Abstract:
An illumination device for use with a product inspection machine inspecting products according to at least one characteristic. The invention also pertains to an illumination device for use in sorting machines that optically sort or separate nonstandard fungible objects from standard objects as they pass a viewing station by viewing such objects illuminated by at least one wavelength. The invention includes a plurality of arrays of semiconductor light sources impinging on passing product and at least one array of semiconductor light sources of wavelength and intensity equal to the plurality of arrays impinging on a background surface for detection and comparison.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a product illumination device for examination of passing product wherein multiple wavelengths and intensities may be selected, and particularly for use in for product sorting. 
     2. Description of the Related Art 
     A typical sorting machine of the type with which the present invention is used is a high-speed sorting machine for use with small products, including fungible products in the food and pharmaceutical industries. As used herein, product refers not only to a manufactured good but also to component items from which production of a good may be accomplished. As a result, the invention may also be used in conveyor sorting machines, for sorting of other flowing materials, such as plastic pellets and ammunition, and for quality control examination of product. 
     For example, individual rice grains may be sorted in a gravity-fed sorter to separate grains selected as “substandard.” In the art, “substandard” may apply to a grain having any undesirable characteristic, including color, shape, size or breakage, or any other characteristic not within the limits for acceptable products for a particular sorting. Alternative feed systems, such as belt driven conveyors, are also well-known in the art. Alternatively, certain rarer products may be desirable and therefore deflected from the flow of the less rare and less desirable remaining products. Likewise other materials may be sorted from the product flow, including, such as in the case of harvested goods, non-product materials such as glass, rocks, sticks and bran. 
     Sorting machines may employ two or more optical sensors to differentiate based on color hues, size, moisture content or other characteristics as determined in radiation bands, which may be outside the visible color spectrum. When such sorting is accomplished by use of two radiation bands, the sorting procedure is referred to as bichromatic sorting. 
     Optical sorting machines of the type generally described above employ optical sensors that include multiple photodetectors, such as a charged-couple device and photodiode arrays. The photodetectors are positioned to observe the illuminated product stream through a light-penetrating window. The product stream typically passes between an optical sensor and a background, where the background has a color shade that matches the product stream in standard color or shade so that only a variation in a product color or shade causes a detection event. The illumination is from one or more light sources directed at the product stream to cause standard reflectivity or transmission (transluminence) from standard products in the radiation bands being observed and to cause nonstandard reflectivity from nonstandard products in those bands. 
     One of the main components of such a sorting system is the illumination assembly. The illumination assembly provides a starting point for the reception quality of the vision system. Typically, the assembly is required to supply a uniform light supply and have a high intensity at the object point (sometimes referred to as the scan line) of the vision system. Most inspection systems include some sort of illuminator. Conventional illuminators include incandescent and fluorescent lamps and light emitting diodes. Various optical arrangements have been designed for better illumination, such as ringed lamp arrays, focused filament projectors, and fiber optic emitters. Uneven illumination in conventional illuminators may result in detection of shadows as defects. While the characteristics commonly measured incorporate illuminators including human-visible light sources, machine vision systems may measure energy waves outside the human vision range. 
     Such sorting machines also include one or more ejector mechanisms located downstream of the sensor or sensors with multiple nozzles associated with one or more valves actuated by an electrical signal coordinated with sensor detection. When a product having or lacking selected criteria is detected, an electrical signal is produced to actuate the valve of the ejector nozzle associated with the predicted location of the selected product at the predicted time the selected product will pass the ejector. The time elapsed between the selected product passing the sensor or sensors and the selected product being ejected is minimal to limit possible vertical and/or horizontal deflection of the selected product upon contact with non-selected products. Each ejector is therefore normally located as close as possible to the plane at which the optical sensor or sensors reviews the passing products, typically referred to as the scan line, ideally being just downstream therefrom and closely adjacent thereto. 
     It would be an improvement over the prior art to provide an illumination device that provides intense, consistent illumination of the products to be viewed along a linear or elongated scan line, thereby providing consistent identification of selected characteristics and substantially reducing mischaracterization of products as having occlusions or other defects actually caused by shadows. 
     The prior art typically utilizes quartz halogen or fluorescent lights as the main illumination source. To adjust the wavelength or wavelengths of light and the light intensity impinging on passing product, prior art teaches the use of filters, typically mounted adjacent the camera. The prior art is prone to waste energy as heat, rather than light, which must then be removed from the sorting machine. Moreover, the combining color band in a monochromatic application is limited. 
     In bi-chromatic sorters, a combination of red/green and red/blue filters is required to limit the wavelengths and/or intensity impinging on the product. Such a system requires significant disassembly, and therefore lost productivity, when any change to the wavelengths and/or intensity is desired. Such a change may be desired if a different product is to be sorted or if a different characteristic is selected for sorting. 
     Additionally, it would be an improvement to the prior art to provide an illumination device that may instantaneously adjust the wavelength or wavelengths and/or wavelength intensity impinging on passing product. 
     SUMMARY OF THE INVENTION 
     It is therefore, a principle object of the present invention to provide an illumination device that may instantaneously adjust both the wavelengths and intensity impinging on passing product. 
     The present invention comprises an illumination assembly for a machine vision viewer for a product sorting machine that provides a flow of objects along a horizontal scan line. The present invention includes a horizontally-disposed product illumination assembly with a plurality of sequenced semiconductor light sources, which may be light-emitting diodes, of one or more colors mounted thereon, and a corresponding horizontally-disposed background surface illuminated by a plurality of sequenced semiconductor light sources of one or more colors. Moreover, the intensity of any emitted color or colors may be adjusted to further vary the light color impinging on passing product and the corresponding background surface against which the product is imaged for sorting. 
     A passage exists between the product illumination assembly and the background assembly through which product to be sorted passes. A linear viewport, parallel to the horizontally-disposed product illumination assembly, is provided for one or more detectors to identify any product passing between the product illumination assembly and the background assembly having a characteristic found in a the minority of product. An ejector is positioned adjacent the illumination device. 
     In the preferred embodiment, a pair of product illumination assemblies are employed, wherein a background assembly is integrated into each product illumination assembly. The two product illumination assemblies are oriented in parallel such that a detector imaging through the linear viewport of the first product illumination assembly images the opposing background surface in the absence of product. 
     Use of semiconductor light sources of a plurality of colors provides advantages over the prior art. The need for replacement or alteration of color filters to obtain different wavelengths and intensities for characteristic selection is eliminated. Likewise, in monochromatic sorting systems, multiple colors may be used to enhance the color difference of the product having the characteristic to be deflected. On bi-chromatic applications, there is no need to add a color filter in front of the detector when using a simple dichroic mirror. Finally, each channel (semiconductor light source array) can be a combination of colors on bi-chromatic applications. 
     The height of each product illumination assembly is limited to the minimum size practicable to contain at least two rows of semiconductor light sources, a background surface of sufficient height, the illumination for the background surface, and sufficient depth for the light emitted from the semiconductor light sources on the product illumination assembly to converge and blend at the scan line and for the light from the semiconductor light sources illuminating the background surface to converge and blend on the background. The semiconductor light sources used to illuminate the product may be concurrently used to illuminate the background surface. Various methods to promote convergence and blending of the light of the semiconductor light sources, particularly light emitting diodes (LEDs), are well known in the art. 
     The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the described features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate only a typical preferred embodiment of the invention and are therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
         FIG. 1  depicts a side view of a typical sorting machine known in the art including the illumination device of the present invention. 
         FIG. 2  depicts a simplified side view of a typical machine viewing system known in the art. 
         FIG. 3  depicts a cross-sectional view of the illumination device of the present invention. 
         FIG. 4  depicts a cross-sectional view of the illumination device of the preferred embodiment of the present invention. 
         FIG. 5  depicts a perspective view of a section of one half of the illumination device of the preferred embodiment of the present invention. 
         FIG. 6  depicts a perspective view of an entire one half of the illumination device of the preferred embodiment of the present invention. 
         FIG. 7  depicts the front of one half of the illumination device of the preferred embodiment. 
         FIG. 8  depicts a perspective view of the rear of one half of the illumination device of the preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to  FIG. 1 , a typical product-sorting machine including the illumination device of the present invention is depicted. The product-sorting machine  10  includes a hopper  16 , a feeder  18 , a slide  12 , a vision system  20 , and an ejector  26 . The components of typical product sorting machine  10  are illustrated in  FIG. 2 , including a container  28  for segregated products and a bin  30 . 
     The products to be viewed and sorted by the typical product-sorting machine  10  are retained in hopper  16  and are ultimately dispensed onto slide  12  by feeder  18 . Feeder  18  may be of any type commonly known in the art, such as a conveyor or a vibratory feeder. 
     In the exemplary product-sorting machine  10 , momentum is imparted to the product to be sorted by the product conveyor  14 , which may be a gravity slide  12  or belt conveyor. Prior to the product passing before vision system  20 , product conveyor ceases to support the product, directing the product along trajectory  32 . The product sorting machine  10  of the embodiment disclosed in  FIGS. 1 and 2  provides for free fall of the products past slide  12 . 
     The product to be sorted may be any of a plurality of organic or inorganic objects, such as, for example, grains, nuts, and plastic pellets. The products may be viewed and sorted based on various criteria determined by the user, including size, color, defects and other characteristics. 
     Referring to  FIG. 3 , vision system  20  includes an illumination device  100  that is composed of a horizontally disposed product illumination assembly  200  and a corresponding horizontally-disposed background assembly  300 , a detector  400 , and an ejector  500 . In free fall, the product passes the first, or upper edge, of illumination device  100  used in conjunction with vision system  20 , and the second, or lower edge, of illumination device  100 . In operation, as a continuous flow of product passes through product-sorting machine  10  and therefore past illumination device  100 , illumination device  100  provides continuous and uninterrupted illumination of the flow of passing product. Horizontally-disposed product illumination assembly  200  and a corresponding horizontally-disposed background assembly  300  are positioned in opposition sufficiently distant to ensure product being directed from conveyor  14 , in particular by slide  12 , passes therethrough without interference. A detector  400  is positioned to image product passing between product illumination assembly  200  and background assembly  300 . Detector  400  has a vertical field of vision. The point at which product passes between product illumination assembly  200  and background assembly  300  is identified as scan line  700 . Scan line  700  is of sufficient height to image passing product. To the extent product is less than the height of the scan line  700 , detector  400  images background surface  302 , which is aligned with detector  400  and scan line  700 . Detector  400  images scan line  700  through product illumination assembly  200  via viewport  202 . To increase the effectiveness of detector  400 , product is illuminated at scan line  700 . To reduce contrast between acceptable product reflecting illumination from product illumination assembly  200 , background surface  302  is illuminated from within background assembly  300  consistent with the wavelength, or wavelengths, and intensity, or intensities, of product illumination assembly  200 . Background surface  302  is of sufficient height and position to include the arc or chord length of the field of vision of detector  400  passing through viewport  202  and scanline  700  at the inner surface  303  of background assembly  300 . One or more ejectors  500 , each having a plurality of ejector nozzles, are positioned adjacent illumination device  100  to deflect selected product from trajectory  32 . When a product passing through scan line  700  is identified by detector  400  as having the characteristic to be separated from the remaining product, the appropriate nozzle of ejector  500  is activated at the approximate time the product will pass the particular nozzle of ejector  500 . 
     It is preferred that product be as completely imaged, particularly both front and back, as possible for sorting. To that extent, in the preferred embodiment, background assembly  300  is integrated into product illumination assembly  200 , as depicted as background assembly  600  in  FIG. 4 , and two product illumination assemblies  200  are utilized. 
     Depending on the product to be sorted and the characteristic or characteristics selected as the basis for sorting, a particular wavelength, or wavelengths, and intensity, or intensities, of light may be desirable for characteristic identification. Problematically, a change in product or in characteristic for sorting may require a change in wavelengths and intensities. In conventional product sorting machines, such a change may require replacement of the existing illumination assembly. 
     As depicted in  FIGS. 3-7 , each product illumination assembly  200  includes a first semiconductor-light-source product-illuminating array  204  of semiconductor light sources  208 , and a second semiconductor-light-source product-illuminating array  206  of semiconductor light sources  208 . Semiconductor light sources include lighting emitting diodes (LEDs), laser diodes, organic LEDs, and any other semiconductor light source. Semiconductor light source refers to lighting devices that utilize semiconductors as a light source and not necessarily the semiconductor itself. First semiconductor-light-source product-illuminating array  204  and second semiconductor-light-source product-illuminating array  206  are positioned sufficiently distant scan line  700  to ensure the light of each semiconductor light source of first semiconductor-light-source product-illuminating array  204  and second semiconductor-light-source product-illuminating array  206  sufficiently blend to provide uniform illumination of scan line  700 . In the preferred embodiment, first semiconductor-light-source product-illuminating array  204  and second semiconductor-light-source product-illuminating array  206  are affixed on supports  210 . Supports  210  are angled to ensure the greatest illuminance of scan line  700  from first semiconductor-light-source product-illuminating array  204  and second semiconductor-light-source product-illuminating array  206 . Illuminance is the total amount of visible light illuminating (incident upon) a point on a surface from all directions above the surface. This “surface” can be a physical surface or an imaginary plane. Supports  210  must be sufficiently located so as not interfere with detector  400 . 
     Likewise, as depicted in  FIG. 3  with respect to background assembly  300 , and in  FIGS. 4-7  with respect to background assembly  600  at least a single semiconductor light source background illuminating array  604  of semiconductor light sources  208 , which may be light-emitting diodes. Semiconductor light source background illuminating array  604  is positioned sufficiently distant background  302  to ensure the light of each semiconductor light source of the semiconductor light source background illuminating array  604  sufficiently blends to provide uniform illumination of background  302 . In the preferred embodiment, semiconductor light source background illuminating array  604  is affixed on support  610 . Support  610  is angled to ensure the illuminance of background  302  consistent with scan line  700  from semiconductor light source background illuminating array  604 . Support  610  must be sufficiently located so as not interfere with detector  400 . A second array of semiconductor light sources may be located opposite semiconductor light source background illuminating array  604 . 
     Alternatively, supports  210  may be altered such that each semiconductor light source array may be relocated within illumination device  100  and the light from each array redirected, by prisms or mirrors, to properly illuminate scan line  700  and background  302  (not shown). Various methods to redirect light and to encourage blending of light sources are well known in the art. 
     In operation, each detector  400  is located above the horizontal centerline of illumination device  100 , views scan line  700  approximately at the center of illumination device  100 , and views background  302  below the horizontal centerline  800 . The wavelength(s) and intensity(ies) impinging product at scan line  700  from first semiconductor-light-source product-illuminating array  204  and second semiconductor-light-source product-illuminating array  206  are replicated on background  302  by semiconductor light source background illuminating array  604  to provide maximum contrast of characteristics on passing product for identification by detector  400  and therefore activation of ejector  500 . 
     First semiconductor-light-source product-illuminating array  204  is composed of a series of semiconductor light sources  208 , which may be of one or more colors. In circumstances where semiconductor light sources  208  in first semiconductor-light-source product-illuminating array  204  are of a plurality of wavelengths, semiconductor light sources  208  cycle through the same sequence of color throughout the array. Repetition of color ensures that the resulting wavelengths blend by the time the light reaches scanline  700 . Likewise, in circumstances where semiconductor light sources  208  of a plurality of wavelengths are arrayed on first semiconductor-light-source product-illuminating array  204 , a corresponding array of semiconductor light sources  208  are fixed for second product-illuminating array  206  in a complementary sequence. For example, a sequence of red and green semiconductor light sources  208  in first semiconductor-light-source product-illuminating array  204  would be complemented by a sequence of green and red semiconductor light sources  208  in second semiconductor-light-source product-illuminating array  204 . In the preferred embodiment, first semiconductor-light-sources product-illuminating array  204  is of a single color, such as red, and second semiconductor-light-source product-illuminating array  206  is of a single color, such as blue. Use of a consistent color semiconductor light sources  208  per first and second array is preferred for ease of repair and manufacture. The number of colors permissible in the assembly is a result of the density of semiconductor light sources and distance from scanline  700  or background  302 . 
     Background array  604  complements both first semiconductor-light-sources product-illuminating array  204  and second semiconductor-light-sources product-illuminating array  204 , such that if the color of first semiconductor-light-sources product-illuminating array  204  is red, and the color of second semiconductor-light-sources product-illuminating array  206  is blue, background array  604  will constitute a combination of red and blue semiconductor light sources. 
     Further, the illuminance on passing product and the background  302  may be controlled by adjusting the intensity of semiconductor light sources  208  contained in first semiconductor-light-source product-illuminating array  204 , second semiconductor-light-source product-illuminating array  206  and background array  604 . The intensity of each semiconductor light source  208  may be independently controlled to affect the intensity of the wavelength(s) emitted. Such control may be via a computer or other device known in the art. Any variance in emitted intensity of any particular semiconductor light source  208  may be controlled to ensure consistent intensity. Similarly, the intensity of all semiconductor light sources  208  of a particular wavelength or wavelengths found in first semiconductor-light-source product-illuminating array  204 , second semiconductor-light-source product-illuminating array  206  and background array  604  may be commonly controlled and adjusted. 
     Illumination device  100  may be positioned perpendicular to trajectory  32  of passing product, regardless of the trajectory&#39;s plane. Additionally, product illumination assembly  100 , whether incorporating background assembly  600  or mating with background assembly  300 , may be fitted with heat sinks  900 . Likewise, if background assembly  300  is used, it too may be fitted with heat sinks  950 . In operation, the heat from semiconductor light sources  208  may be removed from illumination device  100  via such heat sinks. Viewport  202  may be an opening, to additionally permit heat to exit, or may be sealed. The assemblies of product illumination assembly  100 , whether incorporating background assembly  600  or mating with background assembly  300 , may be sealed against passing product, preventing any contaminants from interfering with semiconductor light sources  208  or background  302 . Alternatively background assembly  300  may be the lower of the two assemblies and may contain orifices (not shown) through which passing product not following trajectory  32  and instead falling to into background assembly  300  may exit. 
     By constructing product illumination assembly  200 , and, if applicable, background assembly  300 , as a single component, the component may be removed for service or replacement, rather than requiring removal of the individual assemblies. Such modular construction reduces the time required for repair or replacement and therefore increases productivity of the sorting machine. 
     Construction of illumination assembly  200 , and, if applicable, background assembly  300 , with illumination from light sources onto scanline  700  and background  302 , also eliminates the need for internal reflective surfaces. 
     Use of semiconductor light sources sufficiently distant scanline  700  and background  302  likewise eliminates the need for any diffuser, thereby reducing the number of parts necessary to illuminate scanline  700  and background  302 . 
     To further improve uniformity of illumination, illumination device  100  may be constructed longer than the width of conveyer  14 , or slide  12  if applicable. Thus, the effective area of illumination extends to the full edge of the conveyor  14 , or slide  12 . 
     Referring to  FIGS. 3 and 4 , ejector  500  comprises a series of nozzles  501  for selective intermittent ejection of compressed gas, fluid or air (not shown) into trajectory  32 . Nozzles  501  are aligned parallel to scanline  700  adjacent trajectory  32 , such that any individual product (not shown) identified to be sorted may be diverted to trajectory  32   b  without diverting adjacent product. 
     In operation, upon flow of a quantity of products along trajectory  32  through vision system  10 , detector  400  outputs optical data in relation to a product passing along scan line  700  and transmits such data to a processor for determination whether the acquired data is within a range of acceptable levels or outside such range. If the data is not within specific parameters, the particular nozzle or nozzles  501  of ejector  500  associated with the lateral position of the identified product is engaged to impart a force to the particular item as it passes, thereby changing the trajectory of the identified product. For illustration purposes, the trajectory of a rejected product is depicted as  32   b  and the trajectory of a product that is not rejected is depicted as  32 . 
     The machine vision system  10  of the present invention is useful in a variety of applications to identify measuring characteristics of a product. The high and relatively even intensity of illumination within illumination device  100  at scanline  700  makes the present invention particularly useful in identifying flaws in transparent products, such as plastic pellets. 
     In an application involving a transparent product such as a plastic pellet, a characteristic to be scanned, and upon which sorting is conducted, is the existence of contaminants in the product. Transparent products involve a lensing effect wherein light variations exterior to the product may be reflected by the product. The present invention minimizes such lensing effect in part by limiting the light impinging on product and by controlling the one or more specific wavelengths and intensities detected for processing. Additionally, the plurality of semiconductor light source arrays within illumination device  100  ensures uniform wavelengths and intensities of light at scanline  700  and at background  302  for comparison purposes. 
     Additionally, an opaque contaminant may be identified using the illumination device  100  of the present invention. A method of determining an opaque contaminant is to determine the deviation of the total quantity of light intensity as measured at detector  400  as the product passes through scanline  700 . An opaque contaminant reflects less light to detector  400  than a product that contains no contaminant. The illumination device  100  of the present invention produces illumination levels at scanline  700  that are not distorted by shadows created by uneven lighting and surface imperfections of the product to be scanned and sorted. 
     The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated process may be made within the scope of the appended claims without departing from the spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.