阅读说明：本技术 用于储罐监测和校准的智能涂层装置 (Intelligent coating device for storage tank monitoring and calibration ) 是由 E.博韦罗 A.奥塔 I.M.阿尔-泰 于 2018-07-03 设计创作，主要内容包括：一种能够校准结构的装置和系统包括至少一个细长带,其具有比该结构低的温度系数,以及足以包围该结构的外表面的圆周的长度,以及至少一个衍射光栅,其具有至少与该结构一样高的温度系数,其中所述衍射光栅联接到所述带并且与所述结构的外表面直接接触。结构的外表面中的变形在衍射光栅中引起相应的变形。(An apparatus and system capable of aligning a structure includes at least one elongate band having a lower temperature coefficient than the structure and a length sufficient to encompass a circumference of an outer surface of the structure, and at least one diffraction grating having a temperature coefficient at least as high as the structure, wherein the diffraction grating is coupled to the band and in direct contact with the outer surface of the structure. Deformations in the outer surface of the structure cause corresponding deformations in the diffraction grating.)

1. An apparatus capable of calibrating a structure, comprising:

at least one elongate band having a lower temperature coefficient than the structure and a length sufficient to encompass a circumference of an outer surface of the structure; and

at least one diffraction grating having a temperature coefficient at least as high as the structure, wherein the diffraction grating is coupled to the band and in direct contact with an outer surface of the structure,

wherein a deformation in the outer surface of the structure causes a corresponding deformation in the diffraction grating.

2. The apparatus of claim 1, wherein the at least one elongate band comprises a first band positioned at a first height on an outer surface of the structure and a second band positioned at a second height on the outer surface of the structure.

3. The apparatus of claim 1, wherein one or more of the at least one elongate strip comprises a plurality of segments, each segment of the plurality of segments comprising a diffraction grating.

4. The apparatus of claim 1, wherein the at least one diffraction grating is two-dimensional and includes periodic features aligned in a vertical direction.

5. The device of claim 1, wherein the at least one elongate strip is comprised of a fiberglass material.

6. A system capable of calibrating a structure, comprising:

an indicator device in contact with an outer surface of the structure, the indicator device comprising:

at least one elongate band having a lower temperature coefficient than the structure and a length sufficient to encompass a circumference of an outer surface of the structure; and

at least one diffraction grating having a temperature coefficient at least as high as the structure, wherein the diffraction grating is coupled to the band and in direct contact with an outer surface of the structure,

wherein a deformation in the outer surface of the structure causes a corresponding deformation in the diffraction grating; and

an inspection device for determining dimensional changes of the structure by interrogating the at least one diffraction grating of the indicator device.

7. The system of claim 6, wherein the inspection device comprises:

a radiation source for illuminating a portion of the structure;

a radiation sensor for receiving radiation diffracted from photonic material in the portion of the structure; and

a processor coupled to the sensor and configured to determine a deformation of the at least one diffraction grating according to at least one of: i) intensity, ii) location and iii) wavelength of the received radiation.

8. The system of claim 7, wherein the at least one elongate band of the indicator device comprises a first band positioned at a first height on an outer surface of the structure and a second band positioned at a second height on the outer surface of the structure.

9. The system of claim 8, wherein the radiation source emits monochromatic radiation and the deformation of the at least one diffraction grating is determined from an intensity of radiation received at the radiation sensor.

10. The system of claim 8, wherein the radiation source emits polychromatic radiation and the deformation of the at least one diffraction grating is determined according to the wavelength of the received radiation.

11. The system of claim 10, wherein the polychromatic radiation is in the visible spectrum and the radiation sensor comprises a camera having a plurality of pixel elements with different positions.

12. The system of claim 7, wherein one or more of the at least one elongate band of the indicator device comprises a plurality of segments, each segment of the plurality of segments comprising a diffraction grating.

13. The system of claim 7, wherein the at least one diffraction grating of the indicator device is two-dimensional and includes periodic features aligned in a vertical direction.

14. The system of claim 7, wherein the at least one elongate band of the indicator device is comprised of a fiberglass material.

15. The system of claim 7, wherein the radiation source emits monochromatic radiation and the deformation of the at least one diffraction grating is determined from the intensity of radiation received at the radiation sensor.

16. The system of claim 7, wherein the radiation source emits polychromatic radiation and the deformation of the at least one diffraction grating is determined according to the wavelength of the received radiation.

17. The system of claim 16, wherein the polychromatic wavelength is in the visible spectrum and the radiation sensor comprises a camera having a plurality of pixel elements with different positions.

Technical Field

The present invention relates to monitoring structural changes, including deformations, of a structure, and in particular to devices that can be positioned on a surface of a structure that can be used to monitor such structural changes.

Background

Pipe and vessel structures used in the oil and gas industry are subject to stresses over time that can build up to create defects in the structure. Unfortunately, it is often difficult to determine whether such structures are subjected to destructive stress until an easily observable defect occurs.

The availability of non-destructive inspection techniques for structural materials such as non-metallic pipes used in pipelines is limited. In most cases, the techniques available to date are either destructive to the material or experimental and unreliable. Even considering current experimental techniques for non-destructive inspection, none of the prior art techniques reliably predicts the formation of defects and is therefore typically only used to detect existing defects.

More specifically, existing building materials and corresponding systems and techniques for inspecting materials are insufficient to detect the presence of stresses, such as tensile or compressive stresses, on or in the material with sufficient accuracy and precision so that defects can be predicted in advance. Currently available techniques for sensing material defects are typically based on single-fiber bragg gratings. These fibers provide one-dimensional information: that is, they can only detect stresses that occur along the length of the fiber, and only detect significant stresses corresponding to materials that have been damaged, with significant cracks and breaks in the structural material.

There is a need for a method for accurately detecting disturbances in large structures in more than one dimension. There is also a need for a method that can be performed quickly and without damage.

With respect to these and other considerations, the disclosure herein is set forth.

Disclosure of Invention

According to the present invention, an embodiment of an apparatus for calibrating a structure is provided. An embodiment of the apparatus includes at least one elongate band having a lower temperature coefficient than the structure and a length sufficient to encompass a circumference of an outer surface of the structure, and at least one diffraction grating having a temperature coefficient at least as high as the structure, wherein the diffraction grating is coupled to the band and in direct contact with the outer surface of the structure. Deformation of the outer surface of the structure causes a corresponding deformation in the diffraction grating.

In some embodiments, the at least one elongate strip comprises a first strip positioned at a first height on the outer surface of the structure and a second strip positioned at a second height on the outer surface of the structure. In some embodiments, one or more of the at least one elongate strip comprises a plurality of segments, each of the plurality of segments comprising a diffraction grating. The at least one diffraction grating may be two-dimensional and may include periodic features aligned in a vertical direction. The at least one elongate strip may also be constructed of fiberglass material.

In other embodiments, a system for performing structural calibration is also provided. The system includes an indicator device in contact with an outer surface of the structure. The indicator device includes: at least one elongate band having a lower temperature coefficient than the structure and a length sufficient to encompass a circumference of an outer surface of the structure, and at least one diffraction grating having a temperature coefficient at least as high as the structure, wherein the diffraction grating is coupled to the band and in direct contact with the outer surface of the structure, wherein a deformation in the outer surface of the structure causes a corresponding deformation in the diffraction grating. The system further comprises an inspection device for determining dimensional changes of the structure by interrogating at least one diffraction grating of the indicator device.

An embodiment of the inspection apparatus comprises a radiation source for illuminating a portion of a structure, a radiation sensor for receiving radiation diffracted from photonic material in the portion of the structure, and a processor coupled to the sensor and configured to determine a deformation of the at least one diffraction grating from at least one of the following of the received radiation: i) intensity, ii) location and iii) wavelength. In some embodiments, the radiation source emits monochromatic radiation, and the deformation of the at least one diffraction grating is determined from the intensity of the radiation received at the radiation sensor. In other embodiments, the radiation source emits polychromatic radiation and the deformation of the at least one diffraction grating is determined in dependence on the wavelength of the received radiation. In still other embodiments, two or more radiation sources may be used, including monochromatic and polychromatic radiation sources. In some embodiments using a polychromatic radiation source, the polychromatic radiation is in the visible spectrum and the radiation sensor comprises a camera having a plurality of pixel elements with different positions.

In some embodiments, the at least one elongate strip of the indicator device comprises a first strip positioned at a first height on the outer surface of the structure and a second strip positioned at a second height on the outer surface of the structure. In some embodiments, one or more of the at least one elongate strip of the indicator device comprises a plurality of segments, each of the plurality of segments comprising a diffraction grating. At least one diffraction grating of the indicator device is two-dimensional and comprises periodic features aligned in a vertical direction. Additionally, the at least one elongate strip of the indicator device may be constructed from a fibreglass material.

These and other aspects, features and advantages may be understood from the following description of certain embodiments of the invention and the accompanying drawings and claims.

Drawings

FIG. 1A is a schematic front plan view of an embodiment of an apparatus, shown secured to an exemplary structure, for structural calibration according to the present invention.

FIG. 1B is a schematic front plan view of another embodiment of an apparatus for structural calibration according to the present invention.

FIG. 2 is a schematic front plan view of another embodiment of an apparatus for structural calibration according to the present invention.

Fig. 3A is a schematic front view of an exemplary pattern of a two-dimensional diffraction grating used in an embodiment of an apparatus for structural calibration according to the present invention.

Fig. 3B is a schematic illustration of a diffraction pattern that may be produced by the two-dimensional grating pattern shown in fig. 3A.

Fig. 4 is a schematic block diagram of components of an inspection apparatus according to an embodiment of the present invention.

Fig. 5 is a perspective view illustrating an angular pattern of inspection according to an embodiment of the present invention.

Fig. 6 is a perspective view illustrating an inspected wavelength pattern according to an embodiment of the present invention.

FIG. 7 is a flow diagram of a method of inspecting a structure containing photonic material in accordance with an embodiment of the present invention.

Fig. 8 is a schematic illustration showing an inspection wavelength pattern according to an embodiment of the present invention.

Detailed Description

In one or more embodiments, an apparatus for performing structural calibration is disclosed. For purposes of this application, "calibrating" a structure refers to determining the precise dimensions of the structure, including the precise size of any and all dimensions (i.e., width, length, height) of the structure, as well as any variations in such dimensions, including the location of such variations.

An embodiment of the device includes an elongate strip coupled to at least one diffraction grating. The band is designed to be long enough to encompass the perimeter of the structure; more specifically, if the structure has a variable circumference, the band is designed to surround the circumference of the outer surface of the structure. In some embodiments, the band is tightly wrapped around the structure and secured at a particular height. In other embodiments, multiple straps may be used, and may be secured at different heights on the structure. In addition, a single band may be constructed of multiple segments connected to one another. The material of the ribbon is selected to have a relatively low temperature coefficient (preferably lower than that of the structure being monitored), while the diffraction grating is typically patterned onto a photonic material selected to have a high temperature coefficient (preferably higher than that of the structure being monitored).

When securing the band device to the structure, the band and the diffraction grating coupled to the band are subjected to the same changes, and expand or contract accordingly, to an equal, lesser or greater extent depending on their temperature expansion coefficients, due to the expansion or contraction of the structure due to temperature changes or due to other reasons. The material of the diffraction grating is chosen to have a high index such that it adequately records the deformation of the underlying structure. The diffraction grating may then provide the functionality of a "smart material" because the deformation of the diffraction grating may be determined at very precise limits using diffraction techniques. Since the temperature coefficient of expansion of the grating is at least as high as the underlying structure, the extent of any deformation of the grating sets an upper limit on the extent of deformation of the underlying structure. Furthermore, different effects of temperature on the grating and underlying structure can be compensated for to accurately determine the degree of deformation of the structure. Similarly, when the surface of the structure is deformed for other reasons (e.g., internal pressure), the deformation is transferred to the ribbon and grating which are in direct contact with the surface of the structure.

The inspection device may be used to "interrogate" one or more diffraction gratings located at various locations on the structure being monitored by means of one or more fixation straps. The inspection apparatus includes: a radiation source for emitting radiation onto the one or more diffraction gratings; and a radiation sensor, such as a camera, adapted to receive radiation diffracted by the one or more diffraction gratings. Depending on the inspection mode applied, the magnitude of any deformation or displacement in the one or more gratings may be determined. The respective magnitude of the deformation of the structure is directly determined by the deformation of the one or more gratings.

Fig. 1A illustrates an embodiment of an apparatus 100 for calibrating a structure, which is shown disposed on an outer surface of a structure 105 at a particular height (h 1). The device 100 includes a band 102 and a diffraction grating 104 coupled to the band 102. The grating 104 may be glued to the band or mechanically bonded by pins, clips, stitching, or any other technique that securely couples the grating to the band 102. As will be described in more detail below, the diffraction grating may be interrogated using an inspection device (not shown in fig. 1A) to determine whether it has been displaced or deformed. The band 102 of the device 100 may be secured to the structure 105 in a number of different ways. For example, the band 102 may be attached to the structure 105 using an adhesive, an additional coupling element (which in turn is coupled to a structure such as a ledge, bracket, or fastening member), or by any convenient, non-destructive, and low-cost technique known to those of ordinary skill in the art. The band 102 may be made of a material having a lower temperature coefficient of expansion than the structure being monitoredThe latter are usually made of various types of steel. In some embodiments, a composition having a molecular weight of 4.0 to 8.0X 10 may be used^-6Glass fibers having a temperature coefficient of expansion in the range of m/m K, although other materials having similar suitable properties may also be used. The diffraction grating 104 may be formed of a material having a large temperature coefficient of expansion (e.g.,>50x10^-6m/m K) in which a grating may be embedded, such as but not limited to Polyethylene (PE), polypropylene (PP), or Polydimethylsiloxane (PDMS).

Fig. 1B shows another embodiment in which two devices 120, 130 comprising similar strips and diffraction grating elements are arranged at different heights on the structure 105. By securing the first device 120 at a first height (h1) and the second device 130 at a second height (h2), these devices can capture possible differences in structural variations at different heights on the structure. For example, there may be differences in temperature-induced expansion at different heights of the structure due to differences in exposure to sunlight. The embodiment of FIG. 1B may help monitor this difference.

Fig. 2 shows another embodiment of an apparatus 200 capable of aligning a structure including a plurality of diffraction gratings, e.g., 202, 204, 206, and a plurality of band segments 212 and 214. As shown, the grating 202 is coupled to a first end of the ribbon section 212. The grating 204 is coupled to a second end of the band segment 212 and is also coupled to a first end of the band segment 214. The grating 206 is coupled to a second end of the ribbon 214. Although the apparatus 200 includes three diffraction gratings of similar size coupled by two strips of similar size, the apparatus may include a greater number of gratings and strip segments, and the strip segments and gratings may have different sizes. Embodiments such as depicted in fig. 2 enable the gratings to be positioned at different circumferential locations on the outer surface of the structure to capture variations in deformation that may occur at the different locations.

In the embodiment of fig. 2, the diffraction grating is schematically shown as a series of engraved lines, which shows a one-dimensional diffraction grating. However, two-dimensional and three-dimensional gratings may also be used. Figure 3A shows an exemplary pattern of a two-dimensional diffraction grating 300 that may be used in the apparatus of the present invention. The diffraction grating includes rows and columns of periodic features. For example, a first row includes a series of periodic features, e.g., 302a, 302b, while a third row includes another series of periodic features, e.g., 306a, 306 b. Fig. 3B illustrates an exemplary two-dimensional diffraction pattern that may be produced using diffraction grating 300. A change in the displacement in the vertical direction will change the distance of the diffraction point in the vertical direction, while a displacement in the horizontal direction will change the distance of the diffraction point in the horizontal direction. Thus, a greater range of surface deformations along the structure surface can be captured using a two-dimensional grating.

The inspection device may be operated in different inspection modes, such as an angle mode and a wavelength mode. Inspection methods and modes are discussed in commonly assigned and co-pending U.S. patent application No. 15/594,116, entitled "apparatus and method for smart material analysis". As discussed in the' 116 application, in the angular mode, diffracted radiation is received at the radiation sensor and the distortion is determined from the change in intensity at the location where the diffracted beam strikes the sensor, or more specifically, at the location on the sensor. The change in intensity of the pass-through location is used to determine the displacement distance. In the wavelength mode, the wavelength, rather than the intensity, of light received at one or more particular locations on the light sensor is used to quantify the displacement. By selecting the detection wavelength and the corresponding period of the photonic material, the sensitivity of the detection can be adjusted. In one or more embodiments, multiple inspection modes may be combined to help determine the deformation of the structure 102 with embedded photonic material 103, as will be understood from the discussion below.

Fig. 4 shows an exemplary embodiment of an inspection apparatus 400 according to the present invention for inspecting a structure 402 with embedded photonic material 403. The photonic material 403 may (preferably) comprise a diffraction grating, but may also comprise other structures exhibiting a periodic variation of an optical property, such as refractive index. The apparatus 400 includes a housing 405, the housing 105 containing a plurality of components for inspecting the structure, which can be positioned and moved as a unit along the length of the structure 402. For this purpose, the housing 405 may be connected to a vehicle, such as a robot or drone, or the housing may include a drive mechanism and wheels for automated movement. The housing 405 includes openings 407 for the radiation source and the detector.

Disposed within housing 405 are radiation sources 410, 415 positioned to direct radiation toward a portion of structure 402. Although two radiation sources are depicted, a single source may be used in some embodiments, and in alternative embodiments, more than two sources may be used. In an exemplary embodiment, radiation source 410 is a laser source (e.g., a collimated beam having, for example, a single wavelength), and radiation source 415 is a diffuse radiation source that emits multiple different wavelengths. The diffuse radiation source 415 can take a variety of forms and can emit radiation over a broad or narrow range of wavelengths in and/or outside the visible spectrum. For example, the diffuse radiation source may be implemented using white LEDs, flash lamps, X-ray emitters or natural ambient radiation. One or more lenses, e.g., 420, may be configured to focus radiation emitted by the diffuse radiation source 410 onto the structure 402 for inspection.

Radiation received at the photonic material 403 is diffracted and reflected back to the opening 407 of the inspection apparatus. In some embodiments, the apparatus 100 includes a reflector 425 (as shown) positioned to receive radiation diffracted from the photonic material 403. The reflector 425 and one or more focusing components 428 are oriented to direct and focus incident radiation into the radiation sensor 430. The radiation sensor 430 may be implemented in a variety of ways including a digital camera, an infrared detector, a Charge Coupled Device (CCD) photomultiplier tube, photographic film, and the like. In embodiments where the sensor constitutes a single element, the amplitude or intensity of the sensor output signal is used to determine the displacement. For sensors comprising an array of elements, such as a CCD array, the response of a particular array element (i.e. position) provides information from which displacement can be determined. In the illustrated embodiment, the radiation sensors are coupled to the local processor 440 and transmit the captured sensor data to the local processor 440. In an alternative embodiment, the processor is remotely located and the device includes a wireless communication module (as shown in fig. 2) for transmitting the sensor data to the remote processor.

The inspection apparatus 400 may be arranged with various computer hardware and software components for enabling operation of the inspection device and, more particularly, performing operations related to analysis of information captured by the radiation sensor 430. Fig. 5 is a block diagram depicting exemplary computer hardware and software components of inspection device 400 including processor 440 and circuit board 150. As shown in fig. 2, the circuit board may include a memory 455, a communication interface 460, and a computer-readable storage medium 465 accessible by the processor 140. The processor 440 and/or circuit board 450 may also be coupled to a display 470 for visually outputting information to an operator (user), a user interface 475 for receiving operator inputs, and a voice output 480 for providing voice feedback, as understood by those skilled in the art. As an example, device 400 may emit a visual signal from display 470 or a sound from sound output 480 when a defect or deformation above a particular threshold is encountered. The threshold may be set manually or by default prior to measurement via a user interface 475, which may be a touch screen or suitable keyboard. While the various components are depicted as being separate from circuit board 450 or as part of circuit board 450, it will be appreciated that the components may be arranged in various configurations without departing from the disclosure herein.

Processor 440 is operative to execute software instructions that may be loaded into memory. Processor 440 may be implemented using multiple processors, multiple processor cores, or some other type of processor, as well as distributed processors, which for purposes of this disclosure are collectively referred to as a "processor". The memory 455 is accessible by the processor 440 to enable the processor to receive and execute instructions stored on the memory and/or storage. The memory 455 may be implemented using, for example, Random Access Memory (RAM) or any other suitable volatile or non-volatile computer-readable storage medium. Additionally, the memory 455 may be fixed or removable. Storage medium 465 may also take various forms, depending on the particular implementation. For example, storage medium 465 may contain one or more components or devices, such as a hard disk drive, a flash memory, a rewritable optical disk, a rewritable magnetic tape, or some combination of the above. Storage medium 465 may also be fixed or removable or remote, such as a cloud-based data storage system. The circuit board 450 may also include or be coupled to a power source (not shown) for powering the inspection device.

One or more software modules 485 are encoded in memory 455 and/or storage medium 465. The software modules may include one or more software programs or applications having computer program code or a set of instructions that are executed in the processor 440. Such computer program code or instructions for performing operations and implementing aspects of the systems and methods disclosed herein may be written in any combination of one or more programming languages. When software modules 485 are stored locally on processor 440, the processor may interact with a remote-based computing platform via a local or wide area network, preferably wirelessly, to perform calculations or analysis via communication interface 460.

During execution of software module 485, processor 440 is configured to perform various operations related to analysis of the radiation captured by sensor 430 for detecting and quantifying disturbances in the inspected material as a function of the diffraction pattern, as will be described in more detail below. The program code of software module 485 and one or more non-transitory computer-readable storage devices (such as memory 455 and/or storage 465) form a computer program product that may be manufactured and/or distributed in accordance with the present disclosure, as known to one of ordinary skill in the art. Additionally, information and/or data relating to the configuration and operation of the present devices and methods may also be stored in association with the software modules. Such information may include prescribed settings and parameters, such as expected diffraction patterns, relating to the device and the various materials and photonic materials that may be inspected. Similarly, the inspection apparatus-specific operating parameters and various operating modes (e.g., relative sizes of equipment components, deformation thresholds, radiation intensities) may also be stored.

According to some embodiments of the invention, the software module 485 includes sub-modules for operating the inspection device and analyzing the data in the angular mode 486, the wavelength mode 487, and the three-dimensional mode 488. Fig. 6 is a schematic perspective view showing an angle inspection mode. As shown in fig. 6, an embodiment of the inspection apparatus 400 begins inspection as directed by the angular mode sub-module 486 by first irradiating a portion of the substrate 402 with a radiation source 410, the radiation source 410 preferably being a laser (monochromatic) source. The use of a monochromatic light source allows the wavelength to be a fixed parameter in the analysis. In fig. 6, a radiation source 410 emits an activation beam 502 onto a photonic grating of the structure 402. An incident beam 502 is reflected by a single beam 504 and is also diffracted by the grating along several beam paths 506, 508, 510, 512 in different orders. Beams 506 and 508 are at 1 and-1 orders, respectively, and beams 510 and 512 are at 2 and-2 orders. The relationship between the characteristics of the grating and the diffraction parameters is as follows:

d(sinα-sinβ)＝nλ (1)

where d is the distance between the grooves in the grating, α is the angle of incidence of the beam 502, β is the angle of diffraction of a beam 512, which is detected at the sensor 430, n is the diffraction order, and λ is the wavelength of the radiation in this way, given a constant wavelength (λ), order (n), and activation beam angle (α), any change in grating spacing (d) will depend only on the angle of diffraction detected (β).

The beam 512 having the order n-2 is received by the radiation sensor 430. parameter α is the angle at which the beam 502 is directed with respect to the vertical axis and is therefore known from the configuration and position of the radiation source 410. parameter β can be calculated by considering the distance e between the radiation source 410 and the radiation sensor 430, which can also be known from the configuration of these components in the device 400 and the distance s between the device 100 and the surface of the structure.

Thus, given the wavelength (λ) of the laser, the only unknown in grating equation (1) is the spacing (d) between features. Quantification of this distance provides relative and absolute information about the deformation of the material. This distance is relative and also absolute with respect to the surrounding values, since the values provided are a direct measure of the state of the material in a particular point and not a ratio.

As the spacing between features changes, the value of s in equation (2) also changes in a corresponding manner. The recorded value of s depends on the type of radiation sensor used. In some embodiments where the radiation sensor is a single element, such as an intensity meter, the change in s is captured as a decrease in signal intensity (where the sensor position is calibrated for maximum intensity of zero deformation). The single element sensor does not indicate whether the change in displacement is an extended compression. More preferably, the radiation sensor comprises a plurality of sensitive elements, such as a CCD array. By determining the strength change of a plurality of individual elements, the multi-element sensor can indicate the direction of change (expansion or compression) as well as the magnitude of deformation.

For example, considering a grating with a pitch of 800nm, λ ═ 500nm inspection radiation in angular mode, the angle of incidence α is 45 °, 10nm deformation will change the diffraction angle from 4.7 ° to 5.15 °.

The apparatus 100 may also include a proximity sensor (not shown) to automatically determine the distance e between the radiation source and the surface of the structure.

As described above, in addition to the angular mode, the deformation in the photonic material may also be determined by operating the inspection apparatus in the wavelength mode. In the wavelength mode, the wavelength of diffracted light is a signal for quantifying displacement. In this mode, light having multiple wavelengths (e.g., a polychromatic radiation source such as white light) is directed onto the sample and also diffracted according to grating equation (1). Fig. 7 is a schematic perspective view showing a wavelength inspection mode. Another embodiment of an inspection apparatus 700 is shown in fig. 7. The inspection apparatus comprises a polychromatic light source 710 and a radiation sensor 730, or IR camera, capable of sensing different wavelengths, e.g. visible light, in the relevant part of the spectrum. Radiation sensor 730 may be an array of individual sensing elements capable of detecting multiple wavelengths simultaneously. As noted above, multiple modes of operation may be combined in certain embodiments, with the determination of distortion as an average of the results returned from each method, as a weighted average, or multiple modes of operation may compare the results for verification of the results, or the results of a particular mode of operation may be selected based on prevailing conditions (e.g., humidity at the time of measurement).

Fig. 8 shows a general schematic of wavelength modes. A polychromatic radiation source 710 or white light source (shown on the left in the figure) illuminates a certain extension of the response band. The band scatters the diffracted radiation in all possible directions; however, the directions converge to a limited area where the radiation sensor 730 is placed. The radiation sensor 730 may simply be a camera sensor. From the perspective of the camera sensor 730, the diffraction bands appear as different colors at different locations, since each diffraction point on the diffraction band responsible for sending radiation to the sensor satisfies a different diffraction condition. By taking into account the measured geometry, the level of stretching of the diffraction zone along the entire length of the zone can be determined. This arrangement may also reveal relative differences in the diffraction bands. For relative difference measurements, the exact geometry of the system does not have to be considered, since it is possible to reveal irregular diffraction variations over regular angular variations of the diffraction pattern.

Another advantage of the arrangement schematically shown in fig. 7 is the simplicity of the detection system, which can be extended from the light source to the detection point with very simple elements, such as a continuous radiation source (e.g. a white lamp) and a camera sensor. The size of the detection system is determined by the distance between the two elements. The distance does not necessarily need to be equal to or larger than the size of the diffraction band, since specific diffraction conditions can be chosen, wherein the incident radiation and the diffracted radiation occur at very close angles, and in some cases the incident radiation and the diffracted radiation may even converge.

Turning to FIG. 7, a quilt of a structured surfaceThe illuminated area is covered at an angle α₁And α₂The width of this range is determined by the size of the radiation sensor 730 and/or the aperture in the device 700 leading to the sensor in any case, this range is rather narrow due to the typical geometry of gratings that are commonly manufactured, this narrowing is used for the advantage of detection, as a single wavelength can be associated with each pixel or point in the resulting image generated at the radiation sensor 730, the image collected by the sensor is defined by the field of view of the sensor itself, which is defined by the dashed lines 722 and 724 in fig. 7, this field of view is also defined by the diffraction angle β₁＝β₂More specifically, all radiation collected by the sensor 430 results from the same displacement d, α from different wavelengths from different angles, as shown in fig. 7₁,β₁To α₂,β₂And (4) arriving.

Thus, photonic materials with uniform pitch (i.e., no deformation due to tensile or compressive stress) diffract different wavelengths at different angles, and the diffraction angle and detection position in the sensor image vary uniformly with wavelength. The shift will result in a local variation of the diffraction wavelength for a particular angle or a non-uniform variation of the wavelength over the illuminated area. Therefore, in order to quantify this displacement, it is important to consider several parameters: of the most important are the relative position of the illumination spot with respect to the examination apparatus, and the color (wavelength) detected by the radiation sensor 730.

For example, the angles α, β of diffraction corresponding to a generic point may be represented as a function of the coordinates of the pixel corresponding to a particular point in the collected image.

In equation (3), tga is the tangent of α, y is the size of the image on the surface of the material, and P_yIs the position of the analysis point measured from the end of the image corresponding to pixel coordinate 0. P_yCan be derived from the pixel p_yThe size of the image on the pixel P and the actual size of the image in length Y are calculated as:

by substituting P_yEquation (3) becomes:

similarly, the angle β may be expressed as:

combining equations (5) and (6) into grating equation (1), we obtain grating equation (7) for the wavelength mode:

equation (7) is written in a convenient form because it is generally easy to measure the actual size of the image at a distance from the device. However, equation (7) may also be expressed by considering the angle (γ) of image acquisition. First, the distance (y) can be expressed as:

y＝2e·tgγ (8)

in conjunction with equation (8), equation (7) becomes:

equations (7) and (9) provide the exact value of d, which is used to quantify any displacement in the material. Since all parameters are known from the measurement setup and the architecture of the device, the only measurement variable is λ.

The two modes described so far are applicable to a grating with a planar periodicity or any other two-dimensional structure form of the technology. However, the analysis can also be extended to three-dimensional periodic structures. For three-dimensional photonic materials, both angle and wavelength mode analysis are governed by different mechanisms. In three-dimensional photonic crystals, periodic structures are associated with periodic modulation of the dielectric constant. Photonic materials have regions of allowed band and forbidden band for wavelengths in a similar manner to the way semiconductors cross electronic band structures. An approximation of the forbidden band wavelength can be expressed as a combination of a modified version of bragg diffraction law and Snell's law of refraction as follows:

in equation (10), S is a shrinkage factor that accounts for the final shrinkage of the lattice structure during formation, is a parameter of the photonic crystal responsible for the particular forbidden band under consideration, m is the order of diffraction, h, k, and l are miller indices, Φ is the volume fraction of one of the materials making up the lattice, and n₁、n₂Is the refractive index of both materials. If the photonic material is deformed, the parameter a will change. As a result, by monitoring the change in the wavelength of the forbidden band, the deformation of the material can be monitored. In general, changes in the viewing angle in a three-dimensional periodic structure do not affect changes in wavelength as do two-dimensional photonic materials. Typically, there are a range of angles and the wavelength of the forbidden band will be constant. However, once the angle changes by a certain magnitude, another lattice plane and lattice constant act and change the forbidden band.

Measurements can be easily made with the apparatus as described above. The measurement may be performed in a reflective mode (i.e. by receiving a reflected beam from the photonic crystal) or in a transmissive mode. In the reflection mode, the wavelength measured by the radiation sensor will correspond to the wavelength of the forbidden band. In the transmission mode, the measured wavelength will be complementary to the forbidden band. The angle of the incident radiation does not affect the measurement. One useful form of equation (10) for monitoring deformation of three-dimensional photonic materials is:

in other embodiments, the forbidden wavelength can be determined using the absorption spectrum of the structure. For absorption spectroscopy measurements, the measured value of the peak of the band will correspond to the wavelength of the forbidden band rather than the complementary wavelength.

In some embodiments of the method of the present invention in which the camera is implemented as a radiation sensor, the wavelength measurement may be determined using a tone scale of the camera. The hue (H) of the camera pixel can be used as an approximation of the wavelength. For example, in some cameras, the hue may be modeled as 360 radians from red, through yellow, etc., and back to red. As the wavelength in the visible range decreases, the hue increases. Thus, by matching wavelengths in the visible range from about 650nm to 430nm taking into account a limited range of hues, an empirical correspondence can be written as follows:

λ＝650-1.16H (12)

the quantification of the wavelength by the hue (H) is not necessarily precise, but there is a functional ratio between the wavelength and the hue. Therefore, equation (12) has strong empirical characteristics and may require calibration. This level of accuracy of the tone scale is sufficient for applications where local variations of the deformation are more important than the absolute value.

Illustrative embodiments and arrangements of the present system and method provide a system and computer implemented method, computer system and computer program product for inspecting intelligent structures that includes an apparatus capable of calibration in accordance with the present invention. The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments and arrangements. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

It is to be understood that any structural and functional details disclosed herein are not to be interpreted as limiting the system and method, but are instead provided as representative embodiments and/or arrangements teaching one skilled in the art one or more ways to implement the method.

It should be further understood that throughout the several drawings, like numerals indicate like elements throughout the several views, and that not all of the components and/or steps described and illustrated with reference to the figures are required for all embodiments or arrangements

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The directional terminology used herein is used for purposes of convention and reference only and is not to be construed as limiting. However, it should be recognized that these terms may be used with reference to a viewer. No limitation is therefore implied or inferred.

Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.