Patterned intensities printer

#The present invention relates to computer controlled printers and, more particularly, to such printers printing colored materials on the recording sheets to provide a color image.

#The use of personal computers and, correspondingly, desk top printers controlled in part by such computers has increased very rapidly over the last several years. Many different printing technologies have been developed for these devices beyond that used in the impact printers initially performing in this role, including ink jet, thermal wax transfer and thermal diffusion, or dye sublimation, printing technologies.

#These last technologies have been especially important in the growth of color printers, those having the capability of providing a colored image on a recording medium. The order of listing of these printing technologies above is typically the order of the quality of the results obtained in using them with ink jet technology generally providing the poorest quality of these technologies, and thermal diffusion giving the best. Unfortunately, the order of listing is also the order of cost with ink jet printers generally being cheapest and thermal diffusion printers being the costliest.

#FIG. 1 shows a block diagram of a computing system,

#FIG. 2 shows a block diagram of a printing system,

#FIGS. 3A, 3B, 3C, 3D and 3E show a flow chart for a process in the system of FIG. 1,

#FIG. 1 shows a block diagram of a typical personal computer arrangement having a computer, 10, with peripherals connected thereto, including a keyboard, 11, for providing information and directives to computer 10 from a user thereof. Further included in the peripherals are a monitor, 12, for communicating to the user actions and statuses of computer 10, and a disk memory, 13, for large and nonvolatile storage of information. Computer 10 has internal thereto an active memory which is volatile, and various other subassemblies and components necessary to satisfactory operation thereof. Included in computer 10 is a bus arrangement between the central processing unit therein and various electronic subassemblies for interacting with peripherals, including an output port electronic subassembly, 14. Output port electronic subassembly 14 is suitable for communication with a printing device under the control of computer 10.

#A block diagram of such a printer is shown in FIG. 2. A microcomputer, 15, serves as a printing controller, or at least part of a printing controller in conjunction with computer 10, for the printer. An input port electronic subassembly, 16, is capable of receiving signals from output port subassembly 14 of computer 10, and communicates such signals along a bus to microcomputer 15. Microcomputer 15 has a nonvolatile program memory, 17, and a volatile active memory, 18, to provide both buffer memory and registers for the operation of microcomputer 15. Microcomputer 15 operates a thermal printhead, 19, having a plurality of electrical resistors, 20, electrically isolated both from one another and the substrate provided by the printhead, and arrayed along a line directed into the plane of the sheet on which FIG. 2 is provided. A typical number of such resistors is 1,728, and each represents the minimum pixel size provided in a printed image made on recording sheet by thermal printhead 19 through resistors 20. Such a recording sheet, 21, typically paper, is provided between a roller, 22, and the resistors 20 of thermal printhead 19, as is a coloring materials supply ribbon, 23, on the printhead side of sheet 21.

#During printing, or coloring material deposition, an image line printing signal is shifted into a shift register provided in thermal printhead 19 having one register therein for each of resistors 20, and that register controls in part whether current flows in the register to which it corresponds. This printing signal is a digital signal in the form of a succession of two-state Boolean logic signal portions each of which sets the logic state in the register it last affects after the shifting is completed of that printing signal into the shift register prior to the next line to be printed in the image. A Boolean logic value of "1" in a register results in selecting the one of resistors 20 corresponding thereto to have current flow therethrough in the next current flow event permitting current flow in parallel through at least some of resistors 20, an event which is initiated and terminated by microcomputer 15. During such an event, thermal printhead 19 is pressed against coloring materials supply ribbon 23, pressing it in turn against recording sheet 21 which is thereby pressed against roller 22.