Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-02-11
2004-03-30
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
C347S043000, C347S014000, C358S001200
Reexamination Certificate
active
06712441
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a technique for printing images on a printing medium by ink injection.
2. Description of the Related Art
In recent years, color printers of the type in which inks of multiple colors are ejected from an ink head have become popular as output devices for computers and are now widely used in processes in which images processed by computers are printed in numerous colors and gradations. Such printers are usually provided with improved print resolution in order to allow text and other line drawings to be printed with good results.
However, improving print resolution is accompanied by an increase in the amount of data being processed. The resulting drawback is that, in particular, considerable time is needed to transfer data between computers and printing apparatus, resulting in reduced printing speed.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to smooth the outlines of line drawings while minimizing the reduction in printing speed.
In order to attain the above and the other objects of the present invention, there is provided a printing apparatus capable of selectively forming any of N types of dot recording states which are different in an ink amount and/or in an ink-deposited position in a pixel area on a print medium. N is an integer of 2 at least. The printing apparatus comprises a print head, a receiver, a dot selector, and a drive signal generator. The print head has a plurality of nozzles and a plurality of ejection drive elements for ejecting ink drops from corresponding plurality of nozzles. The receiver is configured to receive print data from an external device, the print data containing gradation data indicative of M values for each pixel in a printed image. M is a positive integer of (N−1) at most. The dot selector is configured to select one type of dot recording state for each pixel from the N types of dot recording states in response to the print data. The selected type of dot recording state is smoothing an outline contained in a printed image. The drive signal generator is configured to generate drive signals for driving the ejection drive elements to form the selected type of dot recording state.
As used herein, the term “dot recording state” has a broad meaning that includes states in which dots may or may not be recorded.
The gradation data received by a printing apparatus from an external device has M gradations (where M is an integer of (N−1) or less), so these gradation data alone can only reproduce a maximum of (N−1) dot-forming states. A dot selector selects a recording state from among those having N types of dots on the basis of these gradation data. In the specific case in which the gradation data received from an external device are binary data, the dot selector selects a state in which no dots are formed when the gradation value is zero, and selects a small or large dot when the gradation value is one.
Therefore, the first printing apparatus of the present invention allows images to be reproduced using a greater number of types of dot recording states in comparison with that provided by the gradation data received from an external device. It is therefore possible to smooth image outlines while minimizing the increase in data transmission from the external device.
In the printing apparatus of the present invention, the N types of dot recording states include at least one dot recording state which is identical to another in the ink amount and different in the ink-deposited position.
Therefore, the outlines of line drawings can be smoothed even by using dots created using the same amounts of ink but formed at different locations.
In a preferred embodiment of the invention, a number of bits per pixel in the gradation data is less than a number of bits per pixel in data indicative of the N types of dot recording states.
Adopting this approach makes it possible to minimize the increase in data transmission from an external device.
In a preferred embodiment of the invention, the dot selector is configured to select one dot recording state for each pixel to smooth an outline contained in the printed image based on a gradation value of the each pixel and a gradation value of a pixel adjacent to the each pixel according to the gradation data.
With this approach, the dot type can be selected with consideration for the gradation values of pixels adjacent to each pixel, making it possible to easily minimize the jaggies commonly developed by line drawings.
In a preferred embodiment of the invention, the drive signal generator comprises an original drive signal generator and an original drive signal shaper. The original drive signal generator is configured to generate an original drive signal having a plurality of pulses within a main scan period for a single pixel. The original drive signal is commonly applicable to the plurality of ejection drive elements. The original drive signal shaper is configured to shape the original drive signal with a masking signal to generate the drive signal. The drive signal is configured to represent any of the N types of dot recording states. The original drive signal shaper comprises a mask pattern storage, a mask pattern selector, a masking signal generation circuit, and a masking unit. The mask pattern storage is configured to store a plurality of mask patterns. Each mask pattern contains a plurality of types of original masking signal data to be used for generating the masking signal. The mask pattern selector is configured to select one mask pattern from the plurality of mask patterns in response to the selection of the dot recording state. The selected mask pattern is capable of reproducing the selected dot recording state. The masking signal generation circuit is configured to select one original masking signal data from the plurality of types of original masking signal data contained in the selected mask pattern in response to the selection of the dot recording state, and also to generate the masking signal with the selected original masking signal data. The masking unit is configured to selectively mask the plurality of pulses in the original drive signals with the masking signals, to thereby generate the drive signal provided to the each ejection drive element.
With this approach, a printing apparatus in which mask patterns are used to control dot size can be employed with ease.
In a second embodiment, there is provided a printing apparatus capable of selectively forming any of N types of dot recording states which are different in an ink amount and/or in an ink-deposited position in a pixel area on a print medium. N is an integer of 2 at least. The printing apparatus comprises a print head, a receiver, a dot selector, a font processor, and a drive signal generator. The print head has a plurality of nozzles and a plurality of ejection drive elements for ejecting ink drops from corresponding plurality of nozzles. The receiver is configured to receive print data from an external device. The print data contains text-specifying data for specifying at least a text to be recorded and gradation data indicative of a gradation value of each of first pixels in a printed image other than text. The dot selector is configured to select one type of dot recording state from the N types of dot recording states in response to the print data. The selected type of dot recording state is to be recorded for each of the first pixels. The font processor is configured to store a scalable font data and also to define gradation values of each of second pixels in response to the text-specifying information and the scalable font data. The second pixels are corresponding to a higher resolution than that of the gradation data. The scalable font data contains data indicative of a text shape in a form of vector information. The drive signal generator is configured to generate drive signals for driving the ejection drive elements to form the selected type of dot recording state. The dot selector selects one type of dot recordi
Otsuki Koichi
Sato Akito
Nguyen Lamson
Seiko Epson Corporation
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