Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-12-17
2002-04-16
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
C347S019000, C347S043000
Reexamination Certificate
active
06371588
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a printhead and a printing apparatus using the printhead, and more particularly, to a printhead which performs printing in accordance with an ink-jet method and a printing apparatus using the printhead.
Recently, ink-jet printers capable of color printing are widely used. In these printers, it is necessary to discharge a plurality of color ink such as yellow ink, magenta ink and cyan ink, as well as black ink, to a printing medium. For this purpose, an increasing number of printers have a plurality of printheads on a carriage. The printheads are arrayed in a moving direction of the carriage (main-scanning direction). Otherwise, a number of printers have an integrated type printhead where a plurality of arrays of ink discharge nozzles, corresponding to the respective ink colors, are arranged in the main-scanning direction, as one printhead.
On the other hand, in any construction of printhead or arrangement of nozzle arrays as above, to realize high precision color printing, the most important problem is how precisely dots of respective color ink are overlaid on a printing medium.
Regarding such registration adjustment, in the printers with a plurality of printheads, it is almost impossible to mechanically precisely adjust registration of respective color ink dots. Generally, these printers are constructed such that the driving timing for each printhead can be freely changed. For example, electrical adjustment means is provided to shift a dot position at ± several 10-dot pitch in the main-scanning direction. Prior to actual printing, a registration adjustment pattern is printed on a printing medium, then a user judges the amount of registration shift by visual measurement and adjusts the registration.
However, in conventional ordinary low-price color printers, it is almost impossible to provide a head driving signal in each of the printheads because such arrangement increases complexity of the system and the price, from the following reasons:
(1) The number of signal lines in the printheads increases.
(2) The driving timing circuits, corresponding to the number of printheads, must be provided.
Generally, a signal (signal line) other than a print data transmission signal is provided for common use among the printheads. In these printers, as all the printheads are driven with the same head driving timing, registration adjustment is simply performed in 1-dot pitch units but registration shift at the maximum ½ dot pitch cannot be solved.
On the other hand, in the integrated type printhead having plural nozzle arrays, the maximum level of registration adjustment is about several 10 &mgr;m in manufacturing. However, in a printhead having a printing resolution of 600 dpi, the above shift amount is intolerable since the dot pitch of this printhead is about 42 &mgr;m.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a printhead which performs high-precision registration adjustment on print dots even in use of plural printheads or a printhead having plural printing element arrays and a printing apparatus using the printhead.
According to one aspect of the present invention, the foregoing object is attained by providing a printhead capable of printing by dividing a plurality of printing elements constituting a printing element array into a plurality of blocks and time-divisionally driving the plurality of printing elements in block units, comprising: a memory circuit for storing a value based on an amount of registration shift equal to or less than a printing resolution in a direction in which the printing element array is scanned relative to a printing medium; and a changing circuit that changes an order of blocks to be driven in accordance with the value stored in the memory circuit.
It is preferable that a number of the printing element array is two or more, the plurality of printing element arrays (e.g. a first and second printing element arrays) are arranged at an interval along the scanning direction of the printing element arrays, and the changing circuit changes the order of blocks to be driven in at least one of the plurality of printing element arrays.
Note that division of the plurality of printing elements into blocks may be made by dividing the plurality of printing elements of the first and second printing element arrays into blocks by N printing elements sequentially, or by dividing the plurality of printing elements of the first and second printing element arrays into blocks by K printing elements each selected from every M printing elements. For example, the plurality of printing elements are divided into four, eight, sixteen or thirty two blocks.
It is preferable that the direction of the plurality of printing elements of the first and second printing element arrays is diagonal to the scanning direction.
Further, it is preferable that the printhead further comprises a delay circuit that delays print data output to printing elements of each block of the printing element array, in accordance with change of the order of blocks to be driven by the changing circuit.
Note that it is preferable that the printhead is an ink-jet printhead that performs printing by discharging ink. Further, the ink-jet printhead has electrothermal transducers for generating thermal energy to be supplied to ink, for discharging the ink by utilizing the thermal energy.
It is preferable that such printhead further comprises third and fourth printing element arrays in the first direction in parallel to the first and second printing element arrays, and color printing is performed by discharging yellow ink, magenta ink, cyan ink and black ink from the first, second, third and fourth printing element arrays.
Further, it may be arranged such that the first and second printing element arrays are respectively assembled in separate printheads.
According to another aspect of the present invention, the foregoing object is attained by providing a printing apparatus which performs printing by using the printhead having the above construction, comprising: scanning means, carrying the printhead, for reciprocate-scanning the printhead along the scanning direction; and output means for outputting print data to the printhead.
According to still another aspect of the present invention, the foregoing object is attained by providing a printing apparatus which performs printing by dividing a plurality of printing elements constituting a printing element array into a plurality of blocks and time-divisionally driving the plurality of printing elements in block units, comprising: a memory circuit for storing a value based on an amount of registration shift equal to or less than a printing resolution in a direction in which the printing element array is scanned relative to a printing medium; and a changing circuit that changes an order of blocks to be driven in accordance with the value stored in the memory circuit.
Note that it may be arranged such that the printing apparatus further comprises a delay circuit that delays print data output to printing elements of each block of the printing element array, in accordance with change of the order of blocks to be driven by the changing circuit.
In accordance with the present invention as described above, registration adjustment can be performed with the value equal to or less than the printing resolution in the direction in which the printing element array is scanned relative to a printing medium without transmitting a specific control signal from the printing apparatus, by changing the order of blocks to be driven within the printing element array in accordance with a value based on the amount of registration shift stored in a memory circuit.
The invention is particularly advantageous since almost all the registration shift can be solved.
Accordingly, high quality images can be printed.
Especially, in case of a printhead having a plurality of printing element arrays, the precision of registration adjustment in manufacturing can be relaxed. Further, as the registration adj
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hsieh Shih-Wen
Le N.
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