System and method for wet inspection of molding defects in eyeglass lenses

Abstract

To detect a defect in a cosmetic ophthalmic lens immersed in a saline solution.SOLUTION: A system comprises: a) a camera for obtaining an image of a cosmetic ophthalmic lens; b) an illumination module designed with a visible LED and an infrared LED, and installed along a vertical optical axis for directing light at different angles of the cosmetic ophthalmic lens; c) a glass cuvette designed with concave, concentric and spherical surfaces to avoid adding more optical power to the cosmetic ophthalmic lens under inspection, and allowing installation of the cosmetic ophthalmic lens to the center of the cuvette during inspection; d) a strobe controller integrated with the camera that can capture a number of images under different lighting conditions; and (e) image processing means for determining if the cosmetic ophthalmic lens is acceptable or rejected.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a system and method for inspecting spectacle lenses stationary in physiological saline within a cuvette or lens holder. More particularly, the present invention relates to a system and method for detecting molding defects of contact lenses placed within a concave cuvette made of glass material and stationary in physiological saline.

Background Art

[0002] "Contact lenses or spectacle lenses" refer to flexible lenses that can be placed on or inside the wearer's eye. Contact lenses can correct, improve, or alter a user's vision, but are not limited to doing so. Contact lenses can also have a cosmetic appearance based on the type of color and design printed on the front side of the lens or the other side called the convex side. Cosmetic appearances can be applied in many forms. One commonly used method is to print the above designs on soft lenses, hard lenses, or hybrid lenses using appropriate approved materials. Contact lenses can be in a dry or wet state. "Dry state" refers to the state of a soft lens before hydration or the state of a hard lens under storage or use conditions. "Wet state" refers to a soft lens in a hydrated state. The front or anterior surface of a contact lens refers to the surface of the lens that faces away from the eye when worn, and the anterior surface, which is typically substantially convex, is sometimes also called the anterior curve of the lens. The posterior or posterior surface of a contact lens refers to the surface of the lens that contacts the surface of the eye. Typically substantially concave, the posterior surface is sometimes also called the base surface of the lens. Colored contact lenses refer to contact lenses (hard or soft) that have a color image printed on the anterior surface, or contact lenses that have a light color. Printed colored lenses may consist of cosmetic patterns, such as pupil-like patterns, made-to-order (MTO) patterns, etc. Cosmetic contact lenses can be produced by printing a high-quality color image directly onto the anterior surface of the contact lens, either layer by layer or in a single step. First, the contact lens may be clear before printing, or it may be lightly colored before printing. It is important to note that any cosmetic appearance of a contact lens is applied around the IRIS. The central area, called the IRIS, is usually clear and transparent.Printing techniques are beyond the scope of this invention and will not be discussed.

[0003] Eyeglass lenses or contact lenses are produced by injection molding, a process for forming contact lenses in a concave cavity between the front (outer) and rear (inner) mold portions of a contact lens assembly. Monomer is added to the rear mold and then capped using the front mold, forming the curved shape of the lens according to the profile of the concave cavity. Polymerization is then initiated by ultraviolet light, after which the lens is hydrated. Lens molds are manufactured with a high degree of precision because any imperfection would affect the quality of the final product. There are many other process-related parameters that can affect the quality of contact lenses. In addition to water droplets, scratches, and aberrations, there are other fatal defects where air bubbles are trapped inside the lens. All of these defects can be very difficult to detect, especially in cosmetic contact lenses after the pattern has been printed. Such products result in lenses that are medically unsuitable for use in the eye due to the possibility of infection and other related problems.

[0004] In the manufacturing process of eyeglass lenses, it is common knowledge that mass production of lenses includes a molding process that not only increases productivity but also ensures process efficiency and quality. However, due to the nature of the manufacturing process, defects can occur during the lens molding, cutting, and separation processes. Eyeglass lenses, especially daily-use soft contact lenses, are intended for use on the human eye not only to correct vision but also for cosmetic reasons, using attractive patterns printed on the lenses. The printed patterns can also camouflage fatal defects embedded in the lenses, thus making automated quality inspection far more difficult and requiring the implementation of special lighting, optical mechanisms, and intelligent algorithms. Because eyeglass lenses are manufactured in large quantities, manual inspection, or even sampling inspection, is not an option for manufacturers.

[0005] Prior art addresses some of these concerns by implementing inspection systems at the final packaging stage, which can sometimes be too late to prevent the production of numerous defective products. The significant losses resulting from late-stage defect inspection lead manufacturers to demand that inspection systems be incorporated immediately after the molding process in which molding defects occur, so that appropriate measures can be taken to resolve the problem and minimize the production of defective lenses.

[0006] In one other prior art, images acquired at different rotation angles of a contact lens are compared to detect problems within a stationary lens in a cuvette filled with saline solution. Traits or features that move according to the angle of lens rotation are identified as defective and therefore sorted out. Because this method involves mechanically or otherwise rotating the lens, while effective, it is time-consuming and complex, making it unsuitable for inline inspection systems.

[0007] Several other prior art defect inspection methods exist for lenses. However, these inspection methods utilize numerous LED lighting modules to capture bright-field and dark-field images, and these lighting modules are not optimized for detecting molding defects. Such inspection systems are limited in their ability to detect molding defects (defects) within the body of eyeglass lenses while they are stationary in saline solution. In addition, these inspection systems result in complex setup procedures and complex configuration processes during product changeovers, which reduces the flexibility and scalability of the inspection system.

[0008] Another commonly used inspection method is to use a microscope to manually check the lenses. However, this type of equipment is unsuitable for mass production. Random sampling is another option used by some manufacturers, but the high risk of defective products reaching customers makes this option unreliable.

[0009] In a typical contact lens inspection process, the process is usually performed further downstream in the line, at the final stage of manufacturing where the lenses have printed patterns and are hydrated with saline solution. Inspection at this stage of the process also involves considering light absorption as well as refractive index when analyzing the images, resulting in increased complexity. More importantly, if molding defects are detected at the final stage of the process, delayed flagging also results in significant material loss for the manufacturer.

[0010] A major challenge in inspecting eyeglass lenses is that the inspection is performed after lens hydration at the end of the molding process. If the inspection were performed immediately after the molding process, all problems or defects detected could be quickly analyzed and resolved, reducing the amount of defective eyeglass lenses produced. Therefore, there is a need for an accurate, repeatable, and consistent apparatus for detecting molding defects in cosmetic eyeglass lenses, and such an apparatus can be easily integrated into existing automated manufacturing lines. This is the objective of the present invention. [Overview of the project] [Means for solving the problem]

[0011] The present invention provides a system and method for automated inspection of cosmetic contact lenses after the molding process in a lens manufacturing system. The system includes the use of dark-field imaging, which utilizes an infrared LED illumination module to highlight defects in spectacle lenses that are stationary in a cuvette filled with saline solution.

[0012] The object of the present invention is to provide a system comprising a black and white high-resolution camera, a customized optical module, a glass cuvette designed to precisely position the contact lens when stationary in saline solution, an infrared LED lighting module for illuminating the contact lens, and an image processing computer capable of capturing high-resolution images and processing high-resolution images of defects within the cosmetic contact lens. Essentially, different refractive indices affect the angle of refraction at the same wavelength, while different wavelengths also affect the angle of refraction at the same index. When a contact lens is illuminated using visible LED lighting, due to the narrow field of view of the imaging lens, it is possible that not all of the refracted light passes through the lens, resulting in some defects not being highlighted. Longer wavelength infrared LED lighting has a lower refractive index in saline solution and lower light absorption in the contact lens material compared to illumination using visible LED lighting. Therefore, infrared LED lighting can pass through patterned contact lenses and refract light at a lower angle at defects within the lens, resulting in enhanced defect detection and consistent inspection accuracy and repeatability.

[0013] A further object of the present invention is to provide apparatus and methods for utilizing long-wavelength (980 mm) infrared illumination, which improves image acquisition of eyeglass lenses, particularly regarding molding defects and many other types of defects, affecting uniform properties in both the optical zone and the pattern zone.

[0014] A further object of the present invention is to provide a device integrated with an infrared LED lighting module designed to be electronically controlled to emit light at a selected intensity and with a programmed pulse width at a pre-selected segment of the LED.

[0015] A further object of the present invention is to provide an integrated device with an IR LED lighting module that can generate a configuration during setup that includes recipe files for different devices and parameters such as LED intensity, trigger pulse width, trigger delay, lighting module segment selection, and in particular the position of the lighting module relative to the object under test.

[0016] A further objective of the present invention is to provide a device integrated with an IR LED lighting module for measuring the intensity of illumination in order to maintain consistent and stable light brightness on an object under inspection through current control of the intensity controller.

[0017] A further object of the present invention is to provide a device in which a customized glass cuvette profile and a mold for each lens are paired, which conform to the front profile of the lens when stationary in saline solution, in order to achieve optimally intensified illumination to highlight molding defects.

[0018] Another aspect of the present invention is to provide a device for use as an inline inspection module that can be easily integrated into an automated contact lens manufacturing system.

[0019] Other features and objectives of the present invention will become apparent from the detailed description of preferred embodiments and from the drawings included herein below.

[0020] The present invention should be understood through further explanation of the following detailed description in conjunction with the accompanying drawings. Consequently, the specificity of the accompanying drawings should not be understood as replacing the generality of prior descriptions of the invention. [Brief explanation of the drawing]

[0021] [Figure 1]FIG. 0 is a diagram of a preferred embodiment of the present invention. The apparatus 100 includes an image processing computer 90 electrically integrated with a high-resolution camera 10 and a strobe LED controller 65 connected to a lighting module 60. The camera 10 mounts an optical lens 20 to view a glasses lens 40 stationary within a glass cuvette having physiological saline 30. The LED-based lighting module 60 directs illumination toward the contact lens 40. The camera, cuvette, and illumination are properly aligned with the optical axis 25. The lighting module 60 is connected to a programmable strobe LED controller 65 to control the illumination trigger pulse width, the intensity of the LED segments, and various other parameters. FIG. 70 shows an IR LED lighting module manufacturing structure. [Figure 2] FIG. 3 is a captured image of a defective glasses lens showing a defect B1 extending from an optical zone to a pattern zone using a visible LED lighting module. [Figure 3] FIG. 6 is an enlarged image of area B1 of FIG. 2. [Figure 4] FIG. 9 is a captured image of the same defective glasses lens of FIG. 2 when using an IR LED lighting module, showing a defect B2 extending from the optical zone to the pattern zone. [Figure 5] FIG. 12 is an enlarged image of area B2 of FIG. 4. [Figure 6] FIG. 15 is a captured image of a defective glasses lens using a visible LED lighting module, showing another defect B3 extending from the optical zone to the pattern zone. [Figure 7] FIG. 18 is an enlarged image of area B3 of FIG. 6. [Figure 8] FIG. 21 is a captured image of the same defective glasses lens of FIG. 6 when using an IR LED lighting module, showing a defect B4 extending from the optical zone to the pattern zone. [Figure 9] FIG. 24 is an enlarged image of area B4 of FIG. 8. [Figure 10]An image of a defective glasses lens captured using a visible LED illumination module, showing another defect B5 extending from the optical zone to the pattern zone. [Figure 11] An enlarged image of area B5 in FIG. 10. [Figure 12] An image of the same defective glasses lens in FIG. 10 captured when using an infrared LED illumination module, showing a defect B6 extending from the optical zone to the pattern zone. [Figure 13] An enlarged image of area B6 in FIG. 12.

Mode for Carrying Out the Invention

[0022] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, which is disclosed in this specification. Generally, the terms used in this specification are well known and commonly employed in the art. Conventional methods are used for these procedures as provided in the art and various general references. When a term is given in the singular, the inventor also contemplates plural of that term.

[0023] The preferred embodiment of FIG. 1 is composed of a high-resolution camera 10 coupled to a customized optical lens 20, an illumination module 60 triggered synchronously or asynchronously with the camera shutter through a lighting control unit and composed of an infrared LED-based lighting structure 70, and a strobe system 65 that enables control of pulse width, strobe delay, illumination intensity, and LED segment selection. The glasses lens 40 under inspection is stationary within a customized glass cuvette 30 containing physiological saline.

[0024] The customized glass cuvette 30 is designed with concave, concentric, and spherical inner and outer surfaces to avoid additional light power caused by the cuvette surface. The radius of the inner surface of the cuvette is designed to be larger than the radius of the contact lens in order to position the contact lens at the center of the cuvette, coinciding with the principal optical axis 25.

[0025] In another embodiment, the IR lighting module 60 may consist of multiple visible and infrared LED segments. Depending on the selected LED segments within the lighting module, the user can achieve multiple incident angles at the contact lens to be inspected. However, infrared LED wavelengths are suitable for bypassing the large refraction angles that are typically apparent with visible LED lighting wavelengths. For inspection of contact lenses with radii less than 15 mm, the infrared illumination beam angle will be limited using an anti-reflective surface structure 70 to keep the incident light angle to the cuvette surface within 10 degrees. This angle, however, can be controlled by adjusting the distance from the lighting module 60 to the bottom of the cuvette 30. When infrared LED lighting is selected, the refractive index of saline is small compared to visible LED lighting, which substantially means that the profile of the saline surface never affects image quality. Therefore, infrared illumination is suitable for inspecting molding defects in clear, lightly colored, and printed cosmetic contact lenses.

[0026] In a further embodiment of the present invention, the lighting module 60 may be controlled to emit light synchronously or asynchronously with the camera shutter in order to reduce the power consumption required to operate the LEDs, maintain uniform brightness, and simultaneously extend the lifespan of the LEDs. This may be achieved by utilizing an electronic lighting strobe controller 65. The electronic lighting strobe controller allows software control of pulse width, the intensity of a selected LED segment, and, depending on the application, the timing delay between the camera shutter and the lighting trigger during the camera image acquisition process. The timing delay allows the selected LED segment to achieve the programmed intensity before the camera shutter is triggered for image acquisition. This feature enables consistent image uniformity between several image acquisitions, which translates to optimal repeatability and accuracy during image analysis.

[0027] Various lighting techniques using different wavelengths of LEDs can be used to help identify ambiguous or undesirable elements. For example, filters can be used to filter out undesirable wavelengths of light and allow only selected wavelengths. This improves the contrast between different types of defects. Polarized, uniform, and heterogeneous lighting conditions can be employed to help identify the desired defects.

[0028] Figure 2 shows an image of a spectacle lens captured by system 100 in Figure 1 using visible LED lighting. A likely defect is indicated within box B1. A magnified image of the defect is shown in Figure 3, where the defect appears as a white streak against a dark background. The important part remains very blurred and hidden against the printed pattern in the foreground. Depending on the inspection threshold tolerance, the defect may or may not be detected as a defect. This ambiguity can lead to unreliable inspection results that may be interpreted as a BAD lens or a GOOD lens.

[0029] Figure 4 shows an image of the same eyeglass lens from Figure 2, captured by system 100 from Figure 1, using infrared LED illumination. A likely defect is indicated within box B2. A magnified image of the defect is shown in Figure 5, where the defect is seen as a bright white streak extending along the clear zone and printed pattern foreground of the IRIS. It is clear that infrared LED illumination clearly outperforms visible LED illumination when highlighting defects in the clear and transparent zones and printed pattern zones of the eyeglass lens under two different conditions.

[0030] Figure 6 shows an image of a spectacle lens captured by system 100 in Figure 1 using visible LED illumination. A likely defect is indicated within box B3. A magnified image of the defect is shown in Figure 7, where the defect appears as a faint, parallel white line that is barely visible against the printed pattern foreground, but only along the clear zone of the IRIS. Depending on the inspection threshold tolerance, the defect may or may not be detected as a defect, and even if detected, the defect dimensions may not be precise enough to reflect accurate and consistent results. This ambiguity can lead to unreliable inspection results that may be interpreted as either a BAD lens or a GOOD lens.

[0031] Figure 8 shows an image of the same eyeglass lens from Figure 6, captured by system 100 from Figure 1 using infrared LED illumination. A likely defect is indicated within box B4. A magnified image of the defect is shown in Figure 9, where the defect is enhanced in both the clear zone and the printed pattern zone. It is again evident that infrared LED illumination clearly outperforms visible LED illumination when highlighting very faint defects, regardless of whether the defect occurs within the clear zone or the printed pattern zone of the eyeglass lens.

[0032] Figure 10 shows an image of a spectacle lens captured by system 100 in Figure 1 using visible LED lighting. The defect is indicated within box B5. A magnified image of the defect is shown in Figure 11, where the defect is not visible in the clear zone (IRIS) of the spectacle lens and is faintly visible in the printed pattern zone. The defect is never detected in the IRIS zone but may be detected in the pattern zone depending on the inspection threshold tolerance. The defect dimensions may not be precise enough to reflect accurate results. This ambiguity can again lead to unreliable inspection results.

[0033] Figure 12 shows an image of the same eyeglass lens from Figure 10, captured by system 100 from Figure 1, using infrared LED illumination. Box B6 is indicated as a likely defect. A magnified image of the defect is shown in Figure 13, where the defect is enhanced in both the clear zone and the printed pattern zone. Indeed, the defect in the clear zone is enhanced very well, leading to a more reliable inspection process. Here again, it is clearly evident that infrared LED illumination clearly outperforms visible LED illumination when highlighting very faint defects, regardless of whether the defect occurs in the clear zone or the printed pattern zone of the eyeglass lens.

[0034] The above detailed description of embodiments of the present invention is provided solely for clarity of understanding, and no unnecessary limitations should be understood or implied from the detailed description. Modifications to the present invention in various embodiments will be apparent to those skilled in the art upon reading this disclosure and may be made without departing from the scope of the invention as encompassed by the claims set forth separately. From the above viewpoint, it will be seen that some objectives of the invention are achieved and other advantages are obtained. Since many modifications can be made to the above configurations and methods without departing from the scope of the invention, all matters contained herein are intended to be interpreted as illustrative and not limiting in a sense.

Claims

1. A system for identifying defects in cosmetic eyeglass lenses immersed in physiological saline and for measuring their geometric dimensions, a) At least one camera for obtaining an image of the cosmetic eyeglass lens, the camera having an optical axis, b) At least one electronically controlled lighting module designed using visible LED and infrared LED segments, configured to direct light from the visible LED and infrared LED segments onto the cosmetic glasses lens at different angles of incidence, c) A customized glass cuvette designed with concave, concentric, and spherical surfaces to avoid applying excessive light power to the cosmetic eyeglass lens during inspection, and with an inner radius of the cuvette designed to be larger than the lens to allow the cosmetic eyeglass lens to be positioned at the center of the cuvette during inspection, d) A lighting strobe controller integrated with the lighting module, which utilizes the visible LED and infrared LED segments, and a camera capable of capturing a large number of images in succession under different lighting conditions, e) comprising image processing means for taking in, processing, and analyzing a large number of images in order to determine whether the cosmetic eyeglasses lens is acceptable or unacceptable, f) The lighting module includes a non-reflective surface structure configured to maintain the angle of incidence of the infrared LEDs within a predetermined angle relative to the surface of the cuvette, system.

2. The system according to claim 1, wherein the lighting strobe controller is designed to control the intensity of the segment, the type of lighting, the duration of the lighting, and the time delay between the lighting trigger pulse for image acquisition and the camera shutter trigger, in order to minimize power consumption.

3. The system according to claim 1, wherein the illuminated infrared LED segments within the lighting module are selected to enhance morphological defects of the cosmetic eyeglass lenses in the printed pattern area and optical zone.

4. The system according to claim 1, wherein infrared LED lighting exhibits a low refractive index when passing through saline solution, effectively removing distortion during image acquisition of cosmetic eyeglass lenses immersed in saline solution.

5. The system according to claim 2, wherein all configurations related to the lighting module setup are programmed according to parameters stored in a recipe file for a specific type of cosmetic eyeglass lens.

6. The system according to claim 1, wherein the lighting module lighting configuration selection varies for each type of defect, including water droplets, scratches, and trapped bubbles in the printed pattern area and optical zone of the cosmetic eyeglass lens.

7. The system according to claim 1, wherein the image processing means is further operable to analyze the obtained image and identify defects in the cosmetic eyeglass lens.

8. A method for inspecting cosmetic eyeglass lenses, a) The step of placing the lens in a customized glass cuvette, which is installed below the cuvette and includes a lighting module and a camera for capturing images of the lens, b) Taking an image of the lens immersed in saline solution illuminated using the visible LED segment of the illumination module, and an image of the lens illuminated using the infrared LED segment of the illumination module; c) The non-reflective surface structure of the lighting module is used to maintain the angle of incidence of the infrared LEDs on the surface of the cuvette within a predetermined angle; d) The steps of analyzing and determining whether additional images should be acquired after processing the image, modifying illumination module parameters including trigger pulse width, intensity, and segmentation, along with camera shutter acquisition delay relative to the illumination trigger, and finally determining whether to select infrared LEDs, visible LEDs, or a combination of both, based on the defects to be highlighted, e) The step of further processing the image using image processing means to identify the defect, and then classifying and sorting the lens according to the defect, f) A step of utilizing the refractive index properties of the saline solution when illuminated with infrared LED lighting to accurately identify the location and dimensions of molding defects within the printed pattern area and optical zone of the lens. Methods that include...

9. The method according to claim 8, wherein the image processing means includes a recipe file for all different types of cosmetic eyeglass lenses, for a configuration that includes intensity, type of illumination i.e., infrared LED or visible LED, position of the illumination relative to the lens cuvette, trigger pulse timing delay between the camera and the illumination, and the number of images to be captured under each illumination configuration.

10. The method according to claim 8, wherein the image processing means utilizes illumination with a longer wavelength to enhance defects, including molding defects, in the printed pattern area and the optical zone of the lens.

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