Initialization method for establishing process control parameters

An automatic process of setting control set-points, control rates, calibrations, timing parameters and maximum density levels for color modules within a color print engine by utilizing addressable settings of multiple configurable parameters for each color module. The parameters can be independently controlled and maintained. Each color module maintains a list of parameters by storing the parametric values in a non-volatile memory. At initialization, the parameters for each module are read out of the non-volatile memory to set the correct settings for the specific color module.

FIELD OF THE INVENTION

The present invention relates to parametric control of color printing modules, and more particularly to the automated employment of distributed parameters for multiple color modules using a single software routine.

BACKGROUND OF THE INVENTION

Color print engines employing multiple color modules exist within the prior art that have parameters such as process control set-points, control rates, calibrations, timing parameters and maximum density levels for each color module that typically, are set to a predetermined level at initialization. However, the optimum values for these parameters can differ for each color module and the same parameter can vary over time. These prior art systems typically provide parameter values for each color module during initialization. In order to change these initial settings, manual intervention is usually required. Once the parameters are initialized, the settings or personality of each color module is established. This manual intervention requires skilled effort on the part of machine operators and can result in less than optimum performance of the color print engine. Accordingly, there is a need within the prior art for automated techniques that initialize and update these parameters.

In view of the foregoing discussion, there remains a need within the art for an automated system and method for providing process controls, calibrations, and timing parameters to provide superior control for each color module.

SUMMARY OF THE INVENTION

The invention addresses the aforesaid needs within the art of color print engines employing multiple color modules by automatically providing different process control set-points, control rates, calibrations, timing parameters and maximum density levels for each color module. The invention realizes these settings through multiple configurable parameters for each color module. The parameters can be independently controlled and maintained. Each color module maintains a list of parameters by storing the parametric values in a non-volatile memory. At initialization, the parameters for each module are read out of the non-volatile memory to set the correct settings for the specific color module.

These and other features are provided by the invention in a color printing system having multiple color modules, at least one processing element associated with the color modules, a set of configurable parameters for each of the color modules stored such that it is accessible by the processing elements and a manner for updating the configurable parameters.

The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIGS. 1aand1b, which are illustrations of the color printer engine10used within the preferred embodiment of the invention, four electrophotographic (EP) modules22,24,26,28have respective color modules12,14,16,18. The color printer engine10has the ability to automatically process and control set-points, control rates, calibrations, timing parameters and maximum density levels for the color modules12,14,16,18through the use of multiple parameters that are configurable for each of the color modules12,14,16,18. The invention envisions that these parameters can be independently controlled and maintained. The color modules12,14,16,18each maintain a list of parameters identifications (PIDs) that are retained as parametric values stored in a non-volatile memory. The stored parameters are stored locally to allow access by one of the Central Processing Units (CPUs)32,34,36,38that are associated with each of the color modules12,14,16,18. The result is to create a distributed processing environment wherein CPUs32,34,36,38are individually associated with respective EP modules22,24,26,28. The PIDs are applied to system software that is controlled by the master processor30across the common bus. The CPUs32,34,36,38are slave devices to master processor30in the preferred embodiment illustrated inFIG. 1a. It will be understood that instead of employing a processor with individual modules, that a single processor37, shown inFIG. 1bcan track and update separate tables containing PIDs for each module.

The color print engine10illustrated inFIGS. 1a,1bhas multiple EP modules22,24,26,28, however, the number of EP modules22,24,26,28is not limited to four, and it is for example envisioned that there be a fifth module (not shown). Furthermore, the color print engine10is not limited to a particular number or configuration of modules. The EP modules22,24,26,28are typically configured to contain a different color toner and, therefore, the EP modules22,24,26,28will each typically require a different setting for process control set-points, control rates, calibrations, timing parameters, and maximum density levels. Each of these settings can be realized through application of multiple configurable parameters for each of the EP modules22,24,26,28, allowing independent control and maintenance of the settings. A list of PIDs are maintained for each of the EP modules22,24,26,28, and the list of PIDs is preferably stored in non-volatile memory that is locally accessible to their respective CPUs32,34,36,38, in order that the PIDs are not lost during power-down. As previously stated, a single processing element (37ofFIG. 1b) could be employed with a suitable communication bus structure whereby all the lists for the PIDs could be maintained by the single processing element.

An initialization process will take place during the assembly of the print engine or during software installation. Initialization requires that the PIDs for each module be set to the correct settings for the specific color module12,14,16,18. The invention envisions that each of the CPUs32,34,36,38(or single CPU37) operate on the same software supplied by the system to control the individual EP modules22,24,26,28via implementation of the PIDs that are specific for each of the color modules12,14,16,18. The system software for the color printer engine10maintains parameter values for each of the color modules12,14,16,18that are currently defined for the print engine. The color printer engine10, also defines the order of application and positioning for each of the color modules12,14,16,18. During the initialization process, the system software uses a communication bus20attached to several addressable nodes as inputs for each color module12,14,16,18in order to initialize the PIDs. The node identification within the preferred embodiment is referred to as the Node ID and the communication bus20is preferably an ARCNET® communication ring. The node identification procedure employed by the invention is not limited to being implemented on an ARCNET® communication ring and could easily be extended to a TCP/IP address if the communication bus20employed uses an Ethernet TCP/IP communication protocol. Additional communication busses are equally well suited for the invention based on specific designs.

During this initialization process, each of the color modules12,14,16,18will have PIDs set using a unique identification number that allows fully independent configuration and control for the PIDs to each of the EP modules22,24,26,28by an external user. Once the PIDs are initialized, the settings, or personality, for each of the color modules12,14,16,18is established. The invention employs system software to perform regular checks on the various components of the color modules12,14,16,18to insure that they match the personality that has been previously loaded. For example, in the preferred embodiment, the color modules12,14,16,18are electrophotographic modules wherein color identifications are read from the toning station TS (FIG. 3) and replenishing units to be compared with the expected colors defined by the PIDs. If the color identifications do not match the PIDs, there are possible hardware problems, toning station TS color mismatching, or improper seating of the toning and replenisher subsystems. As more toners/colors are developed, configuration files can be maintained externally and loaded into the PIDs for each of the EP modules22,24,26,28, to create new process control settings.

The present invention allows added flexibility to the order in which the color/toner is applied, and provides for dynamic configuration in the application of the color/toner. During the initialization process, the system software will be able to interrogate the toning station TS identifications within each of the color modules12,14,16,18and initialize the parameter sets accordingly, rather than having a fixed order method using the communication bus20node/address. The configurable parameter settings can be loaded and/or exchanged between modules and allow the running of specific jobs that require different color toners or require different color application orders to create desired special effects.

Referring now toFIG. 2, the communication bus20of the preferred embodiment of the invention forms a logical ring50containing several independently addressable nodes. Preferably, communication bus20is an ARCNET® communication ring having CPUs32,34,36,38in the first four addresses. The fifth address is another CPU39for a fifth color in the color printing engine10. Additional addresses on communication bus20are held by Print Imaging Electronics (PIE)91, fuser92, Main Machine Control (MMC)93, paper supply94, paper path195, paper path296Auto Sheet Positioner (ASP)97and Web Exposure Control (WEC)98, which are shown for example only, and do not constitute a substantial ingredient of the invention. EP module22, is configured for use with black toner and is an addressable node on the logical ring50located at address1through CPU34. It is specifically envisioned that any of EP modules22,24,26,28can be addressed by a single processor within color printer engine10. Table 1 illustrates a few of the color dependent parameters that can be configured for use in accordance with the specific colorant used. The first EP module22as a functional unit, is required to have an identification that matches the color black, which is contained in Table 1 as COLOR_ID. The EP modules22,24,26,28each have a device that identifies that module, preferably the toning station will have a physical hardware 5-bit switch which can be configured at the time toner is first installed. In the case of EP module22, the 5-bit switch would be set to identify that module as containing toner “1”, and, the software parameters for controlling black toner must match the identified color of the toning station. The 5-bit switch can identify up to thirty-two different colors, therefore, while Table 1 has only five columns, Table 1 should be looked as an example only and thirty-two colors are specifically envisioned in the present embodiment. Other addressing mechanisms could easily be configured to provide more than thirty-two color selections.

The parameters ALPHA and BETA contained in Table 1 control the proportional gain adjustment to electrophotographic parameters in response to measured density errors. ALPHA is the proportionality constant between a measured VTD(voltage transmissive density) error and the required Vochange. BETA is the proportionality constant between the VTDerror and the Eochange. The ALPHA and BETA values control the magnitude of the Voand Eocorrections needed to correct a density error. An increase in Voand Eoyields an increase in density.

Each of the EP modules22,24,26,28will have their individual color controlled by reading the density of the applied color via a densitometer. The densitometer receives a transmission density and reports the transmission density (as the log of the transmission density) as a 5000 millivolt per decade response. The log representation of the transmission density is then compared with the desired density, referred to herein as the aim voltage transmission density, and represented on Table 1 as VTD-aim. For the first EP module22, the VTD-aimdensity value is 3410 millivolts, and if the comparison of measured transmission density to the VTD-aimdensity shows that they are not equal, then a density error is generated. The occurrence of a density error is used to initiate the computation of a new electrophotographic aims for operating the primary charger, exposure and toning station as fixed ratio adjustments in proportion to the density error. The toners for each of the EP modules22,24,26,28contain different pigments in varying concentrations, resulting in the measured density having a different relationship to the actual mass density of toner present. The electrophotographic process controls require adjustment to insure that the proper ratio of Vo/Eofor the amount of mass applied, and thus the proportional gains, ALPHA and BETA will be unique for each of the EP modules22,24,26,28according to their respective colorant.

FIG. 3is a logical illustration of the process control loop used to determine the density baseline for a single color module52. The color module52seen inFIG. 3is representative of those previously discussed. The color module52illustrated inFIG. 3is explicitly shown to detail the density loop. As shown inFIG. 3, an electrophotographic printing system of the module52includes a primary charger61is used to generate a surface potential on the photoconductive member63by spraying a defined surface charge density. The surface potential on the photoconductive member63immediately following the charger is referred to as Vo. Typically, if no other parameters are changed, the print density will increase when Vois increased. An exposure source64is used to image-wise illuminate the photoconductive member63to create a latent electrostatic image. The amount of photodischarge, measured as a change to the surface potential of the photoconductive member63, is related to the intensity of the exposure source64. Preferably, the exposure source64is a digital source wherein the image-wise exposure can be done as a multilevel exposure, as an area modulated halftone, or a mixed dot halftone which combines intensity and area modulation to form the tonal information of the image.

In multiple color electrophotographic systems, it is desirable to use the same arrangement to image toners pigmented with different colorants. The constants used in the above system must be adjusted to the particular light absorption characteristics of the colorant. For example, to be able to create a neutral density output made up of yellow, magenta and cyan pigmented toners, the mass that is applied for each of the toners needs to be uniquely defined. Likewise, each toner color will have a unique relationship between the mass amount applied and the signal received from the transmission densitometer. Thus, each colorant has a unique aim value, VTD-aim. In addition, the proportionality constants for controlling the electrophotographic system will need to be adjusted, such that a measured VTDerror will be corrected by adjusting Voand Eo.

The density loop controls the transmission density of the image transferred to the transport web68by fixed ratio changes to Voand Eo. A patch is generated in an area between receiver elements referred to as the interframe, by timing the application of the patch to the transport web68so that the patch does not transfer to any of the receiver elements carried by the transport web. The patch is then read by the densitometer72. The densitometer72produces a voltage output in log proportion to the transmittance of the transport web68. Determine ΔVTD(78) provides adjustments values for a patch by taking the densitometer72reading of the transparent transport web68in an area where there is no receiver element and then subtracting that value from the densitometer62reading of the transport web68where the patch exists to arrive at a net patch voltage VTD. The aim voltage VTD—aimis then subtracted from the measured net patch voltage VTDto determine ΔVTD. The parameters ALPHA and BETA contained in Table 1 are represented as: α for the proportionality constant between a measured VTDand the required Vochange; and β for the proportionality constant between the VTDand the Eochange. Adjustments to Vo-aim(76), which result in the determined value ΔVo-aim, are calculated by relationship (α*ΔVTD) where α is the fixed value gain illustrated in Table 1. Similarly, adjustments to Eo-aim(75), which result in the determined value ΔEo-aim, are calculated by (β*ΔVTD) where β is another fixed value gain. The values for α and β must have the proper ratio to each other to maintain tonescale. The magnitude of these two values, are established so that a VTDerror is substantially corrected by a single Voand Eoadjustment.

Primary charger61is supplied with a grid potential that determines the potential that is applied to the photoconductive member63based on determine ΔVo(81), calculate ΔVgrid(82) and determine Vgridnew(83), which will be discussed more in detail, hereinbelow.

A global exposure variable is used to proportionally change the intensity of the image-wise exposure as a means to control the image density. If the global exposure, referred to herein as Eo, is increased, the density of the output image will also increase. A toning system is used to render the latent image as a visible image using pigmented toner to physically create the image. A toning bias voltage, Vbiasis applied to the toning system with a fixed offset from Vosuch that charged toner is repelled from the unexposed regions of the latent image, but attracted to exposed regions. Vbiasas seen inFIG. 3is offset from Vonewby 85 volts. The mass density of toner developed is related to the toning potential, which is the potential difference between the toning bias, Vbias, and surface potential on the photoconductive member63in exposure areas, Eo. The mass density of toner will increase if either Voor Eois increased. However, the tonescale response of the output image will be best preserved if the Voand Eoadjustments are done in fixed ratio to each other.

Still referring toFIG. 3, the print density control function employed by the process control uses the EP modules52to expose a process control patch on the transport web68in the inter-frame space between receiver sheets. Preferably, numerous patches will be made each using an individual colorant. A transmission densitometer62measures the density of the process control patch on a clear transport web68where the patch is positioned between the receiver elements or sheets. An illumination source, such as an LED (not shown), is positioned above the process control patch, with a photodetector (not shown) located below the patch. A logarithmic amplifier produces a 5 volt per decade output in relation to the current in the photodetector. The circuit is adjusted so that the null reading without a patch is near the bottom range of detection (for example 1 volt on a 0–10 volt scale). If a 1.0 transmission density image is placed within the emitter/detector pair, 90% of the light is absorbed creating a proportional change in current generation in the photodetector circuit, and will cause a 5 volt change in the logarithmic amplifier output from 1 volt to 6 volts. The net change in output from the transmission densitometer is referred to Voltage Transmission Density, or VTD.