Patent Description:
Printers that use a columnar array of print elements or nozzles typically require the column of nozzles be swept horizontally across the printed medium while the nozzles selectively print points that represent printed pixels. Techniques such as interleaving and/or interlacing have been introduced to minimize or conceal printing artifacts caused by the printer components and/or the printed medium. However, such techniques often reduce the throughput of the printers, resulting in longer printing time. There exists a need to minimize printing time while maintaining the desired printing quality.

The disclosed embodiments relate to methods, devices and systems that utilize multiple printing masks to achieve variable printing qualities. Systems using multiple printing masks are described in <CIT> and in <CIT>.

One example aspect of the disclosed embodiments relates to a printer system that includes an array of nozzles and a control device coupled to the array of nozzles. The control device is configured to determine a step size for printing a current section of an image based on a set of masks. The set of masks includes one or more masks used for printing previous sections of the image. The control device is also configured to adjust the set of masks based on a printing mode to be used for the current section of the image. The array of nozzles is configured to print the current section of the image using a combination of the adjusted set of masks. Each mask of the set of masks is associated with a first attribute and a second attribute. The first attribute indicates an amount of shift of the mask with respect to the array of nozzles, and the second attribute indicates a number of nozzles to be used for applying the mask. According to the invention, the control device is further configured to add a new mask to the set of masks upon determining that the printing mode is different from a previous printing mode, and to set the first attribute of the new mask by tracking past changes of first and second attributes of the set of masks.

Another example aspect of the disclosed embodiments relates to a method for printing an image using an array of nozzles. The method includes determining, by a printer system, a step size for printing a current section of the image based on a set of masks. The set of masks includes one or more masks used for printing previous sections of the image. Each mask of the set of masks is associated with a first attribute and a second attribute. The first attribute indicates an amount of shift of the mask with respect to the array of nozzles, and the second attribute indicates a number of nozzles to be used for applying the mask. The method also includes adjusting the set of masks based on a printing mode to be used for the current section of the image and printing the current section of the image using a combination of the adjusted set of masks. According to the invention, the method further comprises a step of adding a new mask to the set of masks upon determining that the printing mode is different from a previous printing mode, and a step of setting the first attribute of the new mask by tracking past changes of first and second attributes of the set of masks.

Printers that use a column of print elements or nozzles typically require the column of nozzles to be swept horizontally across the printed medium while the nozzles selectively print points that represent printed pixels. Inherent print defects can occur in such operations. For example, paper feed inaccuracies and nozzle-to-nozzle variations in drop size or placement can introduce artifacts such as a visible band. Interlacing is a technique to reduce such printing artifacts. Using interlacing, different rows and columns are addressed by the nozzles in different printing passes, thereby reducing the visual impact of artifacts.

<FIG> illustrate several example printing modes. <FIG> illustrates an example printing mode <NUM> without using interlacing. In this mode <NUM>, every pixel is addressed on every pass. Printing all the desired pixels thus requires only one pass. <FIG> illustrates an example enhanced printing mode <NUM>. In this mode <NUM>, pixels are divided vertically into two groups, with one group marked as <NUM> (<NUM>) and the other group marked as <NUM> (<NUM>). In the first pass, only pixels in group <NUM> are addressed and pixels in group <NUM> are passed over. In the second pass, only pixels in group <NUM> are addressed and pixels in group <NUM> are passed over. Printing all the desired pixels thus requires two passes. This mode <NUM> is sometimes referred to as interleaving. <FIG> illustrates an example of an interlacing printing mode <NUM>. In this mode, pixels are divided horizontally into two groups: group <NUM> (<NUM>) and group <NUM> (<NUM>). In the first pass, images rows that are not addressable (i.e., in group <NUM>) are passed over. Only the rows in group <NUM> are printed. In the second pass, the passed over rows are addressed to complete the printing process. This is a common implementation when the nozzle array is at a lower pitch than the finished image. This mode <NUM> is also referred to as the "true interlacing" mode.

<FIG> illustrates an example mode <NUM> that uses both interleaving and interlacing techniques. In this mode <NUM>, the pixels are divided horizontally and vertically into four groups. In the two passes, as in the enhanced mode shown in <FIG>, selected columns of pixels are passed over. The interlacing mode as shown in <FIG> is adopted to print pixel group <NUM> in the first pass and pixel group <NUM> in two passes. The passed over columns are then printed in the subsequent passes, with pixel group <NUM> printed in the third pass and pixel group <NUM> printed in the fourth pass.

On top of interlacing techniques, print masks can be applied to the nozzle array as a way to increase the interlacing effect to further reduce visual impact of the printer defects. In this document, the print masks are also referred to as smoothing masks. <FIG> illustrates an example printing mode <NUM> that utilizes a smoothing mask. In this mode, a checkerboard mask is applied to the addressable pixels in the first pass. In the second pass, the inverse of the original checkerboard is applied so that the remaining pixels can be addressed. It is noted that in order to complete the image, the first and the second masks must complement each other. Thus, they are also referred to as the supplement and complement masks.

Other types of smoothing masks can be designed to create different levels of printing quality. For example, while the <NUM>/<NUM> checkerboard mask can be used to perform smoothing (which allows every pixel to be addressed in two passes), another mask can be designed to perform more smoothing. <FIG> illustrates an example smoothing mask <NUM> that uses a <NUM>/<NUM> checkerboard pattern in accordance with the disclosed technology. This mask allows each pixel to be addressed three times. <FIG> shows another example mask <NUM> that uses a <NUM>/<NUM> checkerboard pattern in accordance with the disclosed technology. Mask <NUM> addressed each pixel twice, thereby providing less smoothing as compared to the mask <NUM> shown in <FIG> but faster throughput.

Designing masks takes a great deal of effort -- various factors such as the printer configuration and desired quality level must be taken into account to generate an effective mask. Currently, once a mask is selected for a given input image, the smoothing level cannot be changed on the fly. However, not all areas in an input image require the same printing quality. Some areas are less susceptible to printer defects and are thus "easier to print," while other areas need multiple passes to ensure the desired quality. Throughput of the printer also becomes an issue when heavy smoothing masks are used. For example, the heavy smoothing masks as shown in <FIG> can double randomization of printing errors, thereby concealing visible defects more effectively. However, the total throughput of the printer is reduced because each pixel is addressed multiple times to complete the printing process. The low throughput increases the printing time. In some cases, high quality printing modes that utilize heavy smoothing can take more than an hour to complete a billboard.

This patent document discloses techniques that can be implemented in various embodiments to manage multiple smoothing masks at the same time, thereby providing variable smoothing levels on the fly. The disclosed techniques can achieve different printing qualities in a single image and can maximize printing speed in easy-to-print areas while providing desired quality in other areas. <FIG> illustrates a schematic diagram of using multiple smoothing masks for printing an image in accordance with the disclosed technology. In <FIG>, the horizontal axis indicates the passes that the printer takes to print a step (e.g., one or more rows of pixels). The vertical axis indicates the top-to-bottom direction that the printer head moves to print the image. In some embodiments, a technician responsible for printing the image determines which masks are needed based on the image content and the desired quality. The technician can also manually determine which section of the image requires which masks and provides commands to the printer indicating when transitions between the masks need to happen. In some embodiments, the printer system can automatically determine, in part based on analysis of the image, which smoothing mask is applicable to which section of the image. For example, the printer system can be trained using supervised training to learn the proper masks to choose.

The printing process in <FIG> starts with a printing mode that requires two passes to perform a printing step, as <FIG>. The addressed pixels and the printing direction are indicated in each pass (represented by a rectangle). For example, the first pass <NUM> is printed from left to right (indicated by arrow ">") and the addressed pixels include the odd columns (indicated by letter "O"). The next pass <NUM> is printed from right to left (indicated by arrow "<") and the addressed pixels include the even columns (indicated by letter "E"). As the printer progresses downwards, a command <NUM> can be used to indicate that a change is about to happen. The change can be a shift of the mask to compensate the movement of the printer head (e.g., the change between "<E O>" to "O> <E" in the two passes that the printer performs), a switch of the mask (e.g., a switch between a two-pass mask to a three-pass mask), or a combination thereof. For example, a command <NUM> can be provided to the printer system to indicate a switch from the first mask to a second mask, which requires three-passes to complete a printing step. The command <NUM> can be given ahead of time (e.g., two to three passes before the change needs to complete) so that the printer system can adjust the masks accordingly or the process can begin on the pass when the signal is first read.

<FIG> illustrates an example of using multiple masks for printing an image in accordance with the disclosed technology. Each of the masks can be associated with the following attributes:.

In this specific example, two masks are used: a non-smoothing mask <NUM> and a smoothing mask <NUM>, as shown in <FIG>. Because the smoothing mask <NUM> requires more passes to complete than the non-smoothing mask <NUM>, the corresponding printing rate is lower (that is, the printer system prints at a lower speed). As an example, the non-smoothing mask <NUM> has a rate of <NUM> pixels (px) while the smoothing mask <NUM> has a rate of 960px. It is noted that there is no interlacing in this example -- one nozzle indicates one pixel in the printed image. With a density of <NUM> Dots Per Inch (DPI), for example, a rate of <NUM> px is about <NUM> / <NUM> = <NUM> inches. The maximum number of nozzles to apply the mask is <NUM> px.

The printing process begins with one active mask -- the non-smoothing mask <NUM>. <FIG> illustrates an example pass for applying the non-smoothing mask <NUM> in accordance with the disclosed technology. In every pass, the step size can be set to the smallest rate of the current masks. The initial step size used by the printer is <NUM> px according to the rate of the only active mask -- the non-smoothing mask <NUM>.

After several passes, the printer system receives a command that indicates a change of printing mode. The printer system then prepares for the change by adding the smoothing mask <NUM>, which corresponds to the new printing mode, into the current mask(s). <FIG> illustrates an example pass in which the printer system transitions into the new smoothing masks <NUM> in accordance with the disclosed technology. Because the printing rate is getting slower (due to the fact that a more complex mask is introduced), the step size needs to be adjusted accordingly. Here, the step size is adjusted to be the smallest rate of the current masks, which now becomes <NUM> px, the rate of the smoothing mask <NUM>.

The shift of the previous mask is increased by (the mask's rate - step size). In this case, the initial shift for the previous non-smoothing mask is <NUM> px. The non-smoothing mask has a rate of <NUM> px. The new shift for the non-smoothing mask is thus increased to <NUM> - <NUM> = <NUM> px. Overlap of the new smoothing mask is increased by the step size and becomes <NUM> px. The overlap nozzles replace the previous non-smoothing mask, resulting in an intermediate mask <NUM>.

<FIG> illustrates a subsequent pass after the example pass shown in <FIG> in accordance with the disclosed technology. The current masks are still the non-smoothing mask <NUM> and the smoothing mask <NUM>. Therefore, the step size remains at <NUM> px. The shift of the non-smoothing mask is increased again by (mask's rate - step size) and becomes <NUM> px. The shift of the smoothing mask is increased by (<NUM> - <NUM>) = <NUM> px. Overlap of the smoothing mask is increased by the step size and reaches the maximum value of <NUM> px. The overlap nozzles replace the previous non-smoothing mask -- the full smoothing mask <NUM> is now being used. The non-smoothing mask can thus be removed from current mask(s) after this pass. The switch to the smoothing mask is then complete.

<FIG> illustrates another example of using multiple masks for printing an image in accordance with the disclosed technology. In this specific example, two masks are used: a 3x smoothing mask <NUM> and a 2x smoothing mask <NUM>, as shown in <FIG>. Because the 2x smoothing mask <NUM> requires fewer passes to complete than the 3x smoothing mask <NUM>, the corresponding printing rate is higher. As an example, the 3x smoothing mask <NUM> has a rate of <NUM> px and the 2x smoothing mask <NUM> has a rate of <NUM> px. It is noted that there is also no interlacing in this example -- one nozzle indicates one pixel in the printed image. The maximum number of nozzles to apply the mask is <NUM> px.

The printing process begins with one active mask -- the 3x smoothing mask <NUM>. The initial step size is <NUM> px. The printer system receives a command to indicate a change in the active mask(s). The printer system then prepares for the transition by adding the 2x smoothing mask <NUM> into the current masks. <FIG> illustrates an example pass in which the printer system transitions into the 2x smoothing mask <NUM> in accordance with the disclosed technology. The step size remains at <NUM> px.

The shift of the previous 3x smoothing mask <NUM> is increased by (the mask's rate - step size). In this case, however, the shift becomes a negative value of -<NUM> due to the fact that a less complex mask has been introduced yet the step size still remains the same. The actual shift performed to the 3x smoothing mask <NUM> is <NUM> px -- that is, no shift is performed to the previous mask. Instead, the new mask is shifted upwards by <NUM> px. Overlap is still calculated the same way -- overlap of the new 2x smoothing mask is increased by the step size and becomes <NUM> px. An intermediate mask <NUM> is determined based on a combination of the 3x smoothing mask <NUM> and the 2x smoothing mask <NUM>.

In some embodiments, the printer system may face multiple consecutive changes of the modes/masks. As demonstrated in the examples above, sometimes multiple passes are needed before the printer system can completely switch from one mode (using one mask) into another mode (using a different mask). To allow the printer system to adjust the masks properly under consecutive changes, the system can keep track of the past movements of the masks and predict a shift location based on the past information.

<FIG> illustrates an example of pseudocode for determining the mask of a pass in accordance with the disclosed technology. For each step of printing, the printer system keeps track of a set of active masks. Some of the masks have been used in the previous passes and remain active. For each pass, the step size is calculated based on the set of active masks. For example, the step size is the smallest printing rate associated with the set of masks. The shift and overlap of each mask are then updated based on the step size. If the printer system receives an indication that a new pass mode is used, a new mask is added to the set of active masks. Some of the mask attributes (e.g., the shift amount) are adjusted based on the step size. If the pass mode remains the same, the printer system checks if old unused masks can be discarded from the set. The adjusted active masks are then combined based on the respective attributes to produce an intermediate mask (e.g., the intermediate masks <NUM> and <NUM> as shown in <FIG> and <FIG>) for printing the current pass.

<FIG> is a flowchart representation of a method <NUM> for printing an image using an array of nozzles in accordance with the disclosed technology. The method <NUM> includes, at operation <NUM>, determining, by a printer system, a step size for printing a current section of the image based on a set of masks. The set of masks includes one or more masks used for printing previous sections of the image. The method <NUM> includes, at operation <NUM>, adjusting the set of masks based on a printing mode to be used for the current section of the image. The method <NUM> also includes, at operation <NUM>, printing the current section of the image using a combination of the adjusted set of masks.

<FIG> is a block diagram illustrating an example of the architecture for a computer system or a control device <NUM> of the printer system that can be utilized to implement various portions (e.g., controlling the array of nozzles) of the presently disclosed technology. In <FIG>, the control device <NUM> includes one or more processors <NUM> and memory <NUM> connected via an interconnect <NUM>. The interconnect <NUM> may represent any one or more separate physical buses, point to point connections, or both, connected by appropriate bridges, adapters, or controllers. The interconnect <NUM>, therefore, may include, for example, a system bus, a Peripheral Component Interconnect (PCI) bus, a HyperTransport or industry standard architecture (ISA) bus, a small computer system interface (SCSI) bus, a universal serial bus (USB), IIC (I2C) bus, or an Institute of Electrical and Electronics Engineers (IEEE) standard <NUM> bus, sometimes referred to as "Firewire.

The processor(s) <NUM> may include central processing units (CPUs), graphics processing units (GPUs), or other types of processing units (such as tensor processing units) to control the overall operation of, for example, the host computer. In certain embodiments, the processor(s) <NUM> accomplish this by executing software or firmware stored in memory <NUM>. The processor(s) <NUM> may be, or may include, one or more programmable general-purpose or special-purpose microprocessors, digital signal processors (DSPs), programmable controllers, application specific integrated circuits (ASICs), programmable logic devices (PLDs), or the like, or a combination of such devices.

The memory <NUM> can be or include the main memory of the computer system. The memory <NUM> represents any suitable form of random access memory (RAM), read-only memory (ROM), flash memory, or the like, or a combination of such devices. In use, the memory <NUM> may contain, among other things, a set of machine instructions which, when executed by processor <NUM>, causes the processor <NUM> to perform operations to implement embodiments of the presently disclosed technology.

Also connected to the processor(s) <NUM> through the interconnect <NUM> is a (optional) network adapter <NUM>. The network adapter <NUM> provides the computer system <NUM> with the ability to communicate with remote devices, such as the storage clients, and/or other storage servers, and may be, for example, an Ethernet adapter or Fiber Channel adapter.

Using the disclosed techniques, an image can be printed using variable quality levels on the fly, thus eliminating the need to print the same image multiple times. Optimal printing speed can be achieved by the printer system while maintaining the desired quality level.

In one example aspect, a printer system includes an array of nozzles, and a control device coupled to the array of nozzles. The control device is configured to determine a step size for printing a current section of an image based on a set of masks. The set of masks includes one or more masks used for printing previous sections of the image. The control device is also configured to adjust the set of masks based on a printing mode to be used for the current section of the image. The array of nozzles is configured to print the current section of the image using a combination of the adjusted set of masks.

In some embodiments, each mask of the set of masks is associated with a printing rate, and wherein the step size is determined by a smallest printing rate of all masks in the set of masks.

According to the invention, each mask of the set of masks is associated with a first attribute and a second attribute. The first attribute indicates an amount of shift of the mask with respect to the array of nozzles, and the second attribute indicates a number of nozzles to be used for applying the mask. In some embodiments, the control device is further configured to determine, for each mask in the set of masks, the first attribute based on the step size and a printing rate of the mask. The control device can be further configured to determine, for each mask in the set of masks, the second attribute based on the step size.

According to the invention, the control device is configured to add a new mask to the set of masks upon determining that the printing mode is different from a previous printing mode. The control can be configured to set the first attribute of the new mask based on a printing rate of the new mask and the step size. According to the invention, the control device is configured to set the first attribute of the new mask by tracking past changes of first and second attributes of the set of masks.

In some embodiments, the control device is configured to determine the second attribute of the new mask based on the step size. In some embodiments, the control device is further configured to shift each of the set of masks according to the first attribute of the mask and determine, based on second attributes of all shifted masks in the set of masks, an overlapped area in the array of nozzles to be used for printing the current section of the image. The control device can be configured to adjust the set of masks by removing one or more unused masks from the set of masks upon determining that the printing mode is same as a previous printing mode.

In another example aspect, a method for printing an image using an array of nozzles includes determining, by a printer system, a step size for printing a current section of the image based on a set of masks. The set of masks includes one or more masks used for printing previous sections of the image. The method also includes adjusting the set of masks based on a printing mode to be used for the current section of the image and printing the current section of the image using a combination of the adjusted set of masks.

In some embodiments, each mask of the set of masks is associated with a printing rate, and the step size is determined by a smallest printing rate of all masks in the set of masks. In some embodiments, each mask of the set of masks is associated with a first attribute and a second attribute. The first attribute indicates an amount of shift of the mask with respect to the array of nozzles, and the second attribute indicates a number of nozzles to be used for applying the mask.

In some embodiments, the method includes determining, for each mask in the set of masks, the first attribute based on the step size and a printing rate of the mask. In some embodiments, determining, for each mask in the set of masks, the second attribute based on the step size. According to the invention, the adjusting of the set of masks includes adding a new mask to the set of masks upon determining that the printing mode is different from a previous printing mode.

In some embodiments, the method includes determining the first attribute of the new mask based on a printing rate of the new mask and the step size. According to the invention, the method includes determining the first attribute of the new mask by tracking past changes of first and second attributes of the set of masks. In some embodiments, the method includes determining the second attribute of the new mask based on the step size. In some embodiments, the combination of the adjusted set of masks is determined by shifting each mask of the set of masks based on the first attribute of the mask, and determining, based on second attributes of all shifted masks in the set of masks, an overlapped area in the array of nozzles to be used for printing the current section of the image. In some embodiments, the adjusting of the set of masks includes removing one or more unused masks from the set of masks upon determining that the printing mode is same as a previous printing mode.

The control device(s) that are described in connection with the disclosed embodiments can be implemented as hardware, software, or combinations thereof. For example, a hardware implementation can include discrete analog and/or digital components that are, for example, integrated as part of a printed circuit board.

Various embodiments described herein are described in the general context of methods or processes, which may at least in part be implemented by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), Blu-ray Discs, etc. Therefore, the computer-readable media described in the present application include non-transitory storage media. Computer-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein.

Claim 1:
A printer system, comprising:
an array of nozzles, and
a control device coupled to the array of nozzles configured to:
determine a step size for printing a current section of an image based on a set of masks (<NUM>, <NUM>; <NUM>, <NUM>), wherein the set of masks (<NUM>, <NUM>; <NUM>, <NUM>) includes one or more masks (<NUM>; <NUM>) used for printing previous sections of the image;
adjust the set of masks (<NUM>, <NUM>; <NUM>, <NUM>) based on a printing mode to be used for the current section of the image,
wherein the array of nozzles is configured to print the current section of the image using a combination of the adjusted set of masks (<NUM>, <NUM>; <NUM>, <NUM>),
wherein each mask of the set of masks (<NUM>, <NUM>; <NUM>, <NUM>) is associated with a first attribute and a second attribute, wherein the first attribute indicates an amount of shift of the mask with respect to the array of nozzles, and wherein the second attribute indicates a number of nozzles to be used for applying the mask,
characterized in that the control device is further configured to:
add a new mask to the set of masks (<NUM>, <NUM>; <NUM>, <NUM>) upon determining that the printing mode is different from a previous printing mode; and
set the first attribute of the new mask by tracking past changes of first and second attributes of the set of masks (<NUM>, <NUM>; <NUM>, <NUM>).