Identification of recording media

#The present invention relates generally to devices and methods for identifying media and more specifically to devices and methods for identifying recording media in a printer or reproduction device.

#Modern printing devices, for example, ink jet and laser printers, print on a wide range of print media. Such media include plain paper, glossy or coated papers, and plastic films including overhead transparency film. For optimal print quality, operating parameters of these printers can be adjusted to meet the requirements of each print medium. Parameters in the image rendering process, in a host computer or in an “on-board” computing engine in the printer, also depend upon media type. For example, the “gamma” (i.e., tone reproduction curve) used for reflective prints (on paper and other reflective media) is different than that used for transparency media. This is required to adapt the printed image to the characteristics of the human visual response under different lighting and viewing conditions. Therefore, both the recording process in the printer and the image rendering process, in a host computer or on-board computing engine, may require knowledge of media type for optimal print quality.

#The software controlling the rendering process and the printer, including the printer driver, sometimes gives the user the opportunity to specify the recording medium. Parameters of the rendering and recording processes are then adjusted according to the recording medium and the quality mode selection. However, users may not always make the correct choice. In addition, specifying the choice is often inconvenient when multiple copies on different media are desired as occurs when overhead transparencies and hardcopy for handouts must be produced from the same data file.

#FIG. 1A is a schematic view of the illumination sources and photodetector array, according to a portion of one embodiment of the present invention;

#FIG. 1B is a schematic view of a portion of the illumination sources and photodetector array, according to another embodiment of the present invention;

#FIG. 1C is a diagram illustrating the angles and planes of incidence in one embodiment of the present invention;

#A method and device for identifying recording media in a printer is described below. The method is based on imaging the fine structure of the recording media. Plain and special papers as well as photographic papers and other recording media have a detailed structure that when viewed under magnification and suitably illuminated is useful for discrimination between media types.

#Visible features used for media identification result from choices of illumination source and imaging optics, and the optimal choice can be different for each medium. Different media can produce different features not only by using different illumination angles-of-incidence but also by using different orientations of the plane of incidence used for the illumination. Bond paper has a rich surface structure with characteristic feature sizes in the range between about 1 and 100 μm. In addition, it can have a granular directionality that shows up under different directions of illumination about the surface normal. When these features are highlighted with grazing light (light that has large angles of incidence relative to the surface normal), this light interacts with the bulk of paper fibers at or near the surface to create contrast-enhancing shadows much larger than the diameters of individual fibers. Viewed with resolution-limiting optics, only the larger shadow features are seen and produce an image unique to bond paper. Thus, a preferred choice for bond paper is grazing illumination and low-resolution optics that together highlight the lower spatial frequency features. Use of low-resolution optics has the additional benefit of permitting a relatively deep depth-of-field.

#When bond paper is illuminated at higher angles off the paper surface (lower angles of incidence relative to the normal to the surface) and imaged with higher magnification, the higher spatial frequency features caused by individual fibers will have lower contrast. Moreover, since higher magnification is associated with a shallower depth-of-field, imaging with high magnification requires tighter alignment tolerances on the distance from the optics to the surface of the medium.