Quantitative image analysis system for evaluating coating performance

Abstract

A system (100) for quantitative analysis of a coated substrate (35), the system comprising: an imaging system (10) for acquiring one or more images of the coated substrate, where the imaging system is configured to acquire images for a plurality of channels, where each channel of the plurality of channels comprises a predetermined range of wavelengths; an illumination system (20) comprising at least one light source for illuminating the coated substrate; a holder (30) for holding the coated substrate in a position to be irradiated by the at least one light source; and an analysis unit (40) configured to transform the one or more images and quantitatively analyze the one or more transformed images to determine a defect in the coated substrate, where the coated substrate comprises a coating layer formed on a surface of the substrate.

Description

Technical Field

[0001] The present invention generally relates to quantitative image analysis systems for evaluating the properties of coated substrates. Background Art

[0002] The appearance of a coated substrate is one of the most important performance evaluation criteria used by consumers and researchers. Defects in a coated substrate can manifest themselves in many different ways, including color anomalies, surface or texture differences, or other visible deviations. For example, the smoothness or leveling of a coated substrate may manifest as surface defects caused by shading or changes in appearance. Resistance to defects caused by, for example, water, corrosion, dirt, grease, and weathering may manifest as changes in the color of the coated substrate. Other defects in a coated substrate may be more difficult to visually observe, such as migration / secretion or extraction of components within the coated substrate.

[0003] Such defects in coated substrates are typically observed or measured by humans. Due to the difficulty in assessing many defects in coated substrates, defect measurement is often difficult to quantify accurately and / or reproducibly. Most defect measurements are highly subjective and are typically measured on a simple scale, such as a numerical scale of 1 to 5, where a human observer assigns a value based on their interpretation of the coated substrate's surface. Variation in the values ​​assigned from one observer to the next is common, and defect quantification often results in rough estimates. Human observation and quantification are even more difficult for defects related to the migration / secretion or extraction of components, as these defects can be very difficult to see with the naked eye. Due to the subjective nature of the measurements, observations are typically normalized within each study. Consequently, data acquired through human observation from one study cannot be reliably combined with data from another.

[0004] Attempts have been made to automate the defect detection process. U.S. Patent Application Publication No. US2022 / 0082508 discloses a method for providing a coating composition-related prediction program, which includes providing a database of qualitative and / or quantitative characterizations of coating surfaces, and training a machine learning model to develop a composition quality prediction program for predicting the properties of the coating surface to be produced. However, the database of qualitative and / or quantitative characterizations is generated by manually identifying and labeling digital images, wherein the qualitative and / or quantitative characterizations of the images are based on a scale having values ​​assigned by human observers. Therefore, the database is compiled using data based on human observations.

[0005] There is a need for a system that can more accurately and reproducibly detect defects in coated substrates for identification and quantification of the defects. Summary of the Invention

[0006] The present invention relates to a system for quantifiable analysis of a coated substrate, the system comprising:

[0007] an imaging system for acquiring one or more images of the coated substrate, wherein the imaging system is configured to acquire images for a plurality of channels, wherein each channel of the plurality of channels includes a predetermined range of wavelengths;

[0008] an illumination system comprising at least one light source for illuminating the coated substrate;

[0009] a holder for holding the coated substrate in a position to be illuminated by the at least one light source;

[0010] an analysis unit configured to transform the one or more images and quantitatively analyze the one or more transformed images to determine defects in the coated substrate,

[0011] The coated substrate includes a coating formed on the surface of the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of a system for acquiring and analyzing images according to an embodiment of the present invention.

[0013] Figure 2 is a schematic diagram of the position of a light source relative to a coated substrate according to an embodiment of the present invention.

[0014] Figure 3 is an image from a weathering test analyzed by an image analysis system according to an embodiment of the present invention.

[0015] Figure 4 are images from an early rainfastness test analyzed by an image analysis system according to an embodiment of the present invention.

[0016] Figure 5 is an image from an adhesion test analyzed by an image analysis system according to an embodiment of the present invention.

[0017] Figure 6 is an image from an application hiding power test analyzed by an image analysis system according to an embodiment of the present invention.

[0018] Figure 7 is an image from an antifouling test analyzed by an image analysis system according to an embodiment of the present invention.

[0019] Figure 8 is an infrared image of a coated substrate used for surfactant leaching testing according to an embodiment of the present invention.

[0020] Figure 9 is a visible light image of a coated substrate used for surfactant leaching testing according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present inventors have discovered a method and system for reproducibly and accurately identifying and quantifying defects in coated substrates.

[0022] As used herein, the term "coated substrate" refers to a substrate that includes a coating on its surface, such as a paint coating on a metal or paper substrate. The coating preferably has a thickness of less than 500 μm, more preferably less than 300 μm, and even more preferably less than 200 μm, and preferably a thickness of greater than 50 nm, more preferably greater than 100 nm, and even more preferably greater than 250 nm. Multilayer coatings may have greater thicknesses. The coated substrate may also include multiple layers, including, for example, a primer or basecoat.

[0023] Preferably, the coated substrate comprises a coating selected from a polyurethane coating, an epoxy coating, an acrylic coating (including, for example, acrylic coatings, vinyl-acrylic coatings, and styrene-acrylic coatings), an alkyd coating, and a zinc-rich coating. More preferably, the coated substrate comprises a paint. The substrate may comprise metal, plastic, wood, glass, composites, fiberglass, paper, fabric, leather, or other substrates. For testing, it is preferred that the substrate have a flat or planar surface.

[0024] Defects in or on a coated substrate may be caused by a variety of problems. Examples of defects include, but are not limited to, color defects, surface or texture defects, and migration / secretion or extraction defects.

[0025] Color defects may include stains from dirt, household stains (e.g., wine, pencil, lipstick, crayon, ink, marker, etc.), adhesion defects where the coating does not adequately adhere to the substrate, hidden defects where the coating allows the underlying substrate or sublayer to show through, grease resistance which assesses the penetration of oil through the coating, early rain resistance which tests the ability of the coating to resist rain washout shortly after the coating is applied and cured, and weathering resistance which tests the coating's ability to resist efflorescence formation and efflorescence.

[0026] Texture or surface defects can be indicated by smoothness or leveling problems where the coating may have an irregular or imperfect surface. Other texture or surface problems can include, for example, cracking or flaking.

[0027] Migration / secretion and / or extraction can occur when a component separates from other components or travels through a coating. Migration / secretion and / or extraction can occur due to material contact with the coating or incompatibility of components within the coating. For example, when a coating is in contact with water, surfactant leaching can occur when water-soluble materials leach onto the surface of the coating. Other examples include the migration of adhesives or additives when affected by time, temperature, or environmental conditions. Although migration / secretion and / or extraction can result in visible defects, such defects are typically not easily visible. However, the present inventors have surprisingly discovered that infrared and / or ultraviolet spectroscopy can be used to identify and analyze migration / secretion and / or extraction defects. Substances that migrate / secrete or can be extracted can have different properties that can be observed in infrared and / or ultraviolet spectroscopy. For example, when analyzing surfactant leaching, the present inventors have discovered that the migrating component has a different thermal conductivity than the remaining components, making those defects easily identifiable in infrared spectroscopy.

[0028] For analyzing coated substrates, a system for analyzing and quantifying defects is provided. Figure 1 A schematic diagram of a system 100 for analyzing and sizing defects is shown. The system 100 comprises an imaging system 10, an illumination system 20, a holder 30 for holding a coated substrate 35, and an analyzing unit 40.

[0029] The imaging system 10 is configured to acquire one or more images of the coated substrate 35. The imaging system 10 is configured to acquire images for a plurality of channels, wherein each of the plurality of channels includes a predetermined range of wavelengths. For example, each of the channels may be comprised of wavelengths associated with a single color of light in the visible spectrum (e.g., red = 620nm to 780nm, orange = 585nm to 620nm, etc.). Alternatively, each channel may be comprised of a predetermined range of wavelengths (e.g., channel 1 = 400nm to 500nm, channel 2 = 500nm to 600nm, etc.). In yet another example, one channel may include the visible spectrum and a second channel may include the ultraviolet spectrum or the infrared spectrum. In another example, one channel may include wavelengths in the near infrared range (800nm ​​to 1000nm) and a second channel may include wavelengths longer than the infrared wavelengths (e.g., 1000nm to 1500nm). Preferably, the imaging system is configured to acquire images in at least one channel comprising wavelengths in the visible spectrum and at least one channel comprising wavelengths in the infrared spectrum, the ultraviolet spectrum, or both. More preferably, the imaging system is configured to acquire images in at least one channel comprising wavelengths in the visible spectrum and at least one channel comprising wavelengths in the infrared spectrum. In embodiments where the system is used to detect migration / secretion and / or extraction defects, the imaging system 10 is configured to acquire images in the infrared spectrum, the ultraviolet spectrum, or both.

[0030] In embodiments where the defect being analyzed is color-based, the imaging system can be configured to acquire an image in the channel most relevant to the color of the defect. For example, when analyzing a coated substrate for early rainfastness testing, the substrate may be provided with a blue primer and then painted with white paint. When exposed to water, the defect will reveal the underlying blue primer. Imaging system 10 can then be configured to acquire at least one image in a channel that includes a blue wavelength. A second channel can be used as a control.

[0031] The imaging system 10 may include, for example, a camera, a thermal imaging system, an ultraviolet imaging system, or an image sensor. The imaging system 10 may further include a filter for preferentially or selectively transmitting or blocking light of predetermined wavelengths, such as at least one channel of predetermined wavelengths. For example, when the imaging system 10 is configured to detect in the ultraviolet spectrum, a filter may be used to block the channel of visible light. Alternatively, if ultraviolet light is used to cause a particular component to fluoresce, a filter may be used to selectively transmit the fluorescent wavelengths, and the imaging system may be configured to acquire images in the channel including the fluorescent wavelengths. Similarly, when the infrared spectrum is used, a filter may be used to block visible wavelengths and allow transmission of infrared wavelengths.

[0032] The illumination system 20 includes at least one light source for illuminating the coated substrate 35. The illumination system 20 can be configured to emit radiation in the visible spectrum, infrared spectrum, ultraviolet spectrum, and combinations thereof. Preferably, the illumination system is configured to emit radiation in a wavelength associated with at least one of the multiple channels used by the imaging system 10. For example, when detecting migration and / or segregation defects, the illumination system 20 can be configured to emit radiation in the infrared spectrum and / or ultraviolet spectrum, and the imaging system can be configured to acquire images at the same wavelength. The at least one light source can include a single light source or multiple light sources. When using a single light source, the light source can include a ring light or a diffuser to provide uniform illumination of the coated substrate 35. When using multiple light sources, the light sources can be arranged to provide uniform illumination. The multiple light sources can also be controlled individually or in predetermined groups to control the illumination of the coated substrate 35. Preferably, the illumination system 20 is configured to allow adjustment of the light intensity, the angle of incidence on the coated substrate 35, or the wavelength of the emitted light. To reduce the potential effects of external lighting, system 100 may be covered or enclosed (not shown) so that only light from illumination system 20 is used to acquire the image.

[0033] The substrate holder 30 is used to hold a coated substrate 35 for imaging by the imaging system 10. The holder 30 is configured to hold the coated substrate in a position to be illuminated by the illumination system 20 when it is imaged. The holder 30 can be configured to hold a single coated substrate 35 or a plurality of coated substrates. The holder 30 can be stationary or adapted to allow for automated loading / unloading of samples.

[0034] Preferably, at least one of the imaging system 10 and the holder 30 is adjustable so that the position of the coated substrate 35 can be changed relative to the imaging system 10. For example, Figure 1 As shown, the imaging system 10 can be mounted on an arm 101 attached to a vertical support 102. The arm 101 can be configured to be adjustable so that the distance between the imaging system 10 and the holder 30 can be selected. Alternatively, the arm 101 can be movable between more than one position. In another alternative, the holder 30 can be adjustable to raise or lower the holder 30 using a base 103, or to adjust the angle of the holder relative to a fixed position.

[0035] Preferably, at least one of the lighting system 20 and the holder 30 is adjustable relative to each other so that the position of the coated substrate 35 can be changed relative to the lighting system 20. For example, the lighting system 20 can be height or angle adjustable relative to the holder 30 to change the position of the substrate 35. Figure 2 The incident angle α of the light 25 is shown. For example, the illumination system 20 can be adjustable to allow for shallower or steeper angles of incidence on the coated substrate 35. Additionally, the illumination system 20 can be adjustable to allow the illumination system 20 to be rotated about the coated substrate 35 so that the incident angle α is the same, but the light is directed onto the coated substrate 35 from a different angle, for example, from the side of the coated substrate 35 rather than the front.

[0036] The system 100 further includes an analysis unit 40 configured to transform the images acquired by the imaging system 10. The analysis unit 40 further quantitatively analyzes the transformed images to identify and / or quantify the amount or percentage of defects in or on the coating of the coated substrate 35. The analysis unit 40 may include, for example, a computer, a workstation, a laptop, a tablet computer, or a smartphone. The analysis unit 40 may include an application or program suitable for transforming and analyzing images from the imaging system 10. The information obtained and / or generated by the system 100 may be stored locally in the analysis unit 40, a server, a cloud storage device, or a media storage device.

[0037] The analysis unit 40 is preferably configured to transform the acquired image by processing the acquired image using an algorithm selected from the group consisting of image thresholding, wavelet transforms, morphological transforms, color detection, pattern detection, contrast detection, clustering, and combinations thereof. The transformed image can then be analyzed by the analysis unit 40 to identify and / or quantify defects in or on the coating of the coated substrate 35 and provide an analyzed output. Preferably, the output includes a value symbolizing the number / percentage of defects and / or an image or dataset identifying the location, size, and / or number / percentage of defects.

[0038] Preferably, analysis unit 40 includes or is connected to a display including a graphical user interface (GUI). The GUI is preferably configured to display the output of analysis unit 40. For example, the GUI may display a value quantifying the amount or percentage of defects present in coated substrate 35. Alternatively, the GUI may display a transformed image identifying the location, size, and / or number / percentage of defects.

[0039] A method for identifying and quantifying defects in a coated substrate according to the present invention includes: providing a system for acquiring and analyzing images; loading a substrate on a holder; illuminating the coated substrate with an illumination system; acquiring at least one image of the coated substrate with an imaging system; transforming the at least one image of the coated substrate with an analysis unit to provide at least one transformed image; and identifying and quantifying defects on the coated substrate based on the at least one transformed image; and providing an output.

[0040] To identify and quantify defects based on migration / secretion and / or extraction of one or more components from a coating on a coated substrate, illuminating the coated substrate with an illumination system includes illuminating the coated substrate with radiation in the infrared spectrum, the ultraviolet spectrum, or both. The image captured by the imaging system includes an infrared image and / or an ultraviolet image. Migration / secretion and / or extraction can be determined by a transformed image that displays distinct regions based on different absorbances or reflectances of the migrating / secreting or extracting components at wavelengths in the infrared spectrum and / or the ultraviolet spectrum.

[0041] Example

[0042] A 5MP camera was used as the imaging system, an 8-channel multispectral light ring was used as the illumination system, and a customizable sample holder was used to hold the coated substrate for imaging and analysis. Figure 1A similar arrangement is shown in FIG. The 8-channel multispectral light ring is configured to emit in channels consisting of ultraviolet, blue, green, yellow, red, far infrared, infrared, and white light. The camera is configured to have the ability to acquire an image in each of the channels emitted by the illumination system.

[0043] All or a subset of the acquired images are then transformed using an image analysis algorithm t. The image analysis algorithm identifies and quantifies defects in the coated surface.

[0044] Weathering Test (Prophetic Example)

[0045] To test the weathering resistance of the primer, a coated substrate was prepared by coating the substrate with the primer and topcoat. The bottom of the coated substrate was contacted with an alkaline liquid to determine whether the primer could block the penetration of the alkaline liquid.

[0046] The samples will be observed by humans and analyzed by the system of the present invention. Figure 3 A representative image to be analyzed is shown, where light-colored areas are expected to show corroded areas, i.e., areas where the coating fails to block migration of the alkaline solution, and dark-colored areas are expected to show uncorroded areas, i.e., areas where the coating is effective. Human observation is performed by estimating the areas where color change is observable. The analysis performed by the system of the present invention is expected to be quantifiable and reproducible.

[0047] Early Rain Resistance Test (Prophetic Example)

[0048] To test the water resistance of wet paint cured for 20 minutes, a substrate with a blue primer will be coated with a topcoat of white paint. The topcoat will cure for 20 minutes, after which water will be applied to the top of the coated substrate for a predetermined period of time. As the water is run over the coated substrate, portions of the white topcoat are expected to fall off, revealing the blue primer underneath. Figure 4 Images of coated substrates after similar water resistance testing are shown.

[0049] Then, the sample will be analyzed manually and analyzed by the system of the present invention. Human observation is used to estimate the amount or percentage of blue color that is displayed through the white surface layer. The sample is also analyzed by the system of the present invention, which is expected to provide reproducible and quantifiable results.

[0050] Adhesion test

[0051] A paint sample is applied to a substrate and cured. A crosshatch tool is used to mark a set of lines. Adhesion tape is applied and pulled away from the crosshatch area. The adhesion of the paint is quantified by a human tester who counts the number of grid cells where the paint remains in the crosshatch area. The system of the present invention also uses frequency space to analyze the image of the sample ( Figure 5 ) to locate the area and quantify the percentage of paint remaining.

[0052] The system of the present invention is also able to quantify the adhesion of a clearcoat based on the light distribution used.It is difficult for a human tester to observe a clearcoat accurately and reproducibly.

[0053] Application hiding power test

[0054] The paint sample was applied to a Leneta chart, i.e., a chart with a combination of black and white areas, at a natural spreading rate. After the paint dried, the painted chart was analyzed by a human tester who provided a rating of 1 to 5 based on how much of the underlying black area was visible. An image of the same sample was analyzed using the system of the present invention ( Figure 6 ), the system uses wavelet transform to locate regions and quantifies coverage by constructing a linear regression between pixel intensity and manual ratings. Compared to human observation, the analysis performed by the system of the present invention is more quantitative and reproducible.

[0055] Antifouling test

[0056] The stain repellency test is performed by first applying a selected stain to the painted substrate. Possible stain types include household stains such as pencil, wine, crayon, coffee, narrow and wide marker stains, and dirt. The sample is then washed or scrubbed with a sponge for a defined number of cycles. The color change before and after washing is then used to quantify the paint's stain repellency. Figure 7 Images of painted substrates stained with various materials including markers, pencils, and crayons are shown.

[0057] Surfactant leaching test

[0058] To test for surfactant leaching, paint was applied to a substrate and dried in a constant temperature and humidity chamber for 4 hours. While the coated substrate was placed horizontally on a workbench, three separate areas of the paint were impregnated with water. After a period of time, the coated substrate was hung vertically to allow the water to drain. The samples were allowed to dry before analyzing the coated substrate.

[0059] The coated substrate is placed on a holder in a system for analyzing the coating. A light source emitting infrared light is used to illuminate the surface of the coated substrate, and a camera is used to acquire an infrared image, such as Figure 8 As shown. We also obtained Figure 9 As shown in the visible light image. Figure 8 and Figure 9 As can be seen, no traces are visible in the visible light image, but clear traces are visible in the infrared image. The acquired infrared image is analyzed using a computer that applies a contrast detection algorithm to maximize the contrast within the image. The algorithm further calculates the total contrast in areas showing surfactant leaching and provides a value that quantifies the amount of leaching present on the surface of the coated substrate.

[0060] For comparison, the same samples were studied by human observation to estimate the amount of leaching. The amount of defects was rated on a scale of 1 to 5.

Claims

1. A system for performing quantifiable analysis on a coated substrate, the system comprising: an imaging system for acquiring one or more images of the coated substrate, wherein the imaging system is configured to acquire images for a plurality of channels, wherein each channel of the plurality of channels includes a predetermined range of wavelengths; an illumination system comprising at least one light source for illuminating the coated substrate; a holder for holding the coated substrate in a position to be illuminated by the at least one light source; an analyzing unit configured to transform the one or more images and quantitatively analyze the one or more transformed images to determine defects in the coated substrate, The coated substrate includes a coating formed on the surface of the substrate. 2 . The system of claim 1 , wherein the plurality of channels comprises channels in at least two spectrums selected from the group consisting of visible spectrum, infrared spectrum, and ultraviolet spectrum. 3 . The system of claim 2 , wherein the imaging system is configured to acquire at least one visible light image in a channel in the visible light spectrum and at least one infrared image in a channel in the infrared spectrum.

4. The system of claim 3, wherein the analyzing unit is configured to transform the at least one visible light image and the at least one infrared image, and the analyzing unit is further configured to compare defects in the at least one visible light image and the at least one infrared image to quantitatively analyze the defects in the coated substrate. 5 . The system of claim 4 , wherein comparing defects in the at least one visible light image and the at least one infrared image comprises identifying a maximum amount of defects detected in the at least one visible light image and the at least one infrared image.

6. A system according to any of the preceding claims, wherein at least one of the imaging system and the holder is adjustable to change at least one parameter, the at least one parameter being selected from the group consisting of an angle between the imaging system and the holder, a distance between the imaging system and the holder, and a relative position between the imaging system and the holder.

7. A system according to any of the preceding claims, wherein at least one of the lighting system and the holder is adjustable to change at least one parameter, the at least one parameter being selected from the group consisting of an angle between the lighting system and the holder, a distance between the lighting system and the holder, and a relative position between the lighting system and the holder.

8. The system of any preceding claim, wherein the at least one light source comprises a plurality of light sources.

9. The system of any one of claims 1 to 7, wherein the at least one light source comprises a ring light or a diffuse light source.

10. The system of any one of the preceding claims, wherein the at least one light source emits light in at least one spectrum selected from the visible spectrum, the infrared spectrum, the ultraviolet spectrum, and combinations thereof.

11. The system of any of the preceding claims, wherein the imaging system further comprises at least one filter, wherein the at least one filter preferentially transmits light of wavelengths in one of the plurality of channels or preferentially blocks light of wavelengths in one of the plurality of channels.

12. The system of any of the preceding claims, wherein transforming the one or more images comprises applying at least one transform selected from image thresholding, wavelet transforms, morphological transforms, color detection, pattern detection, clustering, and combinations thereof.

13. The system according to any of the preceding claims, further comprising a graphical user interface (GUI) for displaying one or more transformed images and for displaying the quantification of the defects in the coated substrate. 14 . The system of claim 13 , wherein the GUI is configured to select one or more channels of the plurality of channels for acquiring the one or more images, and to select a type of defect to be analyzed by the analysis unit.

15. The system of any preceding claim, wherein the coating comprises paint.

Images