JPH0248969A - Density correcting circuit of gradation printing device - Google Patents

Abstract

PURPOSE:To prevent density unevenness and color unevenness from occurring by a method wherein when an address exists on an electrification partition boundary, a gradation data of which an image data is shifted to a thicker side than that of the gradation data paper is so constructed as to be outputted from a ROM. CONSTITUTION:A detection circuit 3 detects a time when a boundary address preset with n switches from 4-1 to 4-n coincides with output of an address generation means 2, generates detection output S5, and outputs one bit content to an address A8 of a ROM. At least two classes or over of gradation data when boundary correction is performed and when not are equipped to the ROM as an output data. That a gradation data after correction (n) gradation becomes equal to density of (n-m) gradation when said density exists on the boundary has been experimentally obtained. When the gradation data of (n-m) gradation is sent from a host computer, the (n) gradation is outputted to a data bus S of the ROM 1 as a correction data, and printing is performed while density decrease of an electrification partition boundary is being corrected in real time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention can be used as a three-dimensional CAD hard copy device that performs combiator graphics or shading, for proofing color printing, or as a substitute for photography. This paper relates to head heat control for full-color printers.

(Summary of the Invention) This is a method that allows correction and printing to be performed simultaneously while receiving image data and reading timing signals sent from a host computer, etc. It counts the signals, detects that the value, that is, the address, is the preset energization division boundary, and outputs the RO containing the correction data.
Output a bit to the address of M. The ROM contains at least the input gradation data and the detection output of the energization division boundary at the address, and the gradation data output by the ROM is gradation data that is modulated to be darker at the boundary than the gradation data that is originally output. is output to the print control unit to erase white streaks at boundaries caused by energization division.

[Conventional technology]

In recent years, full-color line printers have been used in various fields such as video printers, hard copy devices for workstations, and the printing field.

In particular, thermal transfer printers using a sublimation method are rapidly becoming popular due to their ease of operation and maintenance.

In this thermal transfer printer, when the heating elements are energized all at once, a large current flows and the power supply becomes large, so one line is divided into several parts.
When one block is energized, another block is paused for a cooling period, so-called split energization.

However, when using dye-sublimation ink whose density changes sensitively to the head temperature, the edges of the energized blocks tend to radiate heat, resulting in lower temperatures and areas of low density at the boundaries of the energized blocks. , a phenomenon occurs in which this appears as white sushi in the paper feeding direction.

Therefore, in conventional dye-sublimation printers, small-sized printers were handled by not dividing the current supply. Also, for large ones, 1
This was achieved by having a frame memory for the screen and reading the data, manipulating it, and then writing it.

In other words, this was handled by reading the density at the boundary, calculating the amount of lightness due to the boundary, and writing gradation data shifted to the darker side into the frame memory. This processing is performed as part of image processing.

[Problem to be solved by the invention]

The above method of not dividing the current supply requires a large power supply, and
There is a problem in that the resistance of the wiring inside the head from the power source to the head causes a voltage drop in a line with a high printing rate, resulting in density unevenness and color unevenness. Furthermore, the method of image processing for frame memory requires expensive large-capacity memory (50 megabytes for A3 12 pixels/fi), and since the screen size and memory size differ for each application, It is a different model, and there are problems with cost, inventory, distribution, etc.

[Means to solve the problem]

Address generation means that counts timing signals for image data synchronized with read timing signals sent from the host combinator, line head with multiple energization strobe signals that energize the head by dividing it into multiple parts, energization division boundary ROM that stores gradation data for density correction
When there is an address at the energization division boundary, the ROM outputs tone data obtained by shifting the image data to a darker side than the original tone data. The ROM is provided with at least two types of gradation data for each input gradation, one for boundary correction and one for non-border correction, as output data. The corrected gradation data n gradation is when the density is on the boundary (n-m
) Experimentally find that it is equal to the density of the gradation (
When image data of nm) gradation is sent from the host computer, nl gradation is output from the ROM as correction data.

[Effect]

In this way, with the above configuration, image processing for boundary correction and printing can be performed in real tile processing at the same time as image data is input. As a result, the white streaks at the boundaries caused by the energization division are erased.

〔Example〕

FIG. 1 is a circuit diagram of a principle model of the present invention.

In the ROMI, an 8-bit address corresponding to a bit loss of image data S input from a host computer or the like is input to addresses A0 to A1 of the ROMI. The address generating means 2 is composed of a counter, and includes image data S,
It counts the read timing signal S2 inputted in synchronization with the image data, and outputs an n-bit address S4 indicating the position of the image data in one line. The detection circuit 3 detects when the boundary address preset by the n switches 4-1 to 4-n and the output of the address generation means 2 fail, generates a detection output Ss, and outputs a detection output Ss.
Output 1 bit to OMI address A. The ROM is provided with at least two types of gradation data for each input gradation, one for boundary correction and one for non-border correction, as output data.

It has been experimentally determined that the corrected gradation data n gradation is equal to the density of the (n-m) gradation when the density is on the boundary, and the image data of the (n-m) gradation is is sent from the host computer, outputs n gradations as correction data to the data bus S of the ROMI, and prints.

FIG. 2 shows an example of input gradation data and output gradation data, where N is the input/output characteristic when boundary correction is not performed, and E is the input/output characteristic when boundary correction is performed.

In the manner described above, it is possible to correct the density drop at the energized division boundary in real time, and to simultaneously print while making the correction.

In addition, this method: This method modulates the image data itself on the input side before printing the boundary density correction. This is why the density characteristics (gamma characteristics) with respect to the pulse width differ in the boundary portions. It is difficult to change the pulse width for the gradation number only at the boundary portion of one line, and the circuit becomes too complicated.

Therefore, the present invention adopts a method of correcting the gradation number itself at the boundary portion.

FIG. 3 shows an embodiment of the present invention at a practical level.

In addition to the density correction of the energization division part shown in Figure 1, the energy applied to each dot up to three lines before (-gradation number)
The results of calculations for history correction of the applied energy are also stored in the ROM (correction calculation data memory 21 in FIG. 3), and these corrections are performed simultaneously and in real time. In addition, the heat storage data of the head is also manually generated, and the interaction factors with the head temperature are also calculated and corrected.

II is the Centronics interface connector, 1
2 is a data signal, 13 is a strobe signal, 14 is a busy signal, 15 is a clock signal, and 16 is an IC 117 for I10 of the CPU that controls the printer, which counts the strobe signal or clock signal 15, and outputs the address generator of the line memory. 1 is a counter, 1 is a switching circuit that switches between the address bus 19 of the CPU, which is one of the address generation means, and the output of the counter 17, and 20 is a detection circuit that shifts the gradation at a specific address and corrects the density. It is. 21 is a correction calculation data memory, and 22 is a circuit for generating write timing for the line memory. 23 is a line memory for storing data of one line before, 24 is a memory for storing data of two lines before, and 25 is a line memory for storing data of three lines before. 26 is a line memory or latch that stores and holds output data. 27, 28, and 29 are switches composed of three-state bus buffers. 30 is a data input of the heat storage state of the head.

The operations related to the present invention are the same as those shown in FIG. 1, so a description thereof will be omitted.

FIG. 4 is an explanatory diagram of this correction, in which the input 256-level circle is normally converted to 64 gradations, which are practical for printing. There are a maximum of 2 to the 24th power of gradation combinations up to 3 lines before, but among these, up to 3 lines before the extremes, there are white (gradation I = IO) and black (gradation! II =
255) are illustrated.

Nφ indicates the case where the line up to three lines before is white and is not a boundary, and Eφ indicates the case where the line up to three lines before is white and is a boundary part of energization division.

Further, N255 indicates a case where the line up to three lines before is black and is not a boundary, and E255 indicates a case where the line up to three lines before is black and is a boundary part of energization division. These are graphs of calculation results based on experimental data, and the correction calculation data memory 21 stores data regarding all combinations, and instantly outputs correction calculation results when a condition is input to an address. In this way, correction data can be output at the same time as image data is input.

〔Effect of the invention〕

With the above configuration, the present invention has the following effects.

(1) It is possible to eliminate the decrease in density (white streaks) that occurs at the boundaries of the joints of the divisions when energizing the divisions.

(2) Split drive is now possible even in gradation printers,
Power supplies can be made smaller and costs can be reduced.

(3) During non-divided driving, density unevenness and color unevenness that occur in lines with a high printing rate due to voltage drop can be reduced by dividing driving.

Compared to a system that is equipped with memory for 1 ii images and performs thermal correction calculations and 2 image processing before printing, printing can be performed while receiving image data from the host computer and processing it in real time, reducing waiting time. No real print time is short.

0 Improved operability O Large capacity memory (50 MB for A3.12 pixels/■-) is not required, resulting in low cost.

Since there is no need to change the specifications of the image memory for each application, the number of models can be reduced, which is advantageous in terms of cost, inventory, and distribution.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a principle model of the present invention, FIG. 2 is an explanatory diagram showing an example of the correspondence characteristics between input gradation data and output gradation data, and FIG. 3U; J is a circuit diagram for implementing the present invention at a practical level, and FIG. 4 is an explanatory diagram for correcting and converting input gradation data to obtain output gradation data. l ・ ・ ・ ・ ・ ROM 2 ...Address generation means 3.20 . . 4 . . . . 11 . . . . 12 .・ 16・ ・ ・ ・ 17・ ・ ・ ・ 18・ ・ ・ ・ 21・ ・ ・ ・ 23. 24. 25 ・ 27. 28. 29 Counter switching circuit correction calculation data Memory line memory or lunch bus changeover switch Applicant Seiko Electronics Co., Ltd. Agent Patent attorney Takashi Hayashi Assistant person power F! Diagram 2 of the explanation of the contrast between the I-delivery and the output eyebrow-tone tenter for the input.

Claims (1)

[Claims] In line printers that obtain gradation by changing the amount of heat,
Image data and timing signals output from the host computer or the printer's built-in image data generation means,
The apparatus includes an address generating means for counting the timing signals, a line head that receives a plurality of energizing strobe signals that energize the head by dividing the head into a plurality of parts, and a ROM that stores gradation data for density correction of energizing division boundaries, and receives image data. Almost at the same time, the gradation printer outputs gradation data that has been modulated to be darker than the original gradation data at the energization division boundaries to erase white streaks at the boundaries caused by energization division. Density correction circuit.