System and method for adjusting ink jet uniformity based on drop mass history

#This disclosure relates generally to ink jet adjustment systems and, more particularly, to ink jet adjustment systems that evaluate ink drop mass.

#Many document generating systems convert document data into control signals that operate an ink ejecting print head in a printer, for example, to produce an image of a document with ink drops emitted from the print head. In some of these systems, an electronic version of a document from a personal computer (PC) or other type of computing system is used to produce the document on media, such as paper or film. In other systems, an electronic document is generated by scanning an original hard copy document with a light source to generate reflected light representative of the document. The light signals are converted into electrical signals that may be stored in an electronic memory. The document generating system typically includes an image processor that manipulates the electronic data representing a document to a processed form of the document that is used to produce the hard copy version of the document.

#A print engine may be used to manage the subsystems that cooperate to generate a document on media. These subsystems include the image processor and the components that apply or transfer marking material, such as ink, to media to form a document. For example, a direct marking system may include a marking material source, a print head, an image substrate, and a fuser. The marking material source may be an ink cartridge or a solid ink subsystem. Solid ink subsystems have a loader in which sticks of solid ink are loaded and transported to an ink melter that heats the ink sticks to a melting point to generate liquid ink. The liquid ink is collected in a reservoir to supply the print head. Ink cartridge systems are supplied with ink stored in replaceable ink cartridges. When the ink supply within a cartridge is exhausted, the cartridge is removed and replaced with another cartridge.

#The foregoing aspects and other features of a method and system in which the drop mass history of ink jets in a print head is used to adjust document data processing are explained in the following description, taken in connection with the accompanying drawings, wherein:

#FIG. 1 is a side view of an ink jet printing system that forms images of documents on a rotating intermediate image member.

#FIG. 2 is a flow diagram of a process for adjusting document data to compensate for drop mass history effects on ink jet ejection.

#An ink jet system may be used to print monochromatic or color images of documents that have been received from an image output device or a document generator. Document generators include personal computers, scanners, and workstations. The document generator provides input document data produced by application programs or the reception of light signals reflected from a hard copy of a document. These document data are typically processed before they are used to generate the control signals that operate the system components to produce a document. Because the components have particular physical characteristics that vary from ink jet device to ink jet device, some of the document data processing is performed to map the input document data to a form that corresponds to the physical characteristics of the components in a particular ink jet device. For example, a monochromatic version of a document may include pixels having a gray scale value in the range of 0 to 255. In this range, a zero value indicates no colorant is ejected for the pixel and the 255 value indicates the largest mass of colorant produced by an ink jet is ejected for the pixel. The actual ink jet printer components, such as the print head and its associated control circuits, may eject an amount of ink in response to the gray scale value for an input pixel that actually provides an output pixel that presents a different gray scale appearance to a human observer. Thus, the input document data processing includes a mapping of the input document data to device dependent values that cause the ink jet printing components to eject an amount of ink that more closely corresponds to the gray scale value of the input pixel.

#Referring to FIG. 1, a side view is shown of a prior art ink printer 10 that may be modified to implement drop mass history adjustment of ink jets in a print head. The reader should understand that the embodiment of the print process discussed below may be implemented in many alternate forms and variations. In addition, any suitable size, shape or type of elements or materials may be used. As shown in FIG. 1, the ink printer 10 may include an ink loader 40, an electronics module 44, a paper/media tray 48, a print head 50, an intermediate imaging member 52, a drum maintenance subsystem 54, a transfix subsystem 58, a wiper subassembly 60, a paper/media preheater 64, a duplex print path 68, and an ink waste tray 70. In brief, solid ink sticks are loaded into ink loader 40 through which they travel to a melt plate (not shown). At the melt plate, the ink stick is melted and the liquid ink is diverted to a reservoir in the print head 50. The ink is ejected by piezoelectric elements to form an image on the intermediate imaging member 52 as the member rotates. Member 52 is called an intermediate imaging member because an ink image is formed on the member and then transferred to media in the transfix subsystem.

#An intermediate imaging member heater is controlled by a controller to maintain the imaging member within an optimal temperature range for generating an ink image and transferring it to a sheet of recording media. A sheet of recording media is removed from the paper/media tray 48 and directed into the paper pre-heater 64 so the sheet of recording media is heated to a more optimal temperature for receiving the ink image. A synchronizer delivers the sheet of the recording media so its movement between the transfix roller in the transfer subsystem 58 and the intermediate image member 52 is coordinated for the transfer of the image from the imaging member to the sheet of recording media.