MXPA99004327A - Optic inspection of transparent containers using two cameras and a single source of - Google Patents

Abstract

The present invention relates to an apparatus for inspecting a container (14) for variations that affect the commercial acceptance of the container, which includes a light source (16) to direct diffused polarized light energy through a container in both that the container is rotated around its axis. A first chamber (24) is arranged to receive the diffused polarized light energy transmitted from the light source through a portion of the container, such that the first chamber receives an image of the portion of the container in which the variations opaque appear dark against an otherwise bright background. A second chamber (28) receives the light energy transmitted from the light source through substantially the same portion of the container and includes a polarizer (32) in transverse orientation or crossed to the polarizer in the light source. The second chamber receives a bright picture of variations in effort in the container that alter the polarization of the diffused polarized light energy passing through the container, against an otherwise dark background. An image processor (41) is coupled to both of the cameras to scan the associated images of the portion of the vessel displayed by the cameras to detect and distinguish between variations in the vessel as a function of a pixel in pixel comparison between the two image

Description

OPTICAL INSPECTION OF TRANSPARENT CONTAINERS USING TWO CMARTS AND A SINGLE SOURCE OF LIGHT Description of the invention The present invention is concerned with the inspection of transparent containers in terms of commercial variations that affect the optical properties of the containers and more particularly with a method and apparatus for inspecting vessels for variations in opacity and effort in the vessel in a single inspection station when using a single light source.

BACKGROUND AND OBJECTS OF THE INVENTION In the manufacture of transparent containers such as bottles and glass cylinders, various types of anomalies may occur in the side walls, heels, bottoms, shoulders and / or necks of the containers. These anomalies, termed "commercial variations" in the art, can affect the commercial acceptance of the containers. It has been proposed so far to employ electro-optical inspection techniques to detect commercial variations that affect the optical properties of the containers. The basic principle is that a light source is positioned to direct the light energy over the container and a camera is positioned to receive an image of the portion of the container illuminated by the light source. The REF .: 30271 light source can be of uniform intensity or can be configured to have an intensity that varies through a dimension of the light source. Commercial variations in the portion of the container illuminated by the light source are detected as a function of the intensity of the light in the image of the illuminated container received and stored in the chamber. U.S. Patent Nos. 4,378,493, 4,378,494, 4,378,495, and 4,601,395, all of which are assigned to the assignee of the present application, describe inspection techniques in which glass containers are transported through a series of positions or stations where they are inspected physically and optically. In an optical inspection station, a glass container is maintained in vertical orientation and rotated about its central axis. A light source directs the diffused light energy through the side wall of the container. A chamber including a plurality of light-sensitive elements oriented in a linear array parallel to the vertical axis of the vessel is positioned to receive the transmitted light through a vertical strip or strip of the sidewall of the vessel. The output of each element in the linear array is sampled in increments of vessel rotation and event signals are generated when the magnitude of the adjacent signals differ by more than a preselected threshold. An appropriate rejection signal is produced and the container is ejected from the conveyor line. A problem is encountered in the manufacture of glass containers from recycled glass in which materials having different thermal expansion characteristics can be mixed in a single container. For example, it has been found that clear cooking utensils, which have very low thermal expansion characteristics, can be mixed with the glass for recycling. Any unmelted particles from cooking utensils that appear in the container create stress points in the cooling that can fracture or become sites for later failures. Other dehomogenities that can occur in the glass and cause variations in stress include stones or fragments of refractory material of the home or glass nozzle. Thus, it is necessary to provide a method and system to detect variations in effort and opaque effort in the containers. However, space is limited in existing inspection systems and the various inspection stations in the systems in place can not easily accommodate additional inspection devices. The use of cross polarizers has been proposed so far to detect strain variations in the side walls of the containers. The light energy directed through the crossed polarizers and through a container positioned between the crossed polarizers normally have a dark field in the printing chamber in the absence of stress variations in the side walls of the container. Nevertheless, a variation of stress alters the polarization of the light energy passing through the vessel sufficiently to present a bright spot in the camera against the otherwise dark background, indicating the variation of effort. See U.S. Patent No. 4,026,656, assigned to the assignee herein, which discusses such technology as a background to the invention and which proposes to employ infrared light energy and infrared polarization filters to reduce the background effects of ambient light. It is a general object of the present invention to provide a method and apparatus for inspecting transparent glassware, particularly glassware, in terms of commercial variations that affect the optical characteristics of the containers. A more specific object of the present invention is to provide a method and apparatus of the character described which are particularly suitable for detecting variations in stress and opacity variations (stress and non-strain) in the container. Another object of the present invention is to provide a method and apparatus of the described character for the detection of variations of effort and opaque effort in containers in a single inspection station, by using a single light source. A further object of the present invention is to provide a method and apparatus of the described character that are economical to implement and reliable in a long operating life. Still another object of the present invention is to provide a method and apparatus of the described character that are adapted to be implemented in a single inspection station of an existing vessel inspection system.

BRIEF DESCRIPTION OF THE INVENTION The apparatus for inspecting a container for variations that affect the commercial acceptance of the container according to a currently preferred embodiment of the invention, includes a light source for directing the diffused polarized light energy through a container, while the container is rotated about its axis. A first chamber is arranged to receive the diffused polarized light energy transmitted from the light source through a portion of the container, such that the first chamber receives an image of the portion of the container in which the opaque variations appear dark. against a otherwise bright background. A second chamber receives the light energy transmitted from the light source through substantially the same portion of the container and includes a polarizer in cross orientation or transverse to the polarizer in the light source. The second chamber receives a bright picture of the variations of stress in the container, which alter the polarization of the diffused polarized light energy passing through the container against an otherwise dark background. An image processor is coupled to both of the cameras to receive associated images of the container portion displayed by the camera to detect and distinguish between variations in the container. Each of the first and second cameras includes a CCD detector (charge coupled device) of linear array oriented in a coplanar direction with each other and with the axis of the container. The information processor sweeps or scans the linear array detectors in the cameras at increments of rotation of the vessel to develop respective two-dimensional unwrapped images of the inspected portion of the vessel. The variations are detected and discriminated in response to a comparison of these two-dimensional images, by simultaneous display of the two-dimensional images for analysis by the operator and / or by an automatic electronic comparison of the individual pixel signals in the images. The first chamber in the preferred embodiment of the invention is diametrically opposite to the light source through the container, while the second chamber is disposed below the first chamber to view the container at an upward angle. The field of view of the second chamber includes the container bead, in which the variations in stress affecting the polarization of the light energy can be particularly serious due to the impact forces normally applied to the bead portion of the vessel during the use. The light source in a preferred embodiment of the invention comprises a fluorescent source having high emission in the visible range, preferably in the color temperature range (temperature at which a black body emits light of the same color as that of a given font, used to specify the color of a light source) of about 3,000 ° to 5000 ° K. Thus, the invention can be easily implemented in a single station of an existing inspection system by placing the light source within the travel arch of the containers through the inspection system and positioning the cameras on a bracket or bracket of assembly of the system on top of each other to the outside of such travel arch.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with objects, features and additional advantages thereof, will be better understood from the following description, the appended claims and the accompanying drawings in which: Figure 1 is a schematic electro-optical diagram which illustrates an apparatus for detecting strain variations and opaques in containers according to a currently preferred embodiment of the invention; Figure 2 is a top plan view of the apparatus illustrated in Figure 1; and Figures 3A and 3B illustrate two-dimensional images of the container obtained by using the apparatus of Figures 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS "Figures 1 and 2 illustrate an apparatus 10 for inspecting a container 14 in accordance with a currently preferred embodiment of the invention." A light source 16 comprises one or more vertically oriented fluorescent lamps 18 which cooperate with each other. a diffuser 20 for forming a wide area diffuse light source The light energy is directed from the diffuser 20 through a first polarizing lens 22 to a container 14. A first chamber 24 is diametrically opposite to the transverse light source 16 to the container 14 and contains a linear array CCD detector (charge coupled device) 26 on which an opposite narrow strip of the transilluminated container 14 is focused by the light source 16. A second chamber 28 is positioned below the chamber 24 and contains a linear array CCD detector 30, on which the opposite narrow strip of the container 14 transilluminated by the light source 16 and s focused through a second polarizing lens 32. Thus, the chamber 28 displays the container 14 at a slight upward angle, which includes the heel of the container 14. The polarizing lenses 22, 32 are cross-polarized with each other. The linear array detectors 26, 30 are coplanar to each other and coplanar with the axis of the container 14. The linear dimensions of the arrays 26, 30 are coplanar to each other and to the axis of the container 14. The linear dimension of the array 26 is parallel to the axis of the container and the linear dimension, of the arrangement 30 is at a slight angle to the axis of the container .. Such an argon will depend on the curvature of the bead and preferably is about 6 °. Preferably, both chambers 24, 28 visualize a narrow strip or strip of the container from the heel to the finished one. It is currently preferred that the light source 16 includes one or more fluorescent lamps 18 to generate light in the visible portion of the light spectrum, in contrast to the typical incandescent light sources of the prior art. Polarizing lenses for white light are usually much less expensive than polarizers for infrared or near-infrared light generated by incandescent light sources. The bulb or bulb 18 in the preferred embodiment of the invention comprises one or more bulbs of high light emission in the visible light range. There is an exchange between the response characteristics of the detectors 26, 30, which are normally more sensitive in the infrared range and the expense associated with the polarizing lenses 22, 32 which are less expensive in the visible range. A color temperature range of the light source of about 3000 ° to 5000 ° K, is currently preferred, a color temperature of 3000 ° K is particularly preferred. A conveyor 34, which typically includes a star wheel (not shown) and a slide plate 36, is arranged and connected to a container source to move the successive containers through an arcuate path 38 (FIG. 2) and by bringing the successive containers in their position in the apparatus 10, which is arranged in a station of a star wheel conveyor container inspection system. The conveyor 34 and the overall inspection system can be of any suitable type, such as those shown in U.S. Patent Nos. 4,230,319, and 4,378,493, the descriptions of which are incorporated herein for purposes of background. The chambers 24, 28 are mounted in an adjustable manner one above the other on a bracket or camera mounting bracket 37 that extends outwardly from the conveyor 34. Successive containers are held in a fixed position between the light source 16. and the chambers 24, 28 and are rotated by an actuator roller 39 or the like around the central axis of the container. An encoder 40 is coupled to the rotation mechanism of the container to provide signals indicative of the increments of container rotation. Such increments may comprise either fixed angular rotation increments or fixed rotation increments in time at constant speed. An information processor 41 is coupled to the encoder 40 and the camera 24, 28 to scan the detectors 26, 30 in increments of rotation of the container and develop corresponding two-dimensional electronic images of the container 14. These two-dimensional images are formed in one dimension by the signals of the successive elements of the linear array detectors and in the second dimension by the increments of the container rotation. In operation, the successive containers 14 are brought into position by the conveyor 34 between the light source 16 and the chambers 24, 28. Then, the container is held in a fixed position and rotated about its central axis. The diffused and polarized light energy of the light source 16 is directed through the container 14 on the array 26 of the chamber 24 which thus forms a bright background image. Any opaque variations in the vessel will block or absorb the transmission of light energy from the light source 16 to the camera array 26, such that such opaque variations form dark images against an otherwise bright background. (The term "opaque" variations encompasses not only variations that block or absorb light energy, but also refractive variations that are of such size to effectively refract the light energy transmitted through them, from chamber 24 and the reflective variations that reflect the light energy of the camera, in other words, a variation that blocks or absorbs the light energy in the vessel, a variation that refracts the light energy of the camera and a variation that reflects the energy of the camera. camera light, will appear in arrangement 26 of camera 24 as a dark image against an otherwise bright background). At the same time, the polarized diffused light energy of the light source 16 is' transmitted through the container 14 to the polarizer 32 in front of the chamber 28. The crossed or transverse orientations of the polarizing lenses 22, 32 normally create an array 30. from camera 28 a dark background or field. However, any variations in the container 14, such as variations in stress in the side wall of the container, which alter the polarization of the light energy transmitted through it will appear in the arrangement 30 of the camera 28 as a bright image against an otherwise dark field or background. Figures 3A and 3B illustrate two-dimensional unwrapped images of a container 14 scanned by the information processor 41 of the cameras 24, 28, respectively during one revolution of the container. For example, a non-stressing stone is indicated by a dark image 50 in Figure 3A and a non-corresponding image in the same position x-y in Figure 3B. A stress producing stone is indicated by a dark image 52a in Figure 3A and a corresponding dark image 52b in Figure 3B surrounded by a bright image 52c of the stress area surrounding the stone. The images 50, 52a indicate the dimensions of the stones. A bright image 54 in Figure 3B, coupled with the absence of an image in the corresponding site of Figure 3A may indicate a variation in stress produced by the inclusion of a piece or particle of transparent cookware having similar transparency characteristics but thermal characteristics different from those of the surrounding glass in the side wall of the container. The elongated bright image 56 in FIG. 3B against a otherwise dark background may indicate devitrification in the side wall of the container. The variations that produce stress in the container can be indicative of areas of weakness in the container that could be prone to failure as a result of impact during normal handling of the container or as a result of thermal stress when the container is filled or handled. The bead portion of the container - that is, the portion of the container that joins the side wall of the container to the bottom of the container - is particularly sensitive to the inclusion of variations in stress because the bead portion of the container is subjected to stress and impact during normal use. A) Yes, a particularly important advantage of the apparatus of the invention as illustrated in Figure 1, lies in the fact that the chamber 28 visualizes the container 14 at a slight upward angle that includes the entire heel portion of the container. The information processor 41 is coupled to a screen 44 for simultaneously displaying to an operator the two-dimensional unwrapped images (Figures 3A and 3B) generated from the camera 24, 28. The operator can analyze the information thus displayed and implement appropriate corrections in the cycle of manufacture. Alternatively or simultaneously, the information processor 41 can automatically electronically compare the two-dimensional images by appropriate pixel comparison techniques to implement the automatic correction of the manufacturing process (see, for example, U.S. Patent No. 4,762,544) and / or activating a mechanism 42 for ejecting or removing an unsatisfactory container from the transport line. It is also advantageous not to recycle the containers that have stones, since the stones can be presented again in the new containers formed from the recycled glass. The information provided by the present invention can be used to give more accurate indications of rejected containers that should not be recycled. The provision of two developed two-dimensional images for analysis, with images that are obtained by different optical techniques sensitive to different types of variations, provide an improved opportunity for the classification of variations - for example, size, shape and effort or no effort . The image processor can easily classify the type of variation, such as stress stone, effortless stone, viscous knot, bladder or blister, tape tear, impurity, etc. Thus, in accordance with the present invention, a method and apparatus for inspecting glassware such as containers for commercial variations affecting the optical characteristics of the containers, in particular variations in effort and opaque variations in the containers, has been provided. The method and apparatus of the invention can be implemented by employing a relatively inexpensive polarizing material sensitive to light energy in the visible region. The techniques of the invention can be easily employed in relation to clear (flint) and colored (e.g., amber) glass. The method and apparatus of the invention can be implemented in a single station in a vessel inspection system, by employing a single source of light and can be easily updated in existing star wheel type inspection systems and other systems. of inspection of containers. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (15)

1. Claims Having described the invention as above, the content of the following claims is claimed as property: 1. An apparatus for inspecting a container for variations affecting the commercial acceptance of the container, comprising: means or elements for rotating a container; vessel around its axis, a light source including a diffuser and a polarizer, for directing the energy of diffused polarized light through a container in the means or elements of rotation, a first chamber arranged with respect to the rotating elements for receiving the diffused polarized light energy transmitted from the light source through a portion of the container, such that the first chamber receives an image of the portion of the container in which the opaque variations appear dark against a background otherwise bright, a second chamber arranged with respect to the rotating or rotating elements to re citing the light energy transmitted from the light source through substantially a portion of the container and including a second polarizer in transverse or cross orientation to the first polarizer, such that the second chamber receives a bright image of the stress variations in the portion of the vessel that alters the polarization of the diffused polarized light energy passing through it against an otherwise dark background, and an image processor coupled to the first and second chambers to receive associated images of the portion of container, including means or elements for detecting and discriminating between variations in the container, characterized in that the first and second cameras receive images of the same portion of the container as it is illuminated by the light source and because the image processor detects and discriminates between variations in the container as a function of a comparison between the first and second images. The apparatus according to claim 1, characterized in that the detection and discrimination elements comprise means or elements for automatically comparing the pixel images in pixel. 3. The apparatus in accordance with the claim 1 or 2, characterized in that each of the first and second chambers includes a coupled charge device (CCD) detector of linear array oriented in a direction coplanar with each other and with the axis of the container in the rotating elements or elements of rotation. 4. The apparatus according to claim 3, characterized in that the information processor includes means or elements for scanning the linear array detectors in the cameras at increments of rotation of the container to develop respective two-dimensional images of the container portion and wherein the means or elements to detect and discriminate between variations are sensitive to a comparison of two-dimensional images. The apparatus according to claim 4, characterized in that the means or elements of detection and discrimination comprise a screen for the operator in which an operator can view the two-dimensional images simultaneously. The apparatus according to any of the preceding claims, characterized in that the first chamber is diametrically opposite to the light source transverse to the container and in which the linear array detector is parallel to the axis of the container and wherein the second chamber it is arranged under the first • chamber to visualize the container at an angle upwards. The apparatus according to claim 6, characterized in that the portion of the container visualized by the second chamber includes the heel of the container. The apparatus according to claim 7, characterized in that both of the chambers display substantially all of the container from the heel to the finished one. 9. The apparatus according to claim 7 or 8, characterized in that the means or elements for rotating the container comprise a conveyor for indexing or adjusting a series of containers through an arc, the light source is arranged in the arc and the chambers are arranged outside the arc and to retain to each container in turn in a stationary position between the light source and the chambers and to rotate the container around its axis. The apparatus according to any of the preceding claims, characterized in that the light source comprises a fluorescent light source. 11. The apparatus in accordance with the claim 10, characterized in that the fluorescent light source has a color temperature in the range of about 3000 ° K to about 5000 ° K 12. A method for inspecting a vessel for variations affecting the commercial acceptance of the container, characterized in that it comprises the steps of: (a) directing the light energy of a light source through a container to first and second chambers simultaneously, (b) receiving in the first chamber an image of a portion of the container, in which opaque variations appear dark against a bright background, (c) receiving in the second chamber an image of the same portion of the container, in which the variations of effort appear bright against an otherwise dark background, and (d) detect opaque variations and effort in the vessel as a function of a comparison between the images in the first and second chambers. The method according to claim 12, characterized in that the comparison in step (d) is carried out from pixel to pixel between the images. The method according to claim 13, characterized in that it comprises the additional step of: (e) rotating the container about its axis and wherein step (d) includes the step of scanning the cameras at rotational increments of the container. 15. The method according to any of the preceding claims, characterized in that the steps (a) and (c) include the step of positioning crossed polarizers in the light source and the second chamber.