Abstract: Inkjet printing of barcodes is enhanced by several methods. In a printhead having two staggered columns of nozzles, using only the even (or odd) column enhances resolution of a vertical barcode element. Filling interior portions of the barcode element with the odd (or even) column improves barcode appearance. Barcode swelling, due to ink migration after application, is reduced by use of a depletion matrix to lessen the quantity of ink applied. Application of the depletion matrix to the edges of the barcode elements resists swelling where resolution is most required. Where a printing mask is applied to the edges of the barcode elements, the edges may be printed only by one column of printhead nozzles, or only during one direction of printhead movement, or both. Alternately, removal of one or more pixels along the edge of a barcode element allows each barcode element to swell to the desired size.

Abstract: Apparatus defines a dither mask (DM) and printmask (PM) with corresponding dimensions. In one invention form the DM dimension is not an integral factor or multiple of the PM dimension. The two dimensions may be lengths or widths; preferably the apparatus manages both; the corresponding dimensions differ by at least three pixels, and by a multiple of two pixels—more preferably eight or a multiple of eight. Preferably one dimension is an integral multiple of 256 pixels differing by eight pixels from the other. Another invention form has a scanning printhead making multiple passes across a print medium to form swaths of marks, a mechanism to define an offset smaller than at least one of the two dimensions, and a unit to index one mask by that offset between forming of successive swaths. This is valuable if DM and PM are established by preprogrammed circuits (e.g.

Abstract: To save time between printing passes of a unidirectional printer, the print medium is advanced in two phases separated in time by the fast return of the carriage. The print medium advance movements coincide, at least partly, with the periods of acceleration and deceleration which immediately precede and follow a printing pass and during which the carriage is changing from printing speed to return speed or vice versa. If the total print medium advance time exceeds these acceleration and deceleration times, the extra print medium advance occurs at a single end of the carriage movement.

Abstract: Multiple-pass printing is performed with no print medium advance between selected pairs of printing passes. In some embodiments, an entire printing operation (20, 30) can be conducted in one multiple-pass mode. Alternatively, a switch from n-pass to m-pass mode may occur during a printing operation (50, 70, 90) but with a uniform print medium advance throughout. Different printing masks are used for the different stages.

Abstract: Inkjet printing of barcodes is enhanced by several methods. In a printhead having two staggered columns of nozzles, using only the even (or odd) column enhances resolution of a vertical barcode element. Filling interior portions of the barcode element with the odd (or even) column improves barcode appearance. Barcode swelling, due to ink migration after application, is reduced by use of a depletion matrix to lessen the quantity of ink applied. Application of the depletion matrix to the edges of the barcode elements resists swelling where resolution is most required. Where a printing mask is applied to the edges of the barcode elements, the edges may be printed only by one column of printhead nozzles, or only during one direction of printhead movement, or both. Alternately, removal of one or more pixels along the edge of a barcode element allows each barcode element to swell to the desired size.

Abstract: An inkjet printer prints swaths which overlap by, typically, one eighth of their width at each edge, each edge region having a reduced print density so that the combined density of the overlapping regions matches or exceeds that of non-overlapping regions. In a first embodiment, each edge region is printed with 50% printing density. In a second embodiment, the printing mask is modified so that each edge region comprises two sub-regions with differing print densities, e.g. a first outer sub-region with a printing density of 15% and a second sub-region with a printing density of 85%. In a third embodiment only one edge region has a reduced print density and comprises 3 sub-regions with different print densities, e.g. a first sub-region with a printing density of 6.75%, a second one with a printing density of 12.5% and a third one with a printing density of 25%.

Abstract: It is first determined whether any printing element of a printhead has failed. If so, functions of the failed element are reassigned to other elements. Some aspects of the invention do this in such a way as to maintain essentially single-pass operation. Ordinarily the reassigned functions are applied to control operation of the head or heads, to print images on a print medium, and functions of the apparatus and method are effected automatically by program instructions—in nonvolatile memory. One approach to the reassignment includes removing from service all printing elements between the failed element and a nearer end of the head, inclusive—and then preferably operating all remaining in-service elements as a shorter printhead. If the printhead operates in conjunction with a print-medium advance mechanism, then also preferably each operation of that mechanism is shortened to correspond to a height of the shorter head.

Abstract: To save time between printing passes of a unidirectional printer, the print medium is advanced in two phases separated in time by the fast return of the carriage. The print medium advance movements coincide, at least partly, with the periods of acceleration and deceleration which immediately precede and follow a printing pass and during which the carriage is changing from printing speed to return speed or vice versa. If the total print medium advance time exceeds these acceleration and deceleration times, the extra print medium advance occurs at a single end of the carriage movement.