Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2001-12-12
2003-05-13
Lee, Susan S. Y. (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C399S015000, C399S049000, C399S072000, C399S081000
Reexamination Certificate
active
06563524
ABSTRACT:
FIELD OF THE INVENTION
The invention claimed and disclosed herein pertains to imaging devices and more particularly, to optimizing color plane registration for imaging devices.
BACKGROUND OF THE INVENTION
Various types of imaging devices are known in the art. The term “imaging device” as used herein refers to any device that is configured to produce a visual image on an image media. Imaging devices include devices commonly known as printers, copiers, facsimile machines, and the like. Image media includes paper and plastic sheet material. Generally, imaging devices employ various techniques to deposit ink or powdered toner onto an image media to produce an image-product. The term “image-product” as used herein denotes a piece of image media that bears at least one image thereon.
Imaging devices that are configured to produce multi-colored images are also known in the art. The term “multi-colored image” means an image that comprises more than one color, wherein one of the “colors” can be black. Various types of printed graphics as well as photo-quality images can be produced on prior art imaging devices. Such prior art imaging devices are also generally capable of producing monochromatic images. For example, many prior art imaging devices, in addition to having the capability to produce multi-colored images, are also capable of producing images in the form of monochromatic text comprising black alpha-numeric characters on white image media.
Of the various types of prior art imaging devices in use, one of the more popular types is that commonly known as the “laser printer.” It is understood that the “laser printer” is used for most types of image devices including copiers and facsimile machines in addition to printers. Thus, the term “laser printer” is generally used within the art to denote any imaging device that employs the laser scanning process for producing image-products. Laser printers are available with multi-color capability, although many laser printers have only monochromatic capability.
Laser printers having multi-color capability generally employ four “colors” of toner to produce images that can comprise a substantially full color gamut. Such imaging devices are often referred to as “four-color laser printers.” The four colors of toner generally utilized are those of black, cyan, magenta, and yellow. Known techniques of applying various combinations of the four different toners can yield a wide array of colors in an image-product.
Laser scanning imaging devices (“laser printers”) generally employ at least one beam of light which is commonly a laser beam. The beam is scanned laterally across a moving, electrostatically charged, photosensitive surface in order to “expose” selected portions of the surface in accordance with a particular image to be produced. That is, the beam generally scans a latent image-into the photo-sensitive surface, wherein the latent image is characterized by a difference in electrical potential relative to portions of the surface that do not form the image. Powdered toner is then applied to the latent image which results in an image formed from toner. That is, the toner is attracted to the latent image and is not attracted to portions of the photo-sensitive surface that are not part of the latent image. The toner image is then ultimately transferred to an image media such as a sheet of paper or the like.
In a four-color laser printing process, the above-described process of forming an image from toner is performed separately for each of the colors of toner used to thereby produce the overall image. Each of these images comprising a single toner is referred to as a “color plane.” The overall image comprises all of the color planes together (i.e., all of the color planes used for the overall image, which can be one, two, three or four of the colors). Generally, each of the color planes is formed separately in this manner and then all the color planes are brought together to form the overall image. There are several known methods of forming the color planes to make up an overall image. Two of these methods are known respectively as “single-pass” and “four-pass” color imaging.
Turning now to
FIG. 1
, a side-elevation schematic diagram is shown which depicts some of the major components of a typical prior art single-pass, four-color laser imaging device (“printer”)
10
. As is seen, the prior art printer
10
comprises a plurality of electro-statically chargeable photosensitive surfaces (“photoconductors”)
11
that are substantially in the form of cylindrical drums. Each of the photoconductors
11
is configured to rotate in a process direction indicated by the respective arrow, as marked. The prior art printer
10
also comprises a plurality of laser devices
13
. Each one of the laser devices
13
corresponds to a respective photoconductor
11
as shown. Further, each of the laser devices
13
is configured to generate a laser beam “LB.” The laser beam “LB” is selectively pulsed and is laterally scanned across the respective photoconductor
11
in a scan direction (not shown) as the photoconductor rotates. The scan direction is generally substantially perpendicular to the process direction. As a result of the scanning laser, the respective latent color plane is generated on the surface of each photoconductor
11
, as explained above.
In addition to the laser devices
13
, several toner hoppers
15
are included in the prior art printer
10
. As is seen, each one of the toner hoppers
15
corresponds to a respective photoconductor
11
. Each of the toner hoppers
15
are configured to deposit, on the respective photoconductor
11
, one of the toners of which there are four colors as explained above. Thus, each of the four color planes which can make up a given image is produced on a respective photoconductor
11
by way of the corresponding laser device
13
and toner hopper
15
.
The prior art printer
10
typically also includes a controller
20
as shown. The controller
20
is generally linked in signal communication with each of the laser devices
11
. The controller
20
can be linked with other components of the printer
10
as well. The controller
20
is configured to control the selective pulsing and scanning of the laser devices
11
so as to generate the latent color plane on each respective photoconductor. The controller
20
can also be configured to control various other operational aspects of the printer
10
as will be explained below. The prior art printer
10
can comprise a sensor
21
which is linked in signal communication with the controller
20
. The operation of the sensor
21
will be explained below.
As revealed in
FIG. 1
, a print path “PP” is defined by the printer
10
. The print path “PP” is generally defined by various media-handling components such as feed rollers (not shown), media guides (not shown), and the like. The print path “PP” is configured to convey there along an image media “M,” such as a sheet of paper, in the direction indicated by the arrow
30
. As the media “M” is conveyed along the print path “PP,” each of the color planes that are to be produced on the respective photoconductors
11
is successively transferred there from, one on top of the other, to the media “M.” Thus, by the time the media “M” passes the sensor
21
, all of the color planes have been generated and transferred to the media, to form the overall image thereon. It should be observed that an overall image does not need to be formed from all of the available colors, and can be formed from individual colors or any combination thereof.
Because all four of the color planes together can form the overall image, the quality of the overall image is dependent upon the alignment of each of the color planes relative to one another. That is, in order to produce a perfect overall image, the four color planes are preferably superimposed upon one another in perfect alignment as defined by the alignment of colors in the image source (i.e., a data file representative of the image, or an original document which is optically scanned to read an im
Regimbal Laurent A.
Smith David E.
Hewlett--Packard Development Company, L.P.
Lee Susan S. Y.
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