Patent Publication Number: US-6671479-B2

Title: Selective depopulation and/or repopulation of a full color image forming device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to systems and methods for generating monochrome and/or highlight color images at high speed. 
     2. Description of Related Art 
     In electrophotographic printing, a photoconductive surface is charged, and is then selectively exposed to image data to selectively discharge portions of the charged photoconductive surface. This forms a latent electrostatic image on the photoconductive surface. Charged toner material is then applied to the latent-image-bearing portion of the photoconductive surface to convert the latent electrostatic image into a developed image. 
     In full color image-on-image systems, this process is repeated a number of times to build a multi-layer full color image. This developed, or toner, image is then transferred, either directly, or indirectly via a transfer member, to a sheet of recording material. The developed, or toner, image is then at least semi-permanently fixed to the sheet of recording material. An example of this process is more fully described in U.S. Pat. No. 2,297,691. 
     In the image-on-image technique, a first latent toner image is developed onto a portion of the photoconductive surface. Subsequent latent toner images are exposed through the first image, on the same portion of the photoconductive surface, and then developed. 
     Different color features of an input image are formed at separate stations of the image forming device. Each station typically contains a charging substation, an exposing substation and a developing substation. These stations and substations are arranged around, and can be strategically spaced relative to, the photoconductive surface. Thus, in such image forming devices, the photoconductive surface is often a photoconductive belt. The speed that the belt moves past these different stations can be strategically set to allow adequate time for: 1) uniform charging of the photoconductive surface, 2) sufficient exposing of the latent image and 3) sufficient developing of the image. 
     Commercial demands require the reliable, high-speed production of quality images. Most full color image forming devices are capable of printing about 40-80 pages per minute. More sophisticated full color image forming devices can print up to 100 pages per minute. 
     SUMMARY OF THE INVENTION 
     Current full color xerographic image forming devices are able to form monochrome and highlight color images, but only at the lower full color rate, as the operating speed of such image forming devices is optimized for full color printing. Additionally, each station is dedicated to creating and developing a single color of toner. 
     However, the inventors have recognized that, when printing monochrome or highlight color images, various charging, exposing and/or developing substations of different color stations that are not being used, because the image does not contain that color toner, could be used in tandem with other charging, exposing and/or developing substations from other stations, to allow an increase in the process speed. Moreover, those stations and/or substations that are not being used can be physically absent or functionally-omitted in the monochrome and/or highlight color image forming device. For example, a full color xerographic image forming device can be converted to a dedicated monochrome or highlight color image forming device by physically or functionally removing some substations of the now-unused color toner stations. The remaining substations of the currently-unused color toner stations can now be used in tandem with some of the substations of the in-use color stations to allow an increase in the process speed. 
     This invention relates to selectively depopulating and/or repopulating a full color image forming device. 
     This invention also relates to using a multiplicity of charging substations in tandem to uniformly charge the photoconductive surface. 
     This invention also relates to using a multiplicity of developing substations in tandem to develop a single latent image. 
     This invention provides an image forming device having a set of image forming substations that have been selectively depopulated and/or repopulated relative to a full color image forming device. 
     This invention also relates to using multiple, functionally-equivalent, substations in tandem to perform charging, exposing, and/or developing actions on a photoconductive surface of a selectively depopulated and/or repopulated full color image forming device. 
     This invention separately provides systems and methods for selectively depopulating a full color image forming device and for generating the depopulated image forming device according to a set of operating parameters that allow higher speed printing of monochrome and/or highlight color images. 
     This invention separately provides a depopulated and/or repopulated image forming device that includes: 
     In various exemplary embodiments of the systems and methods according to this invention, substations, or even entire stations, of a full color image forming device can be removed from that full color image forming device to generate monochrome and/or highlight color images at a higher printing speed. As a result, the photoconductive surface does not spend time at stations and/or substations that are not needed to produce the monochrome and/or highlight color images of interest. 
     In various exemplary embodiments, a depopulated and/or repopulated image forming device is formed by physically omitting stations and/or substations relative to the stations and substations that are included on a full color image forming device. Additionally, stations and/or substations that are not normally included, or arranged differently, in the full color image forming device can be included to form a repopulated image forming device. 
     In various other exemplary embodiments, a depopulated and/or repopulated image forming device is functionally obtained from a full color image forming device by using an operation control scheme that functionally omits some of the stations and/or substations that are physically present in the full color image forming device and usually functionally active when forming full color images. Additionally, stations and/or substations that are physically present in the full color image forming device, but that are not necessarily functionally active when forming full color images, can become active under this operations control scheme to repopulate the depopulated image forming device. 
     In various other exemplary embodiments of the systems and methods according to this invention, multiple, functionally-equivalent, substations from different stations of a selectively depopulated and/or repopulated full color print engine can act in tandem to perform their function on a single portion of the photoconductive surface. As a result, the photoconductive surface can spend less time at a particular substation and still generate a monochrome or highlight color image having sufficient image quality, by making up for charging, exposing and/or developing deficiencies occurring in one substation with one or more other substations along the photoconductive belt. In this way, a single portion of the photoconductive surface may be charged, exposed and/or developed, multiple times in tandem, using different substations. 
     In addition to selectively depopulate and/or repopulate the print stations that are arranged along the circumference of the photoconductive surface, various exemplary embodiments of the systems and methods according to this invention use image-next-to-image printing. With image-next-to-image printing, different toner images are exposed onto different portions of the photoconductive surface. As a result, image generation can occur at a fast rate, because there is no need to expose through previously-developed toner images. 
     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 systems and methods according to this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various exemplary embodiments of this invention will be described in detail, with reference to the following figures, wherein: 
     FIG. 1 is a block diagram outlining the elements of a known full color image forming device; 
     FIG. 2 is a schematic diagram of one exemplary embodiment of the known full color image forming device of FIG. 1; 
     FIG. 3 is a schematic diagram outlining one exemplary embodiment of the image forming device of FIG. 1 depopulated and/or repopulated for high speed monochrome printing according to this invention; 
     FIG. 4 is a schematic diagram outlining one exemplary embodiment of the image forming device of FIG. 1 depopulated and/or repopulated for high speed monochrome and/or single highlight color printing according to this invention; 
     FIG. 5 is a schematic diagram outlining one exemplary embodiment of the image forming device of FIG. 1 depopulated and/or repopulated for high speed monochrome, single highlight color and/or dual highlight color printing according to this invention; 
     FIG. 6 is a flowchart outlining a method for generating full color images using a full color image forming device; 
     FIG. 7 is a flowchart outlining one exemplary embodiment of a method for generating monochrome images at high speed according to this invention using a first exemplary embodiment of a depopulated and/or repopulated image forming device; 
     FIG. 8 is a flowchart outlining one exemplary embodiment of a method for generating monochrome and/or single highlight color images at high speed according to this invention using a second exemplary embodiment of a depopulated and/or repopulated image forming device; and 
     FIG. 9 is a flowchart outlining one exemplary embodiment of a method for generating monochrome, single highlight color and/or dual highlight color images at high speed according to this invention using a third exemplary embodiment of a depopulated and/or repopulated image forming device. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In various exemplary embodiments, an image forming device can be depopulated and/or repopulated by removing or adding stations and/or substations to generate monochrome and/or highlight color images. Each station of the full color print engine can be selectively depopulated and/or repopulated with a charging substation, exposing substation and/or developing substation. The rate of generation of a final image can be increased by increasing the speed of the belt. The increase in belt speed necessarily leads to the images spending less time in each individual substation. This decrease in time spent in an individual substation is compensated for by moving the photoconductive surface through multiple functionally-equivalent substations that work in tandem to generate an image, and by the spacing of the substations along the photoconductor belt. 
     In various exemplary embodiments, the depopulated and/or repopulated image forming device may involve the physical addition or removal of various substation relative to a full color image forming device. In various other exemplary embodiments, the depopulated and/or repopulated image forming device may involve an operation control scheme that functionally omits or includes various substations that are physically present in the image forming device. 
     In various exemplary embodiments, an image forming device can be depopulated, relative to a full color image forming device, for monochrome printing. The depopulated image forming device may contain three charging substations, one exposing substation and two developing substations, for example. The multiple charging stations work in tandem to ensure uniform charge of the photoconductive surface, thus compensating for the decrease in time spent at the individual charging substations. Similarly, the multiple development substations work in tandem to ensure sufficient development of a single latent image, thus compensating for the decrease in time spent at the individual developing substations. As a result, the rate of image generation can be increased to approximately 225-240 pages per minute. In various other exemplary embodiments, speeds greater than 240 pages per minute may be reached. 
     In various exemplary embodiments, an image forming device can be depopulated, relative to a full color image forming device, for monochrome and/or single highlight color printing. The depopulated image forming device may contain two charging substations, one exposing substation and one developing substation for the highlight color feature of the image and two charging substations, one exposing substation and two developing substations for the monochrome feature of the image, for example. As a result, the rate of image generation can be increased to approximately 133-166 pages per minute. In various other exemplary embodiments, speeds greater than 166 pages per minute may be reached. As mentioned above, the multiplicity of functionally-equivalent substations working in tandem to generate a single image compensates for the increased belt rate and subsequent decrease in time spent at a particular substation. 
     In various exemplary embodiments, an image forming device can be depopulated, relative to a full color image forming device, for monochrome, single highlight color and/or dual highlight color printing. The depopulated image forming device may contain one charging substation, one exposing substation and one developing substation for the first highlight color feature of the image; two charging substations, one exposing substation and one developing substation for the second highlight color feature of the image and two charging substations, one exposing substation and one developing substation for the monochrome feature of the image, for example. As a result, the rate of image generation can be increased to approximately 133-166 pages per minute. In various other exemplary embodiments, speeds greater than 166 pages per minute may be reached. As mentioned above, the multiplicity of functionally-equivalent substations working in tandem to generate a single image compensates for the increased belt rate and subsequent decrease in time spent at a particular substation. 
     FIG. 1 is a generalized block diagram of a known full color image forming device  100 . The full color image forming device  100  is connectable to an image data source  90  over a signal line or link  95 . The image data source  90  provides input image data to the full color image forming device  100 . 
     In general, the image data source  90  can be any one or more of a number of different sources, such as a scanner, a digital copier, a facsimile device that is suitable for generating electronic image data, or a device suitable for storing and/or transmitting electronic image data, such as a client or server of a network, such as the Internet, and especially the World Wide Web, for example. Thus, the image data source  90  can be any known or later-developed source that is capable of providing image data to the full color image forming device  100 . The signal line or link  95  can be implemented using a public switched telephone network, a local or wide area network, an intranet, the Internet, a wireless transmission channel, or any other known or later-developed distributed network, or the like. 
     When the image data source  90  is a personal computer, the link  95  connecting the image data source  90  to the full color image forming device  100  can be a direct link between the personal computer and the full color image forming device  100 . The link  95  can also be a local area network, a wide area network, the Internet, an intranet, or any other distributed processing and storage network. Moreover, the link  95  can also be a wireless link to the image data source  90 . Accordingly, it should be appreciated that the image data source  90  can be connected using any known or later-developed system that is capable of transmitting data from the image data source  90  to the full color image forming device  100 . 
     The image data provided by the image data source  90  is received by the input/output interface  105 . The image data from the input/output interface  105 , under the control of the controller  110 , is forwarded either directly to the appropriate station or is initially stored in the memory  107 . If the image data first is stored in the memory  107 , the controller  110  can subsequently forward the image data from the memory  107  to the appropriate station. 
     The memory  107  can be implemented using any appropriate combination of alterable, volatile or non-volatile, memory; or non-alterable or fixed memory. The alterable memory, whether volatile or non-volatile, can be implemented using any one or more of static or dynamic RAM, a floppy disk and disk drive, a writeable or re-writeable optical disk and disk drive, a hard drive, flash memory or the like. Similarly, the non-alterable or fixed memory can be implemented using any one or more of ROM, PROM, EPROM, EEPROM, an optical ROM disk, such as a CD-ROM or DVD-ROM disk, and disk drive or the like. 
     It should be appreciated that, while the electronic image data can be generated at the time of printing an image from an original physical document, the electronic image data could have been generated at any time in the past. Moreover, the electronic image data need not have been generated from the original physical document, but could have been created from scratch electronically. The image data source  90  is thus any known or later developed device which is capable of supplying electronic image data over the link  95  to the full color image forming device  100 . The link  95  can thus be any known or later developed system or device for transmitting the electronic image data from the image data source  90  to the full color image forming device  100 . 
     A known full color image forming device prints cyan, magenta, yellow and black and white. These four colors are typically generated separately at stations  2 - 5 ,  130 - 160 , respectively. Station  1   120  may be used for custom color toner, or not at all. If station  1   120  is not used, it is still retained in the architecture of the full color image forming device. Substations for charging, exposing and developing the different color images are located in each of stations  1  ( 121 - 123 , respectively), station  2  ( 131 - 133 , respectively), station  3  ( 141 - 143 , respectively), station  4  ( 151 - 153 , respectively) and station  5  ( 161 - 163 , respectively). 
     FIG. 2 is a schematic diagram of one exemplary embodiment  200  of the known full color image forming device  100  of FIG.  1 . The photoconductive belt  190  moves, in a counterclockwise direction, through the various substations located along the circumference of the photoconductive belt  190 . The charging substation  121  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 121  through the charging substation  121 . The charged photoconductive belt  190  then travels a distance D 1  to reach the exposing substation  122 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 1  between the exposing substation  122  and the charging substation  121  are predetermined to allow uniform charging of the portion of the photoconductive belt  190 . 
     The exposing substation  122  exposes a portion of the photoconductive belt  190 . The portion of the photoconductive belt  190  travels a distance DT 122  through the exposing substation  122 . The portion of the photoconductive belt  190  then travels a distance D 2  to reach the developing station  123 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 2  between the developing substation  123  and the exposing substation  122  are predetermined to allow sufficient exposure of the portion of the photoconductive belt  190 . 
     The developing substation  123  develops the first color toner image. The portion of the photoconductive belt  190  travels a distance DT 123  through the developing substation  123 . The speed of the photoconductive belt must allow sufficient development of the first color toner image over the distance DT 123 . 
     The photoconductive belt continues to move, in a counterclockwise direction, to the charging substation  131 . The charging substation  131  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 131  through the charging substation  131 . The charged photoconductive belt  190  then travels a distance D 3  to reach the exposing substation  132 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 3  between the exposing substation  132  and the charging substation  131  are predetermined to allow uniform charging of the portion of the photoconductive belt  190 . 
     The exposing substation  132  exposes a portion of the photoconductive belt  190 , through the previously exposed latent image. The portion of the photoconductive belt  190  travels a distance DT 132  through the exposing substation  132 . The portion of photoconductive belt  190  then travels a distance D 4  to reach the developing station  133 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 4  between the developing substation  133  and the exposing substation  132  are predetermined to allow sufficient exposure of the portion of the photoconductive belt  190  through the previously exposed image. 
     The developing substation  133  develops the second color toner image. The portion of the photoconductive belt  190  travels a distance DT 133  through the developing substation  133 . The speed of the photoconductive belt must allow sufficient development of the second color toner image over the distance DT 133 . 
     The photoconductive belt continues to move, in a counterclockwise direction, to the charging substation  141 . The substation  141  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 141  through the charging substation  141 . The charged photoconductive belt  190  then travels a distance D 5  to reach the exposing substation  142 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 5  between the exposing substation  142  and the charging substation  141  are predetermined to allow uniform charging the portion of the photoconductive belt  190 . 
     The exposing substation  142  exposes a portion of the photoconductive belt  190 , through the previously exposed latent images. The portion of the photoconductive belt  190  travels a distance DT 142  through the exposing substation  142 . The portion of the photoconductive belt  190  then travels a distance D 6  to reach the developing station  143 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 6  between the developing substation  143  and the exposing substation  142  are predetermined to allow sufficient exposure of the portion of the photoconductive belt  190  through the previously exposed images. 
     The developing substation  143  develops the third color toner image. The portion of the photoconductive belt  190  travels a distance DT 143  through the developing substation  143 . The speed of the photoconductive belt must allow sufficient development of the third color toner image over the distance DT 143 . 
     The photoconductive belt continues to move, in a counterclockwise direction, to the charging substation  151 . The charging substation  151  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 151  through the charging substation  151 . The charged photoconductive belt  190  then travels a distance D 7  to reach the exposing substation  152 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 7  between the exposing substation  152  and the charging substation  151  are predetermined to allow uniform charging of the portion of the photoconductive belt  190 . 
     The exposing substation  152  exposes a portion of the photoconductive belt  190 , through the previously exposed latent images. The portion of the photoconductive belt  190  travels a distance DT 152  through the exposing substation  152 . The portion of the photoconductive belt  190  then travels a distance D 8  to reach the developing station  153 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 8  between the developing substation  153  and the exposing substation  152  are predetermined to allow sufficient exposure of the portion of the photoconductive belt  190  through the previously exposed images. 
     The developing substation  153  develops the fourth color toner image. The portion of the photoconductive belt  190  travels a distance DT 153  through the developing substation  153 . The speed of the photoconductive belt must allow sufficient development of the fourth color toner image over the distance DT 153 . 
     In this schematic diagram of one exemplary embodiment of the known full color image forming device  100  of FIG. 1, a fifth set of charging, exposing and developing substations are present to generate a fifth color toner image. In this exemplary embodiment, the photoconductive belt continues to move in a counterclockwise direction to the charging substation  161 . The charging substation  161  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 161  through the charging substation  161 . The charged photoconductive belt  190  then travels a distance D 9  to reach the exposing substation  162 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 9  between the exposing substation  162  and the charging substation  161  are predetermined to allow uniform charging of the portion of the photoconductive belt  190 . 
     The exposing substation  162  exposes a portion of the photoconductive belt  190 , through the previously exposed latent images. The portion of the photoconductive belt  190  travels a distance DT 162  through the exposing substation  162 . The portion of the photoconductive belt  190  then travels a distance D 10  to reach the developing station  163 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 10  between the developing substation  163  and the exposing substation  162  are predetermined to allow sufficient exposure of the portion of the photoconductive belt  190  through the previously exposed images. 
     The developing substation  163  develops the fifth color toner image. The portion of the photoconductive belt  190  travels a distance DT 163  through the developing substation  163 . The speed of the photoconductive belt must allow sufficient development of the fifth color toner image over the distance DT 163 . 
     It should be appreciated that the rate at which the belt may move through the stations is a function of the time required at each substation (i.e., dwell time), the distance through each substation and the distance between the substations within a particular station. 
     It should also be appreciated that the fifth set of charging, exposing and developing substations are not required to generate the full color image. These substations may be physically present and unused. In various exemplary embodiments, charging substation  121 , exposing substation  122  and developing substation  123  are the substations reserved for an optional fifth color. 
     Upon development of the image, the photoconductive belt  190  continues to move, in a counterclockwise direction, through the pre-transfer station  170 . The pre-transfer station  170  prepares the image for transfer to a recording material  185  at the transfer station  186 . The recording material  185  is fed by the recording material housing  184  to the transfer station  186 , where the image is transferred from the photoconductive belt  190  to the recording material  185 . The recording material  185  then moves in the direction of  182  to the fixing device  188 . The fixing device  188  receives the recording material  185  and fixes, at least semi-permanently, the image onto the recording material  185 . 
     FIG. 3 is a schematic diagram outlining one exemplary embodiment  300  of the image forming device  100  of FIG. 1 depopulated and/or repopulated for high speed monochrome printing according to this invention. In this exemplary embodiment, the photoconductive belt  190  moves, in a counterclockwise direction, through the various substations located along the circumference of the photoconductive belt  190 . The charging substation  121  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 121  through the charging substation  121 . 
     The charged photoconductive belt  190  then travels a distance D 1  a to reach a second charging substation  131 . The charging substation  131  charges the photoconductive belt  190 , for a second time. The charged photoconductive belt  190  travels a distance DT 131  through the charging substation  131 . The charged photoconductive belt  190  then travels a distance D 1   b  to reach a third charging substation  141 . The charging substation  141  charges the photoconductive belt  190 , for a third time. The charged photoconductive belt  190  travels a distance DT 141  through the charging substation  141 . 
     The charged photoconductive belt  190  then travels a distance D 1   c  to reach the exposing substation  142 . The total distance traveled by the photoconductive belt  190 , from the first charging substation  121  to the exposing substation  142 , is D 1 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distances D 1   a , D 1   b , D 1   c  and D 1  are predetermined to allow uniform charging of the portion of the photoconductive belt  190 . 
     In this exemplary embodiment, a multiplicity of charging substations are used in tandem to ensure uniform charge of the photoconductive belt  190  at higher belt speeds, compared to a full color image forming device, to compensate for a decreased amount of time spent at any single charging substation. 
     The exposing substation  142  exposes a portion of the photoconductive belt  190 . The portion of the photoconductive belt  190  travels a distance DT 142  through the exposing substation  142 . The portion of the photoconductive belt  190  then travels a distance D 2   a  to reach the developing station  153 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 2   a  between the developing substation  153  and the exposing substation  142  are predetermined to allow sufficient exposure of the portion of the photoconductive belt  190 . 
     The developing substation  153  develops the monochrome image. The portion of the photoconductive belt  190  travels a distance DT 153  through the developing substation  153 . The portion of the photoconductive belt  190  continues over a distance of D 2   b  to a second developing substation  163 . The developing substation  163  further develops the monochrome image. The portion of the photoconductive belt  190  travels a distance DT 163  through the developing substation  163 . The speed of the photoconductive belt must allow sufficient development of the monochrome image over the distances D 153  and DT  163 . 
     In this exemplary embodiment, a multiplicity of developing substations are used in tandem to ensure sufficient development of a monochrome image at higher belt speeds, compared to a full color image forming device, to compensate for a decreased amount of time spent at any single developing substation. 
     FIG. 4 is a schematic diagram outlining one exemplary embodiment  400  of a the image forming device  100  of FIG. 1 depopulated and/or repopulated for high speed monochrome and/or single highlight color printing according to this invention. In this exemplary embodiment, the photoconductive belt  190  moves, in a counterclockwise direction, through the various substations located along the circumference of the photoconductive belt  190 . The charging substation  121  charges the photoconductive belt  190 . The charged the photoconductive belt  190  travels a distance DT 121  through the charging substation  121 . The photoconductive belt  190  then travels a distance D 1   a  to reach a second charging substation  131 . The charging substation  131  charges the photoconductive belt  190  for a second time. The charged photoconductive belt  190  travels a distance DT 131  through the charging substation  131 . 
     The charged photoconductive belt  190  then travels a distance D 1   b  to reach the exposing substation  132 . The total distance traveled by the first portion of the photoconductive belt  190 , from the first charging substation  121  to the exposing substation  132 , is D 1 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distances D 1   a , D 1   b  and D 1  are predetermined to allow uniform charging of the first portion of the photoconductive belt  190 . 
     In this exemplary embodiment, a multiplicity of charging substations are used in tandem to ensure uniform charge of the photoconductive belt  190  at higher belt speeds, compared to a full color image forming device, to compensate for a decreased amount of time spent at any single charging substation. 
     The exposing substation  132  exposes a first portion of the photoconductive belt  190 . The first portion of the photoconductive belt  190  travels a distance DT 132  through the exposing substation  132 . The first portion of the photoconductive belt  190  then travels a distance D 2  to reach the developing station  133 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 2  between the developing substation  133  and the exposing substation  132  are predetermined to allow sufficient exposure of the first portion of the photoconductive belt  190 . 
     The developing substation  133  develops the single highlight color image. The first portion of the photoconductive belt  190  travels a distance DT 133  through the developing substation  133 . The speed of the photoconductive belt must allow sufficient development of the single highlight color image over the distance DT 133 . 
     The photoconductive belt continues to move, in a counterclockwise direction, to the charging substation  141 . The charging substation  141  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 141  through the charging substation  141 . The charged photoconductive belt  190  then travels a distance D 3   a  to reach a second charging substation  151 . The charging substation  151  charges the photoconductive belt  190  for a second time. The charged photoconductive belt  190  travels a distance DT 151  through the charging substation  151 . 
     In this exemplary embodiment, a multiplicity of charging substations are used in tandem to ensure uniform charge of the photoconductive belt  190  at higher belt speeds, compared to a full color image forming device, to compensate for a decreased amount of time spent at any single charging substation. 
     The charged photoconductive belt  190  then travels a distance D 3   b  to reach the exposing substation  152 . The exposing substation  152  exposes a second portion of the photoconductive surface  190 . The total distance between the exposing substation  152  and the charging substation  141  is D 3 . The second portion of the photoconductive belt  190  then travels a distance D 4   a  to reach the developing station  153 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 3  (which includes the distances D 3   a  and D 3   b ) between the exposing substation  152  and the charging substation  141  are predetermined to allow uniform charging of the second portion of the photoconductive belt  190 . 
     The developing substation  153  develops the monochrome image. The second portion of the photoconductive belt  190  travels a distance DT 153  through the developing substation  153 . The second portion of the photoconductive belt  190  continues over a distance of D 4   b  to a second developing substation  163 . The developing substation  163  further develops the monochrome image. The second portion of the photoconductive belt  190  travels a distance DT 163  through the developing substation  163 . The speed of the photoconductive belt must allow sufficient development of the monochrome image over the distances D 153  and DT 163 . 
     In this exemplary embodiment, a multiplicity of developing substations are used in tandem to ensure sufficient development of a monochrome image at higher belt speeds, compared to a full color image forming device, to compensate for a decreased amount of time spent at any single developing substation. 
     FIG. 5 shows is a schematic diagram outlining one exemplary embodiment of the image forming device of FIG. 1 depopulated and/or repopulated for high speed monochrome, single highlight color and/or dual highlight color printing according to this invention. The photoconductive belt  190  moves, in a counterclockwise direction, through the various substations located along the circumference of the photoconductive belt  190 . The charging substation  121  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 121  through the charging substation  121 . The charged photoconductive belt  190  then travels a distance D 1  to reach the exposing substation  122 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 1  between the exposing substation  122  and the charging substation  121  are predetermined to allow uniform charging of the photoconductive belt  190 . 
     The exposing substation  122  exposes a first portion of the photoconductive belt  190 . The first portion of the photoconductive belt  190  travels a distance DT 122  through the exposing substation  122 . The first portion of the photoconductive belt  190  then travels a distance D 2  to reach the developing station  123 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 2  between the developing substation  123  and the exposing substation  122  are predetermined to allow sufficient exposure of the charged portion of the photoconductive belt  190 . 
     The developing substation  123  develops the first highlight color image. The first portion of the photoconductive belt  190  travels a distance DT 123  through the developing substation  123 . The speed of the photoconductive belt must allow sufficient development of the first highlight color image over the distance DT 123 . 
     The photoconductive belt continues to move, in a counterclockwise direction, to the charging substation  131 . The charging substation  131  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 131  through the charging substation  131 . The charged photoconductive belt  190  then travels a distance D 3   a  to reach a second charging substation  141 . The charging substation  141  charges t the photoconductive belt  190  for a second time. The charged photoconductive belt  190  travels a distance DT 141  through the charging substation  141 . 
     The charged photoconductive belt  190  then travels a distance D 3   b  to reach the exposing substation  142 . The total distance traveled by the photoconductive belt  190  from the first charging substation  131  to the exposing substation  142  is D 3 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 3  (which includes the distances D 3   a  and D 3   b ) are predetermined to allow uniform charging of the second portion of the photoconductive belt  190 . 
     In this exemplary embodiment, a multiplicity of charging substations are used in tandem to ensure uniform charge of the photoconductive belt  190  at higher belt speeds, compared to a full color image forming device, to compensate for a decreased amount of time spent at any single charging substation. 
     The exposing substation  142  exposes a second portion of the photoconductive belt  190 . The second portion of the photoconductive belt  190  travels a distance DT 142  through the exposing substation  142 . The second portion of the photoconductive belt  190  then travels a distance D 4  to reach the developing station  143 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 4  between the developing substation  143  and the exposing substation  142  are predetermined to allow sufficient exposure of the second portion of the photoconductive belt  190 . 
     The developing substation  143  develops the second highlight color image. The second portion of the photoconductive belt  190  travels a distance DT 143  through the developing substation  143 . The speed of the photoconductive belt must allow sufficient development of the second color toner image over the distance DT 143 . 
     The photoconductive belt continues to move, in a counterclockwise direction, to the charging substation  151 . The charging substation  151  charges the photoconductive belt  190 . The charged photoconductive belt  190  travels a distance DT 151  through the charging substation  151 . The charged photoconductive belt  190  then travels a distance D 5   a  to reach a second charging substation  161 . The charging substation  161  charges the photoconductive belt  190  for a second time. The charged photoconductive belt  190  travels a distance DT 161  through the charging substation  161 . 
     The charged photoconductive belt  190  then travels a distance D 5   b  to reach the exposing substation  162 . The total distance traveled by the photoconductive belt  190  from the first charging substation  151  to the exposing substation  162  is D 5 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 5  (which includes the distances D 5   a  and D 5   b ) are predetermined to allow uniform charging of the photoconductive belt  190 . 
     In this exemplary embodiment, a multiplicity of charging substations are used in tandem to ensure uniform charge of the photoconductive belt  190  at higher belt speeds, compared to a full color image forming device, to compensate for a decreased amount of time spent at any single charging substation. 
     The exposing substation  162  exposes a third portion of the photoconductive belt  190  to a latent image of the input image. The third portion of the photoconductive belt  190  travels a distance DT 162  through the exposing substation  162 . The third portion of the photoconductive belt  190  then travels a distance D 6  to reach the developing station  163 . In various exemplary embodiments, the speed of the photoconductive belt  190  and the distance D 6  between the developing substation  163  and the exposing substation  162  are predetermined to allow sufficient exposure of the third portion of the photoconductive belt  190 . 
     The developing substation  163  develops the monochrome image. The third portion of the photoconductive belt  190  travels a distance DT 163  through the developing substation  163 . The speed of the photoconductive belt must allow sufficient development of the monochrome image over the distance DT 163 . 
     It should be appreciated that the rate at which the belt may move through the stations is a function of the time required at each substation (i.e., dwell time), the distance through each substation and the distance between the substations within a particular station. 
     FIG. 6 is a flowchart outlining a method for generating full color images using a full color image forming device. Beginning in step S 100 , the operation proceeds to step S 200 , where initial image data is input. Then, in step S 300 , the photoconductive surface is charged, exposed and a first color toner image is developed at a first station. Next, in step S 400 , the photoconductive surface is charged, exposed and a second toner color image is developed at a second station. Operation then continues to step S 500 . 
     In step S 500 , the photoconductive surface is charged, exposed and a third toner color image is developed at a third station. Then, in step S 600 , the photoconductive surface is charged, exposed and a fourth toner color image is developed at a fourth station. Next, in step S 700 , the final image is output. Operation of the method continue to step S 800 , where operation of the method stops. 
     FIG. 7 is a flowchart outlining one exemplary embodiment of a method for generating monochrome images at high speeds according to this invention using a first exemplary embodiment of a depopulated and/or repopulated image forming device. Beginning in step S 1000 , operation proceeds to step S 1100 , where initial image data is input. Then, in step S 1200 , the photoconductive surface is charged for a first time at a first charging substation. Next, in step S 1300 , the photoconductive surface is charged for a second time at a second charging substation. Operation then continues to step S 1400 . 
     In step S 1400 , the photoconductive surface is charged for a third time at a third charging substation. Then, in step S 1500 , the photoconductive surface is exposed at a fourth exposing substation. Next, in step S 1600 , a monochrome image is developed for a first time at a fifth developing substation. Operation then continues to step S 1700 . 
     In step S 1700 , the monochrome image is developed for a second time at a sixth developing substation. Next, in step S 1800 , the monochrome image is output. Operation then continues to step S 1900 , where operation of the method stops. 
     FIG. 8 is a flowchart outlining one exemplary embodiment of a method for generating monochrome and/or single highlight color images at high speed according to this invention using a second exemplary embodiment of a depopulated/repopulated image forming device. Beginning on step S 2000 , operation proceeds to step S 2100 , where initial image data is input. Then, in step S 2200 , the photoconductive surface is charged for a first time at a first charging substation in step S 2300 , the photoconductive surface is charged for a second time at a second charging substation. Operation then continues to step S 2400 . 
     In step S 2400 , a first portion of the photoconductive surface is exposed at a third exposing substation. Then, in step S 2500 , a highlight color image is developed at a fourth developing substation. Next, in step S 2600 , the photoconductive surface is charged for a first time at a fifth charging substation. Operation then continues to step S 2700 . 
     In step S 2700 , the photoconductive surface is charged for a second time at a sixth charging substation. Then, in step S 2800 , a second portion of the photoconductive surface is exposed at a seventh exposing substation. Next, in step S 2900 , a monochrome image is developed for a first time at an eighth developing substation. Operation then continues to step S 3000 . 
     In step S 3000 , the monochrome image is developed for a second time at a ninth developing substation. Then, in step S 3100 , the monochrome image is output. Operation then continues to step S 3200 , where operation of the method stops. 
     FIG. 9 is a flowchart outlining one exemplary embodiment of a method for generating monochrome, single highlight color and/or dual highlight color images at high speed according to this invention using a third exemplary embodiment of a depopulated and/or repopulated image forming device. Beginning on step S 4000 , operation proceeds to step S 4100 , where initial image data is input. Then, in step S 4200 , the photoconductive surface is charged at a first charging substation. Next, in step S 4300 , a first portion of the photoconductive surface is exposed at a second exposing substation. Operation then continues to step S 4400 . 
     In step S 4400 , a first highlight color image is developed at a third developing substation. Then, in step S 4500 , the photoconductive surface is charged for a first time at a fourth charging substation. Next, in step S 4600 , the photoconductive surface is charged for a second time at a fifth charging substation. Operation then continues to step S 4700 . 
     In step S 4700 , a second portion of the photoconductive surface is exposed at a sixth exposing substation. Then, in step S 4800 , a second highlight color image is developed at a seventh developing substation. Next, in step S 4900 , the photoconductive surface is charged for a first time at a seventh charging substation. Operation then continues to step S 5000 . 
     In step S 5000 , the photoconductive surface is charged for a second time at an eighth charging substation. Then, in step S 5100 , a third surface of the photoconductive surface is exposed at a ninth exposing substation. Next, in step S 5200 , monochrome image is developed at a tenth developing substation. Operation then continues to step S 5300 . 
     In step S 5300 , the monochrome image is output. Operation then continues to step S 5400 , where operation of the method stops. 
     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 in above are intended to be illustrative not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims. 
     It should be appreciated that the full color image forming device of FIG. 2 may be adapted for the generation of monochrome images at high speed. For example, the fifth, unused, station can be depopulated so that only the developing substation is present and/or active. This developing substation may then be used in tandem with a second developing substation for generating a monochrome image at high speed. 
     It should also be appreciated that the exemplary embodiments detailed above can be combined to achieve a depopulated and/or repopulated image forming device for generating monochrome, single highlight color and/or dual highlight color printing at high speed. For example, if one were to combine the exemplary embodiment of FIG. 3 with that of FIG. 4, the resulting image forming device would be identical to that of FIG. 4, with the addition of exposing substation  142 . 
     It should also be appreciated that the exemplary embodiments detailed above can be modified independently of each other to achieve a depopulated and/or repopulated image forming device for generating monochrome, single highlight color and/or dual highlight color printing at high speed. For example, it is possible to remove the charging substation  131  from FIG. 5 without preventing the generation monochrome, single highlight color and/or dual highlight color printing at high speed.