Abstract:
The present invention relates to an automated inspection apparatus for detection of anomalies in a 3D translucent object, the apparatus having a scanhead assembly including an image processing unit and image capture device, a first and a second light source, and conveyor means, the improvement comprising a light block member positioned along a substantially common axis of the image capture device and a light source.

Description:
FIELD OF INVENTION 
     The invention relates to an automated inspection apparatus and method for use in the optical inspection of 3-dimensional (3D) translucent objects such as fish, to simultaneously identify surface, embedded and semi-transparent edge anomalies and distinguishing features. 
     BACKGROUND ART 
     Translucent objects, such as fish, often contain defects or conditions which lead to or cause contamination of the object. It is necessary to eliminate these, contaminated areas or objects and, as such, a reliable method for detecting these features or anomalies has been the subject matter of certain prior art. 
     Reliable detection of optical characteristics of a translucent object poses difficulties due to illumination, which is used during inspection, being either adsorbed by the object or scattered unevenly over the object. Conventional illumination can be too bright in certain areas or too dim in others. Another problem associated with detection of foreign objects is the creation of shadows or extreme brightness which results in an image capture device “stopping-up” or “stopping-down” the aperture to prevent under or overexposure. 
     Typical light sources range from conventional light fixtures to ultra violet spectrum. As an example, halogen lighting can be used to provide an overall light source for the inspection of an object such as a fish fillet. The use of UV is standard for the purposes of inspecting glass. 
     Surface, embedded and semi-transparent edge anomalies in translucent objects such as fish are characteristically only manifested under appropriate dark field or bright field illumination. As such, dark and bright field illumination are typically addressed individually due to light path propagation during compensation for individual manifestation characteristics of the anomalies. 
     For example, bright field lighting is a lighting technique which directs specular or diffuse reflections of light to the camera. Surface defects, such as blood and skin are detected with this technique. Dark field lighting is a lighting technique which directs back scattered light from the surface of an object to the camera. Embedded, anomalies, such as a parasite, and semi-transparent edge anomalies, such as transparent bones, in a fish fillet are detectable. with this technique. However, use of either technique presents known difficulties as summarized hereinafter. Changing light levels or the creation of geometrical shadows can distort accurate sensor detection. 
     Conventional methods used for anomaly detection for fish processing entail placing a fish on a light table having a surface illuminated. At least one lamp is used to illuminate the target area in bright field light. Operators visibly inspect a fish fillet to identify surface, embedded and semi-transparent edge anomalies. 
     Inherent to this method is visual fatigue, inconsistent visual perception by an operator and optical disparity between operators. Attempts have been made to overcome these difficulties by known art. 
     Examples of art that discuss several ways of properly illuminating and inspecting an object. include U.S. Pat. Nos. 4,585,315; 5,845,002; 6,022,124; 6,049,379; 5,493,123; international patents PCT/US95/11318 (equivalent to U.S. Pat. No. &#39;002); PCT/US97/20058; Japanese patents 3165534A2; 8201222A2; and 11108637A2. 
     U.S. Pat. No. &#39;315 discusses a bright field and dark field microscope illuminator with two axicon mirrors, a third plane mirror and shutters positioned in the paths of the light beams. Through use of the disclosed embodiments, simultaneous bright and dark field illumination or alternatively singularly bright or dark field illumination is achieved through the opening and closing of the appropriate shutters. However, the advantages of even illumination of a translucent object would technically obviate from detection of translucent or transparent anomalies that would manifest under variant light intensities. Simultaneous detection of surface, embedded and semitransparent edge anomalies is not possible with the use of only dark or bright field illumination. 
     U.S. Pat. No. &#39;002 teaches a method of statistical evaluation of a translucent object by scanning graphic images of an object and processing incident light frequencies enabling a pixel by pixel analysis of topographic surface features of a fruit. A selected frequency, or combinations of frequencies, of light is directed at the fruit according to porosity of the peel. A computerized optical scanner having two light sources disposed at approximately 120 degrees from a vertical plane emit incident light towards an object, or to mirrors, to effectively scatter incident light within the fruit and cause the fruit to “glow”. A frequency spectrum is selected based on maximum, minimum and standard deviation of the intensity of the entire pixel pattern constituting the image. Both hemispheres of a fruit are analyzed; an algorithm assists in eliminating portions of the graphic information that are not relevant (such as bright field illumination or reflected light sources), and which do not constitute “glow” from the fruit. Sharp transitions are evaluated by filtering the image and comparing aberrations pixel by pixel. International application WO 96/14169 is derived from U.S. Pat. No. &#39;002. Application of the above methodology prohibits bright field illumination techniques that enable detection of transparent anomalies such as skin and bones embedded or on the surface of a fish fillet. 
     U.S. Pat. No. &#39;124 discloses a ring-light source and reflective ring focusing element wherein LED&#39;s are strung in one or more circular rows and strobe (or pulse) light to ring reflectors provides uniform lighting of an object. Light emissions from the LED&#39;s approach the object at an angle oblique or perpendicular to the optical axis. The effective dark field illumination patterns are intended to minimize light from the illumination source from entering the camera. However, use of only a dark field technique during inspection of a translucent object, such as a fish, severely diminishes the manifestation of those anomalies, thus requiring bright field techniques. 
     U.S. Pat. No. &#39;379 shows a method of scanning multiple images of a translucent object and applying brightness ratios to the scanned images for the detection of flaws in the target area. A glass bottle is disclosed wherein light intensity readings are analyzed based on an acceptable range of ratios determined by a target area and a control area. The allowable range is calculated by analyzing an object with known defects and an object that is known-to be non-defective. The disclosure notes that “blind spots” may arise during inspection for defects. 
     The techniques of U.S. Pat. No. &#39;123 involves the use of ultra violet radiation during a predetermined inspection period of glass. Use of ultra violet radiation during the inspection of organic materials for consumption is not desirable. 
     International patent PCT/US97/20058 discloses an automated inspection system with bright field and dark field illumination. The detection of “macro-defects” such as scratches, incomplete photoresist coverage and non-uniform edge bead removal on a semiconductor wafer are detectable through the use of simultaneous bright and dark field illumination. Image data acquisition is achieved through illumination of an object by at least two light sources wherein light striking the patterned surface of a wafer respectively propagates dark and light field light paths which are collected by an imaging lens. Light sensitive sensors are positioned behind the lenses which concentrate the light passing through them on the light receiving surfaces of the sensors. Data captured by the light sensors is output in a form of digital data streams. The streams of digital data are processed for creation of a gray level deviation map from which an absolute difference image is used to detect bright field and dark field, defects. Although the above addresses nanometer topographical defects, subtleties of light degradation impede detection of transparent anomalies such as bones and parasites in translucent objects. Fish is not described for use in the method. 
     Japanese patent &#39;534 A2 shows a device for inspecting defects. A binary image is formed using a light-field comparator by the instruction of the controller. Bright field illumination is removed and the roughed part of the object is inspected using only dark field illumination. Dark field illumination is removed and the plane part of an object is inspected using only light field illumination. This Japanese patent does not disclose a method of simultaneous detection of anomalies. 
     Japanese patent &#39;222 A2 discusses a method for inspecting lenticular lens sheet. 
     The inspection apparatus reflects only dark field illumination to comprise the image using a “pickup means of” CCD line sensor cameras. Use of only dark field illumination impedes detection of anomalies only detectable by use of bright field illumination techniques. 
     Finally, an inspection device is disclosed in Japanese patent &#39;637 A2. Use of a bright field lighting source or a dark field lighting source is selected according to the object being inspected, optionally both may be used. 
     The above references are known to improve the overall detection of distinguishing features and anomalies in objects, but none of the above art provides a solution for simultaneous detection of surface, embedded and semi-transparent edge anomalies. 
     The purpose of the invention is therefore to provide an automatic inspection apparatus and method for simultaneous detection of surface, embedded and semi-transparent edge anomalies in translucent objects. 
     SUMMARY OF THE INVENTION 
     It is therefore a feature of certain embodiments of the present invention to provide an automated imaging apparatus for detection of anomalies in 3D translucent objects. 
     In one embodiment, there is provided an automated inspection apparatus detection of anomalies in a 3D translucent object, the apparatus having a scanhead assembly including an image processing unit and image capture device, a first and a second light source, and conveyor means, a light block member positioned along a substantially common axis of the image capture device and a light source. 
     A further aspect of the present invention of the above embodiment is where the scanhead assembly has an image capture device, a computer processing unit in use with the image capture device to store and/or output scanned images and the assembly also includes an illumination member having illumination means which operates to illuminate the object being inspected as well as support means for moving an object in the desired direction and the light block member includes a signal isolation means. 
     In another preferred aspect of the above embodiment of the present invention the apparatus has the first and second light sources being comprised of bright and dark field, respectively, the conveyer is made of a translucent material having diffusion properties, the light block member is made of a material having selective light transfer properties, and the signal isolation means is video paint which can be positioned therein or thereon. 
     A particularly preferred aspect of the scanhead assembly is where it includes at least one reflection member and the object displacement for isolating the objects having anomalies includes the use of pneumatic ejector arms. 
     In another embodiment of a preferred aspect of the invention, there is provided a frame assembly, having object displacement means, a conveyor means, a scanhead assembly, and further includes a light block member, and a first and a second illumination member, whereby the light block member being positioned between an illumination member and the translucent object. The frame assembly mounts the scanhead assembly. Those skilled in the art will understand the varying positioning of the assembly (separate, or otherwise), the illumination members and the light block member are in a spaced apart relationship whereby the scanhead assembly, the light source and the light block member are positioned along a substantially common axis. 
     It is also an aspect of the above embodiment that the scanhead assembly has an illumination member, an image storage device, a computer processing unit, an image capture device and at least one mirror, whereby the image capture device is adapted to be used with the computer processing unit; the image capture device, the light member and the translucent object are positioned coaxially. 
     A further aspect of the above embodiment is where the apparatus includes the first and second light sources being comprised of bright and dark field, respectively, the conveyer is made of a translucent material having diffusion properties, the light block member is made of a material having selective light transfer properties, and the signal isolation means includes video paint which can be positioned therein or thereon, the isolation means for isolating objects with anomalies includes pneumatic ejector arms. 
     According to another aspect of the present invention, there is provided a method of simultaneously detecting surface, embedded and semi-transparent edge anomalies in 3D translucent objects, includes the steps of: 
     providing a translucent object; 
     providing an image capture means for recording or viewing scanned image of translucent object; 
     illuminating an object with spaced apart first and second illumination members together with light diffusion member; 
     providing a light block member positioned between the second illumination means and the translucent object; 
     aligning an image capture device, a light block member and a second illumination member along a substantially common axis; and, 
     scanning a translucent object for anomalies with an image capture device to acquire data images for simultaneous detection of anomalies. 
     In preferred embodiments of the above invention, there is included the step of providing the images to an image processing unit for the detection of anomalies present on or within a translucent object. In a further desirable embodiment scanning a translucent object may be achieved while an object moves between the illumination members and an image capture device. Preferably, a translucent object is an edible foodstuff. Furthermore, it is desirable the above embodiment includes use during food manufacture. 
     The present invention will also find use in other fields for detecting anomalies. An example of additional fields would be meat processing, such as chicken, as well as other edible foods stuffs, such as fruits and legumes. Further fields for the invention may be used includes glass, plastics, foam and the like where defects and anomalies are to be detected. 
     A 3D translucent object, at least a portion of whose surface region is translucent or absorbs light is, for the purposes of the description used in the specification, is to be considered to be a translucent object, since some absorption or reflection would occur in such an object and would permit application of the methods and apparatus of this. invention. An example of such an object would be a fish fillet wherein light would be absorbed by embedded and semi-transparent edge anomalies (which may also reflect light) and reflected by surface anomalies. Such imperfections would allow for the detection of these anomalies according to this invention. 
     Reference to objects herein can therefore be understood to include any object falling within the foregoing, including but not limited to a fish fillet. Likewise, reference to fish or particular nomenclature thereof can be understood to refer to any object which might be sorted according to the method and apparatus of this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the invention, reference will now be made to the accompanying drawings illustrating the preferred embodiments in which: 
     FIG. 1 is a schematic side-elevational view showing diagramatically a manual inspection operation according to Prior Art; 
     FIG. 2 is an perspective-elevational view, showing an apparatus of one embodiment of the present invention; 
     FIG. 3 is an exploded perspective-elevational view showing the interior of the scanhead assembly of FIG. 2; 
     FIG. 4 is a perspective-elevational view of a portion of the scanhead assembly of FIG. 3; 
     FIG. 5 is an side elevation view of the apparatus of FIG. 4, illustrating in greater detail various components; and 
     FIG. 6 is an enlarged view of light block member used in the apparatus of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a prior art, conventional imaging device, which is typical of the manual type of system used heretofore. In this system, an object to be scanned indicated by reference numeral  100  and which includes an embedded anomaly  110 , a surface anomaly  105  and a semi-transparent edge anomaly  115  is placed manually on a transparent table  138 . A source of light indicated by reference numeral  142  is provided as back light to illuminate the object  100  from beneath the table  138 . An operator (indicated generally by reference numeral  144 , visually scans the object  100  for anomalies. If the operator detects a surface anomaly  105  and a semi-transparent edge anomaly  115 , the operator will either discard the object or put it aside for separate treatment. As explained previously, apart from human error, it is sometimes difficult to detect embedded anomalies  110  and consequently, an object with the embedded anomaly may erroneously be overlooked. 
     With reference to a typical apparatus according to the present invention as illustrated in FIGS. 2 through 6, there is provided an apparatus for the purposes of simultaneous detection of surface, embedded and semi-transparent edge anomalies in translucent objects. The apparatus is a two-lane embodiment where parallel rows of, e.g. fish fillets on a conveying system, are to be inspected. It will be understood that either single lane or three or more lanes can be used by modifying the apparatus of the present invention. 
     Referring to FIG. 2, the inspection apparatus includes a support frame  85 , a movable surface, such as a conveyor belt  140  made of a light diffusing material for diffusing light from the second illumination member  40  and for movement of a fish fillet from a loading station (not shown) to and through a detection step and finally to a discharge station. 
     Suitable conventional means are provided for driving the conveyor belt, preferably the belt is an endless belt and with the belt continuously moving between loading station and discharge station (not shown). 
     To this end, the fish fillet is preferably transported by the conveyor  140  at a constant velocity, using a conventional servo-mechanism controlled by a suitable motor  99 . The object to be scanned thus travels in a direction along a fixed scan axis further described herein. A scanhead assembly, indicated generally by reference numeral  70 , is mounted by suitable means above the conveyor  140  in a fixed relationship thereto. 
     With reference to FIG. 3 the scanhead assembly  70  includes a camera  20 , a computer processing unit  90 , and a frame grabbing device  98  for grabbing or storing the images. The scanhead assembly may also include the first illumination member  30  and reflection members  95 , such as mirrors. This embodiment may be employed to reduce the overall height of the scanhead assembly  70  but, obviously, if height is not a factor, such reflecting members need not be employed. 
     The apparatus of the present invention may include pneumatic ejection means for removing objects  100  having surface  105 , embedded  110 , or transparent edge  115  anomalies from the conveyor belt  140 . Such ejection means may be in the form of movable arms actuated in response to the detection of an anomaly by the scanhead assembly so that the objects are removed either for further processing or to be discarded. The structure of the ejector arms  80  and their operating mechanism is known per se in different fields and consequently, they will not be described in further detail. 
     It will be seen from FIG. 3, that the apparatus includes an image capture device  20  (or camera), a first illumination member (or front illumination member)  30 , a second illumination member which is lamp  40 , a light block member  50  having selected light transfer properties, one being a signal isolation means  60 , a computer processing unit  90 , image storage device  98 , a conveyor belt  140  for light diffusion and movement of a translucent object  100 . The light block member  50  will be described hereinafter in greater detail with reference to FIG.  6 . In general, the light block member includes a signal isolation component with an impermeable barrier or stripe position thereon which the line scan camera  20  is focused thereon. In one embodiment, the barrier or stripe can be in the form of a light impermeable layer formed by use of a coating known as Ultimatte Super Blue (TM) video. paint as the signal isolation means. 
     As illustrated in FIG. 3, the camera  20  includes a lens  25  for detection and a scanning of the translucent object  100  for any anomalies. Detection of these anomalies, designated by reference numerals  105 ,  110 , and  115 , involves illumination of the translucent object  100 . As an object  100  moves into the scan area, shown as a line of sight from the lens (being indicated by reference numeral  25  and shown as a dotted line in FIG.  5 ), and the signal isolation component  58 , the camera records a signal, which is processed as described hereinafter. In this arrangement, light from light source  30  strikes the object  100  and in turn is received by the sensors of the line scan camera. 
     In a preferred embodiment, the scanning involves a continuous or sequential two dimensional array technique providing a two dimensional graphic image of an object. Bright field image data and dark field image data are simultaneously captured by a single imaging device. The output data from the imaging device is fed to a computer processing unit. 
     A central processing unit (CPU) can be any conventional type and is known in the art. The scanned image is then processed by the computer processing unit  90  which is conventional and is the same as those used in the art. For this reason, portions of the computer processing unit  90  will not be discussed in further detail other than to describe the operation of the unit. The illumination energy is of sufficient intensity to maintain the image capture speed and minimum image blur requirements. 
     FIGS. 4 and 5 show the first illumination member  30 , in a preferred embodiment, providing a Bright Field frontal lighting means  35  (FIG. 5) and the second illumination member  40  providing Dark Field back lighting means  45  (FIG.  5 ). The lamp  40  is positioned in coaxial alignment with the camera  20  (illustrated by a broken line  1 — 1  in FIG.  5 ). The front illumination member  30  is positioned at an oblique angle relative to the surface of an object to be scanned to provide bright field light paths that strike the surface of the object. The front illumination source  30  can be mounted in different positions although, as illustrated in FIG. 5 a preferred position is at an oblique angle to the object to be scanned and to the light block member  50 . The reason for this is simply for limiting the size of the apparatus. Other coaxial arrangements may be employed, so long as the camera  20  does not directly tee the light emitted from the lamp  30 . 
     Skilled persons in the art will appreciate that conventional lamp configurations such as halogen lamp tubes and the like may be used for illumination of an object. Other lamp sources such as light beams formed by LED&#39;s or laser beams may also be used and achieved by a string of point sources positioned in optical association with a light diffusing element. Thus, any suitable type of illumination can be employed for this invention within the Ultra Violet to IR light spectrum. Preferred light sources are fiber optic line array devices for each member  30  and  40 . 
     The light block member  50 , illustrated in FIG. 6, includes a block support member being a solid transparent material. The size of the light block member  50  in terms of the physical dimensions of the signal isolation means  60  will vary depending on the light source and/or imaging lens magnification. In other words, the width of the signal isolation component  60  will vary depending on the capability of the line scan camera  20 , it being understood that normally this isolation strip will be relatively narrow when the camera  20  is scanning a relatively narrow area. 
     The block member  50  is preferably formed from an illumination pervious or transparent material  58  such as glass, optically clear plastic or some other such suitable material. The transparency of this material may vary depending on the type of system used and the degree of illumination required by the back lighting. 
     The signal isolation means  60  is positioned on or in the light block member  50  (as desired for optimum manufacturing assembly). Desirably, it is positioned coaxially with the lamp  40  and the camera  20 . For the purposes of sanitation for food inspection the light block member is protectively encapsulated by a thin plastic material or the like which allows the light block to function in a similar manner. 
     The camera  20 , as shown in FIGS. 3 through 5, may be a conventional camera such as a line scan camera or other suitable known image capture device, and is aligned axially (illustrated by a broken line  1 — 1 , in FIG. 5) with a lamp  30  and/or  40 , the light block member  50  and the translucent object  100 . In the preferred embodiment; the light block member is positioned between a conveyor belt  140  and the lamp  40 . The conveyor belt  140  acts as a light diffusing member wherein the light block member  50 , provides for the simultaneous detection of surface  105 , embedded  110  and semi-transparent edge  115  anomalies in translucent objects  100 . 
     As illustrated in FIG. 6, the light block  50  includes a signal isolation means  60  positioned therein or thereon. The signal isolation means  60  is preferably video paint and corresponds to the operational characteristics of the camera  20 . In use the signal isolation means  60  blocks, or otherwise obstructs, the light emitted from the lamp  40  such that the camera  20  does not detect direct light and overexposure of the scanned image is prevented. The light block supporting member  58  is preferably made of an illumination pervious material, such as glass, which allows the light from the lamp  40  to be distributed evenly on remaining portions of the translucent object  100  during scanning. 
     Effective blocking of the light from the direct perspective of the camera  20  enables the reliable detection of surface anomalies  105  with frontal lighting  30 . It will be understood that other means of forming the light block can be employed such as thin bands of tape suitably secured to or mounted in the light block supporting member  58 . 
     Similarly, overall detection of surface  105 , embedded  110  and semi-transparent edge  115  anomalies is improved due to the position of the light block member  50  since increased illumination values will not saturate the camera  20 . 
     It is desirable at times to eliminate ambient light from the inspection area of the object  100 . For example, extreme brightness from ambient light sources will result in “stray” light being directed at the object  100 , forming shadows and the like, which prevent proper illumination of the object  100 . Thus, use of a shroud (not shown) allows for controlled conditions during inspection of the object  100 . Although use of a shroud (not shown) is an embodiment of the invention it is not limiting to use of the present invention. 
     It is therefore evident from this disclosure that defects or anomalies associated with inspection of a translucent object  100  can be simultaneously detected by use of the present invention  10 . The present invention  10  enables the simultaneous detection of surface anomalies  105  (white skin, black skin, scales, fins with skin, melanin spots, etc.) embedded anomalies  110  (parasites, blood, bruises, soars) and semitransparent edge anomalies  115  (bones without skin) to be detected in the translucent objects (e.g. fish). 
     A primary advantage of the invention is that it is capable of automatically and concurrently identifying and processing distinguishing features or anomalies, the characteristic signatures of which are revealed by either one or a combination of bright field illumination and dark field illumination. The invention detects the presence of any such distinguishing features or anomalies and is especially useful during inspection of 3D translucent objects, such as a fish fillet. 
     The preferred embodiment described herein shows the inspection apparatus in use after a fish has been processed (i.e. entrails removed). However, the inspection apparatus can be used before or after any process step at any stage of preparation of a fish fillet. 
     Those skilled in the art to which the invention pertains understand the invention has been described by way of a detailed description of a preferred embodiment and departures from and variations to this arrangement may be made without departing from the spirit and scope of the invention, as the same is set out and characterized in the accompanying claims.