Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-03-28
2003-03-04
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S012000
Reexamination Certificate
active
06527359
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a technique that carries out bidirectional, reciprocating main scan to prints an image on a printing medium. More specifically the present invention pertains to a technique that adjusts misalignment of dot recording positions in a main scanning direction between a forward pass and a backward pass of the main scan.
BACKGROUND ART
Recently color printers having a print head that ejects a plurality of different color inks have been widely used as an output device of computers. Some of such color printers have the function of “bidirectional printing” for the purpose of enhanced printing speed.
In bidirectional printing, misalignment of recording positions in a main scanning direction between a forward pass and a backward pass of main scan often arises due to backlash of a driving mechanism in the main scanning direction or a warp of a platen that supports a printing medium thereon. One of the known techniques proposed to relieve such positional misalignment is disclosed in JPA 5-69625 filed by the applicant of the present invention. This prior art technique registers in advance a potential amount of positional misalignment (deviation in printing) in the main scanning direction and adjusts the dot recording positions on the forward pass and on the backward pass, based on the registered amount of positional misalignment.
One of the applicable methods to adjust the recording positions in the main scanning direction actually prints a specific test pattern on the printing medium, and specifies the amount of positional misalignment in the main scanning direction based on the printed result of the specific test pattern, so as to determine the correction value. The process of printing the specific test pattern to specify the amount of positional misalignment generally accompanies sub-scan. The sub-scan feed may, however, cause deviation of the dot recording positions in the main scanning direction, due to backlash of a sub-scan driving mechanism or any inclined feed of the printing medium. The greater feeding amount and the greater number of feeds in the sub-scanning direction generally cause more significant misalignment of recording positions. Namely a large number of feeds in the sub-scanning direction by a large feeding amount in the process of printing the specific test pattern to specify the amount of positional misalignment in the main scanning direction undesirably causes error due to the sub-scan feed to be reflected on the printed result. This makes it difficult to accurately specify the amount of positional misalignment in the main scanning direction.
The object of the present invention is to solve the problem of the prior art technique discussed above and accordingly to provide a technique that relieves positional misalignment in the main scanning direction between a forward pass and a backward pass of main scan with regard to a nozzle array in a bidirectional printing apparatus.
DISCLOSURE OF THE INVENTION
In order to attain at least part of the above and the other related objects, one technique of the present invention prints positional misalignment test pattern with a nozzle group without sub-scan feed. The technique determines a correction value according to correction information that represents a favorable correction state selected based on the printed positional misalignment test pattern, and then actually corrects misalignment of recording positions in a main scanning direction occurring in bidirectional printing, using the correction value thus determined.
The sub-scan feed in the course of printing the “positional misalignment test pattern” causes working error of each mechanism relating to the sub-scan feed to be reflected on the printed “positional misalignment test pattern.” This makes the correction value include some error. The arrangement of the present invention, however, prints the “positional misalignment test pattern” without any feed in the sub-scanning direction, thus preventing any such problem. This arrangement thus enables the correction value to be determined accurately, based on the properly printed “positional misalignment test pattern.”
Another technique of the present invention prints a front test sub-pattern with a front nozzle sub-group on a printing medium on a selected one of the forward pass and the backward pass of the main scan of the print head. Here the front nozzle sub-group is part of the nozzle group and includes nozzles located in a relatively forward section of the nozzle group in a sub-scanning direction. The technique also prints a rear test sub-pattern with a rear nozzle sub-group on the printing medium on the other of the forward pass and the backward pass of the main scan of the print head. Here the rear nozzle sub-group is part of the nozzle group and includes nozzles located in a relatively backward section of the nozzle group in the sub-scanning direction. The technique subsequently determines a correction value according to correction information that represents a favorable correction state selected based on positional misalignment test pattern. Here the positional misalignment test pattern includes the rear test sub-pattern and the front test sub-pattern printed at different positions shifted in the sub-scanning direction. The technique then actually corrects using the correction value the misalignment of recording positions in the main scanning direction occurring in bidirectional printing thus determined. The “forward (section) in the sub-scanning direction” represents a direction from the print head, which moves relative to the printing medium, to the part of the printing medium that has not yet scanned by the print head. The “backward (section) in the sub-scanning direction” is just opposite to the “forward (section) in the sub-scanning direction.”
This arrangement of the present invention enables the rear test sub-pattern and the front test sub-pattern, which are shifted in the sub-scanning direction, to be printed without any feed of the print head in the sub-scanning direction. The resulting “positional misalignment test pattern” is thus printed with little error and enables the user to readily select a favorable correction state and accurately determine the correction value according to the selected favorable correction state. In the above application, the “positional misalignment test pattern” is printed without any feed of the print head in the sub-scanning direction. One modified application may print the “positional misalignment test pattern” with small feeds in the sub-scanning direction, for the purpose of facilitating the determination of the correction value.
The following configuration is preferable when the nozzle group includes a low density nozzle group that forms only noncontiguous dots in the sub-scanning direction at a predetermined recording density on the printing medium by one pass of the main scan. The memory stores a first correction value therein, where the first correction value is used to correct misalignment of recording positions in the main scanning direction on the forward pass and the backward pass of the main scan with regard to the low density nozzle group. The first correction value is determined according to correction information that represents a favorable correction state selected based on a first positional misalignment test pattern. Here the first positional misalignment test pattern includes a first front test sub-pattern and a first rear test sub-pattern printed with the low density nozzle group at different positions shifted in the sub-scanning direction. The first front test sub-pattern includes a plurality of vertical ruled lines that extend in the sub-scanning direction and are formed using a first front nozzle sub-group by repeatedly carrying out a selected one of the forward pass and the backward pass of the main scan of the print head in combination with sub-scan feeds interposed between the main scan passes. Here the first front nozzle sub-group is part of the low density nozzle group and includes nozzles located in a re
Barlow John
Mouttet Blaise
Seiko Epson Corporation
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