Abstract:
In one example embodiment, a seed sensor is disclosed adapted to fit a conventional mounting location in existing seed tubes that provides improved performance by providing a wide light source (more LEDS), a wide photodetector and a current profiling scheme for the LEDs that provides more light at the opposite ends of the LED array. A result of such an arrangement is to improve seed resolution and to reduce seed spatial variability within the seed tube.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority to and the benefit of the following provisional patent applications having Ser. No. 61/693,573 and filed on Aug. 27, 2012, and Ser. No. 61/698,163 Sep. 7, 2012, respectively, which are hereby incorporated by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    As is known in the art, a field seed planter includes a group of seed chutes or seed discharge tubes, one for each row for simultaneous planting. Each of these seed chutes or tubes convey individual seeds from a seed dispenser in conjunction with a hopper or other seed supply to individual furrows formed in the ground by the planter as it moves across a field. Various monitoring and counting arrangements have been utilized for obtaining a count of the number of seeds dispensed by such seed planters. Such counting is particularly useful in determining and controlling the density or population of seeds planted in order to optimize crop yield. Also, more recently, seed spacing information is of interest since yield is positively affected by the uniform spacing of such seeds. 
         [0003]    The prior art has generally utilized photoelectric devices to sense the passage of individual seeds through the seed chutes or tubes. Such arrangements generally have included a light source such as a light emitting diode (LED) positioned to one side of the seed chute or tube and a light responsive element such as a photoresponsive transistor or diode positioned at the opposite side of the tube. Hence, the photoresponsive element normally produces a steady state signal level in response to the light incident thereupon from the light source. However, as a seed passes through the chute and comes between the light source and light responsive element, the level of light incident upon the light responsive element momentarily decreases. Responsively, the light responsive element produces a momentary change in the normal or steady state signal level output, which represents potentially a seed. 
         [0004]    Various electrical and electronic circuits have been devised to receive the light responsive element output signal and respond to the changes in the level thereof due to the passage of a seed through the seed chute. Ideally, such electronic circuits should produce a discrete signal or pulse for each seed passing through the chute. Accordingly, accurate information as to the number of seeds dispensed by a given chute may be obtained by counting these pulses. 
         [0005]    However, various challenges to accuracy of seed counting are encountered including considerable dirt, dust and the like as the planter moves through the field. Moreover, various coatings are commonly provided on seed grains, and these coatings often accumulate in the seed chutes or tubes. Accordingly, the foregoing accumulations of material in the seed tube tend to interfere with proper operation of the photoresponsive system. Additionally, the characteristics of the photoresponsive element and light source change somewhat over time, thus changing both the ambient light level incident upon the photoresponsive element and its response thereto and to changes in light level due to the passage of seeds. These changes may, if uncompensated for, greatly reduce the reliability of the response of the photoresponsive element. A related problem is that of drift or changes over time in the nominal characteristics of the circuit elements utilized in the electronic circuits. For example, various circuit parameters such as gain, voltage levels, or the like may vary or drift somewhat over time. Such drift may occur for example due to environmental changes, detracting from optimum operation of the circuits and hence from the reliability of the count obtained therefrom. 
         [0006]    Yet another challenge occurs as seed deposition rates increase the ability to reliably count multiple seeds which fall through the seed chute in close proximity or even partially overlapping decrease. In such instances, both the photoresponsive element and the associated electronic circuit may be unable to respond rapidly enough to reliably produce a separate counting pulse for each seed. A related problem is often encountered with relatively small, fast moving seeds such as soybeans. Additionally, soybeans are generally dispensed at a relatively high rate or density. Hence, today&#39;s seed sensing systems may be incapable of sufficiently rapid response to reliably count each seed and to distinguish between seeds and dust or other foreign matter. 
       SUMMARY OF INVENTION 
       [0007]    In one example embodiment, a seed sensor was developed to fit the conventional mounting location on existing seed tubes but still provide improved performance over the current production sensors by providing a wide light source (more LEDS), a wide photodetector and a current profiling scheme for the LEDs that provides more light at the opposite ends of the LED array. A result of such an arrangement is to improve seed resolution and to reduce seed spatial variability within the seed tube. 
         [0008]    In one example embodiment, a seed counting device is provided for counting seeds passing through a longitudinal portion of a seed tube having a front, back and two side walls, the counting device including a sensor assembly adapted to be mounted on a front and back wall of the seed tube, said sensor assembly including an LED (light emitting diode) array disposed opposite a photodetector device adapted to receive light from the LED array, the photodetector device configured to generate signal pulses in response to interruptions in light received from the LED array, the LED array comprised of a plurality of LEDs that are disposed in a line that is substantially perpendicular to the longitudinal portion of the seed tube. The seed counting device further includes a controller means configured to control a current driving each of the plurality of LEDs so as to generate a current profile for a selected LED array, controller means further configured to increase the drive current of at least one LED located adjacent to the tube side wall so as to increase its intensity, thereby improving spatial position detection of seed counting device of a seed passing through the seed tube and allow for adjustments to improve seed deposition accuracy. 
         [0009]    In another example embodiment, a particle detection system is provided with improved spatial position detection for substantially distinguishing among particles such as seeds and dust, the particle counting system including a sensor assembly adapted to be mounted on opposite sides of a chute member through which the particles are to pass through, the sensor assembly including an LED (light emitting diode) array disposed on the chute member opposite a photodetector device adapted to receive light from the LED array, the photodetector device configured to generate signal pulses in response to interruptions in light received from the LED array, the LED array comprised of a plurality of LEDs that are disposed in a line that is substantially perpendicular to the longitudinal axis of the chute member. The particle detection system also including a controller means configured to control a current driving each of the plurality of LEDs so as to generate a current profile for a selected LED array, controller means further configured to increase the drive current of at least two LEDs located at each end of the LED array so as to increase its intensity, thereby improving spatial position detection of the particle passing through the chute member and allow for adjustments to improve particle deposition accuracy. In a related embodiment, wherein controller means is configured to individually pulse the LEDs in the array so as to improve particle detection and deposition. In another related embodiment, controller means is configured to communicate with a particle deposition system so as to modify a ground speed of the deposition system as a function of a particle detection data received by controller means. 
         [0010]    In yet another example embodiment, a method for detecting seeds in a seed deposition system is provided having an LED array and a photodetector member adapted to receive light from the LED array, the photodetector member generating a signal pulse as a seed interrupts the light received by the photodetector member. The method includes the steps of selecting an LED array with a predetermined number of LEDs as a function of the type of seeds to be detected and the step of generating a current profile for a selected LED array depending on the number of individual LEDs in the array and the type of seeds to be detected. The method also includes the step of driving the current in at least two LEDs at each end of the LED array such an intensity of the at least two LEDs is higher than the LEDs disposed therebetween. 
         [0011]    In yet another example embodiment, a seed counting device is provided herein with improved spatial position detection of a seed passing through a seed tube so as to allow for adjustments that will improve seed deposition accuracy and crop yield in seed farming applications. A seed counting system is also provided herein with improved spatial position detection for substantially distinguishing among seeds, multiple seeds, and foreign material such as dust in seed farming applications. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]      FIGS. 1 and 14  are a top, cutaway view and a perspective view of a seed tube with a seed dropping through the tube with an LED array on one end and a photodetector on the other (there is also a clear window in front of the photodetector). Both the LED source and the photodetector cover the entire width of the tube. 
           [0013]      FIGS. 2A-2B  illustrate circuit diagrams of a 10 LED array and a wide photodetector of  FIG. 1  where the output is used for data acquisition during the testing process. 
           [0014]      FIGS. 3A-3C  illustrate front, side and rear views of the LED source array of a sensor assembly according to the invention. 
           [0015]      FIG. 4  illustrates an alignment exercise for an LED of the invention and the photodetector in a seed tube in the vertical direction. 
           [0016]      FIG. 5  illustrates a variability graph of a 10 LED sensor assembly reflective of the data provided in Table 1 of the specification. 
           [0017]      FIG. 6  illustrates a variability graph of a 3 LED sensor assembly reflective of the data provided in Table 2 of the specification. 
           [0018]      FIG. 7  illustrates a circuit diagram of an embodiment of a sensor assembly according to the teachings of the invention. 
           [0019]      FIGS. 8A-8C  illustrates top, back and side views of a lightpipe or lens element for use in connection with a seed sensor assembly according to the teachings of the invention. 
           [0020]      FIGS. 9A-9B  illustrate side and top views of a lightpipe or lens element within a seed tube for capturing light projecting therethrough for use in connection with a seed sensor assembly according to the teachings of the invention (top view, multiple arrows; side view, one arrow). 
           [0021]      FIG. 10  illustrates side and top views of a lightpipe with or without a circuit board (view A) and at least two lightpipes with or without a circuit board (view B) for using in connection with a seed sensor assembly according to the teachings of the invention. 
           [0022]      FIG. 11  illustrates an LED projecting two beams of light through a lens element through to two detectors for potential dust detection according to the teachings of the invention. 
           [0023]      FIG. 12  illustrates a lightpipe assembly or lens at one end and a microphotodetector at another end as an embodiment of an element in a seed sensor assembly according to the teachings of the invention. 
           [0024]      FIG. 13  illustrates a lightpipe assembly with a Fresnel lens at one end and a microphotodetector at another end as an embodiment of an element in a seed sensor assembly according to the teachings of the invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0025]    Following are more detailed descriptions of various related concepts related to, and embodiments of, methods and apparatus according to the present disclosure. It should be appreciated that various aspects of the subject matter introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the subject matter is not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes. 
         [0026]    Referring now to  FIG. 1 , there is shown one example embodiment of a seed sensor assembly  100  in a seed tube  102 . Specifically, there is shown a top, cutaway view of seed tube  102  with a seed  104  dropping through the tube with a 10 LED array  110 A- 110 J on one end and a photodetector member  120  on the other (in this example embodiment there is also a clear window in front of the photodetector). This figure shows a top view of seed tube  102  with one seed  104  free-falling. Both the 10 LED array and the photodetector member are spaced back from the tube&#39;s (or chute&#39;s) inner wall slightly and photodetector  120  extends slightly beyond the chute&#39;s inner wall in an orthogonal direction (orthogonal to the direction of the falling seed and the length of the seed tube). In this example embodiment, the photodetector is the 880×110 unit (dimensions in mils) covering the full width of seed tube  102  (700 mils). The 10 LED array also attempt to span the entire width of tube  102  providing light rays over the entire area including near the side walls  103 A- 103 B. This example embodiment of sensor assembly  100  consists of a 10-LED array on 72 mils pitch.  FIG. 14  is an example of a circuit board with the 10-LED array that is disposed behind a clear plastic window plate that is secured on one side of the seed tube, opposite a photodetector. In related embodiments, the LED array does not use a window plate or is coated with a special coating to protect the array surface and/or slows down the surface degradation of the array. In related embodiments, the LED array comprises other combinations such as one 3-LED array or a 5-LED array, each of which can be optimized to improve seed counting and identification by varying the current profiling scheme of the LED array used. 
         [0027]    Although this example sensor assembly provides various improvements over current sensors (in the example embodiment, at least three), one or more of these improvements are combined and incorporated into various embodiments of sensor assemblies. A first sensor assembly improvement includes a wide light source comprised of 10-LED array  110  (LEDs  110 A- 110 J) of LEDs that are spaced evenly across the narrow dimension of seed tube  102 . The ten (10) SMD (surface mount devices) LEDs still provide a pitch dimension that would allow the LEDs to be “Pick-n-Placed” by conventional component placement equipment. The ten LED array in this example configuration also provides a fairly even light source considering the dimensions of the seeds falling through the tube. The individual LEDs at each end of array  110  were very close to side walls  103 A and  103 B of tube  102 , thereby providing light coverage across the whole tube. Another improvement illustrated in  FIG. 1  includes the use of a wide photodetector member  120  that is 880 mils wide to cover the entire width of the seed tube versus current photodetectors which are 600 mils wide while the inner seed tube dimension is about 700 mils wide. 
         [0028]    Referring now to  FIGS. 2A-2B , in this example embodiment there are shown circuit diagrams  210  and  220  of 10-LED array  110  and of photodetector  120  of  FIG. 1 , respectively. Circuit  210  illustrates LED array  110  with the LED drive circuitry and circuit  220  illustrates the opposing end circuitry for the photodetector and transmission of data (output  250 ) to a data acquisition system. In this example embodiment, the current is increased for each of the LEDs at each end of the LED array (e.g.,  110 A and  110 J) to improve upon spatial variability according to the teachings herein. Extra current is provided to the two extreme LEDs as well as the adjacent LEDs (e.g.,  110 B and  110 I) in from the extreme LEDs (LEDs  110 A and  110 J). Pulses received at photodetector  120  are eventually outputted (output  250 ) to a data acquisition system. Ordinarily, this output would go to an A/D converter of an embedded controller for processing (such as taught in U.S. Pat. No. 5,635,911 to Landers et al, and is incorporated by reference herein in its entirety). This circuit  220  provides “0” voltage bias to photodetector  120  to obtain a speed advantage and a trans-impedance amplifier  224  then converts the short-circuit photodetector current to a voltage. In addition, this amplifier serves as a log amplifier which is used to provide a consistent voltage pulse for a given blockage percentage no matter the ambient optical attenuation. A level shifter  226  is also provided here to keep the signal in a dynamic range. A fixed gain amplifier ( 222 ) is shown here for experimental testing. Several gain options would be available under the power of the embedded controller (see also  FIG. 7  for more complete description of the seed counting system from a circuit level perspective). 
         [0029]    Referring again to  FIGS. 1 and 2 , another improvement in the sensor assemblies described herein includes the use of Current Profiling for the LEDs located at each end of the LED array (such as  110 A,  110 B,  110 I and  110 J) closest to the tube walls ( 103 A and  103 B). In this example embodiment (and as described above), the wider LED array  110  and wider photodetector  120  provide coverage that aid in reducing the spatial variability between seeds. Hence a seed falling (e.g., seed  104 ) anywhere in the seed tube sensing area (space  105  between walls  103 A and  103 B) will provide much the same signal shape. However, seeds falling near side wall  103 A or  103 B typically do not have the same blockage of light (which generates the signal pulse that represents the seed count) as seeds falling closer to the center of space  105 . In LED array circuit  210 , LED  110 A corresponds to LED  110 A at one end of array  110  and LED  110 J corresponds to LED  110 J of array  110  at the other end of the array on the seed tube wall. To help compensate or correct for this, in one example embodiment, the LED current in each of the two extreme end LEDs (LEDs  110 A and  110 J) is increased to a factor of 1.50 times that of nominal. The next two LEDs are increased by a factor of 1.25. This tends to weight seeds near the side wall more heavily in that they block a larger amount of light. Other LED currents may require adjusting yet to obtain optimum variability. 
         [0030]    A result of the various improvements described above to reduce spatial variability, is that single seeds falling through the seed tube will give much the same signal pulse in terms of amplitude, area, and duration. This allows an algorithm used to differentiate singles from doubles from triples to function better. This consistency in pulse characteristics allows for a cleaner separation between single seeds and double seeds (two seeds falling through the sensing area at much the same time). This also applies to separation of doubles and triples, and so forth. This consistency also helps differentiate between seeds and foreign material. Dust particles can more easily be segregated from seeds and thus not counted. 
         [0031]    In another example embodiment, the accuracy count of the seed sensor is improved by the use of Current Profiling along with the expanded LED array and larger photodetector member when seeds are falling through the sensor at a high rate and are not well singulated. This is particularly a problem with high rate soybeans. This improvement in count accuracy is due to reduced spatial variability of single seed pulses which allows easier separation of seeds falling at about the same time. In yet another related embodiment, seed sensing is improved when implementing the technique of individually pulsing the LEDs in the array. It was determined that a current profile of 1.5/1.25/1.0 would be optimal and operational for the targeted applications, but is not limited to this range. 
         [0032]    Referring now to  FIGS. 3A-3C , there are shown front, side and rear views of a sensor housing to support an LED array according to the invention. In this example embodiment and with reference to  FIG. 14  as well, LED array  110  is disposed on circuit board  112  and covered with a clear window plate  119 . This assembly is coupled to seed tube  102  via a fastening member  109 . In other related embodiments, other fastening means can be used depending upon tube  102  construction or that of the LED array, the window plate may be eliminated. 
         [0033]    Referring now to  FIG. 4 , there is shown an example of an alignment exercise for an LED and the photodetector in a seed tube in the vertical direction. Since the tube walls of interest are not parallel, it is estimated that a 3 degree correction is needed. 
         [0034]    In this example embodiment, 10-LED array  110  was configured to provide the same optical intensity to photodetector member  120  as a 3-LED array. In order to get the 10-LED array to the same level as a 3-LED array, the LED current was set to a nominal (333/178) 6 ma=11.2 ma. Consider the following: 
         [0035]    Center Leg=12 ma 
         [0036]    Right Leg=12+6+3=21 ma 
         [0037]    Left Leg=12+6+3=21 ma 
         [0038]    Total Current=48 ma (3 ma in the right &amp; left legs are common to two LEDs) 
         [0039]    Tables 1 and 2, respectively, provide data from a 10-LED array and a 3-LED array variability test and illustrate the voltages from the first stage trans-impedance amplifier when a 0.19 inch diameter vertical rod is used to block the light between the light source (such as the LED array) and the photodetector. The data is gathered from a top view of the seed tube and shows the position of the rod for corresponding voltages for the 10 LED array (Table 1) and also for comparison a previous 3 LED array (Table 2). The position of the voltage labels in the tube correspond to the position of the rod. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Increased LED current 
                 Top View 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10-LED 
                 No seed 
                 0.561 355.8331 
                   
                   
               
               
                   
                 0.550 
                 0.551 
                 0.549 
               
               
                   
                 0.546 
                 0.543 
                 0.548 
               
               
                 Photodetector 
                 0.543 
                 0.541 
                 0.546 
                 LEDs 
               
               
                   
                 0.545 
                 0.543 
                 0.545 
               
               
                   
                 0 550 
                 0.549 
                 0.545 
               
               
                   
               
             
          
         
       
     
         [0040]    These are top views of the tube with voltages from the 1 st  trans-impedance amplifier when blocking light with a vertical 0.19 inch diameter rod. 
         [0000]    
       
         
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
             
               
                   
                 3-LED 
                 No seed 
                 0.562 363.584 
                   
                   
               
               
                   
                   
                 0.551 
                 0.553 
                 0.551 
               
               
                   
                   
                 0.544 
                 0.539 
                 0.544 
               
               
                   
                 Photodetector 
                 0.536 
                 0.535 
                 0.536 
                 LEDs 
               
               
                   
                   
                 0.543 
                 0.541 
                 0.543 
               
               
                   
                   
                 0.546 
                 0.551 
                 0.546 
               
               
                   
                   
               
             
          
         
       
     
         [0041]      FIGS. 5 and 6  illustrate LED profile and light intensity variability graphs for the 10 LED and 3 LED sensor assemblies, respectively, as described previously. The LED profile pertains to increasing the current of the LEDs at the far end of the array closest to the side walls to compensate for the reduced light blockage of a seed located near the side wall. For these graphs, the photodetector short circuit current is shown in units of μa. These were reverse calculated from the measured voltages from the 1 st  trans-impedance amplifier. Note that with greater light coverage in the tube with the 10-LED array and the use of current profiling that the variability is less, hence having a flatter or more even profile then with the 3-LED array. 
         [0042]    Referring now to  FIG. 7 , in this example embodiment there is shown a circuit diagram  300  of an embodiment of a seed sensor assembly that uses an STM32F101C6T6 microcontroller  302  according to the teachings of the invention. The front end of circuit  300  includes LED circuit  210  and photodetector circuit  220 . The output from the front end or photodetector circuit  220  provides input to the embedded A/D (analog-to-digital) converter of controller  302 . The seed counting algorithm functions are based on the digital information from the A/D. Power supply and other support circuits are shown that enable the invention and algorithms. The sensor assembly provides a single-end output that can also be used by the sensor assembly to receive data from a central control unit. An example of such communications would be a request by the control unit for the sensor assembly to perform a self-test. The embedded controller can modulate some of the LEDs such that a self-test can be conducted by the sensor assembly with results transmitted to the control unit. 
         [0043]    In a related embodiment, a seed sensor assembly is provided that substitutes a single discrete photodiode for the wide photodetector. This detector resides on a circuit board and a light pipe or light tube or prism channels light from the LEDs to the photodetector diode. In another related embodiment, a Fresnel lens  800 A is used in place of the window plate in front of the photodetector (PD)  920  in order to capture more light from the LEDs (see  FIGS. 13 and 14 ). 
         [0044]    Referring now to  FIGS. 8-14 ,  FIGS. 8A-8C and 12  illustrate various view of a lightpipe or lens element  800  (or optical adapter) for use in connection with a seed sensor assembly according to the teachings of the invention. In this example embodiment, lightpipe member  800  includes a front surface  802  for receiving light that is focused to a back end  804 . Instead of directly coupling light into the photodetector, in this example embodiment, optical adaptor element  800 , which is made of glass or/and plastic, is inserted before the photodetector. 
         [0045]    Referring now to  FIGS. 9A-9B , there is shown side and top views of a lightpipe or lens element  800  located within seed tube  102  having LED array  110  that generates light  111 . Lightpipe  800  captures light  111  projecting therethrough from array  110  for use in connection with a seed sensor assembly according to the teachings of the invention. In particular, there is shown a detector assembly  920  of a small area detector coupled to an optical adaptor (or lightpipe). In this example, the optical adaptor transforms the detection area into a long slit which is desirable in seed sensing/counting applications. The back end  804  (exit) of the optical adaptor is connected to the optical sensor by glue, screw, snap, direct contact or other means. The front end  802  (entrance or light receiving end) of the optical adaptor sits where the optical sensor was, as an effective optical sensor. Light is firstly collected by the front end (wide end)  802  of the optical adaptor, transported by reflection and total-internal-reflection (TIR), and eventually coupled via back end  804  into the optical sensor. This apparatus forms a sight waveguide or light-pipe. In an alternative embodiment, a glass window can be attached to the front end of the adaptor, to protect the adaptor from contamination, mechanical scratches or chemical corrosion. The other part of the seed sensing system will work as usual. 
         [0046]    A similar configuration is proposed for the light emitter, in this case, light from an emitter, such as an LED or Laser diode, is coupled into the waveguide at one end and travels through the waveguide to the exit end where the light will emerge to the desired location, such as the seed tube facing the detector aperture. Previous large area optical sensors would normally cover the width of the seed tubing, thereby increasing the price of the overall sensor assembly. The optical adaptor described herein transforms a much cheaper small sensor area (back end of the adaptor) into an effectively large collection area (front end of the adaptor). The small sensor and adaptor combination works exactly as the large area sensor, but costs much less and offers more flexibility in mechanical layout since the adapter may have bends and turns in it. Adapters could be machined parts or molded so as to reduce its cost further. Using the optical adaptor, the sensing area can be effectively and easily reshaped without having to reconfigure other hardware components of the seed sensor. The optical adaptors taught herein apply but is not limited to seed sensors. 
         [0047]    Referring now to  FIGS. 10A-10D , there are shown side and top views of a lightpipe  800  (and  800 A and  800 B) with or without a circuit board  112 A and at least two lightpipes  800 A,  800 B with or without a circuit board for using in connection with a seed sensor assembly according to the teachings of the invention. In particular, the views on the left ( FIGS. 10A and 10B ) illustrate different configurations of optical detectors  800  while the views on the right ( FIGS. 10C and 10D ) illustrate printed circuit board  112 A design flexibility due to optical adaptors  800 A and  800 B. The two detectors can be very close (A′) or some distance apart (B′) using the same detector board  112 . 
         [0048]    Optical adaptors provide for flexible circuit board design, such as when multiple sensors are used, because the size and distance of the sensors are limited by the area of the electrical board. In conventional design, it may be too crowded to put two sensors very close. Using sensor optical adaptors, multiple sensors can be put together to form a sensor array with no physical limit by the individual sensor size and board area, and without using an array detector. 
         [0049]    In one example embodiment, a PCB (printed circuit board) board can be shared by multiple optical sensing geometries by changing optical adaptors to different optical setups. This lowers cost on board designs. Optical adaptors also provide for flexible array detector design, such that when an array detector is desired, the number of elements may not always be available. Hence, it effectively couples light into sensor arrays of different shapes with much lower loss than a mask. All of the above applies to the use of the adaptor as a light emitter as well as detector. 
         [0050]    Referring now to  FIG. 11 , it illustrates an LED  1110  projecting two beams of light  1111 A- 1111 B through a lens element within a seed tube  102  through to two detectors  1120 A- 1120 B for potential dust detection according to the teachings of the invention. In particular, the two close beams of light provide similar attenuations for dust with each detector being vertical to one another. A seed  104  drops from the top to the bottom (arrow) while dust can come from both directions, which can be detected and rejected as dust counts. The time-of-flight distributions can also be used to reject non-seed events. 
         [0051]    The two detectors referred to above can be placed at the front end of an optical detector as shown in  FIG. 12 , which is a lightpipe assembly or lens at one end and a microphotodetector at another end, in an example embodiment of an element in a seed sensor assembly according to the teachings of the invention. In particular, the light is coupled to the detectors more efficiently, improving sensor operation without increasing cost substantially. 
         [0052]    Referring now to  FIG. 13 , it illustrates a lightpipe assembly  800 A with a Fresnel lens  810  at one end and a microphotodetector at another end as an embodiment of an element in a seed sensor assembly according to the teachings of the invention. In this example embodiment, the Fresnel lens assists in channeling light even further into the optical adaptor. 
         [0053]    The following patents that relate to seed sensor devices are herein incorporated by reference in their entirety and constitute part of the disclosure herein: U.S. Pat. Nos. 4,163,507; 4,307,390; 4,555,624; 4,496,211; 5,307,430 and 5,635,911. 
         [0054]    Having thus described several illustrative embodiments, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of this disclosure. While some examples presented herein involve specific combinations of functions or structural elements, it should be understood that those functions and elements may be combined in other ways according to the present invention to accomplish the same or different objectives. In particular, acts, elements, and features discussed in connection with one embodiment are not intended to be excluded from similar or other roles in other embodiments. Accordingly, the foregoing description and attached drawings are by way of example only, and are not intended to be limiting.