JPH02155744A - Correction of deflective distortion of ink droplets in ink jet printer and its device - Google Patents

Abstract

PURPOSE:To perform an exact correction of a deflective distortion of ink droplets by determining a basic correction value of the deflective distortion of noticed ink droplets in accordance with the flying pattern of ink droplets located near an area before and after the noticed ink droplets, and then adjusting the basic correction value according to the number of precedent flying gutter droplets. CONSTITUTION:If the number of precedent gutter droplets Dg in ink droplet data is set at (c), a recorder detects and records the number (c) of precedent gutter droplets. Then a deflective width correction table outputs data referring to a deflective correction factor (m) which meets the number (c) of precedent gutter droplets, while a deflective position shift correction table outputs data referring to deflective position shift correction data which meets the number (c) of precedent gutter droplets. In this condition, a deflective distortion correction value calculation circuit calculates the final correction data of a deflective distortion to noticed ink droplets (Do). Next, said circuit properly corrects the charge control voltage of a charging electrode 12 based on the final correction data. Thus it is ensured that the noticed ink droplets (Do) are deflected to a deflection position (P) targeted on a recording sheet 14.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a multi-nozzle type inkjet printer in which continuously generated ink droplets are charged and then deflected by an electric field to fly to a predetermined position on a recording sheet. Regarding the ink droplet deflection distortion correction method and device used,
In particular, the present invention relates to a method for correcting deflection distortion caused by electrostatic and aerodynamic interactions that a flying ink droplet receives from other ink droplets, and improvements to the device.

[Prior Art] In general, a multi-nozzle type inkjet printer, as shown in FIG. The nozzles 11 are appropriately deflected and moved by the electric field of the deflection electrode 13, and each nozzle 11 is designed to take on a unit image area U of a group of print dots of a plurality of pixels on the recording sheet 14. In FIG. 8, reference numeral 15 is a gutter that accommodates ink droplets that do not reach the recording sheet 14.

By the way, in such an inkjet printer, if the seams (hereinafter referred to as stitching points) SP of images on the recording sheet 14 of adjacent nozzles 11 do not match accurately, overlapping printing or blank areas will occur. , it is usually necessary to match this stitching point SP.

Conventionally, as shown by the imaginary line in FIG. 8, during calibration, the drop sensor 16 is placed at a position spatially equivalent to the stitching point SP.
Detects the passing position of ink dripping by installing
A system is already known in which the above-mentioned ink droplet deflection control system is initialized based on this detection signal, and the corresponding ink droplets are caused to fly to each pixel position in the unit image area U.

However, in such an inkjet printer, even if the stitching points SP are aligned in advance, the ink droplets interact electrostatically and aerodynamically with each other, so that the ink charged to a predetermined level cannot be used. This causes a problem in that the deflection position of the drip changes slightly, and the unit image area mu is deviated from the intended deflection position (pixel position) by the amount of deflection weight.

A deflection distortion correction method for solving this problem is described in, for example, Japanese Patent Laid-Open No. 57-25971.

This uses the flight pattern of a plurality of ink droplets located in the vicinity of the front and rear of the noted ink droplet as a correction parameter. For example, as shown in FIG. A deflection distortion correction table 21 that outputs correction data for the deflection distortion of an ink droplet of interest corresponding to the flight patterns of a plurality of ink droplets, correction data vh from this deflection distortion correction table 21, and a drop sensor 16.
A deflection distortion calculation circuit 22 is used which calculates correction 1ivn of the deflection distortion of the ink droplet of interest based on the initial setting data M and A from the following formula: ``vn=MVh+AJ''.

Then, the deflection distortion correction amount Vn becomes a charging control voltage signal at a predetermined level via the amplifier 24 after being subjected to the front droplet induction correction during charging by the charging electrode 12 in the front droplet guidance correction circuit 23, for example. The voltage is applied to the charging electrode 12 to charge the ink droplet of interest to a predetermined level.

[16 Problems to be Solved by the Invention] However, in such a conventional ink droplet deflection distortion correction method, if the number of ink droplets to be referred to in order to correct deflection distortion is k, then the deflection distortion correction table 21 In order to correct the deflection distortion in each case where the reference ink droplet is printed or not, two memory capacities are required for each ink droplet of interest.

In this case, if the number of reference ink droplets is set to a small number, the memory capacity of the deflection distortion correction table 21 itself can be reduced, but the problem arises that the deflection distortion correction effect is not sufficiently exerted. Furthermore, if the number of reference ink droplets is increased in order to improve the effect of correcting deflection distortion, there is a problem in that the memory capacity of the deflection distortion correction table 21 becomes enormous.

The present invention has been made in view of the above-mentioned problems, and it is possible to correct the deflection distortion without increasing the number of reference ink droplets located in the vicinity of the front and rear of the focused ink droplet. The present invention provides a method and apparatus for correcting ink droplet deflection distortion for an inkjet printer that can sufficiently increase the effect.

[Means for Solving the Problems] In other words, the inventors of the present invention set a parameter for correcting deflection distortion that has a large influence on deflection distortion, in addition to the flight pattern of a plurality of ink droplets located in the vicinity of the front and back of an ink droplet of interest. We have devised a new ink droplet deflection distortion correction method and device that incorporates this heading.

Specifically, if there are a large number of preceding gutter droplets DQ that are not printed and head toward the gutter 15 among the ink droplets that precede the current ink droplet DO of interest, in other words, if the number of printed ink droplets Qi is small, As shown in FIG. 10, the deflection width of the unit image area U by the printing ink droplet Di of each nozzle 11! , the deflection position is kept constant and image synthesis between unit image areas 0 is performed accurately, but conversely, when the number of leading gutter MDg of the noted ink droplet DO is small, in other words, when there are many printing ink droplets Di. As shown in Figure 11,
Unit image area U formed by printing ink droplets DI of each nozzle 11
Deflection width! It was confirmed that the deflection position became smaller by Δl, and moreover, the deflection position was shifted by d toward the gutter 15 side, causing a problem in image composition between unit image areas 0.

This confirms that the gutter flow of the ink droplets toward the gutter 15 has a large influence on the flight behavior of the noted ink droplet DO, and when there is a gutter flow as shown in FIG. The printing ink droplets Di located near the gutter flow are pulled by the air flow accompanying the gutter flow and move at a relatively high speed. However, as shown in FIG. 11, when the gutter flow suddenly disappears, the gutter flow The speed of the printing ink W4D+ located near the gutter flow decreases and its deflection amount increases, while the speed of the printing ink droplet Di located far from the gutter flow increases due to the increase of the nearby printing ink droplet Qi. It is thought that the amount of deflection increases as it is pulled by the accompanying airflow, and the amount of deflection decreases.

Therefore, the inventor of the present application has proposed that the image composition of the unit image area U be performed accurately by appropriately changing the deflection amount of each printing ink droplet D1 of the unit image area U according to the number of preceding gutter droplets D (+). He came to the conclusion that this would become possible, and devised this invention.

That is, the present invention provides an inkjet printer that continuously generates ink droplets, charges the generated ink droplets, and further deflects them using an electric field to fly the ink droplets to a desired position on a recording sheet. When correcting the deflection distortion caused by electrostatic and aerodynamic interactions that a droplet receives from other ink droplets, the deflection of the focused ink droplet is determined in accordance with the flight pattern of multiple ink droplets located in the front and near the focused ink droplet. An object of the present invention is to provide an ink droplet deflection distortion correction method for an inkjet printer in which a basic correction amount of distortion is determined, and then this basic correction amount is corrected according to the number of preceding flying gutter droplets.

As shown in FIG. 1, the ink droplet deflection distortion correction device that realizes this method continuously generates ink droplets using an ink droplet generating means 4, and charges the generated ink droplets using a charging means 5. It is used in an inkjet printer that charges the ink droplet and then deflects it using an electric field at the deflection electrode 6 to fly the ink droplet to a desired position on the recording sheet 7. Based on the image data G, it is used in the vicinity of the ink droplet of interest DO. a basic correction amount setting means 1 for setting a basic correction amount for the deflection distortion of the ink droplet DO of interest in accordance with the flight pattern of a plurality of ink droplets located at the position of the ink droplet DO; gutter droplet correction setting means 2 for setting the gutter droplet correction amount for deflection distortion in DO (based on the number of preceding gutter droplets); and the basic correction gate setting means 1 and the gutter droplet correction amount. and a deflection distortion correction amount determining means 3 for correcting the basic correction amount of deflection distortion based on the output from the setting means 2 to determine the final correction amount of deflection distortion in the target ink W4Do. The band T1fi of ink drips generated based on the output from 3 is controlled.

In such technical means, basic correction amount setting means 1
As long as it is possible to extract the pixel position information, which is the flight target position of the noted ink droplet DO, and the flight pattern of the reference ink droplet from the image data, and set the basic correction amount for deflection distortion based on this, it is appropriate. You may change the design.

In this case, the design of the above-mentioned method for specifying the pixel position may be changed as appropriate, and the method for setting the basic correction amount may be determined based on the physical properties of the ink used, the ink droplet generation means 4, etc.
Although it may be set theoretically after taking into consideration the characteristics of , it is preferable to set it concretely through experiments.

The gutter droplet correction amount setting means 2 may be one in which the gutter droplet correction amount is set through experiments or the like, at least in accordance with the number of preceding gutter drops of the noted ink droplet DO. Since the degree of deflection distortion toward the target ink droplet DO differs slightly depending on the position of the preceding gutter drop, from the perspective of further improving the correction accuracy of deflection distortion, it is possible to add position information to the number of preceding gutter droplets. It is preferable to set a gutter droplet correction amount.

In this case, for the gutter drop corrector, if the parameters are for correcting the basic correction amount of deflection distortion in the deflection distortion correction amount determining means 3, the deflection width coefficient and the deflection position shift m
A combination of these can be selected as appropriate.

Furthermore, the deflection distortion correction amount determining means 3 includes at least the following:
Any device may be used as long as it determines the deflection distortion correction amount based on the outputs from the basic correction amount setting means 1 and the gutter droplet correction value setting means 2, such as data for initially setting the unit image area between each nozzle. There is no difference in adding the following.

Furthermore, from the viewpoint of more accurately correcting the deflection distortion of the ink droplet, it is preferable that the deflection distortion correction amount determining means 3 performs pre-drop guide correction or the like on the ink droplet of interest as a post-processing.

[Operation] According to the technical means described above, the basic correction amount setting means 1 sets the basic correction amount of deflection distortion corresponding to the flight pattern of a plurality of ink droplets located in the vicinity of the front and back of the noted ink droplet DO. On the other hand, the gutter droplet correction amount setting means 2 sets a gutter droplet correction interval of deflection distortion corresponding to the number of gutter droplets Do preceding the ink droplet Do of interest. Then, the deflection distortion correction amount determining means 3 determines the final correction amount of the deflection distortion based on the basic correction amount for the noted ink 100 and the gutter droplet correction value, and appropriately controls the amount of charge of the noted ink droplet DO.

At this stage, the deflection position deviations δ1 and δ2 caused by the flight pattern of the ink droplet of interest QO and the number of preceding gutter droplets are corrected, and the ink of interest W4OO is accurately deflected to the target pixel position @PO.

[Embodiment J] Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

Embodiment 1 FIG. 2 is a block diagram showing an embodiment of an ink droplet deflection distortion correcting device for an inkjet printer according to the present invention. It should be noted that the same constituent means as the conventional one are given the same reference numerals as the conventional one, and detailed explanation thereof will be omitted here.

In the same figure, reference numeral 31 indicates a pixel position tag indicating which pixel position (Pixel, No., This is a pixel register in which the pixel data is stored, and in this embodiment, the pixel data is stored, for example, from 1 to N(
In this example, the pixel positions up to N=60 are expressed as (D00000) or 1110 in a 6-bit data structure.
11).

Further, reference numeral 32 is a pattern register in which 3-inch data corresponding to the flight pattern of a plurality of ink droplets located before and after the noted ink droplet is stored based on the image data G. In this embodiment, the 3+n data is For example, as shown in FIG. 3(b), ? ↑10 ink droplets preceding the eye ink droplet (-10λ,...-5λ,...
...-1λ) and two ink droplets (1λ, 2λ) returning to the target ink droplet, non-printing information (1, 0 information)
This is 12-bit data consisting of:

Furthermore, reference numeral 33 is a deflection distortion basic correction table, and this deflection distortion basic correction table 33 uses the above-mentioned pixel data (Pixel, No., The basic correction data vh of deflection distortion to be applied to 24 is stored in a readable manner.

Further, reference numeral 34 indicates a predetermined number of ink droplet data (in this embodiment, 2
The ink droplet data read from this gutter droplet register 34 is sent to the recorder 35, and the recorder 35 stores the ink droplet data of the preceding gutter 1m (the ink droplet preceding the target ink droplet). The number of ink droplets directed toward the gutter) is detected and recorded. In this embodiment, the number of ink droplet data stored in the gutter droplet register 34 is such that the number of ink droplets existing between the ink droplet position to be charged and the gutter position is normally 100 to 300, and When considering the residual flow, even if we assume that the ink droplets that have already been collected in the gutter pass through the gutter and fly to the recording sheet, the number of ink droplets that exist from the gutter to the surface of the recording sheet is The number is set to 200 based on the fact that the number is about 100.

Furthermore, reference numeral 36 uses the preceding gutter droplet number data from the recorder 35 as an address signal to correspond to the deflection width of the ink droplet (
37 is a deflection width correction table which outputs a correction coefficient m, and reference numeral 37 is a deflection position shift correction table which outputs shift correction data a for the deflection position of an ink droplet using the preceding gutter droplet number data from the recorder 35 as an address signal. There is C.

Then, the deflection width correction table 36 and the deflection position shift correction table 37 are configured such that, as shown in FIG. It stores data a, and its memory capacity is extremely small.

Further, reference numeral 38 indicates initial setting data M and A from the drop sensor 16, basic correction data h from the deflection distortion basic correction table 33, deflection width correction coefficient m from the deflection width correction table 36, and position shift correction within lla. This is a deflection distortion correction amount calculation circuit that calculates final correction data ■n of deflection distortion based on the shift correction data a from the table 37 using the following equation (1).

Vn =mMVh + (a+A) ・−・−・−(1
) The final correction data yn from the deflection distortion correction amount calculation circuit 38 is corrected by the front droplet guidance correction circuit 23, and then becomes a charging control voltage signal which is amplified to an appropriate level via the amplifier 24, and the charging The voltage is applied to the electrode 12.

Therefore, according to the ink droplet deflection distortion correction device according to this embodiment, based on the image data G, pixel data is now stored in the Vicrel register 31, and Bin data is stored in the pattern register 32. For example, if the image data is Pixel, No.
At this time, the deflection distortion basic correction table 33 refers to the correction data Vh=-20,2 and outputs it.

On the other hand, based on the image data G, the gutter droplet register 34 stores 200 ink droplet data preceding the noted ink droplet Do (see FIG. 6). For example, as shown in FIG. Leading gutter drop D in drop data (
When the number J is C, the recorder 35 detects and records the number C of preceding gutter drops. The deflection width correction table 36 refers to the deflection width correction coefficient m corresponding to the number C of preceding gutter drops, and the deflection position shift correction table 37 refers to the deflection position shift correction data a corresponding to the number C of preceding gutter drops. and output it.

In this state, the deflection distortion correction amount calculation circuit 38 calculates the final correction data Vn of the deflection distortion for the noted ink droplet DO based on equation (1), and calculates the final correction data Vn of the deflection distortion for the noted ink droplet DO, and calculates the R1n correction data vn
The charging control m voltage of the charging electrode 12 is corrected as appropriate based on. Then, the noted ink MDO reaches the target deflection position 1! on the recording sheet 14, as shown by the solid line in FIG.
It will definitely be deflected to P (i) (Pixel, No, i).

In this regard, if the charge M voltage of the charge 1tlil12 follows the final correction data of the deflection distortion based only on the flight pattern of the plurality of inks ilD located before and after, the noted ink droplet DO is shown by the virtual line in FIG. For example, the target deflection position P (i) (Pixel, No, i)
It is confirmed that the correction according to the example is more accurate.

Embodiment 2 FIG. 7 is a block diagram showing another embodiment of the ink droplet deflection distortion correction device according to the present invention.

In the same figure, reference numeral 41 denotes a gutter droplet register that stores a predetermined number of preceding ink droplet data preceding the ink droplet of interest based on image data G, and 42 a gutter droplet register 4.
A latch circuit 43 temporarily holds the preceding ink droplet data in a state where the preceding ink droplet data stored in 1 is divided into two groups, a first group on the side close to the noted ink droplet and a second group on the side far from the noted ink droplet. A recorder 44 detects and records the number of preceding gutter droplets among the preceding ink droplet data held in the latch circuit 42, and 44 is a circuit that is synchronized with the switching timing of the data of the first group and the second loop held in the latch circuit 42. Selector to switch, 45.46
is a deflection width first correction table which is selectively connected in response to switching of the selector 44 and stores deflection width correction coefficients ml and R2 corresponding to the number of preceding gutter drops cl and c2, respectively.

Deflection width second correction tables 47 and 48 are selectively connected in response to switching of the selector 44, and are deflection positions in which deflection position shift correction data al and R2 corresponding to the number of preceding gutter drops CI and c2 are stored, respectively. Shift first correction table, deflection position shift second correction table 49, initial setting data M, A from the drop sensor 16, correction data vh% deflection width first and second correction table 45 from the deflection distortion basic correction table 33 Deflection width correction coefficient m from .46
l, R2 and deflection fQtl! Shift correction data a 1°R from shift first and second correction tables 47.48
2, the final correction data Vn of deflection distortion is calculated as follows (
This is a deflection distortion correction amount calculation circuit that calculates using equation 2).

Vn = (ml + m2) MVh + (al + a
2 +A)... (2) Other constituent means similar to those in the first embodiment are given the same reference numerals as those in the first embodiment, and detailed explanations thereof will be omitted here.

Therefore, according to the ink droplet deflection distortion correction device according to this embodiment, the basic correction data vh based on the flight pattern of a plurality of ink droplets located before and after the target ink droplet is output with reference to the deflection distortion basic correction table 33. and this data vh
is sent to the deflection distortion correction amount calculation circuit 49.

On the other hand, after the preceding ink droplet data that precedes the noted ink droplet is stored in the gutter droplet register 41, first, a first group of preceding ink droplet data on the side closer to the noted ink droplet is temporarily held in the latch circuit 42 and is stored in the recorder. 43, this recorder 43 detects and records the number C1 of preceding gutter drops from the first group, and this number C of preceding gutter drops is sent to the deflection width first correction table 45. It is supplied to the deflection position shift first correction table 47 as an address signal. Each of the tables 45 and 47 sends correction data m1 and al corresponding to the number of preceding gutter drops 01 to the deflection distortion correction amount calculation circuit 49.

Next, the second loop on the side far from the noted ink droplet of the preceding ink droplet data is held at -I by the latch circuit 42 and sent to the recorder 43, and this recorder 43 detects and records the number of preceding gutter droplets 02 from among the second loop. The number of preceding gutter drops, 02, is supplied as an address signal to the deflection width second correction table 46 and deflection position shift second correction table 48 via the selector 44. And each table 46
°48 is correction data m2. corresponding to the number of preceding gutter drops C2. Deflection distortion correction 1 for R2! It is sent to the Il calculation circuit 49.

At this stage, the deflection distortion correction amount calculation circuit 49 (
2) Perform the calculation according to the formula to obtain the final deflection distortion correction data Vn
is output, and the charging control voltage applied to the charging electrode 12 is corrected as appropriate based on this data Vn.

In the correction operation process for such deflection distortion, the number of leading gutter drops in the first group of preceding ink droplets on the side closer to the focused ink droplet is corrected, and the leading gutter droplet count in the first group of preceding ink droplets on the side far from the focused ink droplet is corrected. Since the droplet number correction is performed individually, there are differences in the positional relationship of the preceding gutter droplets with respect to the noted ink droplet (for example, r preceding gutter droplets on the side closer to the noted ink droplet and r preceding gutter droplets on the side far from the noted ink droplet). It becomes possible to finely correct the difference in deflection distortion due to r number of droplets, and accordingly, the correction of the number of preceding gutter drops can be performed with higher precision.

[Effect of the Invention J As explained above, according to the ink droplet deflection distortion correction method and device for an inkjet printer according to the present invention, ink droplet deflection distortion based on electrostatic and aerodynamic phase effects can be corrected. When performing the correction, in addition to the flight pattern of multiple ink droplets located before and after the target ink droplet, the number of preceding gutter droplets of the target in-external temperature, which has a large influence on deflection distortion, is taken into account.
This makes it possible to accurately correct the deflection distortion of ink droplets without extremely increasing the number of reference ink droplets located before and after the target ink droplet, reducing the memory capacity for storing correction data. The effect of correcting the deflection distortion of ink droplets can be improved while reducing the deflection distortion of the ink droplets.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing an ink droplet deflection distortion correction device for an inkjet printer according to the present invention, FIG. 2 is a block diagram showing a first embodiment of the ink droplet deflection distortion correction device according to the present invention, and FIG. (a) is an explanatory diagram showing an example of pixel data stored in the pixel register of Example 1,
FIG. 4B is an explanatory diagram showing an example of data stored in the pattern register of the first embodiment, FIG. 4 is an explanatory diagram showing details of the deflection distortion basic correction table used in the first embodiment, and FIG.
6 is an explanatory diagram showing the details of the deflection width correction table and the deflection position shift correction table used in Example 1. FIG. FIG. 7 is a block diagram showing a second embodiment of the ink droplet deflection distortion correction device according to the present invention, FIG. 8 is an explanatory diagram showing an example of a conventional inkjet printer, and FIG. 9 is a block diagram showing a conventional ink droplet deflection distortion correction device. A block diagram showing an example,
FIGS. 10 and 11 are explanatory diagrams showing the state of the correction effect depending on the number of preceding gutter droplets when a conventional ink droplet deflection distortion correction device is used. [Description of symbols 1 D... Ink droplet DO... Attention ink droplet G... Image data... Basic correction amount setting means 2... Gutter droplet correction amount setting means 3... Determination of deflection distortion correction color Means 4...Ink droplet generating means 5...Charging electrode 6...Deflection electrode 7...Recording sheet

Claims (1)

[Claims] 1) Continuously generate ink droplets (D), charge the generated ink droplets (D), and further deflect them by an electric field to form ink droplets (D).
In an inkjet printer that flies ink droplets (D) to a desired position on a recording sheet (1), flying ink droplets (D)
) when correcting the deflection distortion due to electrostatic and aerodynamic interactions that the ink droplet (D) receives from other ink droplets (D). The notable ink droplet (D
An ink droplet deflection distortion correction method for an inkjet printer, characterized in that a basic correction amount for the deflection distortion of 0) is determined, and then this basic correction amount is corrected according to the number of preceding flying gutter droplets. 2) Continuously generate ink droplets (D), charge the generated ink droplets (D), and deflect them by an electric field to form ink droplets (
An ink droplet deflection distortion correction device used in an inkjet printer that flies an ink droplet D) to a desired position on a recording sheet (7), the ink droplet being positioned near the front and back of a noted ink droplet (D0) based on image data (G). a basic correction amount setting means (1) for setting a basic correction amount for deflection distortion of a noted ink droplet (D0) corresponding to a flight pattern of a plurality of ink droplets (D);
G) Gutter droplet correction amount setting that calculates the number of preceding gutter drops of the noted ink droplet (D0) based on the number of preceding gutter drops, and sets the gutter droplet correction amount for the deflection distortion of the noted ink droplet (D0) based on this number of preceding gutter droplets. final correction of the deflection distortion in the ink droplet of interest by correcting the basic correction amount of the deflection distortion based on the outputs from the means (2) and the basic correction amount setting means (1) and the gutter droplet correction amount setting means (2); and a deflection distortion correction amount determining means (3) for determining the amount, and the amount of charge of the generated ink droplet (D) is controlled based on the output from the deflection distortion correction amount determining means (3). An ink droplet deflection distortion correction device for an inkjet printer, characterized in that: