JPH08108549A - Ink jet printer control method and color ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To print a color image at high speed by employing a color ink jet printer of such a type as the swath of an image is printed every time when a head traverses a sheet thereby substantially reducing bi-directional print artifact. SOLUTION: An image to be printed is represented by a color coordinate and converted through RGB-CMYK conversion 100 into device dependent color description to create a coloring agent signal. A part of an image or a scan line corresponding to a swath is stored in a swath buffer 102. The RGB-CMYK conversion performs color correction 104 and halftone processing is carried out at a halftone block 105. A print hrad has two passage of forward direction (from right to left) and reverse direction and comprises a forward swath processor 108 and a reverse swath processor 110. Each processor processes a swath subjected to halftone processing and introduced from the swath buffer 102 to form the image data of a head driver 120 thus driving the print head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drop-on-demand inkjet printing system, and more particularly to a multi-color thermal inkjet printer capable of bidirectional swath printing.

[0002]

BACKGROUND OF THE INVENTION The color of a document (document) is a combination of a limited set of colors over a narrow area at a density selected to integrate the desired color response. The result. This has been achieved in many printing devices by reproducing the separations of the image, each separation having a varying density of one primary color. When combined with other decompositions, the result is a full color image.

Thermal inkjet printers are generally drop-on-demand type ink printing systems that use thermal energy to create bubbles in ink-filled channels and eject droplets. A thermal energy generator or heating element, usually a resistor, is located in the channel near the nozzle, spaced from the nozzle by a predetermined distance. The resistors are individually addressed with electrical pulses to momentarily vaporize the ink and form bubbles that expel ink drops. When the bubble becomes large, the ink swells from the nozzle, and the bulging ink is suppressed by the surface tension of the ink. When the bubble begins to break, the ink in the channel between the nozzle and the bubble begins to move towards the broken bubble, causing volume contraction of the ink at the nozzle and the resulting swollen ink as droplets. To separate. During bubble growth, the acceleration of the ink exiting the nozzle provides the momentum of a droplet that travels in a substantially straight line toward a recording medium such as paper or a transparent sheet or the like (hereinafter "sheet"). The sheet moves past the printhead for imaging.

In one type of inkjet device, a printhead containing an array of nozzles oriented parallel to the direction of movement of the sheet is perpendicular to the direction of movement of the sheet as it traverses the recording medium. Can be moved in the direction. Each pass prints a swath of spots or pixels across the page corresponding to the image. Most inkjet printers print a few scan lines in the swath, which makes the swath boundaries visible in the prints made. The boundaries become visible because of the ink that flows over the edge boundaries of the array (for paper) or the ink that is pulled away from the edge boundaries of the array by surface tension (for transparent sheets). In the former case, the thin line along the border is more inked and the latter is completely inked.

It is clear from the above that printing is accomplished with each pass of the head across the page, and for high speed black (or monochrome) only printing, bidirectional printing is common. Color inkjet printing is usually performed in one direction (either left to right or right to left, but not both). Multiple nozzle arrays arranged in parallel may be provided for printing with multiple inks that print multiple separations. One particular type of color inkjet printer has a single head for each color (corresponding to an array of nozzles) and four heads mounted on the carriage so that they overlap one another in the back direction. , Cyan, magenta, yellow and black (C, M,
All four colors (Y and K) are printed in one pass in a fixed order for separation within one pixel. Bi-directional printing is generally avoided because the colors are printed in the reverse order when the carriage is moving in reverse. For example, printing a cyan pixel on a magenta pixel will give a different color when the print order is reversed.

US Pat. No. 4,9,9, by Trask
No. 99,646 discloses a multi-pass complementary dot pattern inkjet printing process to improve dot formation uniformity and fixability during color inkjet printing to correct interswath boundary artifacts. Disclosed is a unidirectional printing system provided. Such improvements are achieved by minimizing undesired properties such as adhesion, beading, hue transfer, folds, wrinkles and color bleeding when printing on both transparency and plain or specialty paper. It directly affects the overall print quality over the color print area and improves the print quality. Using this process, a continuous print swath is formed by depositing first and second partially overlapping complementary dot patterns on the print medium. At the same time, the dot spacing of the corresponding dot rows in the overlapping portion of the dot patterns changes between the dots of the first pattern and the dots of the second pattern. Also note US Pat. No. 4,748,453 to Lin et al. HP50
Various products available from Hewlett Packard Company of Palo Alto, Calif., Including 0C, HP550C and HPXL300 inkjet printers, are known to use head signature mitigation patterns.

The documents disclosed herein are incorporated by reference for the purpose of teaching.

The present invention uses a color ink jet printer of the type that prints a swath of an image each time it passes across a sheet to print a color image at a relatively high speed with substantially reduced bidirectional print artifacts. Is directed to how to do it.

[0009]

SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, there is provided a method and apparatus for operating a color ink jet printer of the type that prints a swath of an image each time it passes across a sheet. Color is applied to print the image as the four-color printhead passes in the forward and reverse directions across the sheet. The color signal is ANDed with the checkerboard pattern to obtain the first
Determining a first set of print positions for passage, the image is printed at the first set of positions. The same color signal is then ANDed with the complementary checkerboard pattern to determine a second set of print positions for the reverse pass and the image is printed at the second set of positions.

Consistent prints are generally acceptable, although accurate prints are always a desired goal. The present invention proposes to print the correct color in the first set of positions and the somewhat incorrect color in the second set of positions. However, due to the interspersing of correct and incorrect color locations, the different colors forming the image are integrated into the human eye as an approximately accurate image. No printhead signature artifacts are visible. The printed colors are consistent and color correction can occur to correct for predicted deviations from the correct color if desired.

Furthermore, it is conceivable that the speed of the carriage will slow down when printing successive pixels of the scan line due to limitations in the construction of the inkjet head. Since it is known that the apparatus of the present invention does not fire a jet for successive pixels in a scan line, it is possible to double the speed of the carriage. It is assumed that the inkjet carriage makes one pass at time S. In unidirectional mode, time 2S is required to complete one swath (print pass time S + return pass time S). However, the swath must be printed twice, once for the first checkerboard and once for the second checkerboard, because checkerboard formation is desired for head relief reasons. Therefore,
In order to perform checkerboard formation and print swaths in one direction, 4S time is required. However, if bidirectional printing is possible, 2S time is possible even if the checkerboard is formed. Further, if double speed is possible, then double speed bi-directional printing time S for checkerboard formation is possible.

According to a first aspect of the present invention, there is provided an ink jet printer control method, wherein the ink jet printer is capable of reciprocating print capable of controlling swath print of an image by forward pass and reverse pass across a sheet. Having a head and using a set of colorants to print each color pixel forming the swath on the sheet in one of two fixed orders,
The fixed order is determined by the printhead structure and the pass through which the color pixels are printed, the method comprising: a) receiving a set of colorant signals representative of the color pixels in a swath of the image; ) Generating a first swath signal from the colorant signal by ANDing a predetermined head signature mitigation signal and the colorant signal to generate a first pass print signal; and c) the printhead. To print a partial swath of the image with the first pass print signal during a first pass of the print head across the sheet, and d) the predetermined head signature mitigation signal. The colorant signal is complemented by the complementary signal.
Generating a second swath signal from the colorant signal by performing a D operation to generate a second pass print signal; and e) controlling the printhead to traverse the sheet in the reverse direction of the printhead. Printing complementary swaths of the image in the order of reverse pass colorants therein.

According to a second aspect of the present invention, in the first aspect, the sheet and the reciprocating movement for advancing a print amount corresponding to about half of one swath for each successive passage are possible. Providing relative movement of printheads, wherein about half of the partial swaths printed on the forward pass overlaps about half of the partial swaths printed on the reverse pass. including.

According to a third aspect of the present invention, there is provided a color ink jet printer wherein a reciprocable print capable of controlling partial swath prints of an image in a first pass and a second pass of a printhead across a sheet. Printing each color pixel forming the swath on the sheet with a set of colorants having a head and deposited in a predetermined colorant deposition sequence defined by forward pass; A colorant signal input operatively connected to a colorant signal source representing color pixels in a swath of the image; b) said image being printed during a first pass in response to said colorant signal received. A first pass signal processor for producing a first partial swath of the signal source for producing a predetermined head signature mitigation signal and A second pass in response to the received colorant signal, including an AND logic circuit for ANDing a predetermined head signature mitigation signal and the colorant signal to produce a first pass print signal; A second pass signal processor for producing a second partial swath of the image to be printed therein, the processor comprising a source for producing a complementary signal of the predetermined head signature mitigation signal and the complementary A predetermined head signature mitigation signal and the colorant signal are ANDed to produce a second pass print signal, d) controlling the printhead to print across the sheet. Print a partial swath of the image with a forward pass print signal during the forward pass of the head and reverse during the reverse pass of the sheet. A printer control means for printing the complementary swath of the image with over-print signal.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a multi-color thermal ink jet printer 10 including several removable ink supply cartridges 12, each mounted integrally with a printhead 14.
The combination of ink cartridge and print head is
It is removably mounted on the movable carriage 20. During the print mode, the carriage reciprocates back and forth in parallel with the recording medium or the sheet 24, for example, on the guide rail 22 as indicated by an arrow 23. The distance traveled from end to end of carriage and print head is distance B
Indicated by. The carriage is driven back and forth over the entire length of the cylindrical platen 16 by known means, for example by cables and pulleys with reversible motors (not shown). The recording medium such as paper is a platen 16
Mounted on. The platen has a diameter of 10-20 cm and is formed, for example, from an aluminum sleeve 17 having an end cap 13, the platen being attached to one end and driven by a belt 32 via a stepper motor (not shown) a pulley. 33, and includes a shaft 13A extending therethrough. The platen has guide rails 22
It is rotatably attached to the frame side portion 21 including both ends of. The paper is held stationary by the platen while the carriage is moving in one direction. Before the carriage moves in the opposite direction, the paper is moved in the direction of arrow 19 by the platen a distance equal to the swath height of the data printed by the printhead 14 while the carriage is moved in one direction across the paper. Be advanced. The width of the sheet during the passage of the carriage is the print zone or area, indicated by the distance A. The total travel distance B is greater than the print area A to allow printing with all multiple printheads and to accommodate printhead primes and maintenance stations (not shown). Therefore, an encoder (not shown) must be used to monitor the position of the carriage 20 when the printhead is in the print area. Droplets
The sheet is ejected onto the sheet in an on-demand manner along a track 15 from a nozzle (not shown) arranged in front of the print head (not shown). The front of the print head is 0.0
1-0.1 inch (0.0254-0.254 cm),
Preferably approximately 0.02 inches (0.0508 cm)
Separated from the seat. The platen drum 16 and sheet step limits and printhead linear displacements are held within acceptable limits so that successive swaths of information to be printed are printed without gaps or overlaps.

Each cartridge 12 contains a different ink, and is typically one or more cartridges of one black and a different selected color. The cartridge and printhead combination is removed and discarded after the ink supply in the cartridge is empty. In this environment, some nozzles do not fire drops during a complete carriage movement, and typically no nozzles fire drops as the printhead moves past the edge of the platen. At the end of the carriage passage, there is a dwell time as the platen drum advances one swath in the direction of arrow 19. A maintenance and prime station (not shown) is located on one side of the platen drum, with less used nozzles activating nozzle cleaning drops and / or nozzles capped to prevent the printer from drying during idle times. May be.

Referring to FIG. 2, a very schematic system overview is presented. Typically, the printed image will initially have device independent color coordinates r, g, b.
(Colorimetric red, green, and blue). r,
The color description represented by the g and b color coordinates is RG.
Converted to a device-dependent color description in the B-CMYK transform 100 to produce a colorant signal defined by cyan, magenta, yellow and black colorants. A portion of the image may be suitably stored in swath buffer 102, which, as described in detail below, of the image to be printed in forward and reverse passes of the printhead across the sheet. A number of scan lines corresponding to swaths may be stored. The RGB to CMYK conversion, which may include undercolor removal and black addition, is performed in color correction 104.

Many other methods of producing the colorant signal are possible and equivalent to this method. A further discussion of the conversion of device independent to device dependent color description can be found in, for example, Rolleston et al., US Pat.
It is performed in No. 305, 119. Also, Cook
Also note US Pat. No. 5,271,096 (assigned to Light Source).

Halftone processing is performed in the halftone block 105 to reduce the number of bits describing the density of each pixel to the number of levels that can be reproduced by the selected printer, and the halftone processing is performed, for example, in Holladay. According to the halftoning process described in US Pat. No. 4,149,194.

As described above, the print head reciprocates back and forth in parallel with the sheet, and performs swath printing after each passage of the sheet. Forward (typically but not necessarily left to right) forward or first pass and (right to left)
There are two passes in the opposite direction, the second pass. Thus, a forward swath processor 108 and a backward swath processor 110 are provided, each of which is a swath buffer 10.
The halftone-processed swaths directed to them from 2 are processed to form the image data of the head driver 120 from the information and drive the printhead for printing during the corresponding pass.

Referring to FIG. 3A, the forward swath processor 108 is a checkerboard (checkerboard) data either generated by the AND gate 202 and immediately before printing, or stored in a memory such as RAM or ROM. Including the source. The AND gate 202 AND-operates the color signals with the signal representing the first checkerboard pattern. As used herein, a checkerboard pattern represents a head signature mitigation pattern signal, which is a series of alternating on and off signals, each line of the signal from the previous line. Offset by one signal. As a result, the signal looks like a checkerboard when printed. Variations of the checkerboard pattern are possible, such as trying to maintain the mutual relationship between the ON signal and the OFF signal, and swapping the positions of the ON and OFF signals to mitigate the head signature. The checkerboard pattern is used as described in U.S. Pat. No. 4,999,646 by Trask to reduce the artifacts commonly found at swath boundaries.

KCMY (K for forward-passing sheets
Is the lowest possible layer deposited first, Y is the last or highest possible layer) is used for left-to-right printing on the printer, and X is the bitmap checker. It is a board pattern signal, and C, M, Y,
And K are separate bitmap signals representing the image. The forward or first pass is as follows. K _LR = K∧X C _LR = C∧X M _LR = M∧X Y _LR = Y∧X The subscript LR emphasizes that the direction of passage is from left to right,
The symbol ∧ represents an AND operation.

Referring to FIG. 3B, the backward swath processor 110 also has four color signals C, M, Y, K as inputs to determine which pixels are printed in the backward pass. The reverse swath processor 110
AND gate 350 and whether it was generated immediately before printing,
A checkerboard complementary data source, either stored in memory such as RAM or ROM. Again, assume that the KCMY order is used in the printer for right-to-left printing, and C, M, Y, and K are separate bitmaps that represent the image. K _RL = K ∧¬X C _RL = C ∧¬X M _RL = M ∧¬X Y _RL = Y ∧¬X The subscript RL emphasizes that the direction of passage is from right to left, and the symbol ¬X is Represents the complement of X (NOT).

It will be appreciated that the forward and reverse pass adhesion requirements are substantially reversible.

FIG. 4 illustrates the formation of a swath map from the original swath 300. Assume the same example as the forward pass swath 302 printed in KCMY order. Therefore, the reverse swath 304 is printed in YMCK.
The color given to each box is assumed to represent the first letter representing the first layer to be deposited. Note that for the particular example of swath 300, there are only two colorants per pixel printed with respect to colorants for undercolor removal. The combined swath is image segment 3
06 has the color order shown.

A semi-swath step down from the sheet can be used to further improve uniformity, as shown in FIG. 5 and as shown by conventional unidirectional checkerboard formation. Half-swath stepping means that half of the scan lines in the swath initially sweep from right to left (sweep)
While the other half initially requires it to be swept from left to right. As a result, on one half swath, half the pixels printed in KCMY order are printed before half pixels printed in YMCK order, and the other half swath is printed in YMCK order. Pixels are printed first. In fact, there is no visual difference between the half swaths.

It will be appreciated that the present invention is accomplished by hardware logic implementation, or software implementation in a programmable processing device or a combination of hardware and software.

[Brief description of drawings]

FIG. 1 is a schematic isometric view of a multi-color carriage type thermal inkjet printer that includes the present invention for printing multiple separations in a swath across a sheet supported on a platen.

FIG. 2 is a schematic block diagram illustrating a controller of an inkjet printer that operates according to the present invention.

3 (A) is a diagram showing the subsystem of FIG. 2. FIG. FIG. 3B is a diagram showing the subsystem of FIG.

FIG. 4 is a diagram showing a configuration of each swath bitmap from a bitmap describing an image.

FIG. 5 illustrates an array of swaths preferably used to form an image.

[Explanation of symbols]

 100 RGB-CMYK conversion 108 Forward direction swath processor 110 Reverse direction swath processor 202, 350 AND gate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H04N 1/23 101 C B41J 3/10 101 G (72) Inventor Steven Jay. Harrington United States New York 14470 Holly South Main Street 76

Claims (3)

[Claims] 1. A method of controlling an inkjet printer, the inkjet printer having a reciprocable printhead capable of controlling the printing of swaths of an image by forward and reverse passes across a sheet,
A set of colorants is used to print each color pixel forming the swath on the sheet in one of two fixed orders, the fixed order being printhead structure and color. The method is determined by the pass through which the pixels are printed, the method comprising: a) receiving a set of colorant signals representative of color pixels within a swath of the image; and b) a predetermined head signature mitigation signal and the coloration. Generating a first swath signal from the colorant signal by ANDing an agent signal to generate a first pass print signal; and c) controlling the printhead to traverse the sheet. Printing a partial swath of the image with the first pass print signal during the first pass of d. Generating a second swath signal from the colorant signal by ANDing the colorant signal with a complementary signal of the generated head signature mitigation signal to generate a second pass print signal; and e) the printhead. Controlling the printing of complementary swaths of the image in the order of reverse pass colorant during reverse pass of the printhead across the sheet. 2. Providing relative movement between the sheet and the reciprocable printhead for advancing an amount of print corresponding to about half a swath for each successive pass, the forward direction. The method of claim 1, wherein about half of the pass printed partial swaths overlap with about half of the reverse pass printed partial swaths. 3. A color inkjet printer, the first pass and the second pass of a printhead across a sheet.
A set of colorants having a reciprocating printhead capable of controlling the printing of partial swaths of an image in the pass, the set of colorants being applied in a predetermined colorant application sequence defined by forward pass, wherein Printing each color pixel forming the swath on a sheet, a) comprising a colorant signal input operatively connected to a colorant signal source representative of the color pixel in the swath of the image, b) the received A first pass signal processor is responsive to the colorant signal to generate a first partial swath of the image printed during a first pass, the processor providing a predetermined head signature mitigation signal. A signal source to be generated and an AND logic circuit for ANDing the predetermined head signature mitigation signal and the colorant signal to generate a first pass print signal. C) comprising a second pass signal processor for producing a second partial swath of the image printed during a second pass in response to the colorant signal received, the processor comprising: A signal source that produces a complementary signal of a predetermined head signature mitigation signal and the complementary predetermined head signature mitigation signal and the colorant signal AN.
An AND logic circuit for performing a D operation to generate a second pass print signal, d) controlling the printhead to forward the print image of the image during a forward pass of the printhead across the sheet. Print a partial swath,
A color ink jet printer comprising printer control means for printing complementary swaths of the image with a reverse pass print signal during reverse pass of the sheet.