Electrophotography – Supplemental electrophotographic process – Exposure or charging
Reexamination Certificate
2002-02-28
2003-12-02
Royer, William J. (Department: 2852)
Electrophotography
Supplemental electrophotographic process
Exposure or charging
C399S186000, C399S187000
Reexamination Certificate
active
06658225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to image forming systems that incorporate light sensitive photoreceptors.
2. Description of Related Art
Generally, electrophotographically forming an image includes charging a photoconductive member, photoreceptor or photoconductor to a substantially uniform potential. This sensitizes the photoconductive 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.
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.
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.
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
.
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
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
.
This invention provides systems and methods to maintain a relatively uniform distribution of light on the photoreceptor.
The invention separately provides systems and methods that produce an energy of light in the range of 20-40 njoules/mm
2
.
The invention separately provides systems and methods that produce light energy distribution on the photoreceptor having a 2:1 max/min ratio.
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.
This invention separately provides systems and methods that determine an amount of energy placed on a photoreceptor from a single light source.
This invention separately provides systems and methods that vary the spacing between light source elements to optimize uniformity among a plurality of the light sources.
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.
REFERENCES:
patent: 4576464 (1986-03-01), Sakata et al.
patent: 4734734 (1988-03-01), Yano
patent: 4963933 (1990-10-01), Brownlee
patent: 5030992 (1991-07-01), Yoneda et al.
patent: 5272504 (1993-12-01), Omura et al.
Sanchez Franly H.
Savage Ed
Thompson David M.
Royer William J.
Xerox Corporation
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