Abstract:
An image forming system including a charge erasing system that includes a plurality of point light sources that emit a band of light onto a photoreceptor. The plurality of point light sources are variably spaced to substantially uniformly illuminate the photoreceptor.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    This invention relates to image forming systems that incorporate light sensitive photoreceptors.  
           [0003]    2. Description of Related Art  
           [0004]    Generally, electrophotographically forming an image includes charging a photoconductive member to a substantially uniform potential. This sensitizes the surface of the photoconductive member. The charge portion of the photoconductive surface is then exposed to a light image from either a modulated light source or from light reflected from an original document being reproduced. This creates an electrostatic latent image on the photoconductive surface.  
           [0005]    After the electrostatic latent image is created on the photoconductive surface, the latent image is developed. During development, toner particles are electrostatically attracted to the latent image recorded on the photoconductive surface. The toner particles form a developed image on the photoconductive surface. The developed image is then transferred to a copy sheet. Subsequently, the toner particles and the developed image are heated to permanently fuse the toner particles to the copy sheet.  
           [0006]    After the developed image is transferred from the photoconductive surface, the photoconductive surface is ideally clean and fully discharged and thus ready for another charge, exposure and development cycle. Unfortunately, the photoconductor in actual image forming devices is neither clean nor fully discharged at this point. Rather, residual charge and untransferred toner remain on the photoconductor, which need to be removed.  
           [0007]    This is accomplished in part by exposing the photoconductor using a pre-charge erase light source to fully discharge the photoconductor. FIGS. 10 and 11 illustrate a plurality of point light sources  510 ,  520 ,  530 ,  540  located within a conventional pre-charge erase light source  502 . As shown in FIGS. 10 and 11, the centers of the point light sources  510 ,  520 ,  530  and  540  are placed at a fixed distance x from each other. Each point light source  510 ,  520 ,  530  and  540  emits a beam of light onto the photoreceptor  500 . As shown in FIG. 10, the light intensity for point light sources  510 ,  520 ,  530  and  540  is indicated by curves  512 ,  522 ,  532 ,  542 , respectively. As should be appreciated, the intensity of light is greatest at a point on the photoreceptor  500  closest to the individual point light sources  510 ,  520 ,  530  and  540  and decreases at points farther away from the point light sources  510 ,  520 ,  530  and  540 .  
           [0008]    The total light intensity at a given point on the photoreceptor  500  is the sum of the light intensities from the point light sources  510 ,  520 ,  530  and  540  overlapping light intensity curves  512 ,  522 ,  532  and  542 . As shown with respect to a first point  550 , the total light intensity only includes the light emitted from point light source  520 , as neither of the light intensity curves  512  nor  532  overlaps the light intensity curve  522  at the first point  550 . However, at a second point  560 , the total light intensity includes the light intensity from point light sources  520  and  530  as indicated by overlapping shown using the light intensity curves  522  and  532 .  
         SUMMARY OF THE INVENTION  
         [0009]    As should be appreciated, the total light intensity at the second point  560  is greater than the total light intensity at the first point  550 . This occurs, as shown using the light intensity curves  522  and  532 , because the light intensity at the second point  560  supplied by each of the light sources  510  and  520  is closer to the maximum light intensity than the minimum light intensity for a single light source. The closer to the maximum light intensity, the light intensity at the second point  560  from each light source  510  and  520 , the larger the difference in the total light intensity between point  550  and  560 . Thus, large fluctuations in this total light intensity occur along the axis of photoreceptor  500  due to these differences in light intensity. This results in an uneven light intensity distribution on the photoreceptor  500 .  
           [0010]    This invention provides systems and methods to maintain a relatively uniform distribution of light on the photoreceptor.  
           [0011]    The invention separately provides systems and methods that produce an energy of light in the range of 20-40 njoules/mm 2 .  
           [0012]    The invention separately provides a systems and methods that produce light energy distribution on the photoreceptor having a 2:1 max/min ratio.  
           [0013]    This invention separately provides systems and methods that uniformly distributes the light energy while reducing the cost of providing a plurality of light emitting devices.  
           [0014]    This invention separately provides systems and methods that determine an amount of energy placed on a photoreceptor from a single light source.  
           [0015]    This invention separately provides systems and methods that vary the spacing between light sources elements to optimize uniformity among a plurality of the light sources.  
           [0016]    In various exemplary embodiments of the systems and methods for forming and/or operating a pre-charge erase array to obtain a relatively uniform output distribution, uniform output distribution is created by determining the amount of light placed on the photoreceptor. By determining the amount of light on the photoreceptor, a plurality of point light sources are positioned such that the light intensity remains relatively uniform along the photoreceptor. In various exemplary embodiments of the systems and methods according to this invention, by appropriately spacing the point light sources based on the determined light intensity, the amount of point light sources used can be reduced at the same time a uniform light distribution is created.  
           [0017]    These and other features and advantages of this invention are described in or are apparent from the following detailed description of various exemplary embodiments of the apparatuses, systems and methods of this invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    Various exemplary embodiments of this invention will be described in detail, with reference to the following figures, wherein:  
         [0019]    [0019]FIG. 1 is a side view showing the structure of an image forming system incorporating a first exemplary embodiment of a pre-charge erase array system according to this invention;  
         [0020]    [0020]FIG. 2 is a side view showing the structure of an image forming system incorporating a second exemplary embodiment of a pre-charge erase array system according to this invention;  
         [0021]    [0021]FIG. 3 is a side view showing the structure of an image forming system incorporating a third exemplary embodiment of a pre-charge erase array system according to this invention;  
         [0022]    [0022]FIG. 4 is a graph illustrating the light intensity from a plurality of light sources along the photoreceptor;  
         [0023]    [0023]FIG. 5 shows a plurality of light sources placed adjacent to a photoreceptor;  
         [0024]    FIGS.  6 - 9  each show a graph illustrating the light intensity from a different arrangement of a plurality of light sources arranged along the photoreceptor;  
         [0025]    [0025]FIG. 10 a graph illustrating the light intensity from a plurality of light sources along the photoreceptor for a conventional pre-charge erase system; and  
         [0026]    [0026]FIG. 11 shows a plurality of light sources placed adjacent to a photoreceptor in a conventional pre-charge erase system. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0027]    For simplicity and clarification, the operating principles, design factors, and layout of the pre-charge erase array systems and methods according to this invention are explained with reference to various exemplary embodiments of the pre-charge erase array systems and methods according to this invention, as shown in FIGS.  1 - 9 . The basic explanation of the operation of the illustrated pre-charge erase array systems and methods is applicable for the understanding and design of the constituent components employed in the pre-charge erase array systems and methods of this invention.  
         [0028]    [0028]FIG. 1 shows an image forming system incorporating a first exemplary embodiment of a pre-charge erase array system  110  according to this invention. As shown in FIG. 1, the pre-charge erase system  110  is one element of a belt-type made forming apparatus  100 . The pre-charge image system  110  is positioned adjacent to a photoreceptor  115  and connected to a controller  112 . In various exemplary embodiments, the pre-charge erase system  110  includes a plurality of point light sources, such as LEDs laser diodes and the like. The photoreceptor  115  is a belt-type device that rotates in the direction A, and advances sequentially through various xerographic process steps.  
         [0029]    A cleaner  130  is mounted adjacent to the photoreceptor  115  downstream of the pre-charge erase system. The cleaner  130  removes residual toner particles from the surface of the photoreceptor  115  after the developed image is transferred to an image recording medium from the photoreceptor  115  and after the photoreceptor  115  is discharged by the pre-charge erase system  110 . A charger  120  is mounted adjacent to the photoreceptor  115  downstream of the cleaner  130 . The charger  120  charges the photoreceptor  115  to a predetermined potential and polarity. A toner dispenser/developer housing  125  is also mounted adjacent to the photoreceptor  115 . The toner dispenser/developer housing  125  creates a latent image on, stores toner particles and dispenses the toner particles to, the photoreceptor  115  to develop the latent image in an imaging/exposure/developing zone  145 . A transfer dicorotron  155  is also mounted adjacent to the photoreceptor  115 . The area between the transfer dicorotron  155  and the photoreceptor  115  forms an image transfer zone  135 .  
         [0030]    As should be appreciated, each point light source within the pre-charge erase system  110  may be an LED, a laser diode or any other known or later-developed light emitting structure. Further, each point light source may emit radiation in the ultra-violet, visible and/or near infrared regions of the electromagnetic spectrum. However, it should be appreciated that any currently available or later developed light source can be used in the pre-charge erase system  110  to emit a highly directional beam of light onto the photoreceptor  115 .  
         [0031]    If the pre-charge erase array system  110  includes multiple modes, the controller  112  is used to control which mode is active and to controllably turn on and off the light sources within the pre-charge erase system  110 . However, if the pre-charge erase array system  110  does not have either multiple modes or a mode that requires controllably turning on and off the light source  110 , the controller  112  can be omitted. It should be appreciated that the controller  112  can be implemented as an independent control device or as a portion of the main controller of the image forming system  100  in which the pre-charge erase array system  110  is implemented.  
         [0032]    During operation of the image forming system  100 , as a portion of photoreceptor  115  passes by the charger  120 , the charger  120  charges the photoconductive surface of photoreceptor  115  to a relatively high, substantially uniform potential V 0 . Next, the charged portion of the photoconductive surface of photoreceptor  115  advances through the imaging/exposure/developing zone  145 . In the imaging/exposure/developing zone  145 , portions of the photoconductive surface of photoreceptor  115  are selectively discharged to form a latent electrostatic image. This latent image is then developed on the photoconductive surface of the photoreceptor  115 .  
         [0033]    The photoreceptor  115 , which is initially charged to a voltage V 0  by the charger  120 , undergoes dark decay to a voltage level V dd . In various exemplary embodiments, the dark decay voltage V dd  is equal to about −500V. When developed at the imaging/exposure/developing zone  145 , the exposed portions of the photoreceptor  115  are discharged to an exposure voltage V e . In various exemplary embodiments, the exposure voltage V e  is equal to about −50V. Thus, after exposure, the photoreceptor  115  has a bipolar voltage profile of high and low voltages. In various exemplary embodiments, the high voltages correspond to charged areas and the low voltages correspond to discharged or background areas. Thus, the photoreceptor  115  now has an electrostatic latent image formed on the surface of the photoreceptor  115 .  
         [0034]    As the photoreceptor  115  continues to move, the imaged portion of the photoreceptor  115  passes the toner dispenser/developer housing  125 . The toner dispenser/developer housing  125  transfers charged toner particles to the imaged portions of the photoreceptor  115 .  
         [0035]    As the photoreceptor  115  continues to move, the developed image arrives at the image transfer zone  135 . In the image transfer zone  135 , a recording medium moves along a sheet path  150  in a timed sequence so that the developed image developed on the surface of the photoreceptor  115  contacts the advancing recording medium at image transfer zone  135 .  
         [0036]    In various exemplary embodiments of the image forming system, the image transfer zone  135  includes a transfer dicorotron  155 , which applies a bias to the recording medium. In various exemplary embodiments, the dicorotron  155  sprays positive ions onto the backside of the recording medium. This attracts the charged toner particles of the developed image from the surface of the photoreceptor  115  to the recording medium.  
         [0037]    After transfer, the recording medium continues to move along the sheet path  150 . The recording medium is separated from the photoconductive surface of the photoreceptor  115 . Then, the recording medium continues to move along the sheet path  150 . A fusing station permanently affixes the toner particles of the transferred image to the recording medium.  
         [0038]    As the photoreceptor  115  continues to move, the photoreceptor  115  passes the pre-charge erase system  110 . The pre-charge erase system  110  shines high-intensity light onto the photoreceptor  115  to remove any residual charge on the photoreceptor  115  onto the photoreceptor  115 , the high-intensity light from the pre-charge erase system  110  neutralizes any remaining charge remaining from the charges placed on the surface of the photoreceptor  115  by the charger  120 . Thus, any remaining charged toner particles carried on the photoconductive surface of the photoreceptor  115  will no longer be as strongly attracted to the surface of the photoreceptor  115 . As the photoreceptor  115  continues to move, the photoreceptor  115  passes the cleaner  130 . Because any remaining charged toner particles carried on the photoconductive surface of the photoreceptor  115  will no longer be as strongly attracted to the surface of the photoreceptor  115 , the cleaner  130  is able to more easily remove any remaining toner particles from the surface of the photoreceptor  115 .  
         [0039]    In various exemplary embodiments, a plurality of point light sources may be oriented to expose a portion of the photoreceptor  115  to the high-intensity light as that portion of the photoreceptor  115  travels past the pre-charge erase system  110 .  
         [0040]    [0040]FIG. 2 shows an image forming system  200  incorporating a second exemplary embodiment of a pre-charge erase array system  210 . As illustrated in FIG. 2, pre-charge erase array system  210  is connected to a controller  212  and is positioned relative to a photoreceptor  215 , a charger  220 , a toner dispenser/developer housing  225 , a cleaner  230 , and a transfer dicorotron  255 . Each of these elements is generally similar to the corresponding elements discussed above with respect to FIG. 1.  
         [0041]    However, pre-charge erase array system  210  further includes a number of light sealing elements  245 ,  250  and  255 . The light sealing elements  250  and  255  are attached to a housing of the pre-charge erase system  210 . The light sealing element  245  is positioned on the side of the photoreceptor  215  opposite the pre-charge erase system  210 . The light sealing elements  245 ,  250  and  255  are positioned to reduce, if not prevent, any stray light from the light source  210  from entering other areas of the imaging forming devices. In various exemplary embodiments, at least one of the light sealing elements  245 ,  250  and  255  has a reflective surface where the reflective surface faces the photoreceptor  215 . In various exemplary embodiments, the reflective surface of at least one of the light sealing elements  245 ,  250  and  255  reflects light from the pre-charge erase system  210  toward the photoreceptor  215 .  
         [0042]    If the pre-charge erase array system  210  includes multiple modes, the controller  212  is used to control which mode is active and to controllably turn on and off the pre-charge erase system  210 . However, if the pre-charge erase system  210  does not have either multiple modes or a mode that requires controllably turning on and off the light source  210 , the controller  212  can be omitted. It should be appreciated that the controller  212  can be implemented as an independent control device or as a portion of the main controller of the image forming system  200  in which the pre-charge erase array system  210  is implemented.  
         [0043]    [0043]FIG. 3 shows an image forming system  300  incorporating a third exemplary embodiment of a pre-charge erase array system  310  according to this invention. As illustrated in FIG. 3, the pre-charge erase system  310  is positioned adjacent to a drum-type photoreceptor  315  and a controller  312 . In various exemplary embodiments, the pre-charge erase system  310  includes a plurality of point light sources, such as LEDs, laser diodes and the like. The photoreceptor  315  is a drum-type device that rotates in the direction B and advances sequentially through various xerographic process steps.  
         [0044]    A charger  320  is mounted adjacent to the photoreceptor  315 . The charger  320  charges the photoreceptor to a predetermined potential and polarity. An imaging and developing system  325  is also mounted adjacent to the photoreceptor  315 . The system  325  creates a latent image on the photoreceptor  315  and stores and dispenses toner particles to the photoreceptor  315  to develop the latent image. A transfer dicorotron  355  is also mounted adjacent to the photoreceptor  315 . The area between the transfer dicorotron  355  and the photoreceptor  315  forms an image transfer zone  335 . A cleaner  330  is also mounted adjacent to the photoreceptor  315  downstream of the pre-charge erase system. The cleaner  330  removes residual toner particles from the surface of the photoreceptor  315  after the developed image is transferred to an image recording medium from the photoreceptor  315  and after the photoreceptor is discharged by the pre-charge erase system.  
         [0045]    The pre-charge erase system  310 , the photoreceptor  315 , the charger  320 , the toner dispenser/developer housing  325 , the cleaner  330 , and the transfer dicorotron  355  correspond to and operate similarly to the same elements discussed above with respect to FIGS.  1  and/or  2 .  
         [0046]    If the pre-charge erase array system  310  includes multiple modes, the controller  312  is used to control which mode is active and to controllably turn on and off the light sources of the pre-charge erase system  310 . However, if the  310  does not have either multiple modes or a mode that requires controllably turning on and off the light sources, the controller  312  can be omitted. It should be appreciated that the controller  312  can be implemented as an independent control device or as a portion of the main controller of the image forming system  300  in which the pre-charge erase array system  310  is implemented.  
         [0047]    During operation of the image forming system  300  according to this invention, as a portion of the photoreceptor  315  rotates by the charger  320 , the charger  320  charges the photoconductive surface of photoreceptor  315  to a relatively high, substantially uniform potential V 0 . Next, the charged portion of the photoconductive surface of photoreceptor  315  rotates through an imaging/exposure/developing zone  345 . In imaging/exposure/developing zone  345 , portions of the photoconductive surface of the photoreceptor  315  are selectively discharged by the imaging and developing system  325  to form a latent electrostatic image. This latent image is then developed on the photoconductive surface of photoreceptor  315  by the imaging and developing system  325 .  
         [0048]    The photoreceptor  315 , which is initially charged to a voltage V 0  by charger  320 , undergoes dark decay to a voltage level V dd . In various exemplary embodiments, the dark decay voltage V dd  is equal to about −500V. When exposed at the imaging/exposure/developing zone  345 , the exposed portions of the photoreceptor  315  are discharged to an exposure voltage V e . In various exemplary embodiments, the exposure voltage V e  is equal to about −50V. Thus, after exposure, the photoreceptor  315  has a bipolar voltage profile of high and low voltages. In various exemplary embodiments, the high voltages correspond to charged areas and the low voltages correspond to discharged or background areas. Thus, the photoreceptor  315  now has an electrostatic latent image formed on the surface of the photoreceptor  315 .  
         [0049]    As the photoreceptor  315  continues to rotate, the imaged portion of the photoreceptor  315  passes the imaging and developing system  325 . The toner  325  transfers charged toner particles to the imaged portions of the photoreceptor  315  using the transfer roller  340 .  
         [0050]    As the photoreceptor  315  continues to rotate, the developed image arrives at the image transfer zone  335 . In the image transfer zone  335 , a recording medium moves along a sheet path  350  in a timed sequence so that the developed image developed on the surface of the photoreceptor  315  contacts the advancing recording medium in the image transfer zone  335 .  
         [0051]    In various exemplary embodiments of the image forming system, the image transfer zone  335  includes a transfer dicorotron  355 , which applies a bias to the recording medium. In various exemplary embodiments, the dicorotron  355  sprays positive ions onto the backside of the recording medium. This attracts the charged toner particles of the developed image from the surface of the photoreceptor  315  to the recording medium.  
         [0052]    As the photoreceptor  315  continues to rotate, the photoreceptor  315  passes the pre-charge erase system  310 . The pre-charge erase system  310  shines high-intensity light onto the photoreceptor  315 .  
         [0053]    In various exemplary embodiments, the light from the pre-charge erase system  310  neutralizes any remaining changes remaining on the surface of the photoreceptor  315 . Thus, any remaining charged toner particles carried on the photoconductive surface of the photoreceptor  315  will no longer be as strongly attracted to the surface of the photoreceptor  315 . As the photoreceptor  315  continues to rotate, the photoreceptor  315  passes the cleaner  330 . Because any remaining charged toner particles carried on the photoconductive surface of the photoreceptor  315  will no longer be as strongly attracted to the surface of the photoreceptor  315 , the cleaner  330  more easily removes any remaining toner particles from the surface of the photoreceptor  315 .  
         [0054]    In other exemplary embodiments, the pre-charge erase system  310  may include the light sealing elements discussed above with respect to FIG. 2.  
         [0055]    In various exemplary embodiments, a plurality of point light sources expose a portion of the photoreceptor  315  to the high-intensity light before that portion of the photoreceptor  315  travels past the cleaner  330 .  
         [0056]    [0056]FIG. 5 illustrates a plurality of point light sources  410 ,  420 ,  430  and  440  located within one of the light source  110 ,  210 , or  310  placed adjacent to the photoreceptor  115 ,  215  or  315 . FIG. 4 illustrates the distribution of light intensity on the photoreceptor  110 ,  210  or  310 . As shown in FIGS. 4 and 5, the centers of the point light sources  410 ,  420 ,  430  and  440  are placed at a variable distance x i  (i=1, 2, 3, . . . ) from each other. When a beam of light is transmitted from one of the point light sources  410 ,  420 ,  430  or  440  to the photoreceptor  115 ,  215 ,  315 , the intensity of light is shown by the light intensity curves  412 ,  422 ,  432  or  442 , respectively. As should be appreciated, the intensity of the light is the greatest at a point on the photoreceptor  115 ,  215 ,  315  that is closest to the point light source  410 ,  420 ,  430  or  440  and decreases for points on the photoreceptor  110 ,  210  or  310  that is farther away from that point light source  410 ,  420 ,  430  or  440 .  
         [0057]    As should be appreciated, the total light intensity at a given point is the sum of the light intensities from overlapping light beams from the light sources  410 ,  420 ,  430  and  440 , which is represented by the overlapping light intensity curves  412 ,  422 ,  432 , and  442 . As shown relative to a first point  450  or the photoreceptor  110 ,  210  or  310 , the total light intensity includes only the light transmitted by the point light source  420 . At point  460  on the photoreceptor  110 ,  210  or  310 , the total light intensity includes the light intensity from the point light sources  420  and  430 .  
         [0058]    To reduce the difference in light intensity between the first and second points  450  and  460 , the inventors have determined an amount of energy placed on a photoreceptor from a single point light source. Based on the amount of energy placed on the photoreceptor by the point light source, the inventors were thus able to space the point light sources such that the fluctuations in the minimum and maximum light intensity is reduced.  
         [0059]    To reduce the fluctuation between the minimum and maximum light intensity on the photoreceptor, the invention thus provides the following three-dimensional expression to determine the amount of energy placed at a given point on the photoreceptor by a given point light source:  
         E:(x,y,z)=BCosα i Cosβ i /R i   2    (1)  
         [0060]    where  
         [0061]    B is the brightness of the point light source;  
         [0062]    α is the angle between the surface normal to the photoreceptor and the vector to the point light source;  
         [0063]    β is the angle between the surface normal to the point light source and the vector to the photoreceptor;  
         [0064]    i is the ith source illuminating the surface; and  
         [0065]    R is the distance from the point light source to the photoreceptor.  
         [0066]    In various exemplary embodiments, when the point light source and the photoreceptor are parallel, such that the photoreceptor surface normal passes through the point light source, y and z are constant. Thus, when the point light sources are aligned, Cosα i  is equal to Cosβ i . As such, the three-dimensional expression to determine the amount of energy placed on a photoreceptor by a given point light source can be determined as follows:  
           E ( x )= NBΣCos   2 α i   /R   i   2    (2)  
         [0067]    where  
         [0068]    N is equal to the number of point light sources located within the light source;  
         [0069]    α i  is equal to Arctan[(x 1 −x)/K];  
         [0070]    K is equal to the separation between the point light source and the photoreceptor;  
         [0071]    x i  is equal to the lateral offset between point x on the photoreceptor and the ith point light source; and  
         [0072]    1/R i  is equal to the Cosα i /K.  
         [0073]    In various exemplary embodiments, when determining the three-dimensional expression to determine the amount of energy placed on a photoreceptor by a given point light source while using a lens, the following equation is used:  
           E ( x )= MNBΣ Cos j α i Cosβ i   /R   i   2    (3)  
         [0074]    where  
         [0075]    M is equal to the on-axis output relative to the same point light source without the lens; and  
         [0076]    Cos j α i  is a power function that approximates output profile defined by the supplier so that a 50% output matches the angle specified by the supplier.  
         [0077]    Table 1 below outlines the general specifications that can be used to obtain the total light intensity curve shown in FIG. 6.  
                                                                                                                                       TABLE 1                                       S1   S2   S3   S4   S5   S6   S7 . . . S13                X@P/R   0   18   36   54   72   90   108   216   E(x)                     0.000   49.18   0.33   0.00   0.00   0.00   0.00   0.00   0.00   49.513        1.000   48.24   0.52   0.00   0.00   0.00   0.00   0.00   0.00   48.760        2.000   45.54   0.80   0.00   0.00   0.00   0.00   0.00   0.00   46.340        3.000   41.39   1.23   0.00   0.00   0.00   0.00   0.00   0.00   42.619        4.000   36.25   1.86   0.00   0.00   0.00   0.00   0.00   0.00   38.117       . . .       105.000   0.00   0.00   0.00   0.00   0.00   1.23   41.39   0.00   42.703       106.000   0.00   0.00   0.00   0.00   0.00   0.80   45.54   0.00   46.473       107.000   0.00   0.00   0.00   0.00   0.00   0.52   48.24   0.00   48.971       108.000   0.00   0.00   0.00   0.00   0.00   0.33   49.18   0.00   49.845                  
 
       Conventional Spacing  
       [0078]    As shown in Table 1, using e.g., (3), the design specifications for the light intensity output requires a narrow angle lens with a 50% fall-off at 15°, where j=20, the relative output on the axis compared to the same LED without lens (M) to be 1, and 12 (N) uniformly spaced point light sources at a distance of 24.40 mm (R) away from the photoreceptor. As should be appreciated, with the above uniform spacing a maximum/minimum ratio between the highest total light intensity and lowest total light intensity is 2.4. Thus, FIG. 6 illustrates the deficiencies of the fixed spacing based on the conventional pre-charge erase systems.  
         [0079]    Tables 2 outlines the general specifications usable to obtain the total light intensity curve shown in FIG. 7.  
                                                                 TABLE 2                           S1   S2   S3   S11           X @P/R   0   18.0   40.5   216.0   E(x)                                    0   2.02   0.85   0.14   0.00   3.059           1   2.01   0.91   0.15   0.00   3.134           2   1.99   0.99   0.17   0.00   3.201           3   1.96   1.06   0.18   0.00   3.260           4   1.91   1.14   0.19   0.00   3.312       105       0.01   0.01   0.03   0.00   3.464       106       0.01   0.01   0.03   0.00   3.474       107       0.00   0.01   0.03   0.00   3.481       108       0.00   0.01   0.03   0.00   3.483                  
 
       General Specifications for the Sample Light Intensity Output According to this Invention  
       [0080]    As shown in Table 2, using e.g., (3), the design specifications for one exemplary embodiment of a pre-charge erase system according to this invention does not require any lens, where j=1, the relative output on the axis compared to the same LED without lens (M) to be 1, and 11 (N) point light sources with variable spacing, where the point light sources are spaced at a distance of 24.40 mm (R) away from the photoreceptor. As should be appreciated, with the above spacing a maximum/minimum ratio between the highest light intensity and lowest light intensity is 1.05. Thus, FIG. 7 illustrates the improvements obtainable using a variable spacing pre-charge erase system according to this invention.  
         [0081]    Tables 3 outlines the general specifications for usable to obtain the total light intensity curve as shown in FIG. 8.  
                                                                                                 TABLE 3                           S1   S2   S3   S4   S5   S6   S7   S11           X @P/R   0   16.0   39.0   62.0   85.0   108.0   131.0   216.0   E(x)                                    0   8.87   2.20   0.06   0.00   0.00   0.00   0.00   0.00   11.134           1   8.81   2.54   0.07   0.00   0.00   0.00   0.00   0.00   11.428           2   8.64   2.92   0.08   0.00   0.00   0.00   0.00   0.00   11.652           3   8.36   3.35   0.10   0.00   0.00   0.00   0.00   0.00   11.815           4   8.00   3.81   0.11   0.01   0.00   0.00   0.00   0.00   11.927       105       0.00   0.00   0.00   0.04   1.20   8.36   0.46   0.00   10.076       106       0.00   0.00   0.00   0.03   1.02   8.64   0.54   0.00   10.255       107       0.00   0.00   0.00   0.03   0.87   8.81   0.63   0.00   10.368       108       0.00   0.00   0.00   0.02   0.74   8.87   0.74   0.00   10.406                  
 
       General Specifications for the Sample Light Intensity Output According to this Invention  
       [0082]    As shown in Table 3, using e.g. (3), the design specifications for the light intensity output uses a 30° lens, where j=4.8, the relative output on the axis compared to the same LED without lens (M) to be 1, and 11 (N) point light sources at a variable spacing, where the space between the edge and the edge-adjacent light source is 16 mm and the curve space is 23 mm and the light sources are placed at a distance of 24.40 mm (R) away from the photoreceptor. As should be appreciated, with the above spacing a maximum/minimum ratio between the highest light intensity and lowest light intensity is 1.72. Thus, FIG. 8 illustrates the improvements obtainable using a variable spacing pre-charge erase system according to this invention.  
         [0083]    Table 4 outlines the general specifications of usable to obtain the total light intensity curve as shown in FIG. 9.  
                                                                                                 TABLE 4                           S1   S2   S3   S4   S5   S6   S7   S11           X @P/R   0   20.0   42.0   64.0   86.0   108.0   130.0   216.0   E(x)                                    0   8.87   1.20   0.04   0.00   0.00   0.00   0.00   0.00   10.108           1   8.81   1.40   0.05   0.00   0.00   0.00   0.00   0.00   10.258           2   8.64   1.63   0.05   0.00   0.00   0.00   0.00   0.00   10.328           3   8.36   1.90   0.06   0.00   0.00   0.00   0.00   0.00   10.327       105       0.00   0.00   0.00   0.05   1.40   8.36   0.54   0.00   10.375       106       0.00   0.00   0.00   0.04   1.20   8.64   0.63   0.00   10.539       107       0.00   0.00   0.00   0.04   1.02   8.81   0.74   0.00   10.643       108       0.00   0.00   0.00   0.03   0.87   8.87   0.87   0.00   10.679                  
 
       General Specifications for the Sample Light Intensity Output According to this Invention  
       [0084]    As shown by Table 4, using e.g., (3), the design specification for the light intensity requires a 30° lens, where j=4.8, the relative output on the axis compared to the same LED without lens (M) to be 1, and 11 (N) point light sources at a variable pitch wherein the edge spacing between the edge and the edge-adjacent light sources is 20 mm, the interior spacing between light sources is 22 mm and the point light sources are placed at a distance of 24.40 mm (R) away from the photoreceptor. As should be appreciated, with the above spacing a maximum/minimum ratio between the highest light intensity and lowest light intensity is 1.23. Thus, FIG. 9 illustrates the improvements obtainable using a variable spacing pre-charge erase system according to this invention.  
         [0085]    The controller,  112 ,  212  and/or  312  shown in FIGS.  1 - 3 , if implemented as an independent control device, can be implemented using a programmed microprocessor or microcontroller and peripheral integrated circuit elements, and ASIC or other integrated circuit, a digital signal processor, a hardwired electronic or a logic circuit such as a discrete element circuit, a programmable logic device such as a PLV, PLA, FPGA or PAL or the like. In other exemplary embodiments, where the controllers  112 ,  212  and/or  312  are implemented as part of the control system of the image forming apparatus  100 ,  200  and/or  300  in which the pre-charge erase array system  110 ,  210  or  310  is implemented, the controllers  112 ,  212  and/or  312  can be implemented using a programmed general purpose computer or any other device capable of implementing the general control system for the image forming system. Such other devices include a special purpose computer, a programmed microprocessor or microcontroller and a peripheral integrated circuit elements, and ASIC or other integrated circuit, a digital signal processor, a hardwired electronic or logic circuit such as discrete element circuit, a programmable logic device such as a PLV, PLA, FPGA or PAL or the like.  
         [0086]    While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.