is detected in step912using the detector unit208. It is understood that steps908,910, and912can be repeated any number of times, to detect a 3rd, 4th, 5th, etc. sample light303, until an entire web in the web direction108is measured. It is also understood that the movement of the web can be continuous and at a substantially constant speed, where each portion that is measured sequentially corresponds to an area traversed in the web direction130through illumination area206. That is, the first portion can be measured between time point t0and t1which measures the amount of web102that traverses through illumination area206during the time (Δt1-t0); the second portion can be measured between a subsequent time between t1and t2which measures the amount of web102that traverses through illumination area206during that time (Δt2-t1); and the third portion can be measured between a subsequent time between t2and t3which measures the amount of web102that traverses through illumination area206during that time (Δt3-t2). Optionally, there are gaps between each of the measurements, for example, where measurement of web102only occurs at the first portion during Δt1-t0, no measurement occurs at the second portion during Δt2-t1, and measurement occurs at the third portion during Δt3-t2.

The first and second sample lights303are indicative of a web parameter. The web parameter is any web parameter that can be determined by the frequencies of light provided by the SC Laser202and the detector unit208. In some implementations, the web parameter is one or more of a thickness, a composition, and a temperature. For example, the sample light can include —OH stretching and is indicative of a composition having hydroxyl groups, where a change in the —OH stretching band between the first and second positions, indicates a change in —OH containing compounds (e.g., water). In other implementations, transmission of infrared light over a range of frequencies is monitored and changes in the sample light between position 1 and position 2 indicate changes in the amount of material or thickness of the web. In some implementations the parameter relates to an occlusion or foreign material/contaminant. In some implementations the parameter relates to missing material, such as a hole or tear. In some implementations, the parameter relates to a topography such as a roughness.

The method can be used to examine any thin sheet like material or web that is moving or stationary. By way of example, this includes thin resin sheets (e.g., polyethylene), cellulose (e.g., paper), coated sheets, textiles, and laminates. In some implementations, the web includes a coating of one or more material uniformly or non-uniformly (e.g., patterned) distributed over a thin substrate.

Those having skill in the art, with the knowledge gained from the present disclosure, will recognize that various changes can be made to the disclosed apparatuses and methods in attaining these and other advantages, without departing from the scope of the present disclosure. As such, it should be understood that the features described herein are susceptible to modification, alteration, changes, or substitution. For example, it is expressly intended that all combinations of those elements and/or steps which perform substantially the same function, in substantially the same way, to achieve the same results are within the scope of the embodiments described herein. Substitutions of elements from one described embodiment to another are also fully intended and contemplated. For example, the hyperspectral imaging system400described with reference toFIG.4can be implemented in the embodiments shown inFIGS.5A,6,7and8. The specific embodiments illustrated and described herein are for illustrative purposes only, and not limiting of that which is set forth in the appended claims. Other embodiments will be evident to those of skill in the art. It should be understood that the foregoing description is provided for clarity only and is merely exemplary. The spirit and scope of the present disclosure is not limited to the above examples, but is encompassed by the following claims. All publications and patent applications cited above are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication or patent application were specifically and individually indicated to be so incorporated by reference.