U.S. patent application number 15/790181 was filed with the patent office on 2018-02-15 for method and system for real-time in-process measurement of coating thickness.
The applicant listed for this patent is Sensory Analytics, LLC. Invention is credited to Greg Frisby, Vivek Komaragiri.
Application Number | 20180045507 15/790181 |
Document ID | / |
Family ID | 50588890 |
Filed Date | 2018-02-15 |
United States Patent
Application |
20180045507 |
Kind Code |
A1 |
Komaragiri; Vivek ; et
al. |
February 15, 2018 |
Method And System For Real-Time In-Process Measurement Of Coating
Thickness
Abstract
The present disclosure is generally directed to methods and
systems for measuring the thickness of coatings or thin films on
various substrates. For example, one disclosed method includes the
steps of providing and directing light waves of varying wavelengths
toward a moving substrate comprising a coating, linearly polarizing
the light waves, converting the linearly polarized light waves to
circularly polarized light waves, analyzing elliptically polarized
light waves reflected by the moving substrate, capturing analyzed
light waves, generating light wave data based on the captured light
waves, and determining a thickness of the coating based on the
light wave data.
Inventors: |
Komaragiri; Vivek;
(Greensboro, NC) ; Frisby; Greg; (Greensboro,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sensory Analytics, LLC |
Greensboro |
NC |
US |
|
|
Family ID: |
50588890 |
Appl. No.: |
15/790181 |
Filed: |
October 23, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14781457 |
Sep 30, 2015 |
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PCT/US2014/027980 |
Mar 14, 2014 |
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15790181 |
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61792689 |
Mar 15, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01B 11/0633 20130101;
G01B 11/0641 20130101; G01B 11/065 20130101 |
International
Class: |
G01B 11/06 20060101
G01B011/06 |
Claims
1. A system comprising: a processor; a moving substrate comprising
a coating applied by a coating applicator; a light source in
communication with the processor, the light source configured to
provide and direct light waves of varying wavelengths toward the
moving substrate; a polarizer positioned between the light source
and the moving substrate; a wave plate positioned between the
polarizer and the moving substrate; an analyzer positioned to
receive light waves reflected by the moving substrate; a detector,
in communication with the processor, positioned to capture light
waves reflected by the analyzer and configured to generate light
wave data based on the captured light waves; and a memory in
communication with the processor, wherein the memory comprises
computer program code executable by the processor to determine a
thickness of the coating based on the light wave data, and wherein
the memory further comprises computer program code executable by
the processor to, in response to a determination that the thickness
of the coating is outside a predetermined range, generate a signal
instructing the coating applicator to adjust the rate of
application of the coating onto the moving substrate.
2. The system of claim 1, wherein the coating is less than 0.2
microns thick.
3. The system of claim 1, wherein the coating is a lubricious
coating.
4. The system of claim 1, wherein the coating is a liquid
coating.
5. The system of claim 1, wherein the wave plate is a rotating
quarter-wave plate.
6. The system of claim 1, wherein the analyzer is a rotating
analyzer in communication with the processor.
7. The system of claim 1, wherein the computer program code
executable by the processor to determine the thickness of the
coating based on the light wave data comprises computer program
code executable by the processor to determine phase shift and
polarization state changes of captured light waves compared to the
provided light waves based on the light wave data.
8. The system of claim 1, wherein the computer program code
executable by the processor to determine the thickness of the
coating based on the light wave data comprises computer program
code executable by the processor to apply the Levenberg-Marquardt
algorithm to match the light wave data with a theoretical
model.
9. The system of claim 1, wherein a position and an orientation of
the analyzer are adjustable and a position and an orientation of
the detector are adjustable.
10. The system of claim 9, wherein the memory further comprises
computer program code executable by the processor to: detect a
disturbance in the movement of the moving substrate based on the
light wave data; and adjust the position or the orientation of the
analyzer or adjust the position or the orientation of the detector
based on the detected disturbance.
11. The system of claim 9, wherein the memory further comprises
computer program code executable by the processor to: detect a
disturbance in the movement of the moving substrate based on the
light wave data; and adjust the position or the orientation of the
analyzer and adjust the position or the orientation of the detector
based on the detected disturbance.
12. The system of claim 1, wherein the memory further comprises
computer program code executable by the processor to adjust the
intensity of the provided light waves based on the light wave
data.
13. The system of claim 1, wherein the signal instructs the coating
applicator to decrease the rate of application of the coating onto
the moving substrate.
14. The system of claim 1, wherein the signal instructs the coating
applicator to increase the rate of application of the coating onto
the moving substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/781,457 filed Sep. 30, 2015, entitled
"Method & System For Real-Time In-Process Measurement Of
Coating Thickness," which claims priority to PCT Application No.
PCT/US2014/027980 filed Mar. 14, 2014, entitled "Method and System
For Real-Time In-Process Measurement of Coating Thickness,"
published as WO 2014/143838, which claims priority to U.S.
Provisional Patent Application No. 61/792,689 filed Mar. 15, 2013,
entitled "Method and System for Inline Real-Time Measurement of
Thin Film Thickness." The content of each of the aforementioned
applications is incorporated by reference herein in its
entirety.
FIELD
[0002] The present disclosure generally relates to methods and
systems for measuring the thickness of coatings or thin films on
various substrates. Embodiments include methods and systems for
real-time in-process measurement of coating thickness, and more
particularly methods and systems for real-time in-process
measurement of a coating thickness on a moving substrate or a
coated product.
BACKGROUND
[0003] The measurement of thin films and coatings is appreciated in
manufacturing settings. For example, regulating the application of
a thin film or coating to a product within a preferred thickness
range allows manufacturers to ensure that a film or coating is
applied with sufficient thickness to prevent manufacturing defects
while also avoiding wasteful application of film or coating in
excess of a required thickness, thereby minimizing materials costs.
In the context of manufacturing processes, measurement of thin
layers of lubricious coatings on metals allows manufacturers to
ensure that sufficient coating is applied to prevent substantial
damage to expensive manufacturing and processing equipment.
Furthermore, it is preferable to periodically perform measurements
of thin films or coatings in real-time as the films or coatings are
applied before the coated substrate proceeds further through the
manufacturing process.
[0004] There are several currently known techniques for measuring
thin films or coatings. However, the known methods have various
limitations that significantly undermine their respective
usefulness in industrial applications. For example, standard
reflectometry based measurement techniques become unreliable when
the thickness of the subject coating/film under consideration is
below 200 nanometers (1 nanometer=0.001 microns). Known
modeling-based reflectometry techniques are not well-suited and not
robust enough for use in industrial production environments.
[0005] In addition, modeling-based reflectometry techniques for
measuring film or coating thicknesses of less than 0.2 microns have
typically focused on measurement of coatings and films on
semiconductor substrates. However, applications of coatings or
films in the semiconductor manufacturing process are performed on
static (non-moving) substrates. A significant limitation of the
currently known modeling-based reflectometry techniques capable of
measuring coatings of less than 0.2 microns is that they require a
static substrate on which to perform measurements of coatings or
materials deposited thereon.
[0006] The present disclosure is directed to methods and systems
for real-time in-process measurement of thin films or coatings,
including films or coatings of less than 0.2 microns, on a moving
substrate, and therefore overcomes the limitations of known methods
and systems.
SUMMARY
[0007] The present disclosure generally relates to a method
comprising providing and directing light waves of varying
wavelengths toward a moving substrate comprising a coating,
linearly polarizing the light waves, converting the linearly
polarized light waves to circularly polarized light waves,
analyzing elliptically polarized light waves reflected by the
moving substrate, capturing analyzed light waves, generating light
wave data based on the captured light waves, and determining a
thickness of the coating based on the light wave data. In another
embodiment, the method further comprises detecting a disturbance in
the movement of the substrate based on the light wave data and
adjusting an orientation of an analyzer and or an orientation of a
detector based on the detected disturbance.
[0008] The present disclosure is also generally related to a system
comprising a processor, a light source in communication with the
processor, the light source configured to provide and direct light
waves of varying wavelengths toward a moving substrate comprising a
coating, a polarizer positioned between the light source and the
moving substrate, a wave plate positioned between the polarizer and
the moving substrate, an analyzer positioned to receive light waves
reflected by the moving substrate, a detector, in communication
with the processor, positioned to capture light waves reflected by
the analyzer and configured to generate light wave data based on
the captured light waves, and a memory in communication with the
processor, wherein the memory comprises computer program code
executable by the processor to determine a thickness of the coating
based on the light wave data. In another embodiment, an orientation
of the analyzer is adjustable and an orientation of the detector is
adjustable. In still another embodiment, the memory further
comprises computer program code executable by the processor to:
detect a disturbance in the movement of the moving substrate based
on the light wave data; and adjust the orientation of the analyzer
or the orientation of the detector based on the detected
disturbance.
[0009] Illustrative embodiments disclosed herein are mentioned not
to limit or define the invention, but to provide examples to aid
understanding thereof. Illustrative embodiments are discussed in
the Detailed Description and further description of the invention
is provided therein. Advantages offered by various embodiments of
this invention may be further understood by examining this
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other features, aspects, and advantages according
to the present disclosure are better understood when the following
Detailed Description is read with reference to the accompanying
figures, wherein:
[0011] FIG. 1A is a block diagram of a system for measuring thin
film/coating thickness according to one embodiment of the present
disclosure.
[0012] FIG. 1B is an illustration of a configuration comprising
components of system 100 according to one embodiment of the present
disclosure.
[0013] FIG. 2 is a flow diagram of a method for measuring thin
film/coating thickness according to one embodiment of the present
disclosure.
DETAILED DESCRIPTION
[0014] Embodiments according to this disclosure provide methods and
systems for inline real-time measurement of thin film or coating
thickness, and more particularly to methods and systems for inline
real-time measurement of thin film or coating thicknesses,
including films or coatings of less than 0.2 microns, on a moving
substrate.
Illustrative Embodiment
[0015] In one illustrative embodiment, a manufacturer employs the
systems and methods of the present invention to measure the
thickness of a lubricious coating applied to thin metal sheeting to
ensure a sufficient layer of lubricious coating is present on the
thin metal sheeting--used by the manufacturer to create its
products--to prevent damage to expensive manufacturing equipment
that processes the metal sheeting. In the illustrative embodiment,
the manufacturer incorporates a broadband light source that directs
light waves through polarizers and wave plates onto the surface of
the thin metal sheeting containing the lubricious coating as it is
moving through the equipment. The manufacturer further incorporates
detectors that capture reflected light that passes through rotating
analyzers. A computer controlling the manufacturing process is in
communication with the light sources and the detectors and is
programmed to configure the light sources to generate light within
a particular spectrum range based on the particular metal and the
particular lubricious coating being measured. The computer is
further programmed to receive light wave data from the detectors.
The computer quantifies the phase shift and polarization state
changes of the reflected light, compared to the light waves
generated by the light source, and then uses that information to
evaluate and validate thickness of the lubricious coating at
various locations on the metal sheeting as it is moving through the
equipment.
[0016] In addition, rotating analyzers and detectors are coupled to
an adjustment mechanism in communication with the computer. The
computer operates to detect flutters, vibrations, or other
disturbances in the movement of the metal sheeting and
automatically adjusts the positions of the analyzers and detectors
to ensure accuracy of the thickness measurements.
[0017] In the illustrative embodiment, a preferred thickness range,
warning thickness level and a critical thickness threshold are
defined and programmed into the computer. If the measured thickness
of the lubricious coating is well within the preferred thickness
range, the computer allows the manufacturing process to continue.
If the computer detects that the lubricious coating is outside of
the preferred thickness range, the computer provides feedback to
the system controlling the application of the lubricious coating.
In response, that system adjusts the application of the lubricious
coating to bring it back within the preferred thickness range. In
the event that the coating thickness reaches the warning thickness
level, the computer alerts the equipment operators of a potential
malfunction in the lubricious coating application system. The
operators may then choose whether to shut down the manufacturing
process to investigate or to continue the process.
Illustrative System
[0018] FIG. 1A is a block diagram of a system for measuring thin
film/coating thickness according to one embodiment of the present
disclosure. FIG. 1A illustrates a configuration comprising
components of system 100 according to one embodiment of the present
disclosure. System 100 may comprise one of a variety of form
factors. In one embodiment, system 100 may be a self-contained
system comprising a single housing. In one embodiment, the system
100 may comprise a portable housing. In other embodiments, the
system 100 may be integrated directly into manufacturing or testing
equipment. In still another embodiment, system 100 may comprise a
number of components in separate physical locations, but coupled
through wired and/or wireless communications and/or networking well
known to those having ordinary skill in the art.
[0019] Embodiments of the present disclosure can be implemented in
combination with, or may comprise combinations of: digital
electronic circuitry, computer hardware, firmware, software, light
sources, optical equipment, and/or optical sensors. The system 100
shown in FIG. 1 comprises a processor 102. The processor 102
receives input signals and generates signals for communication,
display, and processing sensor readings to measure thicknesses of
thin films/coatings. The processor 102 includes or is in
communication with one or more computer-readable media, such as
memory 104, which may comprise random access memory (RAM).
[0020] The processor 102 executes computer-executable program
instructions stored in memory 104, such as executing one or more
computer programs for providing a user interface and/or processing
sensor readings to measure thicknesses of thin films/coatings.
Processor 102 may comprise a microprocessor, a digital signal
processor (DSP), an application-specific integrated circuit (ASIC),
one or more field programmable gate arrays (FPGAs), or state
machines. The processor may further comprise a programmable
electronic device such as a PLC, a programmable interrupt
controller (PIC), a programmable logic device (PLD), a programmable
read-only memory (PROM), an electronically programmable read-only
memory (EPROM or EEPROM), or other similar devices.
[0021] Memory 104 comprises a computer-readable media that may
store instructions, which, when executed by the processor 102,
cause it to perform various steps, such as those described herein.
Embodiments of computer-readable media may comprise, but are not
limited to, an electronic, optical, magnetic, or other storage or
transmission device capable of providing the processor 102 with
computer-readable instructions. Other examples of media comprise,
but are not limited to, a floppy disk, CD-ROM, magnetic disk,
memory chip, ROM, RAM, ASIC, configured processor, all optical
media, all magnetic tape or other magnetic media, or any other
medium from which a computer processor can read. Also, various
other devices may include computer-readable media, such as a
router, private or public network, or other transmission device.
The processor 102, and the processing, described may be in one or
more structures, and may be dispersed through one or more
structures.
[0022] Referring still to FIG. 1, the system 100 also comprises one
or more user input devices 108 in communication with the processor
102. For example, in some embodiments a user input device 108 may
comprise a keyboard, mouse, trackball, touchscreen, touchpad, voice
recognition system or any other input device known to one having
ordinary skill in the art.
[0023] The system 100 also comprises a display 106. Display 106 is
in communication with processor 102 and is configured to display
output from the processor 102 to the user. For instance, in one
embodiment, display 106 is a standard computer monitor such as an
LCD display or a cathode ray tube (CRT). In another embodiment,
system 100 may comprise a touch-screen LCD that operates both as a
display 106 and a user input device 108. Various sizes of LCD
displays may be used.
[0024] Referring now to FIGS. 1A and 1B, the system 100 further
comprises a light source 110. For example, in one embodiment light
source 110 is a broadband light source capable of generating light
waves of multiple wavelengths. For example, the wavelengths of the
illuminated light could be in the ultraviolet (UV), visible, or
near infrared (NIR) regions. In one embodiment, light source 110 is
capable of generating light waves having wavelengths in the UV and
visible spectrum regions. In one such embodiment, the light source
110 comprises a xenon arc lamp. In another embodiment, light source
110 is capable of generating light waves having wavelengths in the
visible and NIR spectrum regions. In one such embodiment, the light
source 110 comprises a tungsten halogen lamp. In still another
embodiment, light source 110 is capable of generating light waves
having wavelengths in the UV, visible, and NIR spectrum regions. In
one such embodiment, the light source 110 comprises a xenon arc
lamp and a tungsten halogen lamp.
[0025] In one embodiment, light source 110 is coupled to processor
102 to allow the processor 102 to control the output of the light
source 110. For example, the processor 110 may communicate with the
light source 110 to turn the light source 110 on or off, or to
specify the type of light waves to be provided. In one embodiment,
the processor communicates with the light source to specify light
waves within the UV, visible, and/or NIR spectrum regions, or
subsets thereof. In one embodiment, the processor 102 controls the
amount of light generated to ensure the light levels are not
saturated. In one embodiment, the light source 110 may be
positioned to directly emit light towards a substrate 120, as shown
in FIG. 1B. In other embodiments, the light guides may be used to
direct light emitted from a light source 110 located at another
position, such as within a housing comprising the processor 102 and
memory 104, towards a substrate 120.
[0026] The system 100 further comprises a polarizer 118. Polarizer
118 is an optical device that functions to convert unpolarized
light waves passing through it, such as light waves provided by
light source 110, into linearly polarized light waves. In one
embodiment, a Glan Taylor polarizer with an extinction coefficient
of 10.sup.5:1 is used to convert the non-polarized light beam into
linearly polarized light beam. In the embodiment illustrated in
FIG. 1B, polarizer is positioned such that light waves provided by
light source 110 pass through polarizer 118.
[0027] The system 100 further comprises a wave plate 112. In one
embodiment, the wave plate 112 is a quarter-wave plate Wave plate
112 functions to alter the polarization state of light waves
passing through it. For example, a quarter-wave plate converts
linearly polarized light waves passing through it into circularly
polarized light waves. In the embodiment illustrated in FIG. 1B,
the wave plate 112 is positioned to receive light waves from a
light source 110 that first passes through a polarizer 118. In the
embodiment illustrated in FIG. 1B, the light waves passing through
the wave plate 112 are incident light waves to a substrate 120
comprising a coating or film 122 on the top surface. In some
embodiments, the wave plate 112 is rotatable and comprises a
mechanism (e.g. an electric motor) for rotating the wave plate 112.
In one such embodiment, processor 102 communicates with wave plate
112 to control whether and at what speed the wave plate 112 is
rotating.
[0028] The system 100 further comprises an analyzer 114. In one
embodiment, analyzer 114 is a rotating analyzer that receives
elliptically polarized light reflected by substrate 120 and/or
coating or film 122. The rotating analyzer 114 functions to reflect
light from various angular positions. The analyzer 114 is the same
component as the polarizer 118 except that it is used to analyze
the polarization state of the light wave instead of altering the
polarization state of the incident light beam. In some embodiments,
a rotating analyzer 114 comprises a mechanism (e.g. an electric
motor) for rotating the analyzer 114. In one such embodiment,
processor 102 communicates with the rotating analyzer 114 to
control whether and at what speed the analyzer 114 is rotating.
[0029] The system 100 further comprises a detector 116. Detector
116 operates to detect the reflected light generated from various
angular positions of the rotating analyzer. In one embodiment, the
detector 116 comprises a spectrometer. In some embodiments,
different detectors may be used for different wavelength ranges. In
one embodiment, the detector 116 may be positioned to directly
receive the reflected light generated from various angular
positions of the rotating analyzer 114, as shown in FIG. 1B. In
other embodiments, a probe connected to a light guide may be used
to capture and direct the reflected light generated from various
angular positions of the rotating analyzer 114 to a detector 116
located at another position, such as within a housing comprising
the processor 102 and memory 104. In one such embodiment, the probe
comprises a fiber optic probe. The detector 116 operates to convert
captured light waves into light wave data. In one embodiment, light
wave data may be a voltage signal waveform that corresponds to the
captured light wave. In another embodiment, light wave data
comprises a data structure containing information that describes
the capture light waves.
[0030] The detector 116 is in communication with the processor 102
and provides the light wave data to the processor 102. The
processor 102 is programmed to validate and evaluate the light wave
data. In one embodiment, the processor 102 quantifies the phase
shift and polarization state changes, compared to the light waves
generated by the light source 110, and then uses that information
to evaluate and validate thickness of the coating/film 122 on the
substrate 120. In one embodiment, the processor 102 broadly
calculates the polarization state change and the phase shift of the
incident light waves on the sample to that of the reflected light
waves emanating from the analyzer 114. In one embodiment,
theoretical models are developed for the given substrate coating
combination and the Levenberg-Marquardt algorithm is used to
calculate the best fit to match the light wave data with a
theoretical model to determine thickness. In some embodiments,
triangular smoothing techniques are applied to light wave data to
optimize the quality of spectral response before it is evaluated.
Furthermore, in some embodiments, techniques for determining signal
quality and detecting noise are used to validate light wave data
corresponding to individual measurements. In one embodiment, signal
quality of the light wave data is determined by using predetermined
coating specific spectral signatures to validate individual
measurements. In still another embodiment, the processor 102
determines the strength and quality of the light waves based on the
light wave data and dynamically adjusts the light intensity
provided by light source 110.
[0031] In some embodiments, system 100 may comprise two or more
sets of light sources 110, polarizers 118, wave plates 113,
analyzers 114 and detectors 116. In one such embodiment, the system
100 may simultaneously measure the thickness of the coating/film
122 at multiple locations on substrate 120. In another embodiment,
a single light source 110 and/or a single detector 116 may be used
in conjunction with two or more sets of polarizers 118, wave plates
113, and analyzers 114. In one embodiment, an optical switch and
light guides coupled thereto may be used to provide light from a
single light source to multiple locations on substrate 120. In
another embodiment, an optical switch with light guides attached
thereto and probes coupled to the light guides may be used to
capture the reflected light generated from various angular
positions of multiple rotating analyzers 114 and direct the capture
light to a single detector 116.
[0032] While shown as individual components in FIG. 1B, in some
embodiments two or more of light source 110 (or the emission point
of a light guide coupled to a light source 110), polarizer 118 and
wave plate 112 may reside in a single housing. Similarly, in other
embodiments, analyzer 114 and detector 116 (or a probe coupled to a
detector 116 through a light guide) may reside in a single
housing.
[0033] In one embodiment, analyzer 114 and detector 116 (or a probe
coupled to a detector 116 through a light guide) are coupled to one
or more adjustment mechanisms 124 in communication with processor
102 for adjusting the position of the analyzer 114 and detector 116
(or a probe coupled to a detector 116 through a light guide). In
another embodiment, polarizer 118 and analyzer 114 are coupled to
one or more adjustment mechanisms 124 in communication with
processor 104 for adjusting the position of the polarizer 118 and
analyzer 114. In another embodiment, polarizer 118, analyzer 114,
and detector 116 are coupled to one or more adjustment mechanisms
124 in communication with processor 102 for adjusting the position
of the polarizer 118 and analyzer 114. The one or more adjustment
mechanisms 124 may use electric motors, linear actuators, sliding
tracks, gimbal mechanisms, or any other components known to one
having ordinary skill in the art.
Substrates and Coatings/Films
[0034] The present disclosure contemplates using the disclosed
systems and methods to measure the thickness of a wide variety of
coatings/films 122 on a wide variety of substrates 120.
Contemplated substrates comprise all manner of metals (e.g.
aluminum, copper, nickel, titanium, steel, tin plate and other
metals employed as components of or in the fabrication of products
or processing of materials), a variety of films (e.g. thin
stretched films, thin coatings on PET film substrates, Polyethylene
Film Substrates, etc.), glass, plastics, rubber, latex, silicon
(e.g. circuit boards, wafers), and solar cells. Contemplated
coatings comprise all manner of lubricants, waxes, liquids (e.g.
water), silicone, thin films, UV coatings, nanometric coatings,
adhesives, cold and hot end glass container spray coatings, printed
electronics, anti-reflective (AR) coatings, CdTe coatings, and CdS
coatings. The present disclosure contemplates all methods for
applying such coatings to such substrates known to one of ordinary
skill in the art. For example, some coatings may be sprayed onto a
substrate. Other coatings may be rolled onto the substrate.
Operation of an Illustrative System
[0035] FIG. 2 shows a flow diagram illustrating the operation of a
system according to one embodiment of the present disclosure. In
particular, FIG. 2 shows steps performed by a system to perform
inline real-time measurement of thin film thickness on a moving
substrate. To aid in understanding how each of the steps may be
performed, the following description is provided in the context of
the illustrative diagrams of embodiments of the system shown in
FIGS. 1A and 1B. However, embodiments according to the present
disclosure may be implemented in alternative embodiments.
[0036] Beginning at step 202, light waves are generated and
directed toward a coated substrate 120. For example, the processor
102 communicates with the light source 110 to generate light waves
within a one or more particular spectrum ranges to be directed at a
coated substrate 120. In one embodiment, a user interface provided
by the processor 102 and displayed on display 106 permits a system
operator to identify the substrate and/or coating material and the
processor 102 then determines the appropriate light waves to select
based on materials information stored in memory 104. In another
embodiment, the processor 102 is programmed to take into account
the traits of the substrate and/or coating materials specified by a
system operator to select the appropriate region of the wavelength
spectrum for analysis. In still another embodiment, the user
interface permits a system operator to manually configure the
wavelength range for analysis to be used for the measurement
process.
[0037] At step 203, the light waves provided by the light source
110 are linearly polarized by passing through a polarizer 118. In
addition, the linearly polarized light waves are converted to
circularly polarized light waves by passing through wave plate 112.
In one embodiment, wave plate 112 is a rotating quarter-wave plate.
In one such embodiment, the processor 102 communicates with the
wave plate 112 to configure the speed of the rotation of the
rotating wave plate 112.
[0038] At step 204, elliptically polarized light waves reflected by
the film/coating 122 and/or the substrate 120 are analyzed by an
analyzer 114. In one embodiment, the analyzer 114 is a rotating
analyzer. In one such embodiment, the processor 102 communicates
with the analyzer 114 to configure the speed of the rotation of the
rotating analyzer 114.
[0039] At step 206, the detector 116 captures light waves reflected
by the by the coated substrate 120 and then further reflected from
various angular positions by analyzer 114.
[0040] At step 208, the detector 116 operates to convert the
captured light waves into light wave data for communication to
processor 102. In one embodiment, light wave data may be a voltage
signal waveform that corresponds to the captured light wave. In
another embodiment, light wave data comprises a data structure
containing information that describes the captured light waves.
Once the light wave data is generated, it is communicated to the
processor 102.
[0041] At step 210, the light wave data is processed by processor
102 to determine the thickness of the film/coating 122 on the
surface of substrate 120. In one embodiment, processor 102
quantifies the phase shift and polarization state changes, compared
to the light waves provided by the light source 110, and then uses
that information to evaluate and validate thickness of the
coating/film 122 on the substrate 120 using techniques disclosed
herein. In other embodiments, the processor 102 may process the
light wave data to determine other optical parameters of the
film/coating 122 such as refractive index, surface roughness, and
extinction coefficient.
[0042] At decision point 212, it is determined whether the light
wave data was valid. In one embodiment, the system determines
whether there are vibrations, fluttering, or other disturbances in
the movement of a moving substrate 120 that require adjustment of
system components to obtain accurate measurements. If present,
disturbances such as vibrations and flutter may impact the plane of
incidence and the reflection of the light waves. In another
embodiment, the system determines whether the light source 110 is
providing too little or too much light. In one embodiment,
disturbances and/or light level defects are identified based on the
light wave data detected by detector 116 during the performance of
previous iterations of the presently-described method. In some
embodiments, the quality of the light wave data is validated using
one or more techniques disclosed herein.
[0043] If the light wave data is validated, indicating that there
are no vibrations, fluttering, or other disturbances in the
movement of substrate 120 and no light level defects that require
adjustment then the method proceeds to step 202 to perform another
iteration of the method. However, if the validation process
determines that the data is not valid, the measurement based on the
light wave is discarded and the method proceeds to step 214.
[0044] At step 214, adjustments are made to compensate for detected
disturbances and/or light level defects. In one embodiment, the
orientation and/or position of the optics such as analyzer 114 and
polarizer 118 are adjusted in real-time to accommodate for any
changes in the plane of incidence. In another embodiment, the
orientation and/or position of the analyzer 114 and detector 116
are adjusted in real-time to accommodate for any changes in the
plane of incidence. In another embodiment, the orientation and/or
position of polarizer 118, analyzer 114, and/or detector 116 are
adjusted in real-time to accommodate for any changes in the plane
of incidence. In one embodiment, processor 102 communicates
commands to one or more adjustment mechanisms 124 to cause
adjustment of the polarizer 118, analyzer 114, and/or the detector
116 based on the detected vibrations, fluttering, or other
disturbances in the movement of substrate 120. In another
embodiment, the processor 102 communicates with light source 110 to
adjust the intensity of the light.
General
[0045] The foregoing description of some embodiments of the
disclosure has been presented only for the purpose of illustration
and description and is not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Numerous
modifications and adaptations thereof will be apparent to those
skilled in the art without departing from the spirit and scope of
the invention.
[0046] Reference herein to "one embodiment" or "an embodiment"
means that a particular feature, structure, operation, or other
characteristic described in connection with the embodiment may be
included in at least one implementation of the invention. The
invention is not restricted to the particular embodiments described
as such. The appearance of the phrase "in one embodiment" or "in an
embodiment" in various places in the specification does not
necessarily refer to the same embodiment. Any particular feature,
structure, operation, or other characteristic described in this
specification in relation to "one embodiment" may be combined with
other features, structures, operations, or other characteristics
described in respect of any other embodiment.
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