BACKGROUND OF THE INVENTION

The invention disclosed herein relates to a method for printing monochrome and color images and indicia (collectively referred to as "images") . More particularly, the invention disclosed herein relates to a method for printing in a novel "strip" mode of printing which is different from line mode printing, serial (or raster scan) mode printing and vector mode plotting. The invention finds particular application in the printing of graphic images, particularly of wide format (e.g., wider than about 11 inches (about 28 cm)).

Modern color and monochrome computer or digital printing apparatuses are of the matrix type which typically print in line mode or serial mode an overall image on a sheet medium in small dots or other small geometric configurations.

Line mode matrix printers print an entire line at a time. By convention, the line or scan direction, usually the width direction of the medium being printed upon, is referred to as the Y-axis or Y-direction, and the direction orthogonal thereto, i.e., the length or feed direction of the medium, is referred to as the X-axis or X-direction. Line mode printers utilize a so-called full width print head having a width at least equal to the width of the medium on which the image is to be printed and print one full line of image in each relative position of the print head and the medium. Typically the print head in a line mode printer remains stationary at all times, and after or while each line is printed the medium is moved relative to the print head parallel to the X-axis in the length direction of the medium. (However, since relative motion is required, the print head may be moved parallel to the X-axis relative to a stationary medium, or both the medium and the print head may be moved in opposite directions parallel to the X-axis.)

Thus, line mode printers relatively move the print head and the medium being printed upon in only one direction (parallel to the X-axis) to relatively move the print head and the medium to print one line of the image at a time. Serial mode matrix printers (or raster scan printers) print the dots in desired locations serially along a line as the print head is moved or scanned parallel to the Y-axis. Serial mode matrix printers utilize a so-called flying or scanning print head having a length (Y-axis dimension) substantially less than the width of the sheet medium on which the image is to be printed and a width (X-axis dimension) a number of dots wide, e.g., tens of dots wide. The flying print head serially prints as the print head is continuously moved or scanned in the line parallel to the Y- axis. After each line is printed, the sheet medium is moved relative to the print head parallel to the X-axis. Thus, serial mode printers relatively move the print head and the sheet medium in two directions. Typically the print head is moved parallel to the Y-axis and the medium is moved parallel to the X-axis, although in flat bed type printers, the medium is stationary and the print head is moved parallel to both the X- and"Y-axes.

A number of impact and non-impact technologies may be used for matrix printing in line mode or serial mode including impact wire- or pin-dot, thermal (direct and thermal transfer) , ink jet, solid ink jet, electrostatic and electrographic.

In vector mode plotting, the image is converted into a series of vectors, and the print head and the medium are relatively moved simultaneously in two orthogonal directions (parallel to the X- and Y-axes) to plot each of the vectors. Vector plotters typically use marking devices such as pens, although ink jet vector plotters have been proposed at least in the patent literature (e.g., U.S. Patent Nos. 4,554,556 (Hirata et al.) and 4,621,273 (Anderson)).

A novel strip mode of thermal printing is disclosed in commonly owned, copending application Serial No. 07/920,186 (attorney docket HID-117) , filed on the same date as this application, titled "Strip Mode Printing And Plotting Apparatus And Method," the disclosure of which is incorporated herein by reference. Problems and/or drawbacks in applying or using line mode and serial mode printing and vector plotting technologies for printing or plotting wide format full color images prompted the research which led to the thermal strip mode matrix printing invention disclosed in application Serial No. 07/920,186 (HID-117). Thermal strip mode printing as disclosed in application Serial No. 07/920,186 (HID-117) utilizes a thermal print head in which a plurality of thermal elements are arranged in an elongated narrow array having an overall length arranged parallel to the Y-axis and a narrow overall width arranged parallel to the X-axis, the length being larger than the width.

As disclosed in application Serial No. 07/920,186 (HID- 117) , in thermal strip mode printing, data representing the image to be printed is arranged into a plurality of strips each having a length parallel to the first axis (X-axis) of the medium to be printed upon. The Y-axis length of the strips is less than or equal to the length of the thermal array of the thermal print head, i.e., up to about 4 inches (about 10cm) . In order to print across the full width of a given size medium, it may be necessary to print one or more strips of partial length, i.e., strips having a length less than the overall length of the thermal array, which would typically be printed adjacent the edge or edges of the medium. The data representing each strip of the image to be printed is arranged into a plurality of lines each having a width parallel to the second axis (X-axis) of the medium equal to the width of the thermal array and a length parallel to the first axis (Y-axis) up to the length of the strip.

According to the preferred method disclosed in application Serial No. 07/920,186 (HID-117), the image is printed strip by strip, i.e., the print head and sheet medium are relatively moved to position the print head in a given strip, then the print head and the sheet medium are relatively moved to print all lines of that strip, and then the print head and the sheet medium are relatively moved to position the print head in another strip, etc.

The thermal print head disclosed in application Serial No. 07/920,186 (HID-117) has a very narrow width (parallel to the X-axis) of only one or a few thermal elements wide (e.g., 0.025 inch (about 0.64 mm)) and a longer length (parallel to the Y-axis) (e.g., about 1 inch (about 2.5 cm) to about 4 inches (about 10 cm) ) . Correspondingly, the maximum width of the strips which are printed in thermal strip mode printing are up to about four inches (about 10 cm) . In conventional serial mode thermal printing, the overall length of the thermal array extending parallel to the Y-axis is one or only a few thermal elements long, and the overall width of the thermal array extending in the X- axis is typically tens of thermal elements wide. Thus, the thermal array for strip mode printing is oriented quite differently than for conventional serial mode printing. Moreover, the length of the thermal array in strip mode printing may be up to four inches long; conventional serial mode printers have a width and a length substantially smaller than that. SUMMARY OF THE INVENTION

It is an object of the invention disclosed herein to utilize the novel strip mode of printing disclosed in application Serial No. 07/920,186 (HID-117) in printing technologies other than thermal, particularly for wide format printing.

The invention is a recognition that the novel thermal strip mode of printing disclosed in application Serial No.

07/920,186 (HID-117) may also be utilized with the following matrix printing technologies, electrostatic, electrophotographic (e.g., lat- :, LED, diifect and with toner) , impact-wire or pin-dot matrix, ink jet, and solid ink jet.

Imaging heads using any of the above printing technologies in serial mode or line mode have some or all of the problems discussed in Serial No. 07/920,186 (HID-117). Strip mode printing avoids such problems. Additionally, the cost of a line mode, wide array imaging head creating a line of the image across the full width of the medium is expensive. Strip mode printing enables the use of a much shorter (Y-axis dimension) imaging head, but requires a Y-axis drive system to index the print head from one strip to another. However, a precision Y-axis drive system for indexing the print head would typically be less than the difference in cost between a full width, line mode print head and a shorter, strip mode print head.

The imaging elements of the imaging heads of printers employing the above printing technologies may be arranged in consideration of the teachings in application Serial No. 07/920,186 (HID-117) and the known attributes of the particular printing technology used. Color strip mode printing may be carried out using the above printing technologies in consideration of the teachings for color thermal printing in application Serial No. 07/920,186 (HID- 117) and the known attributes of the particular printing technology used. BRIEF DESCRIPTION OF THE DRAWINGS The method according to the invention is illustrated in the figures of the accompanying drawings which are meant to be exemplary and not limiting, in which like references refer to like or corresponding parts, and in which:

Fig. 1 shows a completed full image printed by the method of strip mode printing; and

Figs. 2A-2E show parts of the image of Fig. 1 and illustrate the sequence for strip mode printing the image of Fig. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal printer and method for printing images in the novel thermal strip mode of printing is disclosed in application Serial No. 07/920,186 (HID-117). The method of strip mode printing in other printing technologies is similar. Referring to the drawings, a strip mode print head (not shown in the drawings) is moved parallel to the Y-axis to position the print head to print in strips 34-38 of sheet medium 27; each has a width up to the length "L" of imaging array of the print head. Sheet medium 27 (e.g., paper, plastic, mylar, etc.) is moved parallel to the X-axis to position the print head to print in lines (not shown) each having a width equal to the width "W" of the imaging array of the print head. Depending upon the particular width of sheet medium 27 and the particular length of the imaging array, one or more partial length strips 38 may have to be printed at either or both edges of sheet medium 27 in order to print on the full width of the media. In the sequence illustrated in Figs. 2A-2E, only one partial width strip 38 is printed. The length of each line of a strip printed in strip mode for each X-axis position of the print head and sheet medium 27 is substantially less than the width of sheet medium 27, in contrast to a line printed by a full width, line mode print head which may extend for essentially the full width of the medium. Also, the length of each strip mode line is much longer than the length of portions of an image printed by a serial print head for each relative Y- axis position of the print head and the medium, which is typically no more than one tenth of an inch long. In strip mode, the width of each line of an image printed in any

strip may be only one or a few imaging elements wide in contrast to matrix serial printing where the width may be tens of thermal elements i s.

The preferred manner of printing image 26 is strip-by- strip, i.e., all lines of image 26 defining a strip, e.g. strip 38, are printed before lines of another strip are printed. In the preferred manner of printing a color image, the image is printed strip-by-strip, one color at a time, i.e., all strips are printed in one color before any strip is printed in another color. In some imaging technologies, a different imaging head may be provided for each color.

To strip mode print, relative motion is required between the print head and sheet medium 27 in two orthogonal directions. These directions are parallel to the Y-axis along the width of sheet medium 27 and parallel to the X- axis along the length of medium 27. In the preferred form of thermal strip mode printing, the print head is moved back and forth parallel to the Y-axis relative to medium 27, and medium 27 is moved back and forth parallel to the X-axis relative to print head 28. For clarity and ease of expression, movement of medium 27 past the print head in the forward direction (from bottom 40 to top 41 of medium 27) will be referred to as "downstream" or positive "X", and movement of medium 27 in the opposite direction will be referred to as "upstream" or negative "X".

Depending on the particular print head used, it and sheet medium 27 may be indexed relative to each other from line to line, dwelling in each line a sufficient time to print therein, or as is typical, the print head and sheet medium 27 may be continuously moved relative to each other in the X-direction at a speed which permits printing as desired in each line, and then indexed in the Y-direction from strip to strip. Also, whether the thermal print head and sheet medium 27 are indexed relative to each other in the X-direction or moved continuously relative to each other

in the X-direction, there may be continuous relative movement in the X-direction and in the Y-direction over lines where no part of the image is to be printed; and for groups of contiguous lines in which no part of the image is to be printed, the print head may be raised or moved away from the sheet medium to a non-printing position to permit higher speed relative movement between the print head and the sheet medium without damaging either.

In the preferred form of strip mode printing, the head is positioned in the left most strip, which in the illustrated embodiment is partial strip 38, and sheet medium 27 is moved upstream in the negative "X" direction relative to print head 28 to position the print head at the top end 40 of medium 27. Medium 27 is then moved downstream in the positive "X direction until all parts of image 26 in strip 38 are printed and print head 28 reaches the bottom end 41 of medium 27, thereby having printed the part of the image shown in Fig. 2A. Then medium 27 is moved in the upstream direction (-"X") to reposition print head 28 at the top end 40 of medium 27, and the print head is indexed to position it in the adjacent full width strip 34. Indexing the print head and moving the sheet medium may be done in any order or simultaneously. Medium 27 is then moved downstream (+"X") relative to print head 28 while printing proceeds in strip 34 as shown in Figs. 2B and 2C, until the print head reaches the bottom end 41 of medium 27. Then medium 27 is moved in the upstream direction (-"X") to reposition the print head at the top end 40 of medium 27, and the print head is indexed to position it in the next full width strip 35. Fig. 2D shows strip 35 being printed as described above, after which medium 27 is moved to reposition print head 28 at the top end 40 of medium 27 and print head 28 is indexed to the next full width strip 36. Strip 36 is printed, after which the print head is indexed to print in strip 37. Fig. 2E shows image 26 with strips 38 and 34-36 printed, and the

last part of the image being printed in strip 37.

As in application Serial No. 07/920,186 (HID-117), the particular sequence of moving the sheet medium, indexing the print head and printing described above, and the starting and stopping points of the print head in each strip before indexing the print head to another strip are not critical, and sequences and start/stop points other than those described above may be employed. For example, sheet medium 27 may be moved to position the print head at the bottom end 41 of sheet medium 27 rather than the top end 40 to start printing in a strip, and medium 27 may be moved upstream (- "X") relative to the print head during printing in a strip. For plotting apparatus employing a thermal transfer ribbon, or an ink ribbon, etc. , further variations may be limited. As described in application Serial No. 07/920,186 (HID-117) with respect to thermal transfer printing, the thermal transfer ribbon system is arranged so that the transfer ribbon moves from a supply reel to a take-up reel in the same direction as the direction of movement of the medium. Therefore, realization of other variations is dependent upon coordinating movement of the transfer ribbon with movement of the medium or the print head, whichever moves during printing, so that the transfer ribbon moves in the same direction as the medium or the print head. While the invention has been described and illustrated in connection with preferred embodiments, many variations and modifications as will be evident to those skilled in this art may be made without departing from the spirit and scope of the invention, and the invention as set forth in the appended claims is thus not to be limited to the precise details of construction set forth above as such variations and modification are intended to be included within the scope of the appended claims.