JP7026099B2 - Actuator element - Google Patents

Description

The present art generally relates to devices and methods for reducing visible artifacts that occur when adjacent actuator elements are misaligned.

Generally speaking, a droplet depositor, eg, an inkjet printer, prints dots by ejecting droplets of liquid (eg, ink) onto a receiving medium. Such a droplet deposition device typically comprises at least one droplet deposition head with a nozzle array. The nozzle array comprises multiple nozzles, each of which is configured to eject a droplet of fluid (eg, ink) in response to a command signal received from a control circuit to reproduce an image on a receiving medium. To.

Typically, the droplet depositor can divide the image (or image swath) into several sub-images. Each sub-image can be printed by a droplet deposition head that passes over the receiving medium multiple times to reproduce each sub-image on the receiving medium. Alternatively, each sub-image may be printed by a plurality of droplet deposition heads located at different positions with respect to the receiving medium, and each droplet deposition head may have a role of printing a specific sub-image. can. In this latter case, each droplet deposition head can remain in a fixed position or pass over the receiving medium multiple times.

Droplet depositors with multiple droplet deposition heads (each with one or more nozzle arrays) and / or multiple nozzle arrays usually have the nozzle array along the medium feed axis (or droplet deposition). Manufactured to be placed parallel (in the direction of) but off-center to each other. This allows the nozzle array to cover adjacent swaths. Such placements often have alignment problems that result in visible defects or artifacts in the printed image at the point where adjacent swaths meet (ie, along the seams between adjacent swaths). ing. Visible defects typically appear in printed images as bright or dark bands that are easily noticed by the human eye. However, in a separate actuator element within the droplet deposition device or within a separate droplet deposition head to limit misalignment and reduce or avoid visible defects in the printed image. Placing the placed nozzle array is time consuming and costly.

Applicants recognize the need for improved techniques to reduce or avoid visible defects that occur when adjacent nozzle arrays are misaligned.

Aspects of the art are described in the appended claims.

These techniques are illustrated in the accompanying drawings as examples.

FIG. 1a is a schematic diagram of two overlapping actuator elements, each of which has a nozzle array. FIG. 1b is a schematic diagram of two overlapping droplet deposition heads. FIG. 2a is a schematic diagram of a nozzle array of actuator elements, the nozzle array comprising a first portion having a constant nozzle pitch and a second portion having a variable nozzle pitch. FIG. 2b shows a nozzle array of actuator elements in which the nozzle array comprises a first portion having a constant nozzle pitch, a second portion having a variable nozzle pitch, and a third portion having a further variable nozzle pitch. It is a schematic diagram. FIG. 3a illustrates a single row of nozzle arrays of FIG. 2a. FIG. 3b illustrates how two single rows of adjacent nozzle arrays of the type shown in FIG. 2a are arranged and overlapped. FIG. 4a illustrates a single row of nozzle arrays of FIG. 2b. FIG. 4b illustrates how two single rows of adjacent nozzle plates of the type shown in FIG. 2b are arranged and overlapped. FIG. 5 is a schematic diagram showing how a fluid can be deposited using overlapping actuator elements. FIG. 6a is a schematic diagram of a nozzle array of actuator elements, the array comprising a plurality of rows of nozzles. FIG. 6b illustrates the arrangement of the nozzle rows in the nozzle array of FIG. 6a. FIG. 7 illustrates a method of depositing a fluid using overlapping actuator elements with multiple rows of nozzles. FIG. 8 illustrates a method of depositing a first fluid and a second fluid using overlapping actuator elements with multiple rows of nozzles. FIG. 9a illustrates the misalignment of the overlapping actuator elements. FIG. 9b illustrates a method for compensating for the misalignment shown in FIG. 9a. FIG. 10a shows a (default) constant nozzle pitch between nozzles in an overlapping region of two overlapping actuator elements. FIG. 10b shows how difficult it is to find a pair of well-aligned nozzles for a 1200 dpi actuator element with a constant nozzle pitch in FIG. 10a as the misalignment between overlapping actuator elements increases. Indicates. FIG. 10c shows how the percentage of absolute pitch jumps at the switching points between the actuator elements of FIG. 10a changes as a function of misalignment. FIG. 10d shows the same information as in FIG. 10b, but shows information about an actuator element of 600 dpi. FIG. 10e shows the same information as in FIG. 10c, but shows information about an actuator element of 600 dpi. FIG. 11a shows two overlapping actuator elements with variable nozzle pitches defined by a sine function. FIG. 11b shows how difficult it is to find a pair of well-aligned nozzles for a 1200 dpi actuator element with a variable nozzle pitch of the sine function of FIG. 11a as the misalignment between overlapping actuator elements increases. Indicates whether it will be. FIG. 11c shows how the percentage of absolute pitch jumps at the switching points between the actuator elements of FIG. 11a changes as a function of misalignment. FIG. 11d shows the same information as 1b, but shows information about an actuator element of 600 dpi. FIG. 11e shows the same information as 1c, but shows information about an actuator element of 600 dpi. FIG. 12a shows two overlapping actuator elements, one actuator element having a first variable nozzle pitch and another actuator element having a second variable nozzle pitch. FIG. 12b shows how it becomes more difficult to find a pair of well-aligned nozzles for a 1200 dpi actuator element with the variable nozzle pitch of FIG. 12a as the misalignment between overlapping actuator elements increases. Is shown. FIG. 12c shows how the percentage of absolute pitch jumps at the switching points between the actuator elements of FIG. 12a changes as a function of misalignment. FIG. 12d shows the same information as in FIG. 12b, but shows information about an actuator element of 600 dpi. FIG. 12e shows the same information as in FIG. 12c, but shows information about an actuator element of 600 dpi. FIG. 13 is a flowchart showing a process for calibrating the droplet deposition apparatus.

As briefly mentioned above, a droplet deposition device (eg, a printer) typically comprises at least one droplet deposition head with at least one actuator element. One or each actuator element or each actuator element comprises a nozzle array having a plurality of nozzles. The actuator element may include a nozzle plate, which is a layer containing the nozzles. In embodiments, the actuator element may be a die stack comprising a plurality of actuators (and thus a plurality of nozzle arrays) and a single nozzle plate comprising nozzles for all the actuators of the actuator element. In either case, one or each nozzle array of actuator elements comprises multiple nozzles arranged in one or more rows, where each nozzle responds to a command signal received from the control circuit. For example, it is configured to eject a droplet of ink) to reproduce an image on a receiving medium. Two or more droplet deposition heads, or two or more actuators within a droplet deposition head, typically to form a droplet deposition device with a long droplet deposition head (eg, for industrial printers). The element can be arranged along the axis of the device. Each droplet deposition head (and / or each actuator element) can include at least one nozzle array. The droplet deposition head or actuator element is arranged along the axis in a staggered arrangement such that adjacent head / actuator elements partially overlap each other. In this arrangement, part or all of the nozzles of one head / actuator element is used to print part of the image, another part of the image uses nozzles of another adjacent head / actuator element, etc. Is printed. In the overlapping area, the printing process switches between adjacent head / actuator elements. The point at which the printing process switches is referred to herein as a "switch point" or "switchover point" or "transition point".

The overlapping arrangement results in inaccuracies or visible artifacts in the seams (ie, overlapping areas) between the sub-images printed by each one of the printhead / actuator elements. For example, visible artifacts are darker lines (because the overlapping nozzles are too close together, i.e. closer to each other than the nominal nozzle spacing), or (overlapping nozzles are too far apart, i.e., nominal nozzle spacing). Because it is farther away than, it becomes a brighter line. Visible artifacts can be caused by misalignment between adjacent head / actuator elements in overlapping areas.

In a droplet deposition head / actuator element where the nozzle pitch (ie, the distance between centers between adjacent nozzles) is constant, the nozzle of one actuator element / head is with the nozzles of the adjacent actuator element / head in the overlapping area. Almost aligned. It is possible to make fine adjustments to the overlapping actuator elements / heads in order to accurately align the nozzles within the overlapping area, and by switching from one actuator element / head to an adjacent actuator element / head, it is visually possible. Does not produce new artifacts (or produces minimal artifacts). For example, the heads can be mounted into the droplet deposition device and then moved relative to each other, and / or the actuator elements can be more accurately fixed within the droplet deposition head during manufacturing. If high precision is required, these processes can be very expensive. The head-to-head precision alignment process must also be repeated each time the head is replaced in the device (eg, if the element fails).

The human eye is sensitive to gradual changes in optical density and can detect small defects in printed images, or even artifacts, caused by slight misalignment between nozzle rows in overlapping areas. The print medium allows the human eye to detect misalignments or imperfections that form gradual changes along print lines about 5 μm wide. In graphics printing and / or when using UV curable inks, the fluid / ink never spreads on the medium, resulting in a slight "bleeding" and otherwise defects to the human eye. May reduce the appearance.

In general, embodiments of the present invention provide devices and methods for minimizing or reducing the effects of misalignment of actuator elements (and thus nozzle arrays). In particular, the present art provides an actuator element comprising at least one array of nozzles. In one or each array, the array nozzles are located in at least two parts: the first part where the nozzles in one row of the array are separated at a constant nozzle pitch, and one row in the array. The second part where the nozzles are separated by a variable nozzle pitch. The variable portion of the nozzle array of the first actuator element is provided in the droplet deposition head containing the plurality of actuator elements, or when it is provided in the adjacent droplet deposition head, the second actuator element. It is arranged so as to overlap the variable part of the nozzle array of. At the same time, the variable portion of the overlapping nozzle arrays provides a mechanism / system such as a vernier scale, increasing the likelihood of finding the most suitable nozzle pair that defines the switching point between the overlapping nozzle arrays. As described in more detail below, the most suitable nozzle pair may or may be the best aligned (ie, minimal misalignment between them) nozzle pair. It may be a pair of nozzles or a combination of both that results in the minimum pitch jump at a point (ie, points where the pitches on either side of the switching point are as equal as possible).

As used herein, the term "variable nozzle pitch" is meant to mean that the nozzle pitch between adjacent nozzles in a particular portion of the nozzle array (ie, the variable pitch portion) changes with the distance of that portion. Used for. The term is not used to mean that the nozzle pitch changes dynamically when the actuator element is used, but the position of each nozzle in the nozzle array is fixed during the manufacture of the actuator element. Rather, the term is used to mean that the nozzle pitch in the variable pitch portion of the nozzle array will be a non-uniform nozzle pitch between successive nozzles. For example, the pitch between the first pair of nozzles in the variable pitch portion can be Δ, the pitch between the next pair of nozzles can be 2Δ, the pitch between the next pair of nozzles can be 3Δ, and so on. .. The term "variable nozzle pitch" is not limited to increasing or decreasing nozzle pitch, and can be defined by a linear or non-linear function that depends on the distance or nozzle position / number of variable pitch portions. ..

At the time of use, a plurality of actuator elements of the type described herein are provided so as to be arranged in an overlapping manner within the droplet deposition head or between adjacent droplet deposition heads. In order to minimize or eliminate visible artifacts in the overlapping area between adjacent actuator elements, one is selected from each actuator element in the nozzle pair, overlapping area, and the selection is adjacent from one actuator element. Determines where the switch to the actuator element is made during the droplet ejection process (ie, determines the switching point during the droplet ejection process). The selected nozzle pair is the best (or most preferably) aligned nozzle and / or the minimum pitch change or optical density (to the human eye) on either side of the switching point. It can be a pair of nozzles that preferably results in undetectable changes, and switching is done with this pair of aligned nozzles. By disabling one of these pair of nozzles, both nozzles will not print the same part of the image. Up to the first nozzle in a pair of nozzles (or until then, if available), using the nozzle of one actuator element, and following (or using) the second nozzle in a pair of nozzles. Droplets are ejected using the nozzles of adjacent actuator elements (which will follow if possible).

The advantage of this technique is that it can compensate for misalignment between adjacent actuator elements without the need for an expensive and time-consuming alignment process. In particular, adjacent actuator elements do not need to be carefully and finely aligned to compensate for misalignment, instead the droplet ejection switches between the first and second actuator elements. A suitable pair of nozzles to determine (one nozzle from the overlapping portion of the nozzle array of each actuator element) is selected. (As described above and, as described in more detail below, a suitable pair of nozzles has the least pitch change on either side of the best aligned nozzle and / or switching point, or It can be a nozzle that results in a change in color density that is undetectable to the human eye.) The variable nozzle pitch of each nozzle array of each actuator element increases the chances of finding a well-aligned pair of nozzles. Switching between nozzle pitches of adjacent nozzles in the variable portion of each nozzle array is a gradual pitch change from nozzle to nozzle (or pair of nozzles). The variable pitch within the variable portion of each nozzle array makes it possible to compensate for large misalignments between overlapping actuator elements, while gradual changes in the dot spacing between dots printed from the relevant nozzles in the switching area. Reduce the size of.

A first aspect of the invention provides an actuator element with a plurality of nozzles arranged in at least one nozzle array, the nozzle array being: a first portion comprising a first subset of the plurality of nozzles. , A first subset of nozzles are located along the nozzle array axis and have a constant nozzle pitch that is constant between the first end of the first part and the second end of the first part. Separated by, the first part; the second part with a second subset of nozzles, the second subset of nozzles arranged along the nozzle array axis, the second Separated by a variable nozzle pitch that varies between the first end of the part and the second end of the second part, the first end of the second part is the second of the first part. It comprises a second portion that abuts on the end;

In a related aspect of the art, a plurality of nozzles arranged in an array; a first portion comprising a first subset of the plurality of nozzles, wherein the first subset of nozzles is along the nozzle plate axis. And separated from the first end of the first part and the second end of the first part at a constant nozzle pitch; A second portion comprising a second subset of nozzles, the second subset of nozzles arranged along the nozzle plate axis, the first end of the second portion and the second portion of the second portion. With a second portion, separated by a variable nozzle pitch that varies from and to the second end, the first end of the second portion abuts the second end of the first portion; , Nozzle plates are provided.

In a related aspect of the art, a plurality of nozzles; a first portion comprising a first subset of the plurality of nozzles, wherein the first subset of nozzles is arranged along the nozzle array axis and the first. A second subset of multiple nozzles, separated by a constant nozzle pitch between the first end of the part and the second end of the first part. A second subset of the nozzles is arranged along the nozzle array axis with a first end of the second part and a second end of the second part. Nozzle arrays are provided that are separated by a variable nozzle pitch that varies between, with a second portion; the first end of the second portion abuts the second end of the first portion. Nozzle.

A second aspect of the art provides a droplet deposition head with at least one actuator element as described herein.

A third aspect of the invention provides a droplet deposition head comprising at least two actuator elements described herein, the actuator element being along the axis of the droplet deposition head (or of the droplet deposition head). It is provided in a staggered arrangement (in a plane) and adjacent actuator elements partially overlap.

A fourth aspect of the present technology is a droplet ejection head including a first actuator element and a second actuator element, in which the actuator elements deposit droplets in a staggered arrangement having overlapping portions between the actuator elements. Provided in the plane of the head, each actuator element is a first portion comprising a plurality of nozzles arranged in at least one nozzle array; a first subset of the nozzles of the nozzle array; A first subset is placed along the nozzle array axis and separated by a constant nozzle pitch between the first end of the first part and the second end of the first part. The first part; the second part comprising a second subset of the nozzles of the nozzle array, the second subset of the nozzles being arranged along the nozzle array axis and the second part. Separated by a variable nozzle pitch that varies between the first end and the second end of the second part, the first end of the second part is the second end of the first part. With a second portion abutting on; a third portion comprising a third subset of multiple nozzles of the nozzle array, the third subset of nozzles being arranged along the nozzle array axis, the third. Separated by a further variable nozzle pitch that varies from the first end of the portion to the second end of the third portion, the second end of the third portion is the first end of the first portion. A droplet ejection head with a third portion and; that abuts on the portion is provided.

A fifth aspect of the invention provides a method of activating the droplet deposition apparatus described herein: a first actuator element in the plane of (or on its axis) the droplet deposition head. (Along) to be placed in the droplet depositor; the droplets so that the second part of the nozzle array of the first actuator element overlaps at least partially with the third part of the second actuator element. It comprises arranging the second actuator element in the depositing device in a staggered arrangement with respect to the first actuator element in the plane of the droplet deposition head.

The following features apply equally to each of the above embodiments.

In embodiments, the variable nozzle pitch of the nozzle array of the actuator element is defined by a first function that varies with the distance between the first end of the second part and the second end of the second part. Will be done.

In the embodiment, the variable nozzle pitch of the second portion gradually changes with the distance between the first end and the second end of the second portion as the distance from the constant nozzle pitch is increased. The variable nozzle pitch may gradually increase or decrease as the distance from a constant nozzle pitch increases. The variable nozzle pitch of the second part gradually changes (that is, increases or decreases) at the first end of the second part as the distance from the constant nozzle pitch increases, and the variable nozzle pitch becomes constant. As you move away from the nozzle pitch of, it changes with the distance towards the second end of the second part. In other words, the farther the nozzles of the second part are from the first end of the second part, the more the pitch between the nozzles is different from the constant nozzle pitch.

In certain embodiments, the variable nozzle pitch of the second portion may be substantially the same (or the same) as the constant nozzle pitch at the first end of the second portion, and is a constant nozzle. As you move away from the pitch, it may gradually change with the distance towards the second end of the second part. In other words, the pitch between the pairs of nozzles in the second part closest to the first part is similar to or equal to the constant nozzle pitch in the first part. Therefore, the variable nozzle pitch at the first end of the second portion may be similar to or equal to a constant nozzle pitch, then gradually with distance towards the second end as it moves away from this pitch. Increase or decrease.

In embodiments, the first function defining the variable nozzle pitch may be a linear function. The linear function can be, for example, equal to a constant multiplied by a distance away from one end of the variable pitch portion (or nozzle position). A linear function can be defined in terms of nozzle position along the variable nozzle pitch portion of the nozzle array of the actuator element, and the first nozzle can be defined as the nozzle closest to the constant nozzle pitch portion of the nozzle array. can. For example, the pitch function P _n can be defined as P _n = P1 + (a ± Δn), where n is the nozzle position (eg, the distance from one end of the variable pitch portion) or (the variable pitch portion). It is a nozzle number (counted from one end), Δ is a fixed value, P1 is a nominal pitch (for example, a constant nozzle pitch in the first part), and a is an arbitrary correction value. Thus, the variable nozzle pitch in this example is in constant quantities between adjacent nozzles, i.e., between the first pair (defined as the first pair closest to the constant nozzle pitch portion of the nozzle array). It decreases from 1Δ pitch to nΔ, such as 2Δ pitch between the second pair and 3Δ pitch between the third pair.

In embodiments, the first function that defines the variable nozzle pitch is a non-linear function. The non-linear function is a nozzle along a variable nozzle pitch portion of the nozzle array or along a variable nozzle pitch portion of the nozzle array (the first nozzle may be defined as the nozzle closest to a constant nozzle pitch portion of the nozzle array). It may depend on the position. The non-linear function can be any non-linear function, such as a sine function or an exponential function. For example, the pitch function P _n can be defined as P _n = P1 + (a ± bsin (x _n )), where 0.5π <x <π, where x is the variable nozzle pitch of the nozzle array. The distance along the portion), a is an arbitrary correction value, and b is a fixed multiplier. In another example, the pitch function can be defined as P _n = P1 + ce- ^dx , where c and d are fixed multipliers and x is the distance along the variable nozzle pitch portion of the nozzle array. It will be appreciated that these are merely exemplary and exemplary functions and are non-limiting.

In a preferred embodiment of the actuator element, the nozzle array comprises a third portion comprising a third subset of nozzles, the third subset of nozzles being disposed along the nozzle array axis and the third portion. It is separated by a further variable nozzle pitch that changes from the first end of the to the second end of the third part.

The second end of the third part abuts the first end of the first part and the second end of the first part abuts the first end of the second part. In addition, the first portion of the nozzle array is provided between the second portion and the third portion. That is, the first portion (constant nozzle pitch portion) is sandwiched between the second portion and the third portion (two variable nozzle pitch portions).

The further variable nozzle pitch of the third part is defined by a second function that changes with the distance between the first end of the third part and the second end of the third part.

In an embodiment, the further variable nozzle pitch of the third portion gradually changes with the distance between the first and second ends of the third portion as it moves away from a constant nozzle pitch. .. The variable nozzle pitch may gradually increase or decrease as the distance from a constant nozzle pitch increases. The variable nozzle pitch of the third part gradually changes (that is, increases or decreases) at the second end of the third part as the distance from the constant nozzle pitch increases, and the variable nozzle pitch becomes constant. As you move away from the nozzle pitch of, it changes with the distance towards the first end of the third part. In other words, the farther the nozzle of the third portion is from the second end of the third portion, the more the pitch between the nozzles differs from the constant nozzle pitch.

In an embodiment, the further variable nozzle pitch of the third portion is substantially the same (or the same) as the constant nozzle pitch at the second end of the third portion and departs from the constant nozzle pitch. As it goes, it gradually changes with the distance towards the first end of the third part. Thus, the variable nozzle pitch at the second end of the third portion is similar to or equal to a constant nozzle pitch, and with distance towards the first end of the third portion as it moves away from this pitch. Gradually increase or decrease.

In embodiments, the second function defining additional variable nozzle pitches may be equal to the first function. For example, both the first function and the second function can be defined as P _n = P1 + (a ± Δn). In other embodiments, the second function can be the same type of function as the first function (eg, linear function, sine function, exponential function, etc.), but with different multipliers and / or correction values. obtain. For example, the first function can be P _n = P1 + (a ± 3n), while the second function can be _Pn = P1 + (a ± 2.5n). In other embodiments, the first and second functions may be different, for example, one can be a linear function and the other a non-linear function, or one can be a sine function and the other an exponential function. It may be possible, etc. The function chosen to define the variable nozzle pitch is determined using computer modeling or simulation, and how likely it is to use that function to find the best aligned nozzle pair. Is shown.

In embodiments, the variable nozzle pitch of the second portion is similar to a constant nozzle pitch at the first end of the second portion, and as the distance from the constant nozzle pitch increases, the second portion of the second portion Gradually increases with distance towards the end; the further variable nozzle pitch of the third part is similar to the constant nozzle pitch at the second end of the third part, as it moves away from the constant nozzle pitch. , Gradually decreases with the distance towards the first end of the third part.

In embodiments, the variable nozzle pitch of the second portion may gradually increase with the distance between the first and second ends of the second portion as it moves away from a constant nozzle pitch. Yes; the further variable nozzle pitch of the third part can gradually decrease with the distance between the first and second ends of the third part as it moves away from a constant nozzle pitch. can. Additional or alternative, the variable nozzle pitch of the second portion can be similar to a constant nozzle pitch at the first end of the second portion, and as the distance from the constant nozzle pitch increases, the first Gradually increases with distance towards the second end of the second part; the further variable nozzle pitch of the third part is similar to the constant nozzle pitch at the second end of the third part. And gradually decrease with distance towards the first end of the third part as it moves away from a constant nozzle pitch. In either case, looking at the entire nozzle array, the nozzle pitch starts at the first value at one end of the nozzle array (ie, the first end of the third part) and gradually moves towards the second value. Increases to a second value at a distance (ie, in the first part), and a third value at another end of the nozzle array (ie, the second end of the second part). Gradually increasing towards, the nozzle pitch increases approximately over the length of the nozzle array.

In an embodiment, the nozzle array comprises at least one row extending across the nozzle array, and the plurality of nozzles in the nozzle array are arranged in at least a row. At least one row can extend across each portion of the nozzle array. In an embodiment, the nozzle array comprises a plurality of staggered rows extending across the nozzle array, with the plurality of nozzles arranged in the plurality of staggered rows. Each row of multiple staggered rows can extend across each portion of the nozzle array.

In embodiments, at least two actuator elements of the type described herein (ie, a first actuator element and a second actuator element) are provided on the droplet deposition head. Various alternative fluids can be deposited by the droplet deposition head. For example, the droplet deposition head moves to a medium that receives the droplets, such as a piece of paper or card, fabric, foil, or other receiving medium, such as ceramic tiles or molded articles (eg, cans, bottles, etc.). Inkjet printing applications that can eject droplets of ink (the droplet deposition head may be an inkjet printhead, more specifically a drop-on-demand inkjet printhead). The image can be formed as in the case of. Therefore, the term "droplet deposition head" is used interchangeably herein with the term "inkjet printhead" or "printhead" without loss of generality. Similarly, the term "fluid" is used interchangeably herein with the term "ink" without loss of generality. The term "ink ejection nozzle" is used interchangeably herein with "nozzle".

Alternatively, a droplet of fluid can be used to build the structure. For example, an electrically active fluid can deposit on a receiving medium, such as a circuit board, to allow prototyping of electrical devices. In another example, the polymer-containing fluid or molten polymer may be deposited in successive layers to produce a prototype model of the object (as in 3D printing). In another embodiment, the droplet deposition head can be configured to deposit droplets of a solution containing a biological or chemical substance onto a receiving medium such as a microarray. Droplet deposition heads suitable for such alternative fluids may generally be similar in structure to the printhead and / or may be configured to handle the particular fluid in question. The droplet deposition head described in the disclosure below can be a drop-on-demand titration head deposition head. In such a head, the pattern of the ejected droplets can vary depending on the input data provided to the head.

In embodiments, the first and second actuator elements are such that the second portion of the nozzle array of the first actuator element overlaps at least partially with the third portion of the nozzle array of the second actuator element. It can be placed in the plane of the droplet deposition head. The plane on which the actuator element is placed can be substantially perpendicular to the direction of droplet ejection from the droplet deposition head.

In an embodiment of the droplet deposition head, the variable nozzle pitch of the second portion of each nozzle array of each actuator element increases from a constant nozzle pitch to the first and second ends of the second portion. It gradually changes with the distance between the parts.

In the embodiment, in the embodiment of the droplet deposition head, the further variable nozzle pitch of the third portion of each nozzle array of each actuator element increases from a constant nozzle pitch to the first end of the third portion. It gradually changes with the distance to the club.

In the embodiment, the constant nozzle pitch of the nozzle array of the first actuator element may be different from the constant nozzle pitch of the nozzle array of the second actuator element. This can be useful, for example, to allow the droplet deposition head to adjust the color density when depositing droplets of different colors.

Generally speaking, the constant nozzle pitch of the nozzle array of the actuator element may differ between the actuator elements and may depend on the resolution of the droplet deposition head in which the actuator element is used. For example, a high resolution droplet deposition head may require actuator elements in which the nozzles are close to each other so that a constant nozzle pitch is small, while a lower resolution droplet deposition head may require an actuator. The nozzles of the elements can be further separated by a larger constant nozzle pitch between them. The variable nozzle pitch (and further variable nozzle pitch if a third portion is present) gradually changes as it moves away from a constant nozzle pitch, and thus may vary in magnitude between actuator elements.

In an embodiment of the droplet deposition head, the nozzle array of each actuator element comprises a plurality of staggered rows extending across each nozzle array, and the plurality of nozzles of each nozzle array have a plurality of staggered rows. Have been placed.

In embodiments, the droplet deposition head may include a plurality of fluid chambers for fluid communication with a plurality of nozzles in each nozzle array. In embodiments, a pair of staggered rows on each nozzle array communicates with a subset of fluid chambers.

In an embodiment, operating a droplet deposition head comprising a first actuator element and a second actuator element selects a first nozzle from a second portion of the nozzle array of the first actuator element. And selecting a second nozzle from the third portion of the nozzle array of the second actuator element, the first nozzle and the second nozzle selected are suitably aligned nozzles. Form a pair of. The suitably aligned nozzle pair may be substantially exactly aligned, or may be the best aligned nozzle pair within the overlap between the actuator elements. In embodiments, the nozzle pair is a nozzle that is best aligned and / or has minimal pitch change on either side of the switching point (or pitch change that is small enough to be invisible to the human eye). be able to. The pair of nozzles selected defines the point at which the droplet ejection switches from the first actuator element to the second actuator element at the overlapping portion.

As mentioned above, one of each actuator element in the nozzle pair, overlapping area is selected to minimize or eliminate visible artifacts arising from the overlapping area between adjacent actuator elements in the droplet depositor. The selection determines where the switch from one actuator element to the adjacent actuator element occurs during the droplet ejection process. The selected nozzle pair is usually best aligned and / or at both sides of the switching point, with a pitch change that is minimal (or small enough to be invisible to the human eye). Change) Nozzles, switching is done with this pair of aligned nozzles. By disabling one of these pair of nozzles, both nozzles will not print the same part of the image. Up to the first nozzle in a pair of nozzles (or until then, if available), using the nozzle of one actuator element, and following (or using) the second nozzle in a pair of nozzles. Droplets are ejected using the nozzles of adjacent actuator elements (which will follow if possible). Therefore, unselected invalid nozzles within the variable pitch portion of the overlapping actuator elements are not used in the droplet ejection process.

The actuator element can include a nozzle array with 355 nozzles in each row and can include four such rows of nozzles. The variable pitch portion of each nozzle array may be relatively small compared to the constant nozzle pitch portion of each nozzle array. For example, one or each variable pitch section can be equipped with 14 nozzles in each row (ie, 56 nozzles in the overlapping region), which is about 4% of the nozzles in the row. Therefore, a nozzle array having one or more variable pitch portions can reduce the occurrence of artifacts in overlapping regions between actuator elements without significantly reducing the number of nozzles in the nozzle array. That is, the nozzle array described herein advantageously reduces or eliminates visually detectable artifacts that occur in overlapping areas between actuator elements without significantly increasing the number of potentially unwanted nozzles. Can be done. The unwanted nozzle is a variable pitch portion nozzle that is not used once a suitable nozzle pair for the switching point is selected.

Choosing the first and second nozzles has the smallest misalignment value, i.e., the first nozzle and the first nozzle and are aligned more closely than the other nozzle pairs. It may include selecting a second nozzle. Additional or alternative, choosing a first nozzle and a second nozzle results in a minimum pitch jump at the switching point between the first actuator element and the second actuator element. It may include selecting a nozzle and a second nozzle. Preferably, the nozzle selected is one that has the smallest misalignment value and results in the smallest pitch jump at the switching point. Since the functions that define the variable pitch of the overlapping variable pitch portions of the nozzle array can be different, pitch jumps (or pitch changes) can occur at the switching points. For example, in overlapping regions, the variable pitch of one nozzle array can result in a continuous increase in distance (n * 0.036) μm between adjacent nozzles in one row (where n * 0.036). Is the number / position of nozzles or the distance of nozzles from a particular end of the variable pitch portion). On the other hand, in other nozzle arrays, variable pitch can result in a continuous increase in distance (n * 0.05) μm between adjacent nozzles in a row. As a result, the selected nozzles may be aligned or close to each other at the switching point, but there can be a large difference in pitch on both sides of the switching point. White lines or gaps may appear during droplet deposition if the pitch on one side of the switching point is sufficiently higher than the pitch on the other side of the switching point. Similarly, dark lines may appear during droplet deposition if the pitch on one side of the switching point is sufficiently smaller than the pitch on the other side of the switching point. Therefore, it can be advantageous to find a pair of nozzles that meet or balance both the requirement to have a minimum misalignment value at the switching point and the requirement to minimize pitch jumps.

In embodiments, activating the droplet deposition head disables one of a pair of aligned nozzles, the first nozzle and the second nozzle, and from the first nozzle selected. Disabling the nozzle of the second part extending towards the second end of the second part and from the selected second nozzle towards the first end of the third part Includes disabling the nozzle in the third part of the extension. For example, the first nozzle may be disabled and the droplet deposition process continues from the aligned pair of second nozzles. Alternatively, the first nozzle may be enabled and the droplet deposition process continues from the nozzle adjacent to the aligned pair of second nozzles.

In an embodiment, activating the droplet deposition head deposits fluid from the nozzles of the nozzle array of the first actuator element and from the nozzles of the nozzle array of the second actuator element, except for the disabled nozzles. Including controlling the droplet deposition device so as to. In embodiments, the droplet deposition head can be a printhead configured to print in a single color (eg, black). In this case, the fluid deposited from each actuator element is the same color.

In embodiments, the droplet deposition head can be configured to operate in multiple modes. For example, the droplet deposition head can be configured to operate in the first mode of the first resolution and in the second mode of the second resolution, where the second resolution is the first resolution. Can be a multiple of. The first resolution can be, for example, 600 dpi (dots per inch), and the second resolution can be, for example, 1200 dpi. The resolution may depend on the number of nozzles on each actuator element. The droplet deposition head, which can operate in multiple modes, can switch between different modes for different droplet deposition operations. As an example, at a resolution of 1200 dpi, each row of nozzles in the nozzle array of actuator elements can be used for droplet deposition operations, while at a resolution of 600 dpi, some of these rows are disabled. .. For example, in 600 dpi mode, alternating columns or alternating pairs of columns can be disabled. This means that if the droplet deposition heads are operated in different modes, the best aligned nozzle pairs within the overlapping area may be different. Therefore, it may be necessary to calibrate the droplet deposition head for each mode of operation in order to select a suitable pair of nozzles for each mode of operation. Nozzle pairs may be the same or different between operating modes.

Therefore, in embodiments where the droplet deposition head is configured to operate in the first mode at the first resolution and in the second mode at the second resolution, the second resolution is the first resolution. The method is, in the first mode, to select the first nozzle from the second part of the nozzle array of the first actuator element, and the third of the nozzle array of the second actuator element. By selecting a second nozzle from the portion, the selected first and second nozzles form the first pair of nozzles that are suitably aligned for the first mode. , Selecting and, in the second mode, selecting the third nozzle from the second part of the nozzle array of the first actuator element, and from the third part of the nozzle array of the second actuator element. By selecting a fourth nozzle, the selected third and fourth nozzles form a pair of second nozzles that are suitably aligned for the second mode, selection. And further include. The first pair of nozzles may be the same as or different from the second pair of nozzles.

Alternatively, the droplet deposition head can deposit a plurality of different fluids. For example, in an embodiment where the droplet deposition head is a printhead capable of printing multiple colors, a row of nozzles in each nozzle array of each actuator element is configured to deposit a fluid droplet of one color. , Another row of nozzles may be configured to deposit fluid droplets of different colors, and so on. Therefore, in the embodiment, at least one row in each nozzle array of the first actuator element and the second actuator element is configured to deposit the first fluid, the first actuator element and the second. At least one row in each nozzle array of actuator elements is configured to deposit a second fluid, and the method is from a row configured to deposit a first fluid of the first actuator element. The first selected is to select the first nozzle in the second part of the nozzle array and to select the second nozzle in the third part of the nozzle array of the second actuator element. The first nozzle and the second nozzle form the first pair of nozzles that are suitably aligned; the first actuator is from a row configured to deposit the second fluid. It is selected by selecting the third nozzle in the second part of the nozzle array of the element and by selecting the fourth nozzle in the third part of the nozzle array of the second actuator element. The third and fourth nozzles include selecting, forming a second pair of appropriately aligned nozzles.

In this multi-fluid actuation mode, actuating the droplet deposition head disables one of the first and second nozzles in a pair of first aligned nozzles; A second extending from the selected first nozzle towards the second end of the second portion in a row configured to deposit the first fluid in the nozzle array of the actuator elements of. Disabling the nozzle of the part; the first of the third part from the second nozzle selected in the row configured to deposit the first fluid in the nozzle array of the second actuator element. Disabling the nozzle of the third part extending towards the end of the; and disabling one of the third and fourth nozzles in a pair of second aligned nozzles. And; in a row configured to deposit a second fluid in the nozzle array of the first actuator element, extending from the selected third nozzle towards the second end of the second part. Disabling the nozzles of the second part present; the third from the fourth nozzle selected in the row configured to deposit the second fluid in the nozzle array of the second actuator element. Includes disabling the nozzle of the third part extending towards the first end of the part of.

In the embodiment, the droplet deposition head is actuated first, not from the disabled nozzle, but from the nozzle of the nozzle array of the first actuator element, and from the nozzle of the nozzle array of the second actuator element. Includes controlling the droplet deposition device to deposit the fluid and the second fluid.

In an embodiment, the actuation of the droplet deposition head uses masking techniques by a non-disabled nozzle of each of the first and second actuator elements in a region where the actuator elements overlap at least partially. Further involves determining the number of subdroplets deposited. This is because changing the pitch between nozzles can affect the quality of the printed image with respect to the portion of the image printed by the nozzles of a fixed pitch portion of each nozzle array, so the two actuators. It is necessary in the area where the elements overlap. In other words, the pixel color density (ie, a value that indicates how many droplets are needed to form each pixel of the image on the receiving medium) can depend on the nozzle pitch, so masking techniques can be used. can. Therefore, in order to ensure that the nozzles in the overlapping area have the required pixel color density, how many droplets should be ejected per nozzle to achieve the required pixel color density and compensate for the variable nozzle pitch. Masking techniques are needed to specify whether or not they must be. This is achieved by constructing a nozzle that is not selected / disabled in the overlapping area, depositing less or more droplets than a nozzle at a given pitch portion, resulting in the required pixel color density. be able to.

Accordingly, in embodiments, the droplet depositor comprises a processor and / or a control circuit for performing the method of operating the droplet depositor described herein.

A related aspect of the art provides a non-temporary data carrier carrier code that, when executed on a processor, causes the processor to perform any of the methods described herein.

As will be appreciated by those skilled in the art, the art can be embodied as a system, method, or computer program product. Accordingly, the present technology may take the form of a complete hardware embodiment, a complete software embodiment, or a combination of software and hardware embodiments.

Further, the present technology can take the form of a computer program product embodied in a computer readable medium having a computer readable program code embodied on the computer readable medium. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. Computer-readable media can include, but are not limited to, for example, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or devices, or any suitable combination thereof.

The art further provides processor control codes (or logic) for performing the above methods, for example on general purpose computer systems, digital signal processors (DSPs), or field programmable gate arrays (FPGAs). These techniques also, at run time, especially on non-temporary data carriers, such as disks, microprocessors, CDs or DVD-ROMs, programmed memory such as read-only memory (firmware), or optical or electrical signal carriers, etc. Provided is a carrier that carries a processor control code for executing any of the above methods on a data carrier. The code may be provided on a carrier such as a disk, microprocessor, CD or DVD-ROM, programmed memory such as non-volatile memory (eg flash), or read-only memory (firmware). The program code or logic (and / or data) for implementing the embodiments of the present technology is a source, object or executable code, assembly code, ASIC of a conventional programming language (interpreter type or compile type) such as C. Code for setting or controlling (integrated circuit for specific applications) or FPGA (field programmable gate array), or code for hardware description language such as Verilog ™ or VHDL (ultra-high speed integrated circuit hardware description language), Can be included. As will be appreciated by those of skill in the art, such codes and / or data may be distributed among multiple combined components communicating with each other. The technique may include a controller including a microprocessor, working memory, and program memory coupled to one or more components of the system.

Computer program code for performing operations for the above techniques can be written in any combination of one or more programming languages, including object-oriented programming languages and traditional procedural programming languages. Code components can be embodied as procedures, methods, etc., from direct machine instructions in a native instruction set to high-level compiled or interpreted language elements, any level of an abstraction or sequence of instructions. Can contain subcomponents that can take the form of.

All or part of the logic method according to a preferred embodiment of the present invention can be suitably embodied in a logic device including a logic element for carrying out the steps of the above method, and such a logic element is It will also be appreciated by those skilled in the art that they may include components such as programmable logic arrays or logic gates in application-specific integrated circuits. Such logical configurations further temporarily place the logical structure in such an array or circuit using, for example, a virtual hardware descriptor language that can be stored and transmitted using a fixed or transmittable carrier medium. It can be embodied in enabling elements to establish objectively or permanently.

Further, the present technology may be realized in the form of a data carrier having functional data in itself. When the functional data is loaded into and activated by a computer system, or processor, or network, the computer system (or processor, or network) performs all steps of the method described herein. It has a functional computer data structure that enables it.

Referring here to the drawings, FIG. 1a is a schematic diagram of two overlapping actuator elements in arrangement 10. In arrangement 10, the first actuator element 12a and the second actuator element 12b are arranged in a plane (or along an axis) in a staggered pattern. The staggered arrangement means that the first actuator element 12a partially overlaps the second actuator element 12b. The region where the two actuator elements 12a and 12b overlap is shown in FIG. 1a as an overlapping region 16. Each actuator element 12a, 12b includes a nozzle array having a plurality of nozzles. In the illustrated example, the nozzle array includes a plurality of rows 14, and the nozzles of each actuator element are arranged in the row 14. It will be appreciated that the actuator elements may have any number of columns and the number of rows may differ between the actuator elements.

In the overlapping region 16, the droplet ejection from the nozzle is switched from being executed by the first actuator element 12a to being executed by the second actuator element 12b. It is important to carefully select the nozzle on which the switch from the first actuator element 12a to the second actuator element 12b is performed in order to minimize or eliminate the possibility of visible artifacts occurring in the overlapping area. Is. Thus, one from each of the actuator elements 12a, 12b in the overlapping region 16 that, in use, determines where the switch from the first actuator element 12a to the adjacent actuator element 12b should occur during the droplet ejection process. A pair of actuator element and nozzle is selected. The pair of nozzles selected is preferably the nozzle with the smallest misalignment value and the smallest pitch jump at the switching point, with this pair of nozzles switching. By disabling one of these pair of nozzles, both nozzles will not print the same part of the image. Up to the first nozzle in a pair of nozzles (or until then, if available), using the nozzle of one actuator element, and following (or using) the second nozzle in a pair of nozzles. Droplets are ejected using the nozzles of adjacent actuator elements (which will follow if possible).

FIG. 1b is a schematic diagram of two overlapping droplet deposition heads 18a and 18b in arrangement 10'. (Elements 12a and 12b may represent a die stack). It will be appreciated that in arrangement 10', each droplet deposit head 18a, 18b comprises two actuator elements, whereas each droplet deposit head 18a, 18b may include any number of actuator elements. The droplet deposition head 18a includes a first actuator element 12a and a second actuator element 12b, which are arranged in a staggered pattern within the droplet deposition head 18a. The staggered arrangement means that the first actuator element 12a partially overlaps the second actuator element 12b. Similarly, the droplet deposition head 18b comprises a third actuator element 12c and a fourth actuator element 12d, which are staggered within the droplet deposition head 18b. The staggered arrangement means that the third actuator element 12c partially overlaps the fourth actuator element 12d. The region where the two actuator elements 12a and 12b overlap at the droplet deposition head 18a is shown as the overlapping region 16.

The droplet deposition heads 18a and 18b are arranged in a staggered pattern, respectively. For example, the droplet deposition heads 18a and 18b may be provided in the droplet deposition apparatus (for example, a printer) and may be arranged in a staggered manner in the plane of the apparatus so that the droplet deposition heads overlap each other. The region where the two droplet deposition heads 18a and 18b overlap is shown as the overlapping region 16a. Each actuator element 12a to 12d includes a plurality of nozzles arranged in an array. In the illustrated example, the nozzle array comprises a plurality of rows 14 such that the nozzles in each nozzle array are arranged in row 14. It will be appreciated that the nozzle array can have any number of rows, and the number of rows can vary between actuator elements.

In the exemplary arrangement of FIG. 1b, it may be necessary to select a pair of nozzles that are suitably aligned for each of the overlapping portions 16, 16a. That is, it is necessary to select a pair of nozzles that are suitably aligned for the overlapping actuator elements in the droplet deposition head and for the overlapping actuator elements in the region where the two droplet deposition heads overlap.

The terms "suitably aligned nozzle pair" and "best aligned nozzle pair" are used interchangeably and have the smallest misalignment value and / or the smallest pitch at the switching point. It is used to mean a nozzle that results in a jump, or a switch that results in a color density change that is virtually undetectable to the human eye.

FIG. 2a is a schematic diagram of an exemplary actuator element 12 having a plurality of nozzles arranged in an array. The array may include a plurality of rows 14 such that the nozzles are arranged in rows on the actuator element 12. The row 14 shown here appears to be aligned so that the nozzles between adjacent rows are aligned in a direction perpendicular to the row direction, but in embodiments, the rows are (as shown in FIG. 6b). ) Can be provided in a staggered arrangement where the nozzles between adjacent rows are offset from each other. The deviation can be smaller than the nominal pitch in each row in the direction perpendicular to the row direction. The nozzle array of the actuator element 12 is divided into two parts as shown by a broken line. The nozzle array of actuator elements 12 comprises a first portion 22 in which nozzles along each row 14 are separated at a constant nozzle pitch. Pitch is defined as the distance between centers between adjacent nozzles. The nozzle array of actuator elements 12 comprises a second portion 24 in which the nozzles along each row 14 are separated by a variable nozzle pitch. This means that the distance between adjacent nozzles in row 14 within the second portion 24 varies with the distance along the length of the second portion 24. This is shown in FIG. 3a and is described in more detail below. At the time of use, the actuator element 12 can be arranged adjacent to the other actuator element (eg, in the arrangement shown in FIGS. 1a and 1b) so that the second portion 24 is within the overlapping region 16.

In an exemplary embodiment, the first portion 22 comprises a first end 221 and a second end 222, and the second portion 24 comprises a first end 241 and a second end 242. The second portion 24 abuts on the first portion 22 such that the second end 242 of the second portion 24 abuts on the first end 221 of the first portion 22. However, it is understood that the second portion 24 may be similarly provided such that the first end 241 of the second portion 24 abuts on the second end 222 of the first portion 22. There will be.

FIG. 2b is a schematic diagram of an exemplary actuator element 12'with a plurality of nozzles arranged in an array. The array can include a plurality of rows 14'so that the nozzles are arranged in rows on the actuator element 12'. The columns 14'shown here appear to be aligned, but in embodiments, the columns can be provided in a staggered arrangement. The nozzle array of the actuator element 12'is divided into three parts as shown by the broken line. The nozzle array of actuator elements 12'includes a first portion 22 in which nozzles along each row 14' are separated by a constant nozzle pitch. The nozzle array of actuator elements 12'includes a second portion 24 in which the nozzles along each row 14' are separated by a variable nozzle pitch. This means that the distance between adjacent nozzles in row 14'in the second portion 24 varies with the distance along the length of the second portion 24. The nozzle array of actuator elements 12'includes a third portion 26 in which the nozzles along each row 14' are separated by a further variable nozzle pitch. This means that the distance between adjacent nozzles in row 14'in the third portion 26 varies with the distance along the length of the third portion 26. In use, in the region 16 where the third portion 26 of the first actuator element (ie, the third portion of the nozzle array of the first actuator element) overlaps, the second portion 24 of the second actuator element (ie). That is, the first actuator element 12'is adjacent to the second actuator element 12' (eg, in FIGS. 1a and 1b) so as to overlap (the second part of the nozzle array of the second actuator element). Can be placed (in the arrangement shown).

In an exemplary embodiment, the first portion 22 comprises a first end 221 and a second end 222, and the second portion 24 comprises a first end 241 and a second end 242. The third portion 26 comprises a first end portion 261 and a second end portion 262. The second portion 24 abuts on the first portion 22 such that the second end 242 of the second portion 24 abuts on the first end 221 of the first portion 22. The third portion 26 abuts on the first portion 22 such that the first end 261 of the third portion abuts on the second end 222 of the first portion 22. However, it will be appreciated that the positions of the second portion 24 and the third portion 26 are interchangeable and the labeling of each end of each portion is optional.

FIG. 3a illustrates a single row 14 of the nozzle array of actuator elements 12 shown in FIG. 2a. The row 14 comprises a plurality of nozzles, some of which are within the first portion 22 of the nozzle array and some of which are within the second portion 24 of the nozzle array. (Here, the second portion 24 is shown to be on the left side of the first portion 22, but in FIG. 2a, the second portion 24 is shown to be on the right side of the first portion 22. It will be appreciated that the array can be in any arrangement). In FIG. 3a, each nozzle 28 (represented by a black circle) in the first portion 22 is separated from the adjacent nozzles at a constant nozzle pitch P1. That is, the nozzle pitch between each pair of adjacent nozzles in the first portion 22 is substantially constant or the same. On the other hand, each nozzle 28 (represented by a white circle) in the second portion 24 is separated by a variable nozzle pitch P2. That is, the nozzle pitch between adjacent pairs of nozzles in the second portion 24 changes, and P2 can be a function that depends on the distance or the nozzle position. For example, the function defining the variable nozzle pitch P2 can be a nozzle pitch that changes with distance D away from the boundary with the first portion 22. As described above, the nozzle pitch P2 can gradually change with the distance D as the distance from the constant nozzle pitch P1 increases.

FIG. 3b illustrates how two actuator elements 12 of the type shown in FIG. 2a can be placed on top of each other in a similar arrangement to that shown in FIG. 1a. For simplicity, only a single row is shown from each overlapping actuator element. In the overlapping arrangement 20, at least one row 14a from the first actuator element 12 partially overlaps with at least one row 14b from the second actuator element 12. Specifically, the actuator element 12 is arranged so that the second portion 24 (that is, the variable nozzle pitch portion) of the nozzle array of each actuator element overlaps in the overlapping region 16. It will be appreciated that the second actuator element is rotated 180 ° with respect to the first actuator element, allowing the second portion 24 of each actuator element to overlap. As shown, the actuator elements are not perfectly aligned because the nozzles in row 14a of the overlapping regions 16 are not aligned with the nozzles in row 14b of the overlapping regions 16. A pair of well-aligned nozzles 28 are selected within the overlapping region 16 and the selection is such that the first actuator element is used to eject the droplet and the second actuator element is used to liquid. A switching point is defined between the ejection and the ejection. This process is described in more detail below.

FIG. 4a illustrates a single row 14'of the actuator element 12'shown in FIG. 2b. Row 14' includes a plurality of nozzles 28, some of which are within the first portion 22 of the nozzle array of the actuator element, some of which are within the second portion 24, and some of which are within the third portion. It is within 26. In FIG. 4a, each nozzle 28 in the first portion 22 is separated from adjacent nozzles in the portion 22 at a constant nozzle pitch P1. That is, the nozzle pitch between each pair of adjacent nozzles in the first portion 22 is substantially constant or the same. On the other hand, each nozzle 28 in the second portion 24 is separated by a variable nozzle pitch P2. That is, the nozzle pitch between pairs of adjacent nozzles in the second portion 24 changes and P2 hits / from one end of the second portion 24 (eg, closest to / from the first portion 22). It can be a function that depends on the distance (from the tangent end) or the nozzle position / number. (Ie, this function depends on the continuous variable, i.e. the distance from the particular end of the second part 24, or the discrete variable, i.e. the number or position of nozzles counted from the particular end of the second part 24. Can be). For example, the function defining the variable nozzle pitch P2 can be a nozzle pitch that changes with distance D away from the boundary with the first portion 22. As described above, the nozzle pitch P2 can gradually change with the distance D as the distance from the constant nozzle pitch P1 increases.

Similarly, each nozzle 28 in the third portion 26 is separated by a variable nozzle pitch P3. That is, the nozzle pitch between pairs of adjacent nozzles in the third portion 26 changes and P3 hits / from one end of the third portion 26 (eg, closest to / from the first portion 22). It can be a function that depends on the distance (from the tangent end) or the nozzle position / number. (Ie, this function depends on the continuous variable, i.e. the distance from the particular end of the third part 26, or the discrete variable, i.e. the number or position of nozzles counted from the particular end of the third part 26. Can be). For example, the function defining the variable nozzle pitch P3 can be a nozzle pitch that changes with a distance D'away from the boundary with the first portion 22. As described above, the nozzle pitch P3 can gradually change with the distance D'as the distance from the constant nozzle pitch P1 increases.

The variable nozzle pitch P2 is preferably different from the variable nozzle pitch P3. In embodiments, one or both of the variable pitches P2 and P3 may be defined by a linear function. The linear function can be, for example, equal to a constant multiplied by a distance D or D'away from one end of the variable pitch portion (or nozzle position). A linear function can be defined in terms of nozzle position along the variable nozzle pitch portion of the nozzle array, where the first nozzle can be defined as the nozzle closest to the first position 22 of the nozzle array. can. For example, the pitch function P _n can be defined as P _n = P ₁ + a ± Δn, where n is the nozzle position / number at portions 24, 26 (as described above), Δ. Is a fixed value and a is an arbitrary positive or negative correction value. (In the example where both pitches P2 and P3 are defined by similar functions, pitch P2 may be defined as P2 = P1 + a−Δn and pitch P3 may be defined as P3 = P1 + a + Δn). Therefore, the variable nozzle pitch in this example, defined by P _n = P ₁ − Δn, is defined as the first pair closest to a constant nozzle pitch portion of the nozzle array, by a fixed amount Δ between adjacent nozzles. It starts with a decrease of 1Δ between the first pair and decreases to a decrease of nΔ, such as a decrease of 2Δ between the second pair, a decrease of 3Δ between the third pair, and so on. Such a linearly decreasing nozzle pitch is schematically illustrated in FIG. 4a by the nozzle position shown in portion 24. Similarly, the variable nozzle pitch, which can be defined by P _n = P ₁ + Δn, is a fixed amount Δ between adjacent nozzles, i.e. (defined as the first pair closest to a fixed nozzle pitch portion of the nozzle array). It increases from an increase of 1Δ between the first pair to an increase of nΔ, such as an increase of 2Δ between the second pair and an increase of 3Δ between the third pair. Such a linearly increasing nozzle pitch is schematically illustrated in FIG. 4a by the nozzle position shown in portion 26. It will be appreciated that the number n of nozzles in portions 24 and 26 does not have to be equal.

In embodiments, one or both of the variable pitches P2 and P3 can be defined by a non-linear function. The non-linear function is a nozzle along a variable nozzle pitch portion of the nozzle array or along a variable nozzle pitch portion of the nozzle array (the first nozzle may be defined as the nozzle closest to a constant nozzle pitch portion of the nozzle array). It may depend on the position. The non-linear function can be any non-linear function, such as a sine function or an exponential function. For example, the pitch function P _n can be defined as P _n = P ₁ + a ± bsin (D _n ), where 0.5 π <D <π, where D is the variable nozzle pitch portion of the nozzle array. ), A is an arbitrary correction value, and b is a fixed multiplier. In another example, the pitch function can be defined as P _n = P ₁ ± ce ^−dD , where c and d are fixed multipliers and D is the distance along the variable nozzle pitch portion of the nozzle array. Is. It will be appreciated that these are merely exemplary and exemplary functions and are non-limiting.

In an embodiment, the variable nozzle pitch P3 of the third portion 26 is the distance D between the second end 262 and the first end 261 of the third portion 26 as the third portion 26 moves away from the constant nozzle pitch P1. It changes gradually with'. The variable nozzle pitch P3 may gradually increase or decrease as the distance from the constant nozzle pitch P1 increases. The variable nozzle pitch P3 of the third portion 26 gradually changes (ie, increases or decreases) at the second end 262 of the third portion 26 as the distance from the constant nozzle pitch P1 increases. As the variable nozzle pitch P3 moves away from the constant nozzle pitch P1, it changes with the distance D'towards the first end 261 of the third portion 26. In other words, the farther the nozzle 28 of the third portion 26 is from the second end 262 of the third portion 26, the more the variable nozzle pitch P3 between the nozzles differs from the constant nozzle pitch P1.

The variable nozzle pitch P2 may be defined by the first function and the variable nozzle pitch P3 may be defined by the second function. In the embodiment, the second function defining the variable nozzle pitch P3 can be equal to the first function defining the variable nozzle pitch P2. For example, both the first function and the second function can be defined as P _n = P1 + aΔn. In other embodiments, the second function can be the same type of function as the first function (eg, linear function, sine function, exponential function, etc.), but with different multipliers and / or correction values. obtain. For example, the first function can be P _n = P1 + a-3n, while the second function can be P _n = P1 + a-2.5n). In other embodiments, the first and second functions may be different, for example, one can be a linear function and the other a non-linear function, or one can be a sine function and the other an exponential function. It may be possible, etc. The function selected to define each variable nozzle pitch P2, P3 is determined using computer modeling or simulation, and if the actuator elements are arranged to overlap, the selected function is used. Shows how likely it is to find the best aligned nozzle pair.

FIG. 4b illustrates how two actuator elements 12'of the type shown in FIG. 2b can be placed on top of each other in a similar arrangement to that shown in FIG. 1a. For simplicity, only a single row is shown from each overlapping actuator element. In the overlapping arrangement 20', at least one row 14'a from the first actuator element 12'partially overlaps with at least one row 14'b from the second actuator element 12'. Specifically, in the actuator element 12', the region 16 in which the second portion 24 of the nozzle array of the first actuator element 12' overlaps with the third portion 26 of the nozzle array of the second actuator element 12'. It is arranged so that it overlaps with each other. A pair of well-aligned nozzles 28 are selected within the overlapping region 16 and the selection is such that the first actuator element is used to eject the droplet and the second actuator element is used to liquid. A switching point is defined between the ejection and the ejection. This process is described in more detail below.

FIG. 5 is an enlarged view of the overlapping region 16 of FIG. 4b. (Here, it will be appreciated that the arrangement depicted is a reflection of the arrangement shown in FIG. 4b with respect to the axis on which the actuator element is arranged, thus the adjacent actuator element is partial. As long as the actuator elements are arranged along the same axis, in the same plane, or along the array direction so as to overlap with each other, the actuator elements can be arranged in any suitable configuration with respect to each other). The second portion 24 of the nozzle array of the first actuator element overlaps the third portion 26 of the nozzle array of the second actuator element. Here, the variable nozzle pitch P2 of the second portion 24 of the nozzle array of the first actuator element is defined by the first function, and the variable nozzle pitch P3 of the third portion 26 of the nozzle array of the second actuator element is defined. Is defined by the second function. In this example, the first function results in a variable nozzle pitch P2 that decreases in the array direction between the first and second ends of the second portion 24. The second function in this example is also variable in the array direction between the first and second ends of the third part 26, with different proportions / different magnitudes compared to P2. It brings the nozzle pitch P3.

To reduce any visual artifacts that occur when printing with overlapping actuator elements, determine the preferred point of switching from printing with the first actuator element to printing with the second actuator element. There is a need. This can be determined by selecting the best aligned nozzle pair (BAP) or the favorably aligned nozzle pair within the overlapping region 16, with one of the pair of nozzles being the first. The other nozzle of the pair is selected from the nozzle array of the second actuator element. The best aligned pair of nozzles is usually aligned closer than any other pair of nozzles, and / or the smallest jump (change) (or human eye) in pitch at the switching point. It is a nozzle that brings about a pitch change that is small enough to go unnoticed. Switching is done with this substantially aligned or well aligned pair of nozzles. By disabling one of these pair of nozzles, both nozzles will not print the same part of the image. Using the nozzles of one actuator element, up to (or include) the first nozzle in a pair of nozzles, and following (or available) from the second nozzle in a pair of nozzles. If so, then) use the nozzles of the adjacent actuator elements to perform droplet ejection. For example, in FIG. 5, all nozzles up to a pair of aligned nozzles in the illustrated row of first actuator elements can be used to eject the droplet. The remaining nozzles in this row are disabled, for example, by not addressing them in the drive signal during the droplet deposition process. Nozzles in the illustrated row of second actuator elements in the overlapping portion are disabled up to a pair of aligned nozzles. The remaining nozzles in this row are used to continue ejecting droplets. In this way, a "super row" is formed across two or more actuator elements.

FIG. 6a is a schematic diagram of an actuator element 12a including a nozzle array having a plurality of rows R1 to R4 of nozzles. The number of nozzles in each row R1 to R4 may be the same or different. In the embodiment, the columns R1 to R4 may be aligned. In another embodiment, the nozzles in each row are not aligned with each other, but the rows R1 through R4 can be staggered relative to each other so that they are offset from each other along the array direction. This is how the rows R1 to R4 of the nozzles are staggered on the actuator element 12a, eg, with a half pitch shift between R1 and R2 and between R3 and R4. The pair of R2 and the pair of R3 and R4 are shown more clearly in FIG. 6b, exemplifying whether they are provided with an additional quarter pitch shift from each other.

The nozzles shown in the rows R1 to R4 of FIG. 6b are separated by a constant nozzle pitch P. For example, the nozzle 28a is separated from the adjacent nozzles 29a in the row R1 at a constant nozzle pitch P. As can be seen from FIG. 6b, there are three other nozzles in the space between the nozzles 28a and 29a: the nozzle 28b in row R3, the nozzle 28c in row R2, and the nozzle 28d in row R4. During use, the number of nozzles used to deposit fluid droplets may depend on the required resolution. For example, if low resolution is acceptable, only the nozzles in row R1 can be used to deposit droplets of a particular fluid. In this case, where P is the distance between the nozzles in row R1, large gaps may appear between the droplets on the droplet deposition medium. If high resolution is required, all nozzles in rows R1 through R4 can be used, in which case the gaps between the droplets can be reduced or eliminated. In high resolution mode, the nozzle 28a deposits droplets first, then at nozzle 28c, then at 28b, and then at 28d, and the gap P between the droplets that can be deposited by nozzles 28a and 29b is It is filled with droplets deposited by intermediate nozzles 28b-28d. Droplets deposited from a contiguous row are ejected with a specific time delay between the droplets so that the droplets are on the same row of pixels on the print medium as the print medium passes under the nozzle. To. If the delay is selected correctly, the droplets will appear on the medium as a row of dots. In this case, the constant nozzle pitch between adjacent nozzles can be substantially the distance between the nozzle 28a and the next nozzle used to deposit the droplets, ie the nozzle 28b. Therefore, as shown, the constant nozzle pitch can be P', where P'= P / 4.

In embodiments, intermediate resolutions may be required. For example, if high resolution (eg 1200 dpi) corresponds to depositing fluid using all nozzles in columns R1 through R4, intermediate resolution (eg 600 dpi) corresponds to using half of all nozzles. obtain. This can be achieved by nozzles arranged in pairs of adjacent rows in the example shown in FIG. 6b. For example, columns R1 and R2 can be used, while columns R3 and R4 are invalidated. In this case, the nozzles in R1 (28a, 29a, ...) Can deposit the droplets first, followed by the nozzles in R2 (28c, 29c, ...), As a result, the nozzles in R1. The gap P between the droplets that can be deposited is filled by depositing the droplets with the intermediate nozzle of R2. In this example, the constant nozzle pitch between adjacent nozzles is substantially the distance between the nozzle 28a in R1 and the next nozzle used to deposit the droplets, ie the nozzle 28c in R2. Can be. Therefore, as shown, the constant nozzle pitch can be P "where P" = P / 2.

Accordingly, as used herein, the term "constant nozzle pitch" means the distance between centers between adjacent nozzles in a single row, or the distance between adjacent nozzles used during droplet deposition. Can be done. The essence of having a fixed and constant distance does not depend on how the "adjacent nozzle" is defined.

Similarly, in one or each variable nozzle pitch portion of an array of actuator elements, the term "variable nozzle pitch" is used during varying center-to-center distances between adjacent nozzles in a single row, or during droplet deposition. It will be appreciated that it can mean a variable spacing between adjacent nozzles. The essence of having a variable distance does not depend on how the "adjacent nozzle" is defined.

FIG. 7 is an enlarged view of an overlapping portion between overlapping actuator elements and a schematic diagram showing how a fluid can be deposited using the overlapping actuator elements. Here, the second portion 24 of the nozzle array of the first actuator element overlaps with the third portion 26 of the nozzle array of the second actuator element. Each nozzle array in this example includes four rows R1 to R4 of nozzles, the rows staggered with respect to each other, as in the arrangement of FIG. 6b. White circles represent nozzles on each actuator element. Black circles indicate which nozzles were / will be used to deposit the fluid droplets, and diagonal circles indicate which nozzles were disabled. In this example, all nozzles in each row are used to deposit the droplets, i.e. this schematic shows a high resolution operating mode.

To reduce any visual artifacts that occur when depositing droplets using overlapping actuator elements, depositing droplets from the nozzle of the first actuator element is the nozzle of the second actuator element. It is necessary to determine a suitable point to switch to depositing droplets from. This can be determined by selecting the best aligned nozzle pair (BAP) or the favorably aligned nozzle pair, with one of the pair of nozzles selected from the first actuator element. The other nozzle in the pair is selected from the second actuator element. A pair of well-aligned nozzles are aligned closer than any other pair of nozzles, and / or are the smallest pitch jumps (or noticed by the human eye) on either side of the switching point. It is a nozzle that brings about a pitch change that is so small that it cannot be. In this case, it is considered that the nozzle 30b of the first actuator element and the nozzle 32a of the second actuator element are the best aligned pair. The pair of nozzles 30b and 32a defines a place (that is, a switching point) where switching occurs between the actuator elements.

As mentioned above, by disabling one of the nozzle pairs, both nozzles prevent fluid from depositing on the same pixel in the image. In FIG. 7, the nozzle 30b is disabled and the nozzle 32a is enabled. Therefore, the deposition of droplets is performed as follows. The nozzle of the first actuator element is used to deposit the fluid up to the nozzle 30a (the nozzle immediately preceding the invalidated nozzle 30b), and the nozzle of the second actuator element starting from the nozzle 32a is used to deposit the fluid. Accumulate. Therefore, all the nozzles of the first actuator element located on the right side of the nozzle 30a are invalidated, or all the nozzles of the second actuator element located on the left side of the nozzle 32a are invalidated. Or not used for droplet ejection. In this way, a "super row" (or "effective row") of nozzles straddling the two actuator elements is formed.

FIG. 7 also shows that the selection of a pair of well-aligned nozzles depends on (i) how close the pair of nozzles are aligned and (ii) the change in pitch on either side of the switching point. Show how it can depend. In the illustrated example, the nozzles 30b and 32a are closely aligned (ie, have a minimum misalignment value), but they also result in a relatively minimal pitch change at the switching point. That is, the pitch between the nozzles 30a and 32a is approximately the same as the pitch between the nozzles 32a and 32b (or within a certain tolerance range), and therefore the first actuator element and the second actuator element At the switching point between, the pitch jump is minimal (or a pitch change that is small enough to be invisible to the human eye).

It can be considered that the nozzle x on the first actuator element and the nozzle 32b on the second actuator element are closely aligned. However, this pair of nozzles does not meet the second criterion, that is, it results in a small change in pitch on either side of the pair of nozzles selected. If nozzle x is disabled in a pair of nozzles, the nozzle up to nozzle y of the first actuator element is used to deposit the droplets, and the nozzle from nozzle 32b of the second actuator element is used. Deposit droplets. As shown in FIG. 7, the pitch between the nozzle y and the nozzle 32b is P', but P'is clearly much shorter than the pitch P'between the nozzle 32b and the nozzle z. Therefore, the nozzle x. , 32b pairs result in relatively large pitch jumps on either side of the switching point, so that the nozzle x, 32b pairs are less suitable than the nozzles 30b, 32a pairs, which better meet both criteria. It is possible, in embodiments, to find a suitable pair of nozzles that meet both criteria near the center of the overlapping region (depending on the function defining the variable pitch within the overlapping region between the actuator elements). Can mean higher.

As mentioned earlier, a row of nozzles can be operated in pairs or groups depending on the resolution required for the droplet deposition operation. Similarly, a row of nozzles can be operated in pairs or groups to deposit different fluids, such as different colored inks. FIG. 8 illustrates how a row of nozzles can be operated in groups to deposit a first fluid and a second fluid. Here, the second portion 24 of the nozzle array of the first actuator element overlaps with the third portion 26 of the nozzle array of the second actuator element. Each nozzle array in this example includes four rows R1 to R4 of nozzles, the rows staggered with respect to each other, as in the arrangement of FIG. 6b. On each actuator element, the nozzle trains R1 and R2 are operated together to deposit the first fluid, and the nozzle trains R3 and R4 are operated together to deposit the second fluid. Nozzles in rows R1 and R2 can be considered as nozzles in the first group G1 (or G1') of nozzles, and nozzles in rows R3 and R4 can be considered as nozzles in second group G2 (or G2') of nozzles. be able to. The frame around the group is provided solely for illustrative purposes. It will be understood that the columns may be grouped together in another way. For example, alternating columns, such as columns R1 and R3, and columns R2 and R4, can be grouped together, depending on the design of the fluid supply to the droplet deposition head or the column within the droplet deposition device. ..

In FIG. 8, groups G1 and G1'deposit a first fluid represented by a black circle, and groups G2 and G2'deposit a second fluid represented by a white circle. Black circles indicate which nozzles were / will be used to deposit droplets of the first fluid, and white circles are used to deposit droplets of the second fluid. Indicates whether it has been / will be used.

As described above, depositing droplets from the nozzle of the first actuator element is to reduce any visual artifacts that may occur when depositing droplets using overlapping actuator elements. It is necessary to determine a suitable point to switch to depositing droplets from the nozzle of the second actuator element. In this case, two pairs of nozzles, one pair for each fluid, are required. That is, a switching point between the nozzles for depositing the first fluid and a switching point between the nozzles for depositing the second fluid are required. As shown, for the nozzle depositing the first fluid, the first best aligned pair BAP1 is determined. One nozzle in the pair BAP1 is selected from the group G1 of the first actuator element, and one nozzle is selected from the group G1'of the second actuator element. This pair of nozzles, BAP1, defines where switching occurs between the actuator elements for the first fluid. For the nozzle depositing the second fluid, determine the second best aligned pair BAP2. One nozzle in the pair BAP2 is selected from the group G2 of the first actuator element, and one nozzle is selected from the group G2'of the second actuator element. This pair of BAP2 of the nozzle defines where switching occurs between the actuator elements for the second fluid.

In embodiments, group G1 of the first actuator element can represent a nozzle used for depositing droplets in low resolution mode. For example, groups G1 and G2 of the first actuator element can both be used in high resolution mode (eg 1200 dpi), where in high resolution mode all nozzles are used and the same fluid (eg black, eg). Deposit one of magenta, yellow, or cyan inks). In low resolution mode (eg 600 dpi), half of the nozzles, or one group of nozzles, can be disabled. Therefore, FIG. 8 also shows how best aligned pairs can be selected for different operating modes or different resolutions. For example, BAP1 can represent the best aligned nozzle pair when operating in the first mode (eg, high resolution) and BAP2 can represent the pair of nozzles that operate in the second mode (eg, low resolution). Can represent the best aligned nozzle pair when doing so. In an embodiment, BAP1 can be the same as BAP2.

FIG. 9a illustrates how overlapping actuator elements can be misaligned. The second portion 24 of the nozzle array of the first actuator element 12a overlaps the third portion 26 of the nozzle array of the second actuator element 12b. The misalignment between the two features to be aligned defines the misalignment between the actuator elements 12a and 12b. For example, the misalignment can be the difference between the ideal (aligned) arrangements of a particular nozzle on the two actuator elements, the difference between the alignment marks on the actuator element, and the like. In FIG. 9a, the misalignment of two nozzles, one from the actuator element 12a and the other from the actuator element 12b, is used to determine the misalignment between the two actuator elements. .. The range of possible misalignment values ranges from 0 (ie, perfectly aligned) to values that represent severe misalignment (eg, nozzles on one actuator element between nozzles on another actuator element). The range is up to (when aligned / partially aligned with a nozzle other than the nozzle to be aligned or to be aligned with the gap). Generally speaking, and as mentioned above, the function that defines the variable nozzle pitch of one or each variable pitch portion of the nozzle array of the actuator element is which function best aligns with the widest range of displacement values. Selected using computer modeling to determine which is most likely to find a pair of nozzles. The maximum delta value (maximum delta) is defined as the difference between the constant nozzle pitch P1 (ie, the ideal pitch between the nozzles forming the "super row") and the displacement E between the nozzles at the switching point. Can be done. For example, FIG. 9a shows the best possible aligned nozzle pair (BAP), one of which is used to deposit fluid droplets and the other is invalid. Be made. FIG. 9b shows switching between actuator elements 12a and 12b. Here, the black circles represent the nozzles used to deposit the fluid, and the white circles represent the disabled nozzles. The nozzle of the second actuator element in the BAP is disabled and therefore at the switching point the adjacent nozzle N is used to continue the droplet deposition process. However, if the best aligned nozzle pair is not perfectly aligned, the spacing E between the nozzles at the switching point may not be equal to the ideal pitch P1. Therefore, generally speaking, a function is needed that defines one or each variable nozzle pitch that minimizes the maximum delta over the maximum range of possible displacements / misalignments.

FIG. 9b also shows how the absolute jump of pitch at the switching point can be defined. Pitch jumps can be calculated by dividing the difference between the pitches on either side of the switching point by one of those pitches. In this example, pitch P'is the pitch between the last two nozzles used to deposit the fluid in the first actuator element, and pitch P'is the pitch in which the fluid in the second actuator element is deposited. The pitch between the first two nozzles used for. Absolute jump in pitch is a coefficient obtained by dividing the difference between P'and P'by P'(to calculate the absolute jump in pitch). It will be appreciated that alternative definitions may be used; for example, pitch jumps can be a coefficient obtained by dividing the difference between P'and P'by P'). The absolute jump of the pitch may be given as a percentage.

Here, with reference to FIGS. 10-12, these show exemplary simulations of the various functions that define the variable nozzle pitch. FIG. 10a illustrates a row of nozzles in the nozzle array of the first actuator element and a row of nozzles in the nozzle array of the second actuator element in the region where the two actuator elements overlap. As described above, in an actuator element with a row of 1420 nozzles, 56 nozzles can be assigned to one or each variable pitch portion of the actuator element's nozzle array. Therefore, FIG. 10a shows how the pitch changes between the 56 nozzles of the variable pitch portion of the two overlapping actuator elements. The nominal nozzle pitch between the nozzles of the actuator element (which may be the same as the constant nozzle pitch of the nozzle array) can be 21.2 μm. In FIG. 10a, the nozzle pitch between the nozzles in the overlapping portion of the first actuator element is 21.2 + 0.5 μm, while the nozzle pitch between the nozzles in the overlapping region of the second actuator element is 21.2-0. It is 5 μm. That is, in this example, the nozzle array has no variable nozzle pitch portion at all. Instead, the nozzle pitch of each array in the overlapping region is fixed / constant, although different from the nominal pitch (ie, the pitch of the constant nozzle pitch portion of the nozzle array). This is the default placement, also known as the "vernier" placement.

FIG. 10b shows how difficult it is to find a pair of well-aligned nozzles for a 1200 dpi actuator element with the non-variable nozzle pitch of FIG. 10a as the misalignment between overlapping actuator elements increases. Is shown. In other words, as the misalignment increases beyond 800 μm, it becomes increasingly difficult to find a pair of nozzles that are well aligned to avoid any visual artifacts. FIG. 10c shows how the percentage of absolute pitch jumps at the switching points between the actuator elements of FIG. 10a changes as a function of misalignment. In this case, since the nozzle pitch of each array in the overlapping region is fixed / constant, the change in pitch at the switching point does not change as a function of misalignment. The pitch jump remains at 4.7% regardless of the misalignment between the actuator elements, simply because the nozzle pitch itself does not change. However, a 4.7% change in pitch at the switching point is important and can result in a sharp, visible change in optical density (ie, a visual artifact in the printed image).

FIG. 10d shows the same information as FIG. 10b, but about 600 dpi actuator elements (or a 1200 dpi nozzle array with half the nozzles disabled), and FIG. 10e shows the same information as FIG. 10c, but 600 dpi. Information about the actuator element of. In FIG. 10d, as the misalignment increases beyond 400 μm, it becomes increasingly difficult to find a pair of nozzles that are well aligned to avoid any visual artifacts. FIG. 10e shows that the percentage of absolute pitch jumps remains at 4.7% despite the misalignment between the actuator elements, as the nozzle pitches in the 600 dpi actuator elements do not change within the overlapping region.

Typical misalignment between actuator elements placed within the droplet deposition head (eg, placement in FIG. 1a) can be very small, eg less than 10 μm. However, the misalignment between two overlapping droplet deposition heads with actuator elements (eg, the arrangement in FIG. 1b) may exceed 100 μm. In this case, the misalignment may depend on the design of the droplet deposition head. The simulations shown in FIGS. 10b to 10e target typical misalignments and more severe misalignments.

Therefore, in the case of the default vernier (ie, the scheme shown in FIG. 10a), a 1200 dpi actuator element or a 600 dpi actuator element that is misaligned with the typical values described above (eg, 0 μm to 200 μm) is preferably positioned. It is very likely that you will find a pair that has been matched and you can tolerate even greater misalignment. However, the 4.7% pitch jump at the switching point between the actuator elements is abrupt and can be detected by the human eye. Therefore, the default invariant nozzle pitch may not be suitable for reducing visual artifacts in overlapping areas between actuator elements.

FIG. 11a illustrates a row of nozzles in the nozzle array of the first actuator element and a row of nozzles in the nozzle array of the second actuator element in the region where the two actuator elements overlap. As described above, in an actuator element with a row of 1420 nozzles, 56 nozzles can be assigned to one or each variable pitch portion of the actuator element's nozzle array. FIG. 11a shows how the pitch changes between the 56 nozzles of the variable pitch portion of the two overlapping actuator elements.

In the example of FIG. 11a, both actuator elements include a constant portion where the nozzle pitch between the nozzles is constant / fixed. This constant nozzle pitch is 21.2 μm. The variable nozzle pitch portion of the first actuator element overlaps with the variable nozzle pitch portion of the second actuator element. The variable nozzle pitch of the first actuator element is defined by a sine function, eg, P1 _n = 21.2 + bsin (x _n ) μm, where xn is from one end of the variable pitch portion (eg, the first end). The distance of the nozzle n measured (from the portion or from the end closest to the constant pitch portion), where b is a fixed multiplier. Similarly, the variable nozzle pitch of the second actuator element is defined by a sine function, eg, P2 _n = 21.2-bsin (x _n ) μm. As shown in FIG. 11a, the pitch between adjacent nozzles in the variable nozzle pitch portion of each actuator element changes with distance (or nozzle position) according to the sine function.

FIG. 11b shows how difficult it is to find a pair of well aligned nozzles for two overlapping 1200 dpi actuator elements with the variable nozzle pitch shown in FIG. 11a as the misalignment between the overlapping actuator elements increases. Indicates whether it will be. In other words, as the misalignment increases by more than 500 μm, it becomes increasingly difficult to find a pair of nozzles that are well aligned to avoid any visual artifacts. FIG. 11c shows how the percentage of absolute pitch jumps at the switching points between the actuator elements of FIG. 11a changes as a function of misalignment. In this example, the change in pitch at the switching point changes as a function of misalignment, and the jump in pitch changes from less than 1% to 5%. Therefore, the change in pitch at the switching point may be lower than the default vernier example in FIG. 10a for some misalignments.

FIG. 11d shows the same information as FIG. 11b but with respect to a 600 dpi actuator element (or a 1200 dpi nozzle array with half the nozzles disabled) and FIG. 11e shows the same information as FIG. 11c but with 600 dpi. Information about the actuator element of. For this particular sine function, the maximum delta value increases significantly faster than for a 1200 dpi actuator element (or operating mode) as the misalignment of the 600 dpi actuator element (or operating mode) increases. 11c and 11d show how the percentage of overall pitch jumps can be reduced by adopting this nozzle placement scheme compared to the default vernier effect shown in FIGS. 10c and 10d. And how the percentage of absolute jumps can be significantly reduced for some misalignment values that may be less than 1%.

FIG. 12a illustrates a row of nozzles in the nozzle array of the first actuator element and a row of nozzles in the nozzle array of the second actuator element in the region where the two actuator elements overlap. As described above, in an actuator element with a row of 1420 nozzles, 56 nozzles can be assigned to one or each variable pitch portion of the actuator element's nozzle array. FIG. 12a shows how the pitch changes between the 56 nozzles of the variable pitch portion of the two overlapping actuator elements. Specifically, in the example of FIG. 12a, the variable pitch of the first actuator element (in the overlapping region) is defined by P1 _n = 21.2 + (n * 0.7 / N) μm and the second actuator. The variable pitch of the element is defined by P2 _n = 21.2- (n'* 0.5 / N') μm, where N and N'are the first actuator element and the second actuator element, respectively. Is the total number of nozzles in the variable pitch portion of the actuator element, where n is defined for the end of the variable pitch portion (eg, the first end, or the end closest to the constant pitch portion) of the actuator element. This is the nozzle number. In other words, the variable pitch of the first actuator element increases from a constant / nominal pitch of 21.2 μm at one end of the variable pitch portion to 21.2 μm + 0.7 μm at the other end of the variable pitch portion. Between one end and the other end of this variable portion, the pitch between each pair of adjacent nozzles gradually increases. Similarly, the variable pitch of the second actuator element in the overlapping portion ranges from a constant / nominal pitch of 21.2 μm at one end of the variable pitch portion to 21.2 μm + 0.5 μm at the other end of the variable pitch portion. Increasing, the pitch between each pair of adjacent nozzles between one end and the other end of this variable portion gradually increases.

FIG. 12b shows how difficult it is to find a pair of well aligned nozzles for two overlapping 1200 dpi actuator elements with the variable nozzle pitch shown in FIG. 12a as the misalignment between the overlapping actuator elements increases. Indicates whether it will be. In other words, as the misalignment increases beyond 800 μm, it becomes increasingly difficult to find a pair of nozzles that are well aligned to avoid any visual artifacts. FIG. 12c shows how the absolute pitch jump at the switching point between the actuator elements of FIG. 12a changes as a function of misalignment. In this example, the change in pitch at the switching point changes as a function of misalignment, and the pitch jump changes by 2-4% over a misalignment in the range 0 μm to 500 μm. Therefore, for some misalignment values, the change in pitch at the switching point is lower than in the default vernier example of FIG. 10a.

FIG. 12d shows the same information as in FIG. 12b but with respect to a 600 dpi actuator element (or a 1200 dpi nozzle array with half the nozzles disabled) and FIG. 12e shows the same information as in FIG. 12c but with 600 dpi. Information about the actuator element of. For these particular linear variable pitch functions, the maximum delta value increases faster than for a 1200 dpi actuator element (or operating mode) as the misalignment of the 600 dpi actuator element (or operating mode) increases. However, compared to the example of the sine function shown in FIGS. 11a-11e, the overall pitch jump in FIG. 12c is reduced to less than 4% over a range of displacements up to 500 μm, with respect to smaller displacements. It decreases to 3%. With a 600 dpi arrangement, FIG. 12e shows that for some displacement values, a small pitch jump rate of about 2% is achieved.

FIG. 12a shows the advantage of having a nozzle array with a first constant portion, a second variable portion, and a third variable portion, as in the arrangement shown in FIG. 2b. In this example, the second variable portion of the nozzle array of each actuator element can have the pitch defined by P1 = 21.2 + 0.7 μm and the third variable portion of the nozzle array of each actuator element is. It can have the pitch defined by P2 = 21.2-0.5 μm. By arranging the first actuator element next to the second actuator element as described above (and as shown in FIG. 4b), the arrangement of FIG. 12a can be realized and the first actuator element The second variable portion overlaps with the third variable portion of the second actuator element. Therefore, this simulation has a nozzle array with a third variable part and a second variable part as compared to a nozzle array with a second and third part having a fixed pitch (which can be different from a constant pitch). It shows how an actuator element with can be used to reduce visual artifacts during droplet deposition.

FIG. 13 is a flowchart showing a process for calibrating the droplet deposition apparatus. The calibration process involves selecting for each pair of overlapping actuator elements a pair of nozzles that are suitable for use in one of the droplet deposition devices or in each mode of operation. That is, the droplet deposition device can include a plurality of actuator elements arranged in a staggered overlapping arrangement, so that each overlapping portion and each operating mode (eg, different resolution, single fluid, multiple fluids, etc.) ), A pair of well-aligned nozzles is required. The calibration process may be performed manually by the user of the device, may be automated, or a combination of both.

The process begins in step S100, in step S102 selecting a pair of nozzles that define switching points between overlapping actuator elements for each overlapping portion. The nozzle pair selected can be the default nozzle pair, that is, the pair that is always selected at the beginning of the calibration process. For example, a pair of nozzles in or near the center of the overlapping area can be selected by default. Then, a test pattern is printed using the selected pair of nozzles to define the switching point (step S104). The test pattern is optically inspected by the user of the device or by an image scanning device coupled to the computer (step S106). The next step in the calibration process involves determining if there are any visual artifacts in the test pattern that occur within the area of the pattern that corresponds to the area of overlap between the overlapping actuator elements (step S108). This may be performed by visual inspection by the user or by using software for analyzing images of test patterns captured by an image scanning device. If no visual artifacts are detected, or if an acceptablely small number of artifacts are detected, the nozzle pair selected is preferably with information about the mode of operation in which they are selected for future use. It is stored (step S114). Then, the process ends in step S118.

As mentioned above, the pixel color density (ie, a value indicating the number of droplets required to form each pixel of the image on the image receiving medium) can depend on the nozzle pitch, so that the pixels of the image are placed on the receiving medium. Masking techniques may be required to ensure that the pixel color densities required to reproduce are produced by the overlapping actuator elements. Therefore, in order to ensure that the required pixel color density for each pixel of the image is obtained by the nozzles in the overlapping region between the actuator elements, each nozzle is used to achieve the required pixel color density and compensate for the variable nozzle pitch. Masking techniques may be required to specify how many droplets must be ejected per hit. This is achieved by constructing a nozzle that is not selected / disabled in the overlapping area, depositing less or more droplets than a nozzle at a given pitch portion, resulting in the required pixel color density. be able to.

In embodiments, the process optionally selects and stores a masking technique that determines the number of subdroplets deposited by each non-disabled nozzle of the overlapping actuator element in the overlapping area. Including (step S116). Examples of suitable masking techniques are described in UK Patent Application GB1522809.1, the contents of which are incorporated by reference in their entirety.

If unacceptable visual artifacts are detected in step S108, different nozzle pairs are selected (step S110) and a new test pattern is printed. Therefore, steps S104 through S112 are repeated until a suitable nozzle pair that reduces or eliminates visual artifacts in the printed image is identified.

In embodiments, selecting the best aligned nozzle pair is a selection criterion: (i) how close the nozzle pairs are aligned, and (ii) the pitch on either side of the switching point. Can include selecting a pair of nozzles that satisfy one, or preferably both, of the variations of. In embodiments, a look-up table or similar data may be provided for the actuator element or for a droplet deposition head with a plurality of actuator elements. Look-up tables can show which nozzle pairs can meet these criteria for different misalignment values. Look-up tables are unique to variable-pitch functions.

No doubt many other effective alternatives will come to those skilled in the art. For example, of course, various concepts have been described above in connection with inkjet printheads, but such concepts are not limited to inkjet printheads and are more suitable for any suitable application in printheads. It will be appreciated that it can be widely applied or even more widely applied in droplet deposition heads. As mentioned above, the drop deposition heads suitable for such alternative applications are generally similar in structure to printheads that have undergone some modifications to address the particular fluid in question. Therefore, it should be understood that the above description is provided as a non-limiting example of applications in which such a droplet deposition head may be used. Further, it will be appreciated that the invention is not limited to the embodiments described, but will include modifications apparent to those skilled in the art within the spirit and scope of the claims attached herein.

Claims (20)

An array of actuator elements having a first actuator element and a second actuator element staggered with respect to a common axis so as to partially overlap.
Each of the first actuator element and the second actuator element
An actuator element having a plurality of nozzles arranged in at least one nozzle array, wherein the nozzle array is
A first portion comprising a first subset of the plurality of nozzles, wherein the first subset of the nozzles is arranged along the nozzle array axis, and the first end of the first portion and said. The first part, which is separated from the second end of the first part by a constant nozzle pitch,
A second portion comprising a second subset of the plurality of nozzles, wherein the second subset of the nozzles is arranged along the nozzle array axis and from the first end of the second portion. The nozzle pitch decreases toward the second end of the second portion. The first end of the second portion is separated by a variable nozzle pitch, and the first end of the second portion is the second end of the first portion. The second part that comes into contact with the part ,
A third portion comprising a third subset of the plurality of nozzles.
A third subset of the nozzles is arranged along the nozzle array axis and has a further variable nozzle pitch that changes from the first end of the third portion to the second end of the third portion. Separated by
The second end of the third portion abuts on the first end of the first portion, and the second end of the first portion is the second end of the second portion. The first portion of the nozzle array is provided between the second portion and the third portion so as to abut on one end.
Arrangement of actuator elements. The variable nozzle pitch is defined by a first function that decreases from the first end of the second portion toward the second end of the second portion, and defines the variable nozzle pitch. The first function is a non-linear function, which is the arrangement of the actuator elements according to claim 1. The variable nozzle pitch of the second portion gradually decreases with the distance between the first end and the second end of the second portion as the distance from the constant nozzle pitch increases. , The arrangement of the actuator element according to claim 1 or 2. The additional variable nozzle pitch is defined by a second function that varies with distance between the first end of the third portion and the second end of the third portion. The array of actuator elements according to any one of claims 1 to 3 . The additional variable nozzle pitch of the third portion gradually increases with the distance between the first end and the second end of the third portion as it moves away from the constant nozzle pitch. The array of actuator elements according to any one of claims 1 to 4, which is variable. The additional variable nozzle pitch of the third portion gradually increases with the distance between the first end and the second end of the third portion as it moves away from the constant nozzle pitch. The arrangement of actuator elements according to any one of claims 1 to 5, which increases. The variable nozzle pitch of the second portion is similar to the constant nozzle pitch at the first end of the second portion, and the second portion as the distance from the constant nozzle pitch increases. Gradually decreases with the distance towards the second end of the
The further variable nozzle pitch of the third portion is similar to the constant nozzle pitch at the second end of the third portion, and the third portion as the distance from the constant nozzle pitch increases. The actuator element arrangement according to any one of claims 1 to 5, which gradually increases with the distance of the portion toward the first end portion. The actuator element arrangement according to any one of claims 1 to 7 .
The second portion of the nozzle array of the first actuator element is at least partially overlapped with the third portion of the nozzle array of the second actuator element. A droplet depositing device comprising an arrangement of at least one actuator element according to any one of claims 1 to 8 . A droplet ejection head including a first actuator element and a second actuator element.
The actuator elements are provided in a staggered arrangement with overlapping portions between the actuator elements in a plane of the droplet deposition head, and each actuator element is
With multiple nozzles located in at least one nozzle array;
A first portion of the nozzle array comprising a first subset of the plurality of nozzles, wherein the first subset of the nozzles is arranged along the nozzle array axis and the first end of the first portion. With the first part, which is separated by a constant nozzle pitch between the part and the second end of the first part;
A second portion of the nozzle array comprising a second subset of the plurality of nozzles, wherein the second subset of the nozzles is arranged along the nozzle array axis and the first of the second portion. The first end of the second portion is separated by a variable nozzle pitch in which the nozzle pitch decreases from the end toward the second end of the second portion, and the first end of the second portion is the said of the first portion. With the second part, which abuts on the second end;
A third portion of the nozzle array comprising a third subset of the plurality of nozzles, wherein the third subset of the nozzles is arranged along the nozzle array axis and is the first of the third portion. The second end of the third portion is separated by a further variable nozzle pitch that varies from one end to the second end of the third portion, and the second end of the third portion is the first end of the first portion. A droplet ejection head comprising a third portion, which abuts on the portion. The method for assembling the droplet deposition apparatus according to claim 9 , wherein the method is:
By arranging the first actuator element in the plane of the droplet depositing device,
The second actuator element is deposited so that the second portion of the nozzle array of the first actuator element at least partially overlaps the third portion of the second actuator element. A method comprising arranging in a staggered arrangement with respect to the first actuator element in a plane of the apparatus. A method of operating the droplet deposition apparatus according to claim 9 .
The method is
Selecting a first nozzle from the second portion of the nozzle array of the first actuator element and selecting a second nozzle from the third portion of the nozzle array of the second actuator element. A method comprising: 12. The method of claim 12 , wherein selecting the first nozzle and the second nozzle comprises selecting the first nozzle and the second nozzle having the smallest misalignment value. Choosing the first nozzle and the second nozzle is the switching point between the first actuator element and the second actuator element, the first nozzle and the second nozzle resulting in a minimum pitch jump. 12. The method of claim 12 or 13 , comprising selecting a nozzle of. Disabling one of the first nozzle and the second nozzle in the pair of aligned nozzles.
Disabling the nozzle of the second portion extending from the selected first nozzle towards the second end of the second portion.
12-14 , further comprising disabling the nozzle of the third portion extending from the selected second nozzle towards the first end of the third portion. The method according to any one of the above. The droplet depositor is configured to operate in the first mode at the first resolution and in the second mode at the second resolution, where the second resolution is a multiple of the first resolution. , The above method
In the first mode, the first nozzle is selected from the second portion of the nozzle array of the first actuator element, and the third portion of the nozzle array of the second actuator element. By selecting a second nozzle from, said first nozzle and second nozzle selected form a first pair of nozzles suitably aligned for said first mode. To do, to choose,
In the second mode, selecting a third nozzle from the second portion of the nozzle array of the first actuator element and the third portion of the nozzle array of the second actuator element. By selecting a fourth nozzle from, the selected third nozzle and the fourth nozzle form a pair of second nozzles that are suitably aligned for the second mode. The method of claim 12, further comprising, selecting, and selecting. At least one row in each nozzle array of the first actuator element and the second actuator element is configured to deposit the first fluid, the first actuator element and the second actuator element. At least one row in each nozzle array of the is configured to deposit a second fluid.
The method selects the first nozzle in the second portion of the nozzle array of the first actuator element from the row configured to deposit the first fluid, and said. By selecting a second nozzle within the third portion of the nozzle array of the second actuator element, the selected first and second nozzles are suitably aligned. Forming the first pair of nozzles, selecting and;
From the row configured to deposit the second fluid, select a third nozzle in the second portion of the nozzle array of the first actuator element, and select the second actuator. By selecting a fourth nozzle within the third portion of the nozzle array of the element, the selected third and fourth nozzles are the second of the appropriately aligned nozzles. 12. The method of claim 12, comprising forming, selecting, and pairing. To invalidate one of the first nozzle and the second nozzle in a pair of the first aligned nozzles;
The second end of the second portion from the selected first nozzle in the row configured to deposit the first fluid in the nozzle array of the first actuator element. To disable the nozzle in the second part extending towards;
The first end of the third portion from the selected second nozzle in the row configured to deposit the first fluid in the nozzle array of the second actuator element. To disable the nozzle in the third part extending towards;
To invalidate one of the third nozzle and the fourth nozzle in the pair of the second aligned nozzles;
In the row configured to deposit the second fluid in the nozzle array of the first actuator element, from the selected third nozzle to the second end of the second portion. To disable the nozzle in the second part extending towards;
The first end of the third portion from the selected fourth nozzle in the row configured to deposit the second fluid in the nozzle array of the second actuator element. 17. The method of claim 17, further comprising disabling the nozzle of the third portion extending towards. A control circuit that executes the method according to any one of claims 12 to 18 . A non-temporary data carrier that, when executed on a processor, carries code that causes the processor to perform the method of any one of claims 12-18 .

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