Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
  • B41J11/0095—Detecting means for copy material, e.g. for detecting or sensing presence of copy material or its leading or trailing end
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
  • B41J11/009—Detecting type of paper, e.g. by automatic reading of a code that is printed on a paper package or on a paper roll or by sensing the grade of translucency of the paper

Definitions

• 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.
• 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.
• the "gamma" i.e., tone reproduction curve
• reflective prints on paper and other reflective 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
• the prior art which relies on gross properties of the print medium either in reflection or in transmission does not allow finer distinctions of the media. Additionally, in particular, the prior art fails to allow a differentiation dependent upon directionality in surface feature granularity, fails to allow a differentiation dependent upon directional structure manufactured into media surface, or both. Further, the existing techniques are typically limited to comparisons of the specular reflections to static, predetermined references for the determination of various recording media.
• the present invention relates to a method and device for identifying recording media.
• a first illumination source is disposed near a media illumination zone providing light incident on the media illumination zone at a first angle of incidence.
• a second illumination source is disposed near the media illumination zone providing light incident on the media illumination zone at a second angle of incidence.
• An image sensor is positioned to receive scattered light from the illumination zone, the image sensor producing signals in response to the received light.
• a processing device receives signals corresponding to outputs of the image sensor. The signals are processed to identify a surface placed within said illumination zone.
• a method of identifying recording media in a printer is disclosed. First, a first illumination source is selected to illuminate a surface of the recording medium at a first plane of incidence. The surface is illuminated from the aid selected plane of incidence. Next, a second illumination source is selected to illuminate the surface of the recording medium at a second plane of incidence. The surface is illuminated from the selected second plane of incidence. Then, the light from the surface is sensed by an image sensor. Responsive to the light from the surface, signal is produced. Then, the signal is processed to form a characteristic vector. Finally, the characteristic vector is compared with a plurality of reference vectors characteristic of different recording media to determine media type .
• 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. IB 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.
• FIG. 2 is a block diagram of the components of the recording media identification device, according to an embodiment of the present invention.
• FIG. 3 is a schematic representation of the characteristic values used to identify recording media.
• FIG. 4 is one example of a printer including the recording media identification device 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 ⁇ m. In addition, it can have a granular directionality that shows up under different directions of illumination about the surface normal.
• Photographic paper typically has closely spaced microscopic pits or depressions on the surface, but does not show much directionality.
• Coated media and the surfaces of transparencies are relatively smooth and flat but often have some small and shallow holes, although with relatively sparse distributions, that can be imaged with some detectable contrast by using grazing illumination and a low or high magnification .
• a suitable compromise enables a device for identifying recording media to use a single choice of imaging or detection optics in combination with both normal and grazing incidence illumination to image distinguishing features of bond paper, coated paper, photographic paper, and transparencies .
• different media may be distinguished directly or by comparisons of such properties as optical density of features, spatial frequency of features, total reflectivity, scattering efficiency, color, wavelength dependence, contrast range, gray-scale histograms, and dependence on orientation of planes of illumination incidence.
• the recording media identification device of one embodiment of the present invention includes one or more illumination sources as shown schematically in FIG. 1A wherein only one of multiple planes of illumination incidence is shown.
• Three sources of illumination 12, 14, and 16 are directed at recording medium 10, supported on a media path (not shown) .
• the transmission illuminator 12 is positioned below the recording medium 10 such that light from source 12 is collimated (or otherwise directed) by illumination optics 13 and passes through the medium 10 within illumination zone 11.
• the illumination zone is that area of the medium 10 that scatters light from one or more illuminators such that the scattered light is detected by a sensor.
• Grazing illuminator 14 provides light on the medium 10 within the illumination zone 11 at a grazing angle of incidence. Light from grazing illuminator 14 is collimated (or otherwise directed) by illumination optics 15 and/or by optics included in illuminator 14.
• the grazing angle which is the complement of the angle of incidence, is preferably less than about thirty degrees. To obtain higher contrast, preferably, the grazing angle is less than about sixteen degrees.
• Light from the illuminators 12, 14, 16 can have different wavelength distributions compared to each other.
• the illumination source 16 for normal incidence illumination (i.e., perpendicular to the plane of medium 10) is also illustrated in FIG. 1A.
• Focal lengths of the illumination optics 13, 15, and 17 are implementation dependent; however, in experiments, focal lengths of 10 mm to 16 mm have been successfully used.
• the recording medium identification device further includes a photodetector array 22, also referred to as an image sensor 22, shown at the top of FIG. 1A.
• a photodetector array 22 also referred to as an image sensor 22, shown at the top of FIG. 1A.
• the photodetector array 22 similarly senses reflected light from normal illuminator 16 and transmitted light from illuminator 12.
• normal illuminator 16, illumination optics 17, and beam splitter 18 could be positioned much further above the plane of medium 10 such that beam splitter 18 is between photodetector array 22 and imaging optics 20, with appropriate modifications to the optic powers of normal illuminator 16 and illumination optics 17.
• an aperture stop of about 2 mm in diameter, providing front numerical aperture of about 0.1 has been used.
• the position in FIG. 1A of the group of elements 16 and 17 could be interchanged with the group of elements 20, 21, and 22, relative to the beam- splitter 18.
• a beam division beam splitter, or other beam selecting device such as a rotatable wheel of multiple apertures and/or mirrors, can be used in place of beam splitter 18.
• beam splitter 18 can alternatively be eliminated altogether by placing both the illuminator 16 and its optics 17 along a first optical axis, placing the photodetector array 22 and its imaging optics 20 and aperture 21 along a second optical axis, and tilting these two optical axes approximately an equal angle away from the normal to the medium surface and from one another, wherein both of these axes remain intersecting within the illumination zone 11.
• the photodetector array 22 (also referred to as photodetection array, photosensor array, or photosensing array) is an array of optoelectronic image sensing devices, elements, or cells, such as comprising CCD or CMOS imaging devices.
• the photodetection cells are arranged in a two-dimensional array.
• the photodetection cells are arranged in a two-dimensional array.
• practical arrays may require as many as 100 by 100 elements, but smaller arrays of as few as 16 by 16 are preferable from design, cost, and signal processing considerations. It is not necessary for the number of elements in the two orthogonal directions of the array to be equal .
• the image resolution for scanning the medium 10 surface can be determined by the most demanding medium to be identified, that is the medium and illumination combination resulting in an image with the smallest maximum feature sizes.
• the appropriate resolution corresponds to a pixel dimension on the surface of medium 10 (i.e., the projected pixel dimension) on the order of 40 ⁇ m on a side.
• a projected pixel dimension of approximately five microns (5 ⁇ m) on a side will allow photographic paper to be better identified.
• each array element of photodetector array 22 is approximately 50 ⁇ m on a side.
• an area of the surface of medium 10 that is at least 1 mm on a side should be illuminated within the illumination zone 11.
• the illumination sources 12, 14, and 16 within a plane of incidence may be one or more light emitting diodes .
• the illumination sources may be other light sources such as incandescent lamps, laser diodes or surface emitting laser diodes.
• the light sources may be pulsed at higher drive levels to assure sufficient photons reach the photodetector during the exposure interval and to prevent significant motion blurring.
• the illumination optics 13, 15, and 17, which may be conventional, may comprise a single element or a combination of lenses, filters, and/or diffractive or holographic elements to accomplish suitably directed and/or generally uniform illumination of the target surface .
• image sensor data from an image of a uniform reflecting surface such as a smooth surface of opal glass, placed in the illumination zone 11, provides calibration image data for compensating any fixed non- uniformity exhibited within the illumination itself.
• a motion-blurred image can be taken of a relatively featureless medium surface, such as clay-coated paper.
• Motion blurring can also be used with the opal glass to reduce the potential of imaging microscopic features (patterns) within or on the opal glass.
• the photodetector array 22 is a linear array and the recording medium is scanned past the photodetector array to produce a two-dimensional image.
• medium 10 is scanned past photodetector array 22 by the medium transport mechanism of a printer to which the recording medium identification device of the present invention is attached.
• photodetector array 22 is a one-dimensional array and forms a one-dimensional image, without the medium moving, that is used for medium identification.
• a single photodetector element is used, and the ink carriage, medium feeding mechanisms of the printer, or both, are used to scan the medium such that a one-dimensional or two-dimensional image is created and used for medium identification.
• FIG. IB and FIG. 1C An embodiment of the invention having a certain alternative configuration is partly shown in FIG. IB and FIG. 1C. Portions of this embodiment are similar to those shown in FIG. 1A.
• components in FIG. IB and FIG. 1C that are similar to components in FIG. 1A are assigned the same reference numerals, analogous but changed components are assigned the same reference numerals accompanied by letters "a,” "b, " and "c,” and different components are assigned different reference numerals.
• illuminators 14a (first illumination source) and 14b (second illumination source) have incidence angles, al and a2, nominally at 45 and 75 degrees, respectively. Incidence angles are given relative to the normal angle to the recording medium 10.
• FIG. IB illuminating the illumination zone 11; however, three, four, or more illuminators can be used to illuminate the medium 10 in ways to obtain a greater differentiation between measured characteristics.
• the illuminators 14a and 14b are shown as lying in a common plane-of-incidence, although oppositely directed.
• the illuminators 14a and 14c are shown as lying in different planes of incidence.
• Such implementation can be used to help discriminate media on a contributing basis of grain-directionality or other feature directionality.
• Using multiple illuminators in such fashion can permit use of illuminations with different colors, different angles of incidence, and different orientations of planes-of- incidence.
• the different colors could include, for example, blue, green, red, and infrared.
• LED Light Emitting Diodes
• the first plane of incidence and the second plane of incidence can be orthogonal to each other.
• one of the angles of incidence can be at an angle ranging between 0 and 85 degrees relative to normal to the illuminated medium surface.
• a media supporting surface 24 is shown on the opposite side of the media 10 from the illuminators 14a and 14b. Also shown is a supporting surface positioner 26 connected to the supporting surface 24. It is important that the reflecting and scattering properties of this supporting surface be well controlled.
• the supporting surface 24 is a light-absorbing black and may have a hole for passing illumination from below. The surface 24 may be removed using the supporting surface positioner 26 when illuminating the media 10 from below, as when using illuminator 12 in FIG. 1A.
• Media such as paper and transparencies are not totally opaque and will therefore scatter a different amount of light to the array 22 from the illuminators 14a and 14b depending upon the properties of this support surface 24, so it is important that it not be an uncontrolled variable.
• the illuminators 14a, 14b, and 14c are typically turned on one at a time.
• a microprocessor controls the illuminators 14a, 14b, and 14c, etc. including selecting which illuminator to turn on at any given time.
• the microprocessor selects the first illuminator 14a to illuminate the surface of the recording medium 10 at a first plane of incidence, thus illuminating the surface from said selected plane of incidence. Then, scattered light from the surface is sensed by at least one sensor element. Next, a signal is produced from the sensed light and the signal is processed alone, or in combination with signals corresponding to other illuminations, to form a characteristic vector.
• the formed characteristic vector is compared with a plurality of reference vectors characteristic of different recording media to determine media type by choosing the closest match.
• a variety of alternatives is available by which to define what is a closest match.
• FIG. 2 is a block diagram of the components of one embodiment of the recording media identification device.
• the photodetector array 22 is connected to an analog to digital converter 40, which provides input to a processor 42 with associated memory 44.
• Converter 40 may use quantization levels for a 256 level gray scale or lower, such as a 16 level gray scale.
• Processor 42 controls the measurement process, including the selection sequence of illumination and image capture, and processes the digitized photodetector values.
• the processor 42 is used as the means for selecting, at any instant in time, one of the available illuminators for providing light within the illumination zone by turning on the selected illuminator.
• processor 42 is connected to a printer controller 46.
• Processor 42 may be a serial processor, or it may be an ASIC designed for rapid extraction of characteristics.
• Processor 42 may involve, for example, software or hardware implemented Fourier Transform.
• processor 42 may actually be the printer controller 46.
• the processor 42 can calculate the characteristic vector as an average of local differences between pixels within an image. Further, the average can be normalized by a local mean. Later, the characteristic vector is compared to a reference vector as discussed herein below. In another implementation, the characteristic vector is proportional to a summation of local differences between pixels within an image.
• Image processing in the printer for media identification may be as simple as compressing the data and transmitting it to a host computer, via communication link 56 attached to the printer controller 46, or as complex as all the operations necessary to derive a characteristic vector.
• pixel values are communicated to the host (with optional data compression) where the characteristic vector is computed and the media identification made. This is attractive because it simplifies the image processing in the printer with a potential saving in cost and increase in flexibility.
• the characteristic vector and media identification may be done very rapidly, and the process and selection criteria can be updated when new drivers are made available.
• the minor disadvantage is a short delay as pixel data are sent back to the host.
• the printer controller 46 is shown controlling the printhead 50, media transport drive 51, printer carriage 52, and user interface 54 including an output device such as a display and an input device such as selection buttons, alpha or numeric keypads, or a combination of these devices. It will be appreciated that other elements of a printer could also be controlled by the printer controller 46 in response to identification of specific recording media.
• the processor 42 is also connected to the illumination sources 12, 14, and 16, the photodetector array 22, converter 40, and support surface positioner 26 via link 48.
• Link 48 is used to send signals from the processor 42 to control, for example, the timing of illumination by each illuminator, positioning of the support surface, and data acquisition by the array 22 and converter 40.
• output from the photodetector array 22 is converted to digital form and processed into a vector of characteristic values (described later) .
• This vector is compared to previously stored reference vectors, each reference vector being characteristic of a different type of recording medium, to determine the medium type.
• the apparatus can also process a new medium type, generating a newly acquired characteristic vector, from one or more samplings of this new medium, and store this newly acquired characteristic vector as a new reference vector representing the new medium. This would comprise a method permitting the apparatus to train itself to recognize new media types.
• the processor 42 may communicate with the printer controller 46, and, ultimately with the user interface 54 to query the operator of the printer whether to store (in the memory 44) the acquired characteristic vector as a new reference vector.
• the user interface 54 can be used to enter an identification or a name for the new reference vector.
• the user interface can also be used by a user to directly command the processor to sample a new media and store its characteristic vector as a new reference vector.
• the medium identification device of the present invention includes one or more illumination sources.
• information from multiple illumination sources is obtained by time sequencing the measurements, first turning on one illumination source and obtaining a signal, and then turning on a second illumination source and obtaining a second signal, etc.
• information from multiple photodetector arrays is obtained and processed together.
• the spectral output of the various sources may be different to provide optimized differentiation of characterization vectors and/or to allow dichroic filters to be used to combine some of the optics when using multiple photodetector arrays .
• Characteristics of the recording medium forming the basis of classification of media may include integrated reflectivity (or scattering efficiency) (or average gray scale value) over the field, distribution parameters of gray scale values, spatial frequency parameters of features in the image, number of features in the image within a specified band of feature parameters, or any combination of these or other characteristics.
• Features are defined, for example, as regions of contiguous pixels, all above (or alternatively below) a threshold gray scale value.
• Spatial frequencies may be determined, for example, by a standard use of one- or two-dimensional Fourier transforms.
• Alternative or additional characteristic values, or parameters can include such parameters as pixel-value mean, median, root-mean- absolute-difference-from-the-mean, and standard deviation.
• Statistical parameters can be normalized by parameters such as mean or median.
• Each characteristic value constitutes one element of the characteristic vector.
• each utilized combination of illumination type, location, or orientation produces a characteristic value or element.
• Each type of illumination could be implemented with a unique spectral property or color, as by choice of illuminant or by incorporation of a color filter in the illumination or imaging optics.
• Some elements of the characteristic vector may be valued on a continuous scale, while others may be on a scale of discrete values.
• the characteristic vector is compared with reference vectors Ri that have been stored in the memory 44 (or within the host computer) to identify the recording medium.
• Each reference vector R ⁇ is characteristic of a different type of recording medium. If P characteristic values provide reliable media identification, then the reference vectors R x and the characteristic vector V have the dimension P. In typical applications, P will range between 3 and 10.
• Each recording medium corresponds to a region in a P-dimensional space representing the range of expected values corresponding to that medium. The size of the range reflects batch to batch variation in manufacture of the media, differences between manufacturers of similar media, and variation of measurement. If the characteristic vector V lies within the region corresponding to a particular medium type, it is identified as that medium.
• the comparison of characteristic vector V with reference vectors Ri is shown schematically in FIG. 3 for the case where the dimension P is three.
• the comparison may take the form of a simple algebraic test of whether the vector V lies within a P-dimensional sphere of radius Si or other region around a reference vector R . Expressed mathematically using spherical regions, vector V is identified as belonging to recording medium i if the inequality: is satisfied, where Sj . is a maximum threshold distance of vector V from reference vector R x .
• standard techniques known in the art for finding membership functions using fuzzy logic such as use of multidimensional polynomials or look-up tables, may be used for the comparison. Weighting factors may be applied to the j -terms on the left-hand-side of the above expression, and the best match with a reference vector can be selected as that which produces the smallest resultant sum.
• FIG. 3 illustrates only three (3) dimensions of analysis, additional dimensions can be utilized to allow even finer distinction among print media.
• printer elements indicated schematically within FIG. 2 are elements, for example, of a desktop ink jet printer 60 as shown in FIG. 4.
• the device of FIG. 1 is internal to the printer 60 along the media path.
• printer 60 has a media tray in which sheets 62 of media are stacked.
• a roller assembly forwards each sheet 62 into a print zone 63 for printing.
• Print cartridges 64 mounted in a carriage 52 are scanned across the print zone, and the medium is incrementally shifted through the print zone.
• Ink supplies 66 for the print cartridges 64 may be external to or internal to the print cartridges 64.
• This and other printers typically operate in multiple, user-specified quality modes, termed, for example, "draft", "normal", and "best” modes.
• properties such as ink type, ink drop volume, number of drops per pixel, printhead scan speed, number of printhead passes over the same area of the medium, and whether pigmented black or composite dye-based black (i.e., combination of cyan, magenta, and yellow dyes) is used, are customized to each recording medium and for each print quality mode.
• pigmented black or composite dye-based black i.e., combination of cyan, magenta, and yellow dyes
• the media feed rate, exposure levels, toner charging, toner transfer voltage, and fuser temperature might be adjusted to optimize performance on different media.
• the main categories of recording media are plain paper, coated matte paper, coated glossy paper, transparency film, and "photographic quality" paper.
• Large format ink jet printers support additional media or material such as cloth, Mylar, vellum, and coated vellum. In printers designed to use these and other additional media, appropriate additional categories can be defined to identify these additional media or materials .
• a new characteristic vector R ⁇ can be developed for new or unknown media type by training the printer with several measurements and samples with user intervention to specify the preferred print mode. This allows old media to be retired and new formulations introduced.
• the print mode can be automatically set to optimize print quality to the formulation of a local special paper, such as an organization' s stationery, which may have a special rag and wood pulp content, filler, sizing, or even applied physical texture.
• a local special paper such as an organization' s stationery
• the description is only an example of the invention' s application and should not be taken as a limitation.
• implementations of various aspects of the invention have demonstrated the utility of a stand-alone, portable, media identification tool, not tied to a printer but given a display and pushbutton controls with which to effectively "read" media types the tool is placed against.
• Various adaptations and combinations of features of the embodiments disclosed are within the scope of the invention as defined by the following claims.

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• Investigating Or Analysing Materials By Optical Means (AREA)
• Controlling Sheets Or Webs (AREA)
• Character Spaces And Line Spaces In Printers (AREA)

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• 2002
  • 2002-04-11 US US10/120,613 patent/US6838687B2/en not_active Expired - Lifetime
• 2003
  • 2003-04-11 WO PCT/US2003/011292 patent/WO2003086771A2/en active Application Filing
  • 2003-04-11 JP JP2003583758A patent/JP4486366B2/ja not_active Expired - Lifetime
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