Abstract:
Apparatus and methods are provided for sensing the presence of bright white paper on a conveyor of a paper sorting system. The conveyor is constantly illuminated with ultraviolet light. When bright white paper is present in the inspection zone of the conveyor, it will re-radiate fluorescent light energy as a result of the ultraviolet light. Periodically, the inspection zone of the conveyor is illuminated with a second light source in the visible light spectrum. Light is collected from the inspection zone of the conveyor, including reflected light from the secondary source and including emitted fluorescent light energy as a result of the ultraviolet light falling on bright white paper. Periodically a microprocessor associated with the sensor senses reflected light from the second source to determine whether any object if present on the conveyor. The microprocessor then senses the level of fluorescent light energy being emitted from any object on the conveyor. The system determines first whether any object is present on the conveyor, as a result of the reflected secondary light, and then determines whether that object is bright white paper depending upon the measured level of emitted fluorescent light energy. Based upon these determinations, the stream of waste paper on the conveyor can be sorted into two fractions, one of which is the bright white paper.A method of sorting waste paper includes spreading waste paper out into a layer that is substantially one unit thick; detecting the presence or absence of a predetermined optical characteristic as the layer of paper is passed by a sensor; and controlling one or more actuators that direct a sheet of paper based on the presence or absence of the predetermined optical characteristic.

Description:
This application is a continuation of our pending application Ser. No. 09/301,715 filed Apr. 29, 1999, now U.S. Pat. No. 6,369,882 B1. 
    
    
     Be it known that I, Russell S. Bruner, a citizen of the United States residing at 726 Poplar Avenue, Mt. Juliet, Tenn. 37122 and I, David R. Morgan, a citizen of the United Slates residing at 9921 U.S. Highway 68 East, Benton, Ky. 42025, and I, Garry R. Kenny, a citizen of the United States residing at 6299 McDaniel Rd., College Grove, Tenn.  37046, and I, Paul G. Gaddis, a citizen of the United States residing at 2000 Alaska Way #156, Seattle, Wash. 98121, and I, David Lee, a citizen of the United States residing at 3614 North 30th Street, Tacoma, Wash. 98407, and I, James M. Roggow, a citizen of the United States residing at 14526 26th Avenue, Court East, Puyallup, Wash. 98374,  have invented a new and useful “System and Method For Sensing White Paper.”  “Method of Sorting Waste Paper.” 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a system and method for sorting mass recyclables and more particularly to a system for sensing and sorting white paper from other objects. 
     It will be appreciated by those skilled in the art that society desires to recycle as much of its waste materials as possible. For example, aluminum cans, plastic bottles, and other items have been the source of mixed recyclable efforts in the past. The assignee of the present application, Magnetic Separation Systems, Inc. (MSS) is a world leader in mixed recyclables. MSS is also the owner of many patents disclosing technologies for sorting and concentrating aluminum and sorting plastics. 
     One other type of mixed recyclable is paper. In the past, recyclable efforts have been dominated by hand sorting of paper by type. One common effort is curbside recycling. Other efforts have been to sort paper from other types of materials. Unfortunately, as with any other procedure, any type of hand sorting requires an intensive use of labor that is not always efficient. 
     What is needed, then, is a method and system that can sort white paper from a stream of other paper. This needed system must also be capable of sorting a stream of material from white paper in case the stream is dominated by materials other than white paper. The system must decrease the amount of labor presently being used. The system must be economical. The system must be effective. The system is presently lacking in prior art. 
     SUMMARY OF THE INVENTION 
     The present invention discloses a method of sorting waste paper, comprising spreading waste paper out into a layer that is substantially one unit thick; detecting the presence or absence of a predetermined optical characteristic as the layer of paper is passed by a sensor; and controlling one or more actuators that direct a sheet of paper based on the presence or absence of the predetermined optical characteristic. 
     The present invention discloses a system and method for sorting white paper, and especially a type of white paper commonly referred to as bright white paper, from other objects. One reason that recycling of bright white paper is very desirable is that the fluorescent chemicals added to such papers are expensive plus the bright white paper tends to be a very high quality paper fiber. Thus, this is a premium paper fraction for recycling. The system may also sort other objects from white paper. 
     The present invention uses an energy source that is preferably an ultraviolet light light that is concentrated in some manner onto an object. The energy is focused on the paper. If the paper is bright white paper, the ultraviolet radiation will cause the brightening agents in the white paper to fluorescence into an energy having a different and longer wavelength. The fluorescence is then measured. 
     The system and method of the present invention is particularly adapted for use in sensing the presence of bright white paper that flows past the sensor on a conveyor. The conveyor is constantly illuminated with the ultraviolet light. Also, a second light source is provided which periodically illuminates an inspection zone of the conveyor with a second light which is in the visible light spectrum, and preferably in the blue-green portion of the visible light spectrum. 
     A sensor located above the inspection zone of the conveyor collects light from the inspection zone of the conveyor. The collected light includes both emitted fluorescence from bright white paper located in the inspection zone and reflected light from the second light source reflected off of objects in the inspection zone. 
     Periodically, the sensing system senses first and second parameters of the light collected from the inspection zone. The first parameter is the level of reflection of the second light source in order to determine whether any object is present on the conveyor in the inspection zone. The second parameter sensed is the level of fluorescent light to determine whether an object present in the inspection zone is bright white paper. 
     Thus, if the sensed level of the reflected light from the second light source is below a certain threshold, the system will determine that no object is present in the inspection zone on the conveyor. If the sensed level of reflected light from the second light source is above a threshold level, the system will sense that some object is present in the inspection zone on the conveyor, but the identification of that object will depend upon the sensed level of fluorescent energy coming from that object. If the sensed level of fluorescent energy from the object is below a threshold level, the system will determine that the object is something other than bright white paper. If the sensed level of fluorescent energy is above a predetermined threshold, the system will determine that the sensed object is bright white paper. 
     The system may then send control signals to an ejection means which will eject either the bright white paper fraction or the non-bright white paper fraction from the paper stream flowing across the conveyor. 
     Accordingly one object of the present invention is to provide a system and method for sensing and sorting bright white paper from other objects. 
     Another object of the present invention is to provide a system that allows someone to sort bright white paper from other objects that is not labor intensive. 
     Another object of the present invention is to provide a system that can sort both bright white paper from other objects and other objects from bright white paper. 
     Still a further object of the present invention is to provide an accurate system for sensing bright white paper. 
     And another object of the present invention is to provide improved methods of sorting waste paper. 
     Other and further objects features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the following disclosure when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of the system and method of the present invention. 
         FIG. 2  is an optical diagram of the system and method of the present invention. 
         FIG. 3  is a block diagram of the secondary light source of the present invention. 
         FIG. 4  is an elevation view of one half of the reflector of the present invention as viewed from the side of the conveyor. 
         FIG. 5a  is a plan view of a lens of a sensor element. 
         FIG. 5b  is an elevation view of the lens of FIG.  5 a. 
         FIG. 5c  is a schematic elevation partly sectioned view of a sensing element showing the lens in place within a collimator tube which, in turn, is in place within a lens housing. 
         FIG. 6a  is a bottom view of a sensor housing, showing the layout of an array of lens cavities and cavities for receiving the second light sources. 
         FIG. 6b  is an elevation sectioned view of the sensor housing, taken along line  6 b— 6 b of FIG.  6 a.  FIG. 6b  shows the cavity in which the lens is received. 
         FIG. 6c  is another elevation sectioned view through the sensor housing, taken along line  6 c— 6 c of FIG.  6 a.  FIG. 6c  illustrates cavities in which the second light source elements are placed. 
         FIG. 7  is an elevation view of the sensor of the present invention as viewed from the side of the conveyor. 
         FIG. 8  is a schematic plan view of the conveyor showing the inspection zone. 
         FIG. 9  is a schematic side elevation view of the sensor in place above a conveyor, and also shows an associated ejection system for ejecting a fraction of the flowing paper stream in response to signals from the sensor. 
         FIG. 10  is a graph illustrating the wavelength of the ultraviolet energy source and of the emitted fluorescent energy from bright white paper. Also shown is a high frequency cut-off of a filter. 
         FIG. 11  is a block diagram of the electrical control system. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now the drawings, and particularly to  FIG. 1 , the system of the present invention is shown and generally designated by the numeral  10 . The system  10  includes a first light source  12  which preferably is an ultraviolet light source  12 . Ultraviolet light energy emitted from source  12  travels along paths  13  to a concentrator means  14  which then directs the light along paths  15  so as to focus the ultraviolet light energy on an inspection zone or focal zone  19  on a conveyor  100  located below the apparatus  10 . A portion of any light energy reflected from or emitted from any objects within the inspection zone  19  will travel upward as indicated by path  17  to a sensor  16 . If an object such as  102  is located in the inspection zone  19 , the light reflected from and/or emitted from the object  102  in inspection zone  109  and received by sensor  16  can be examined to determine the nature of the object  102 , and particularly to determine whether the object  102  is bright white paper. Other objects  101 ,  104  and  106  are also schematically illustrated in place upon the conveyor belt  100 . 
     The system  10  is particularly designed to determine whether an object in the inspection zone  19  is bright white paper. Bright white paper is a common name for a type of high quality paper commonly used in offices for printers and copiers. Bright white paper is typically a high quality paper fiber which has been treated with brighteners which cause the paper to fluoresce in the presence of ultraviolet light. When ultraviolet light energy falls upon bright white paper, the brighteners in the object will fluoresce and will emit light energy having a wavelength in the range of from about 400 to about 550 nanometers, which is in the visible light spectrum. The fluorescent energy emitted from bright white paper when an ultraviolet light is shown on it is great when compared to the amount of fluorescent energy that will be emitted from objects other than bright white paper. 
       FIG. 3  schematically illustrates a second feature of the system  10  which includes a second light source  20 . As will be further described below, the second light source  20  is contained within a common housing with the sensor  16 . The second light source  20  is preferably a source of visible light energy. One preferred second light source  20  is a blue light emitting diode which emits light energy having a wavelength of approximately 480 nanometers. Light from the second light source  20  travels downward along path  21  and is reflected off an object such as object  102  located within the inspection zone  19 . The reflected light energy travels back upward along path  23  where it is also received by the sensor  16 . 
     As will be further described below, the general purpose of the second light source  20  is to provide a means for detecting whether any object is present on the conveyor belt  100  within the inspection zone  19 . The sensor  16  and its associated control apparatus will be calibrated so that when the reflected light  23  exceeds a certain threshold, it will provide a determination that some object other than the black conveyor belt  100  is located within the inspection zone  19 . A second determination will then be made as to the level of fluorescent energy traveling upward along path  17  to the sensor  16 . If an object is present in the inspection zone  19 , but the level of fluorescent energy is below a predetermined threshold, the system  10  will determine that the object is not the desired bright white paper. On the other hand, if an object is determined to be present, and the amount of fluorescent energy  17  emitted by that object is above the predetermined threshold, the system  10  will determine that the object is bright white paper. 
       FIG. 10  is a graphical illustration of the electromagnetic radiation energy which might be picked up by sensor  16 . The horizontal axis represents the wavelength of the electromagnetic radiation, and the vertical axis represents the relative intensity of radiation. 
     There is a peak at approximately 360 nanometers in  FIG. 10  which represents the frequency of the ultraviolet light energy radiating from source  12 . To the extent that ultraviolet energy is merely reflected off of the focal zone  19  and received by sensor  16 , it would create a spike as shown in FIG.  10 . 
     As previously noted, when ultraviolet light energy falls upon a piece of bright white paper containing fluorescing additives, the additives fluoresce, thus converting some of the ultraviolet light energy into visible light energy having a longer wavelength (and thus lower frequency). In  FIG. 10 , a hump in the detected energy generally designated at  118  is representative of the fluorescent energy emitted from a piece of bright white paper. As is apparent in  FIG. 10 , the hump  118  begins at a wavelength of approximately 400 nanometers, peaks at about 440 nanometers, then drops off and is essentially absent at about 550 nanometers wavelength. 
     In order to isolate the fluorescent energy emitted from bright white paper, the sensor  16  preferably has a filtering means associated therewith. Preferably the filtering means is a band pass filter which will allow light energy only within the range of from 400 to 500 nanometers length to pass therethrough. The details of construction of this filtering means are further described below. In  FIG. 10 , the high frequency, and thus short wavelength, cut off of the filter is indicated by the curve  120 . Since this high frequency cut off is at a lower frequency than the ultraviolet light source, reflected ultraviolet light energy will not be sensed by sensor  16 . 
     The secondary light source  20  previously described operates at a wavelength of 480 nanometers, so that when the secondary light source reflects off of an object within the inspection zone  19  that reflected light  23  can pass through the filter means. 
       FIG. 7  is an elevation sectioned view of the sensing system  10  in place over the conveyor  100 . 
     The first light source  12  is a light module  46  which includes four parallel elongated tubular ultraviolet light bulbs  48  which are seen in cross-section in FIG.  7 . The light bulbs  48  extend transversally across the width of the conveyor  100  perpendicular to the direction of paper flow indicated by the arrow  110 . The bulbs  48  are contained within a housing  52 . Electronic starters  50  are associated with the bulbs  48  and cause the same to turn on and off when electrical power is directed thereto in a well known manner. A glass panel  54  covers the lower side of module  46 . 
     Thus, most of the ultraviolet light energy from bulbs  48  is emitted laterally as along the paths  13  previously noted, where it falls upon the concentrators  14 . The concentrators  14  are preferably curved reflectors formed in the shape of an arc of an ellipse so that all light falling thereon will be reflected toward a focal point  58  lying in the center of the inspection zone  19  on the conveyor  100 . The ultraviolet light energy reflected from concentrators  14  follows paths generally designated as  15  to the focal point  58 . 
     The geometric layout of the concentrator  14  is best illustrated in the schematic representation shown in FIG.  2 . As indicated in  FIG. 2 , the light source  12  has a central point  112  which is generally coincident with the upper focal point  112  of an ellipse  114  upon which the reflecting walls of concentrator  14  lie. The lower focal point  58  of the ellipse  114  falls upon the conveyor  100  in the center of the inspection zone  19 . 
     Referring now to  FIGS. 4 and 7 , the concentrator  14  is constructed from first and second reflecting walls  24  and  25  which are supported within a housing  60  of the apparatus  10  by a plurality of brackets such as  26  and  27 . The reflector walls  24  and  25  are preferably polished stainless steel. The brackets such as bracket  26  shown in  FIG. 4  may also be manufactured from stainless steel. 
     The lower end of the housing  60  of apparatus  10  is closed by a transparent glass shield  116  which allows the light energy to pass therethrough while preventing dirt, paper and debris from entering the apparatus  10 . 
     The reflecting walls  24  and  25  may be generally described as an elliptical reflecting lens having focal point  58  within the inspection zone  19 . 
     Referring now to  FIGS. 6a ,  6 b and  6 c, a sensor housing or lens housing is shown and generally designated by the numeral  124 . The sensor housing  124  is an elongated housing which lies across the width of the conveyor  100  and can be described as being transverse to and is perpendicular to the direction of travel  110  along the conveyor belt  100 . 
     The sensor housing  124  has a plurality of lens cavities  42  and a plurality of secondary light source cavities  126  defined therein. An array of sensor elements are carried by housing  124 . 
       FIG. 6b  is a sectioned view taken along lines  6 b— 6 b of  FIG. 6a , showing the details of construction of one of the lens cavities  42 . 
       FIG. 6c  is a sectioned view taken along lines  6 c— 6 c of  FIG. 6a , showing the details of construction of two secondary light source cavities  126 . 
     The sensor housing is held in place by a bracket  56  as shown in FIG.  7 . 
     Turning now to  FIGS. 5a-5c , the details of construction of one of the sensing elements of sensor  16  will be described. 
       FIG. 5c  is a schematic elevation cross-section view similar to FIG.  6 b and schematically illustrating the components of one sensing element  128  of sensor  16 . Each sensing element such as  128  is associated with one of the lens cavities  42 . 
     A collimator tube  40  is received in each lens cavity  42  and held in place therein by set screws received through threaded holes  130  (See FIG.  6 b). In one preferred embodiment each collimator tube is approximately 4″ long, 1″ outside diameter and ¾″ inside diameter. The collimator tube  40  may be an aluminum tube having a matte black finish. The collimator tube  40  ensures that the light being collected by the sensing element  128  is substantially only light traveling directly upward from an object immediately below sensing element  128  in the focal zone  19 . 
     Located at the upper end of each collimator tube  40  is a semi-spherical lens  32 . Plan and side elevation views of one lens  32  are shown in  FIGS. 5a and 5b , respectively. 
     Located immediately above the lens  32  is the filtering means  122  which includes first and second optical filter plates  34  and  36 . The first optical filter plate is a high frequency pass filter  34 , and the second optical filter plate  36  is a low frequency pass plate  36 . As will be understood by those skilled in the art, the filter plates  34  and  36  can be selected to determine the frequencies of light energy which really will not pass therethrough. Filter plates  34  and  36  are standard optical filters which are available from Edmund Scientific. 
     The light energy which passes through the lens  32  is focused within a cone having outer boundaries along the dashed arrows  132  and  134  which focuses that energy upon a photo electric detector  38 . The photo electric detector  38  is a silicone photo diode. 
     Thus, the band pass filter means  122  will pass fluorescent energy having a wavelength longer than a lower limit of about 400 nanometers, which lower limit is longer than the wavelength of the ultraviolet light from source  12 . The filtering means  122  will further block fluorescent energy having a wavelength longer than an upper limit, which in the illustrated embodiment is preferably about 500 nanometers. The range of light energy having wavelength from 400 to 500 nanometers can be described as being in the blue-green portion of the visible light spectrum. 
     As previously noted, the light emitted from second light source  20  has a wavelength of approximately 480 nanometers, which will be passed by the filtering means  122  when said light is reflected from an object in the inspection zone  19 . 
     Referring now to  FIG. 9 , a general layout of the system  10  and associated conveyor apparatus is shown, whereby the sensor system  10  may be utilized to detect bright white paper on the conveyor  100  and to send control signals to an ejector mechanism  70  which uses air jets  80  to eject paper from the conveyor  100 . 
     The conveyor  100 , ejector system  70  and associated apparatus are shown in detail in an application of Michael R. Grubbs et al, entitled PAPER SORTING SYSTEM, U.S. patent application Ser. No. 09/301,992, filed Apr. 29, 1999, now U.S. Pat. No. 6,250,472 issued Jun. 26, 2001, and assigned to the assignee of the present invention. The details of construction of the system shown in the Grubbs et al. patent are incorporated herein by reference as if the same were fully set forth herein. 
       FIG. 8  is a schematic plan view of the conveyor  100  illustrating an elongated strip shaped inspection zone  19  lying across a width  142  of the conveyor belt  100 . The focal point  58  previously described with regard to the side elevation view of the ellipse is in fact a focal line  58  which defines the center line of the inspection zone  19 . 
     In the system shown in  FIG. 9  the first conveyor  100  conveys the paper objects  102  from right to left so that they pass under the sensor  16 . The conveyor  100  is traveling at a very great rate of speed (as much as 1200 ft/min), and as the objects reach the left hand end of conveyor  100  they are launched off of the conveyor  100  and fly through the air across an ejection gap  136  toward a product conveyor  138 . 
     Signals from the photo electric detector  38  are converted into digital signals which are directed to a microprocessor  140  which performs the measuring, sensing, comparing and evaluating functions. The microprocessor  140  will go through the evaluation steps described below, and at appropriate times will send a control signal to the ejector system  70  to direct compressed air to jet  80  so that the air jet  80  will be directed against an object which at that time is passing across the ejection gap  136 . Any object impacted by an air jet as it crosses the gap  136  will be blown downward between the two conveyors  100  and  138  and will be part of an ejected paper stream fraction. Non-ejected paper will flow across the gap  136  and fall onto the conveyor  138  which will lake it to another location. 
       FIG. 11  is a schematic block diagram of the control system of the apparatus  10 . 
     The microprocessor  140  may be a XYCOM model PCD1048 microprocessor available from XYCOM Automation, Inc. The microprocessor  140  preferably has touch screen operated control station  144  which allows system variables to be changed and the sort selection to be changed. The system provides the ability to perform a positive sort where non-bright white paper is ejected or a reverse sort where the bright white paper is ejected when the concentration of the targeted paper is less than that of the non-targeted paper. 
     The microprocessor  140  is connected by interface  146  to power supply ballasts  148  and then to the ultraviolet light source  12 . 
     The microprocessor  140  is connected by a ribbon cable  150  to a rear receiver board  152  which is in turn connected by a ribbon cable  154  to the sensor unit  16  and the secondary light sources  20  contained in the sensor housing. 
     A power supply  156  is connected to the rear receiver board  152 . 
     An LED power supply  158  is connected to the secondary light source  20 . 
     The rear receiver board  152  includes amplifiers and analog to digital converters. Signals from the sensor  16  are communicated over cable  154  to the rear receiver board  152  where they are amplified and digitized before being passed over cable  150  to the microprocessor  140 . 
     The microprocessor  140  also communicates over cable  160  to the ejector control system  70  which includes a plurality of solenoid driver boards  162  and an array of solenoid valves  164  which control the flow of air to the air jets  80 . A solenoid power supply  166  is connected to the driver boards  162 . 
     Methods of Operation 
     The methods of operation of the present invention will now be described with reference to  FIGS. 7 and 9 . 
     The system  10  provides an apparatus and method for sensing the presence of bright white paper on the conveyor  100  of the paper sorting system like that described in the Grubbs et al. application which has been incorporated herein by reference. 
     The conveyor  100  is directing a stream of waste paper from right to left as seen in  FIG. 8  at a very high speed below the sensor  16 . 
     The ultraviolet light source  12  is constantly on and constantly illuminates the inspection zone  19  on the conveyor belt  100  immediately below the sensor  16 . As previously described, that ultraviolet light energy is focused on the inspection zone  19  by means of the elliptical shaped walls  24  and  25 . 
     When a piece of paper such as  102  passes through the inspection zone  19 , if the paper  102  is bright white paper, it will fluoresce and will re-radiate fluorescent light energy from the bright white paper. As previously described with reference to  FIG. 1 , a portion of that fluorescent energy will travel directly upward along the path  17  to the sensor  16 . 
     Throughout this process, the inspection zone  19  will also be periodically illuminated with light from the second light source  20 , which as previously noted is preferably a blue light emitting diode. In a preferred embodiment, the secondary light source  20  illuminates the inspection zone  19  every 3 milliseconds. 
     Light from the inspection zone  19 , including both reflected light and emitted fluorescent light, is collected by the collimator tube  40  and passes through the lens  32  and the filtering means  122  to the photo electric detector  38 . The photo electric detector  38  will convert the light energy into an electrical signal, which, in turn, is converted into a digital electric signal which is directed to the microprocessor  140 . 
     A first measuring step or sensing step is performed by microprocessor  12  when the secondary light source  20  is on. This first sensed parameter will thus indicate the level of reflected light from secondary source  20 , and if that level of reflected secondary light exceeds a predetermined threshold, the microprocessor  140  will determine that some object is present in the inspection zone  19  on the conveyor  100 . Then, when the secondary light source  20  is off, the microprocessor  140  will perform a second measuring or sensing step while only the ultraviolet light illuminates the inspection zone  19 . In this second step, the sensed light energy will be compared to the predetermined threshold for fluorescent energy, and if that threshold is exceeded, the microprocessor  140  will determine that an object present in the inspection zone  19  is bright white paper. 
     The microprocessor  140  can be described as periodically sensing first and second parameters of the light collected by the sensing element. The first parameter is the level of reflection from the inspection zone  19  of light originating with the secondary light source  20 . If this first parameter exceeds a certain threshold, an indication is generated indicating that some object is present in the inspection zone  19  other than the conveyor belt  100  itself. 
     The second parameter sensed by the microprocessor  14  is the level of fluorescent light energy which has been radiated from an object within the inspection zone  19 . If this level of fluorescent light energy exceeds a predetermined threshold, this will generate an indication that an object which is present in the inspection zone  19  is, in fact, bright white paper. 
     If the first parameter indicates that an object is present, but the second parameter indicates that the object is not bright white paper, then it is known that the object is one which should be separated from the bright white paper. 
     Depending upon the signals generated by the microprocessor  140 , a control signal is then sent to the ejection system  70  to direct compressed air to air jets  80  to eject a selected fraction of the stream of paper which is moving along the conveyor  100 . It will be appreciated that the microprocessor  140  can be programmed to either eject the bright white paper or to eject the non-bright white paper. Preferably, whichever type of paper comprises the smaller portion of the stream of paper flowing across conveyor  100  will be ejected, whereas the major portion will be allowed to flow across to the product conveyor  138 . 
     The periodic illumination by secondary source  100  is preferably performed approximately every 3 milliseconds. In general, it may be described as being performed in excess of 100 times per second. Preferably the microprocessor  140  periodically senses the light being collected from the inspection zone  19  at the same periodic rate at which the secondary light source  20  is illuminating the inspection zone  19 . 
     The paper objects will be traveling on the conveyor  100  at a speed of approximately 1200 feet per minute or 20 feet per second, thus by strobing every 3 milliseconds, a piece of letter size paper, 8½″ wide would be strobed at least 10 times as it passed under the sensor  16 . 
     The sensor  16  and associated microprocessor  140  can be described as an evaluating means for evaluating the level of fluorescent energy detected by each of the sensing elements to determine whether bright white paper is located below each sensing element. 
     As previously noted, there is preferably a linear array of sensing elements arranged across the width of the conveyor belt. For example, for a 48″ wide conveyor, there may be 32 sensor elements. Signals from each of the sensing elements are separately analyzed, and control signals are separately sent to an array of 32 air jets  80 , so that there is an ejection air jet  80  associated with each of the sensing elements. Thus, a paper object may be located toward one edge of the conveyor belt and its location will be determined by the identification of the sensing elements which sense the presence of that object therebelow. Then the associated air jets can be activated at the proper time to blow the sensed object through the ejection gap  136  if desired. 
     Thus, it is seen that the apparatus and methods of the present invention readily achieve the ends and advantages mentioned, as well as those inherent therein. While certain preferred embodiments of the invention have been illustrated and described for purposes of the present disclosure, numerous changes in the arrangement and construction of parts and steps may be made by those skilled in the art, which changes are encompassed within the scope and spirit of the present invention as defined by the appended claims.