Laser triggered inkjet firing

Details Laser triggered inkjet firing Laser triggered inkjet firing

2002-04-10

2004-06-08

Pham, Hai (Department: 2861)

Incremental printing of symbolic information

Light or beam marking apparatus or processes

Scan of light

C347S051000, C347S058000

Reexamination Certificate

active

06747684

ABSTRACT:

RELATED APPLICATIONS
(Not applicable)
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(Not applicable)
FIELD OF THE INVENTION
This invention relates to inkjet printing technology, and laser-scanning technology where a laser is used to transfer image data.
BACKGROUND OF THE INVENTION
Currently, two commonly used technologies for imaging are laser (also referred to herein as “electrophotographic”) systems, and ink jet systems. In both of these systems, digital image data, produced by a computer, or the like, is transferred to the printer, which renders this data as a visible image upon a media. In most computer and printer systems, the image data for the printer is digital data which is stored in computer memory. This is the case for inkjet and laser printers, including both color and monochrome. The data is stored in a matrix or “raster” which identifies the location and color of each pixel which comprises the overall image. The raster image data can be obtained by scanning an original analog document and digitizing the image into raster data, or by reading an already digitized image file. The former method is more common to photocopiers, while the latter method is more common to printing computer files using a printer. Accordingly, the technology to which the invention described below is applicable to either photocopiers or printers. Recent technology has removed this distinction, such that a single printing apparatus can be used either as a copier or as a printer for computer files. These apparatus have been known as multifunction printers (“MFPs)”, a term indicating the ability to act as a photocopier, a printer, or a facsimile machine. Accordingly, the expression “printer” should not be considered as limiting to a device for printing a file from a computer, but should also include a photocopier capable of printing a digitized image of an original document. “Original documents” include not only already digitized documents such as text and image files, but photographs and other images, including hybrid text-image documents, which are scanned and digitized into raster data.
In any event, the image to be printed onto tangible media is stored as a digital image file. The digital image data is then used to drive a printing element to create an image. The raster image data file is essentially organized into a two dimensional matrix, that is translated by the printer into an image on the media. The image comprises a number of lines with each line comprising a number of discrete dots or pixels across the line. Each pixel in the image is assigned a binary value in the data file relating information pertaining to its color and potentially other attributes, such as density. The combination of lines and pixels makes up the resultant image.
As described the raster data is stored in computer readable memory as a raster image. That is, the image is cataloged by line, and each line is cataloged by each pixel in the line. A computer processor reads the raster image data line by line, and actuates the printer. For laser printers, this involves actuation of a laser that scans a photosensitive surface to selectively expose a pixel on the surface, based on the presence or absence of coloration, and the degree of coloration for the pixel. Typical pixel densities for images are in the range of 300 to 1200 pixels per inch, in each direction. For inkjet printers, actuation of the printer involves selective actuation of an inkjet nozzle to form, based upon the presence of absence of coloration, pixels upon a media surface.
Scanning in Laser Printers
In laser printers, the method of transferring the digital raster data to a photoconductor via a laser, lasers or LEDs is known as the image scanning process or the scanning process. The scanning process is performed by a scanning portion or scanning section of the electrophotographic printer. The process of attracting toner to the photoconductor is known as the developing process. The developing process is accomplished by the developer section of the printer. Image quality is dependent on both of these processes. Image quality is thus dependent on both the scanning section of the printer, which transfers the raster data image to the photoconductor, as well as the developer section of the printer, which manages the transfer of the toner to the photoconductor.
In the scanning process, a laser is scanned from one edge of the photoconductor to the opposing edge and is selectively actuated or not actuated on a pixel-by-pixel basis to scan a line of the image onto the photoconductor. The photoconductor advances and the next line of the image is scanned by the laser onto the photoconductor. In a multiple laser printer, more than one laser can be actuated simultaneously so as to more quickly generate the complete image onto the photoconductor. The side-to-side scanning of each laser is traditionally accomplished using a dedicated multi-sided or faceted rotating mirror. Such a mirror will be known herein as a “polygon” due to the polygonal shape of the mirror. The reflective surface of the mirrors is typically ground and polished aluminum. The laser beam impinges on one facet of the polygonal mirror and is reflected to a secondary or deflector mirror, which directs the laser beam to a unique, relative lineal position on the light sensitive surface of the photoconductor. By “relative”, it is understood that the photoconductor moves with respect to the linear position, but the position remains fixed in space. As the polygonal mirror rotates, the angle of incidence, and hence the angle of reflection, of the laser beam will vary. This causes the laser beam to be scanned across the photoconductor at the unique relative lineal position from a first edge to a second edge of the photoconductor. As the mirror rotates to an edge of the polygon between facets, the laser is essentially reset to the first edge of the photoconductor to begin scanning a new line onto the photoconductor. These mirrors tend to rotate at very high speeds, often in excess of 20,000 rpm.
Examples of laser scanning systems used in laser printers are disclosed in U.S. Pat. Nos. 5,691,759; 5,745,152; 5,760,817; 5,870,132; 5,920,336; 5,929,892; and 6,266,073 which are hereby incorporated by reference.
Inkjet Printheads
Most commercial inkjet printers use a moving or scanning printhead system wherein a printhead comprising ink nozzles is moved or scanned across the surface of a media. As the printhead moves over the surface, each ink nozzle is selectively activated to eject an inkjet or ink droplet to form a pixel on the media as the head passes over the surface.
To eject the droplet, ink is delivered under pressure to a printhead nozzle area. According to one method, the ink is heated causing a vapor bubble to form in a nozzle which then ejects the ink as a droplet. Droplets of repeatable velocity and volume are ejected from respective nozzles to effectively imprint characters and graphic markings onto a printout.
An inkjet printhead is formed by a substrate plus several layers defining multiple nozzle areas. The substrate and layer qualities and dimensions are selected to achieve desired thermodynamic and hydrodynamic conditions within each nozzle. Various patents teach aspects of printhead fabrication, including U.S. Pat. Nos. 4,513,298 (Scheu); 4,535,343 (Wright et al.); 4,794,410 (Taub et al.); 4,847,630 (Bhaskar et al.); 4,862,197 (Stoffel); and 4,894,664 (Tsung Pan), which are incorporated by reference.
Conventional inkjet printheads extend over a limited portion of a page-width and scan across the page. This contrasts with a page-wide-array (“PWA”) printhead that extends over an entire page-width (e.g., 8.5″, 11″, A4 width) and is fixed relative to the media path. The PWA printhead is formed on an elongated printbar and includes thousands of nozzles. The PWA printbar is generally oriented orthogonally to the paper path. During operation, the printbar and the PWA printhead are fixed while a page is fed adjacent to and moves under the printhead. The PWA printhead prints

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