Patent Application
20080013974
These and/or other aspects and utilities of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.
The image forming apparatus comprises a print head 330, a printing paper 300 and a support 340.
The print head 300 has a plate-like shape with a size corresponding to a printing side of the printing paper 330. The size of the print head may be equal to the size of an image to be printed. The print head 300 may be a thermal print head (TPH) comprising a ceramic insulator and heating elements deposited in a dot pattern on the ceramic insulator.
The print head 300 comprises a group of heating elements 310 and a group of driving elements 320 to form images arranged in row and column directions. The group of the heating elements 310 comprises n heating elements 310 in the row direction and m heating elements 310 in the column direction, thereby being arranged in the form of an n×m matrix.
As illustrated in
The print head 410 comprises a power supply 412, a plurality of heating elements 414, a plurality of driving elements 416, a plurality of power supplying elements 418, and a ground terminal 420.
The plurality of heating elements 414 correspond to a plurality of nozzles of the print head 410, respectively. Typically, the heating elements 414 are heating bodies comprising thin film heaters with resistivity.
The plurality of driving elements 416 comprise switching elements such as transistors (TRs) or field effect transistors (TFTs). The driving elements may be turned on when print data has a high level to drive the heating elements 414.
The power supply 412 supplies power to the plurality of heating elements 414, and the plurality of power supplying elements 418 are connected to rows of the plurality of heating elements 414, respectively, to supply power from the power supply 412 to a row at which the print data is printed.
The print head driver 430 comprises a row driver 440 that controls rows of the heating elements 414, and a data supplying part 450 that supplies the print data to columns of the heating elements 414.
The row driver 440 comprises a timing controller 442 and a gate driver 444. The timing controller 442 receives a horizontal synchronization signal defining a print row of the print data and outputs a control signal to the gate driver 444 to control the rows of the heating elements 414, and the gate driver 444 outputs a signal to sequentially control the power supplying elements 418.
The data supplying part 450 comprises an n-bit shift register 452, an n-bit latch circuit 454, n AND gates 456, and n NOT gates 458.
The n-bit shift register 452 receives serial print data of n bits according to a clock signal received from the controller 470, stores the received serial print data sequentially, and then converts the stored serial print data into parallel print data. The n-bit latch circuit 454 holds the parallel print data for a predetermined period of time. The AND gates 456 perform an AND operation corresponding to output signals of the n-bit latch circuits and strobe signals to drive the heating elements 414.
When the image forming apparatus performs a print operation, the controller 470 transmits the print data serially to the n-bit shift register 452 via a data line according to a clock signal to drive the heating elements 414, and transmits a latch signal to the n-bit latch circuit 454 after completion of the transmission of the print data of n bits. In addition, the controller 470 transmits the horizontal synchronization signal corresponding to each print row to the timing controller 442 to inform the timing controller 442 which row the print data transmitted serially to the n-bit shift register 452 are printed.
Hereinafter, the operation of the image forming apparatus illustrated in
The timing controller 442 of the row driver 440 receives the horizontal synchronization signal from the controller 470 and transmits the horizontal synchronization signal to the gate driver 444, and the gate driver 444 drives the power supplying elements 418 corresponding to each row sequentially whenever the horizontal synchronization signal is input to the gate driver 444. For example, when a first horizontal synchronization signal is input after a print instruction, the timing controller 442 outputs a control signal (i.e., the first synchronization signal) to the gate driver 442 in consideration of timing of the print data provided from the data supplying part 450, and the gate driver 444 outputs a high level signal to its gate-1 according to the control signal. When a second horizontal synchronization signal is input to the timing controller 442, the gate driver 444 outputs a high level signal to its gate-2. In this manner, until an m-th horizontal synchronization signal to drive the last row is input to the timing controller 442, the gate driver 444 outputs a high level signal to the print rows sequentially.
The n-bit shift register 452 of the data supplying part 450 receives the print data serially via a data line and shifts the received print data by synchronizing the received print data with a clock signal. When the n-bit shift register 452 receives data of n bits, the shifted print data is temporarily stored in the n-bit latch circuit 454 by a latch signal. The print data stored in the n-bit latch circuit 454 is supplied to inputs of n AND gates 456, and is held until a next latch signal is input to the n-bit latch circuit 454. Accordingly, a strobe signal is input to the AND gates 456 via the NOT gate 458, as a final print instruction to determine a driving time of the heating elements 414. Since an output signal of the NOT gate 458 has a high level, outputs of n AND gates 456 have a high level or a low level depending on whether the print data has a high level or a low level. If the print data has a high level, the driving elements 416 are turned on, thereby driving the heating elements 414. If the print data has a low level, the driving elements 416 are turned off so that the heating elements 414 can not be driven.
When the horizontal synchronization signal is inputted to the timing controller 442 after the print instruction is input, the gate driver 444 outputs a high level signal to its gate-1. When the gate-1 goes to a high level, since the power supplying elements 418 corresponding to a first row are turned on, power is supplied to a first row of the plurality of heating elements 414. Then, the n-bit shift register 452 receives and shifts the print data in synchronization with the clock signal. When the shift of the n-bit shift register 452 is completed, the n-bit latch circuit 454 receives and temporarily stores the shifted print data from the n-bit shift register 452 by the latch signal. When the strobe signal goes from the high level to the low level, the NOT gate 458 outputs a high level strobe signal and the AND gates 456 output the print data, thereby driving the first row of heating elements 414 to heat the heating elements 414.
Numerals of the print data, 1, 2, 3, . . . , N, are a gray scale representation of color. If N is 256, the print data may be represented with 256 gray scales.
When representation of 256 gray scales at the first row is completed, the timing controller 442 receives the second horizontal synchronization signal and the gate driver 444 outputs a high level signal to the gate-2. When the gate-2 goes to a high level, since the power supplying elements 418 corresponding to a second row are turned on, power is supplied to a second row of the plurality of heating elements 414. Then, when the print data output from the AND gates 456 has a high level, the driving elements at the second row are turned on, thereby driving the heating elements 414 at the second row to print an image on a printing paper.
Although one shift register 452 and one gate driver 444 are illustrated in
As disclosed above, the present general inventive concept provides an image forming apparatus which is capable of forming an image of high quality by eliminating mechanical deviations occurring at the time of feeding a printing paper and image deviations due to skews occurring at the time of feeding the printing paper.
In addition, according to the present general inventive concept, various printers including a photoprinter can be miniaturized by removing parts such as a motor and a feeding roller to feed a printing paper.
Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-66533 | Jul 2006 | KR | national |
