Abstract:
The single-camera multi-mirror imaging method and apparatus is an inspection system configured to examine a whole surface of a rotating object, preferably a spheroidal object such as a fruit or vegetable. The system includes a plurality of mirrors that direct an image of the inspected object into a digital line scan camera with an associated processor. The processor produces an image of the inspected object showing any detected surface defects and selected contamination on the outer surface of the object.

Description:
FIELD OF THE INVENTION 
     The disclosed method and apparatus relates to imaging a whole surface of a rotating object. Specifically, the method and apparatus relates to imaging a whole surface of a spheroidal rotating object using a single camera and a plurality of mirrors. 
     BACKGROUND OF THE INVENTION 
     Currently, the most common method for inspecting essentially spherical objects (such as fruits and vegetables) involves production line personnel visually inspecting the objects as the objects are conveyed along a production line. However, the human visual inspection process is both slow and unreliable and some contaminating materials (such as fecal matter and bacterial contamination) that pose serious health risks are hard to identify particularly on a moving production line. Further, the inspected objects are not generally rotated so that all surfaces of the object are visible to the inspector. 
     To address these vulnerabilities, fruit and vegetable processors are developing machine vision systems to identify defects and contaminants. One example of such a system is disclosed in U.S. Pat. No. 7,787,111 to Kim et al. (hereinafter “Kim”), which is hereby incorporated by reference. The system disclosed by Kim comprises a rapid online line-scan imaging system capable of both hyperspectral/multispectral reflectance and fluorescence imaging. Reflectance imaging at multiple wavelengths detects quality and surface anomalies, while fluorescence imaging at multiple wavelengths is used to detect fecal matter and other types of bacterial contamination. 
     Although these examination tools and techniques improve the inspection process, the imaging systems are complex and expensive. For example, in accordance with Kim, multiple cameras may be required to adequately inspect all surfaces of a spheroid. Further, the data collected from all cameras must be processed and synchronized to accurately portray the three-dimensional spheroidal object. For maximum efficiency and minimal error, synchronization and processing should occur almost immediately to ensure that defective objects are not comingled with non-defective items. 
     The current invention simplifies the imaging process by providing an imaging system that utilizes only one camera and associated processor. The system described herein quickly and effectively gathers the imaging data and processes the data to produce a two-dimensional concatenated “image cube” that allows for the identification of essentially all surface defects as well as selected types of bacterial (including fecal) contamination. 
     SUMMARY OF THE INVENTION 
     This disclosure is directed to an inspection system which includes a plurality of peripheral image collecting mirrors positioned around a targeted rotating object. The peripheral mirrors direct reflected images of the object to a central collecting mirror. The central collecting mirror directs the reflected images to a camera with an associated processor. The processor receives the images from the camera and produces image data for the object. The inspected object is retained or rejected based on the image data. 
     The disclosure is also directed to a method of inspecting a targeted object. In accordance with the method, a plurality of peripheral image collecting mirrors are positioned so that each of the peripheral image collecting mirrors attains an image of the inspected object. Images of the inspected object are directed from each of the peripheral image collecting mirrors to a central collecting mirror. The central collecting mirror directs the images to a camera and an associated processor. The images are processed so that a decision is made to retain or reject the inspected object based on the processed images of the object. 
     The disclosure is further directed to a method of inspecting a spheroidal object. At least one mirror is positioned around the object and the object is rotated. Images of the object are reflected from the mirror into a digital line scan camera with an associated processor. The processor produces an image of the object showing any detected surface defects and any detected contamination that is present on an outer surface of the object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of the current inspection system positioned to inspect a rotating spheroid. 
         FIG. 2  is a concatenated image of the rotating spheroid shown in  FIG. 1 . 
         FIG. 3  is the concatenated spheroid image of  FIG. 2  modified so that the image shows one rotation of the spheroid. 
         FIG. 4  is the concatenated spheroid image of  FIG. 3  after removal of overlapping portions of the image. 
         FIG. 5  is an image cube representing the spheroid shown in  FIG. 1 , as modified in  FIGS. 2-4 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As generally shown in  FIG. 1 , the method and apparatus described herein comprises an inspection system  10  that includes a central image-consolidating mirror  12 , and a plurality of peripheral image collecting mirrors  14 ,  16 . As an inspected object  20  rotates (in the direction of the arrow  21 ), the inspection system  10  collects and processes a line scan image of the object  20  to determine whether the object  20  is rejected or retained for further processing. 
     In the preferred embodiment, as best shown by the dashed lines  18 , an image of a rotating spheroidal object  20  is collected by the two peripheral first-surface mirrors  14 ,  16 . A portion of the images collected from each of the respective mirrors  14 ,  16  create an overlap area  17 . The mirrors  14 ,  16  are angled inwardly toward the object  20  at approximately 45°. As best shown by the dashed lines  22 , the images collected by the peripheral mirrors  14 ,  16  are then directed to the central collecting mirror  12 . 
     Although not specifically shown in the drawings, the inspection system  10  includes a lighting system that illuminates the rotating object  20 , as disclosed (for example) in Kim. Specifically, the lighting system may include a quartz-tungsten halogen (QTH) reflectance lamp. Near infrared (NIR) light emitting diodes (LEDs) or an NIR laser with (or without) a long pass filter can also be used as a reflectance lamp. The lighting system may also include a micro discharge lamp (MDL)-high intensity ultraviolet light. LEDs, a laser, or a pressurized vapor lamp can also be used for fluorescence excitation. The system may further include long pass filters and a variety of other lighting and camera accessory equipment, as required to elicit reflectance, fluorescence, or other responses useful in detecting defects or contamination on the inspected object. 
     As generally shown in  FIG. 1 , the central collecting mirror  12  comprises a first surface mirror with opposing faces  13 ,  15  positioned so that each face  13 ,  15  collects an image from a respective peripheral mirror  14 ,  16 . As indicated by the dashed lines  24 , the images collected by the central collecting mirror  12  are reflected into a digital line scan camera  30  and processed by an associated processor  23 . 
     In the preferred embodiment, the central collecting mirror  12  comprises a prism-shaped triangular polyhedron with two mirrored faces, i.e. the mirror body  12  has a rectangular base and oppositely disposed rectangular sides (which comprise first surface mirror faces  13 ,  15 ) with parallel oppositely disposed triangular surfaces forming the respective ends. However, the only critical elements of the central collecting mirror  12  are the orientation of the mirror&#39;s faces  13 ,  15  relative to the peripheral image collecting mirrors  14 ,  16  and the camera  30 . In the preferred embodiment, the mirrored faces  13 ,  15  have one abutting edge and form a relative angle of approximately 90°. However, in alternative embodiments, other relative angles and configurations should be considered within the scope of this disclosure. 
     As shown in  FIG. 2 , once the images are collected and communicated to the processor  23 , the processor  23  translates the images into image data and creates a concatenated image  25  of the surface of the spheroid  20  as the spheroid  20  rotates. Processing software measures the diameter  26  of the spheroid  20  (as reflected by the concatenated spheroid image  25 ) and calculates the amount of rotation (as expressed by the distance  28 ) for the spheroid  20  to travel one complete rotation. The image  25  shown in  FIG. 2  is then cropped to form a concatenated image  27  that represents one rotation of the spheroid, as shown in  FIG. 3 . The area between the dashed lines  32  (shown in  FIG. 3 ) is a portion of the overlap between the images gathered by each of the peripheral mirrors  14  and  16 . The overlap area  17  is best shown in  FIG. 1 .  FIG. 4  shows a modified concatenated image  29  after removal of the overlap area  32  identified in  FIG. 3 . 
     In  FIG. 5 , the two separate portions of the image  29  are joined to create a single “image cube”  31 . The image cube  31  comprises a concatenated line scan image of the complete outer surface of the spheroid  20 . The image cube  31  incorporates and displays any surface defects collected from the reflectance scan as well as any contamination resulting from the fluorescence scan—using a fluorescence scanning apparatus such as the apparatus disclosed in Kim. The image cube data is then scrutinized based on pre-determined contamination and defect standards (expressed as defect/contamination thresholds). Examined objects that are determined to meet the standards are retained for further processing and objects that are substandard are rejected. 
     Although the preferred embodiment comprises two fixed stationary peripheral mirrors  14 ,  16  angled at approximately 45° and directed into a two-faced image collecting mirror  12 , more than two mirrors may be used with an image collecting mirror  12  having a corresponding number of faces. Further, the angles of the peripheral mirrors  14 ,  16  and the corresponding faces of the image collecting mirror  12  may have a different fixed angle or may change angles and positions as the spheroid  20  is rotated. Additionally, although the spheroid  20  rotates in an essentially horizontal plane, the plane of rotation may be varied so that selected surfaces of the rotating spheroid  20  are more clearly visible. 
     For the foregoing reasons, it is clear that the method and apparatus provides an innovative system for inspecting three dimensional objects, preferably spheriodal objects on a conveyance line. The system may be modified in multiple ways and applied in various technological applications. For example, although the method and apparatus described herein is generally directed to spheroidal food products, in alternative embodiments, the device may have some application to the inspection of non-spheroidal food or non-food items (such as manufactured products). 
     The current method and apparatus may be modified and customized as required by a specific operation or application, and the individual components may be modified and defined, as required, to achieve the desired result. Although the materials of construction are not described, they may include a variety of compositions consistent with the function described herein. Such variations are not to be regarded as a departure from this disclosure&#39;s spirit and scope, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.