Handheld printer minimizing printing defects

#Generally, the present invention relates to handheld printers. Particularly, it relates to improving print quality in handheld printers of the type able to print in random motion patterns. In one aspect, stitching together overlapping print swaths is contemplated. In another, dithering per edges of columns of nozzles of an inkjet printhead is contemplated. Still other aspects relate to methods and structures for accomplishing same.

#As is known, handheld printers afford mobile convenience to users. Unlike their immobile or stationary counterparts, however, users determine the path of a given swath of printing. In some instances, this includes random movement over a substrate. In others, it includes back-and-forth movement attempting to simulate a stationary printer.

#A common problem with handheld printers is poor alignment between adjacent swaths of print because position of the print element is often less accurate than with other types of printer. Alignment errors usually result in noticeable defects in the print. The most common print defects are called “print banding” and include both dark bands and white bands at the boundary between swaths where ink drops at the edge of a swath are printed too close or too far from drops in the adjacent print swath. Another category of print banding is a directional effect similar to the banded appearance of mowed glass when adjacent swaths are cut in different directions. These print banding defects may appear with other serial printers, but the defects can be minimized by printing a dithered image in multiple passes over the paper. With a handprinter, print banding is a problem because alignment errors are more likely, and requiring multiple passes is an unaccepted demand on the operator.

#The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:

#FIG. 1 is a diagrammatic view in accordance with the present invention of a handheld printer;

#FIG. 2 is a diagrammatic view in accordance with the present invention of a representative inkjet printhead for use in the handheld printer of FIG. 1;

#In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention and like numerals represent like details in the various figures. Also, it is to be understood that other embodiments may be utilized and that process, mechanical, electrical and/or other changes may be made without departing from the scope of the present invention. In accordance with the present invention, a handheld printer that minimizes printing defects is hereafter described.

#With reference to FIG. 1, a handheld printer of the invention that minimizes printing defects is given as 10. During use, an operator 12 maneuvers or manipulates a housing 14 of the printer back and forth over a substrate 16 in order to print an image 18. In various embodiments, the image will be text, figures, combinations of text and figures or the like. They will be typified in color and/or black and white.

#In FIG. 2, an inkjet printhead of the printer internal to the housing is shown generally as 110. It includes a housing 112 having a shape that depends upon the shape of the printer. The housing has at least one internal compartment 116 for holding an initial or refillable supply of ink. In one embodiment, the compartment contemplates a single chamber holding a supply of either black ink, cyan ink, magenta ink or yellow ink. In other embodiments, it contemplates multiple chambers containing multiple different colored inks. In one instance, it includes supplies of cyan, magenta and yellow ink. In still other embodiments, it includes plurals of black, cyan, magenta and/or yellow ink. It will be appreciated, however, that while the compartment 116 is shown as locally integrated within a housing 112 of the printhead, it may alternatively be separable from the housing 112 and/or printhead 110, for example.