Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-10-05
2002-01-15
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S010000
Reexamination Certificate
active
06338542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing apparatus that creates dots to print an image on a printing medium. More specifically the present invention pertains to a printing apparatus that is capable of arbitrarily creating different types of dots in respective pixels.
2. Discussion of the Background
A diversity of printers have widely been used to print multi-color, multi-tone images as an output device of a computer. One of such printers is an ink jet printer that creates dots with several color inks ejected from a plurality of nozzles provided on a print head, so as to record an image. The ink jet printer generally enables expression of only two tones, that is, a dot-on state and a dot-off state, in each pixel. The ink jet printer accordingly carries out halftone processing, which expresses multiple tones of original print data by a distribution of dots, prior to printing an image.
Multi-valued printers that enable tone expression of greater than two values, the dot-on state and the dot-off state, have been proposed to attain richer tone expression. The multi-valued printers include printers that create dots with different quantities of ink and printers that create a plurality of dots in each pixel in an overlapping manner to express multiple tones. The multi-valued printers ensure a smoother tone expression and high-quality printing.
It is desirable, on the other hand, that the printer attains the desired printing speed and picture quality according to the requirements of the user. In order to meet such requirements, the printer typically has a diversity of print modes, for example, a high-speed print mode and a high-quality print mode. Some multi-valued printers may create different types of dots in respective print modes, in order to attain the desired printing. Such printers mainly use larger-sized dots that enable a solid area to be sufficiently formed in pixels of a relatively low resolution in the high-speed print mode. In the high-quality print mode, on the other hand, such printers mainly use smaller-sized dots corresponding to a relatively high resolution. These dots are selectively used by changing over the driving waveform output to the print head according to the selected print mode.
The recent trend is, however, to further improve picture quality of the printers. This leads to printing at a higher resolution and increases the tone values expressible in each pixel. There is accordingly a significant difference between the printing speed and the picture quality in the high-speed print mode and the printing speed and the picture quality in the high-quality print mode. The user may require a diversity of other print modes, for example an intermediate print mode that carries out printing at an intermediate picture quality and an intermediate printing speed between those of the high-quality print mode and the high-speed print mode.
It is extremely difficult to provide a print head that stably creates dots in response to a diversity of driving waveforms corresponding to respective print modes. Providing the driving waveforms corresponding to the respective print modes leads to an increase in the number of circuits generating the driving waveforms with an increase in the number of print modes. This undesirably raises the manufacturing cost of the printer. The background art printers can not sufficiently attain a required increase in number of print modes, because of these factors. The background art printers can thus not ensure printing that sufficiently fulfills the requirements of the user regarding the printing speed and the picture quality. This problem is found not only in the ink jet printers but in a variety of printers including multi-valued printers and two-valued printers.
SUMMARY OF THE INVENTION
An object of the present invention is thus to provide a technique that enables flexible setting of a print mode in a printing apparatus that ensures the expression of different densities in respective pixels according to the print mode.
At least part of the above and the other related objects is attained by a printing apparatus that moves a print head back and forth relative to one axis of a printing medium in response to a driving signal, so as to create a dot in each pixel and print an image on the printing medium. The printing apparatus includes “n” output units that periodically output driving signals corresponding to “n” different print modes (where n is an integer of not less than 2), in which different dots are created in each pixel and a mixing output unit that periodically uses “m” output units (where m is an integer satisfying 2≦m≦n), which are selected out of the “n” output units, thereby outputting a specific driving signal that is used in a specific print mode, which is different from any of the “n” different print modes.
In the printing apparatus of the present invention, a combination of at least two driving signals output from the “n” output units attains (n+1) or greater print modes. One example provides a first driving signal used in a print mode that carries out printing with two variable-size dots L
1
and M
1
(L
1
>M
1
), and a second driving signal used in a different print mode that carries out printing with two variable-size dots L
2
and M
2
(L
2
>M
2
). In the printing apparatus of the present invention, the mixing output unit periodically uses the first driving signal and the second driving signal, so as to attain a print mode using the four variable-size dots L
1
, L
2
, M
1
, and M
2
.
Here it is assumed that the print mode using the first driving signal is a high-speed print mode. In this case, the two variable-size dots L
1
and M
1
are relatively large-sized dots, so as to enable a solid area to be formed even in pixels of a relatively low resolution. In order to attain printing at a high speed, it is desirable to raise the driving frequency of the print head. In this print mode, the driving signal corresponding to the other variable-size dots L
2
and M
2
, which are not used for printing, is not output to the print head.
The print mode using the second driving signal is a high-quality print mode. In this case, the two variable-size dots L
2
and M
2
are relatively small-sized dots to attain printing at a relatively high resolution. There are an extremely large number of pixels in the high-quality printing. In order to implement high-quality printing at a practical speed, it is desirable to keep the driving frequency of the print head at a sufficient level. In this print mode, the driving signal corresponding to the other variable-size dots L
1
and M
1
, which are not used for printing, is not output to the print head.
A specific print mode attaining both an appropriate printing speed and an appropriate picture quality is provided, in addition to the above two print modes. The printing apparatus of the present invention combines the first driving signal with the second driving signal corresponding to the specific print mode. The specific print mode uses the relatively large-sized dots L
1
and M
1
, and thus enables printing at a low resolution equivalent to that in the high-speed print mode. The specific print mode also uses the relatively small-sized dots L
2
and M
2
as in the high-quality print mode and thus ensures smooth tone expression. The specific print mode accordingly attains an intermediate picture quality and an intermediate printing speed between those of the high-speed print mode and the high-quality print mode.
The printing apparatus of the present invention combines the output units, which are provided to output driving signals corresponding to preset print modes, in the above manner and thereby enables a driving signal to be output corresponding to a different print mode having a different printing speed and a different picture quality, without raising the manufacturing cost of the printing apparatus. The example discussed above addresses a case of setting a third print mode by combining two driving signals. The combination of driving si
Nguyen Thinh
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Seiko Epson Corporation
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