Print response compensation mechanism

Abstract

To provide a printing system that efficiently performs calibration of a printer.SOLUTION: The printing system includes at least one physical memory device that stores compensation logic and one or more processors that are coupled to the at least one physical memory device and execute the compensation logic. The compensation logic includes: receiving print response measurement data corresponding to a print image printed on a print substrate by using a transfer function applied to print image data that defines the print image; generating first processed print response data on the basis of the print response measurement data; determining whether an absolute difference between the first processed print response data and a target response exceeds a first threshold; and when the absolute difference is determined to exceed the first threshold, generating an updated compensation transfer function on the basis of the first processed print response data and the target response.SELECTED DRAWING: None

Description

[Technical Field]

[0001]

[0001] The present invention relates to the field of image reproduction, and in particular to printer calibration. [Background technology]

[0002]

[0002] Entities with significant printing demands typically implement high-speed production printers for high-volume printing (e.g., 100 pages per minute or more). Production printers may include continuous-feed printers that print on a web of print media (or paper) stored on a large roll. Production printers typically include a local print controller that controls the overall operation of the printing system and one or more print engines that include one or more printhead assemblies, each of which includes a printhead controller and a printhead (or an array of printheads). Each printhead includes multiple nozzles (e.g., inkjet nozzles) for ejecting ink or some other colorant suitable for printing on the media. Summary of the Invention

[0003] In one embodiment, a printing system is disclosed that includes at least one physical memory device that stores compensation drift logic, and one or more processors coupled to the at least one physical memory device that execute the compensation logic, the compensation logic including receiving print response measurement data corresponding to a print image to be printed on a print substrate using a transfer function applied to print image data that defines the print image; generating first processed print response data based on the print response measurement data; determining whether an absolute difference between the first processed print response data and a target response exceeds a first threshold; and, upon a determination that the absolute difference exceeds the first threshold, generating an updated compensation transfer function based on the first processed print response data and the target response. [Brief explanation of the drawings]

[0004]

[0004] A better understanding of the present invention can be obtained from the following detailed description taken in conjunction with the following drawings: [Figure 1]

[0005] FIG. 1 is a block diagram of one embodiment of a printing system. [Figure 2A]

[0006] FIG. 2A is a block diagram illustrating an embodiment of a print controller. [Figure 2B] FIG. 2B is a block diagram illustrating an embodiment of a print controller. [Figure 3]

[0007] FIG. 3 illustrates one embodiment of the compensation module. [Figure 4]

[0008] Figure 4 shows one embodiment of the calibration engine. [Figure 5]

[0009] FIG. 5 illustrates one embodiment of print substrate calibration logic. [Figure 6]

[0010] FIG. 6 shows one embodiment of the transfer function. [Figure 7]

[0011] FIG. 7 is a flow diagram illustrating one embodiment of a process for generating a print substrate transfer function. [Figure 8]

[0012] FIG. 8 is a flow diagram illustrating one embodiment of a process for generating sub-range transfer functions. [Figure 9]

[0013] FIG. 9 illustrates one embodiment of the composite transfer function generation logic. [Figure 10]

[0014] Figure 10 shows one embodiment of the compensation drift logic. [Figure 11]

[0015] FIG. 11 is a flow diagram illustrating one embodiment of a process for performing print density drift compensation. [Figure 12]

[0016] FIG. 12 is a flow diagram illustrating one embodiment of a process for generating an updated compensation transfer function. [Figure 13]

[0017] FIG. 13 illustrates one embodiment of a compensation module implemented in a network. [Figure 14]

[0018] FIG. 14 illustrates one embodiment of a computer system. DETAILED DESCRIPTION OF THE INVENTION

[0005]

[0019] The print output optical density (OD) of a production printer changes over time as components undergo wear. For example, in an inkjet printer, OD increases as droplet size increases due to wear on printhead components and other factors. This change in performance is undesirable because it impacts color management consistency. One approach to maintaining consistency is to recalibrate the primary colors to a specific target OD using the customer's substrate (e.g., paper). However, having to perform substrate recalibration is a time-consuming process.

[0006]

[0022] According to one embodiment, a mechanism is described that monitors a printer for print density drift variations and automatically updates print image compensation to achieve a target print response. In such an embodiment, the target print response is achieved by using a compensation transfer function applied to the print image data. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the principles underlying the present invention.

[0007]

[0021] References in the specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification do not necessarily all refer to the same embodiment.

[0008] FIG. 1 is a block diagram illustrating one embodiment of a printing system 130. A host system 110 communicates with the printing system 130 to cause a printer 160 (e.g., one or more print engines) to print sheet images 120 onto print media 180. The print media 180 may include paper, card stock, paperboard, corrugated board, film, plastic, synthetic, fiber, glass, composite, or any other tangible medium (e.g., print substrate) suitable for printing. The format of the print media 180 may be continuous form, cut sheets, or any other suitable format for printing. The printer 160 may be inkjet, electrophotographic, or any other suitable printer type.

[0009]

[0023] In one embodiment, printer 160 includes one or more print heads 162, each print head including one or more pel forming elements 165 that directly or indirectly (e.g., by transfer of marking material via an intermediate) form a representation of a picture element (pel) on print medium 180 using marking material applied to the print medium. In an ink-jet printer, pel forming elements 165 are tangible devices (e.g., ink-jet nozzles) that eject ink onto print medium 180, while in an electro-photographic (EP) printer, pel forming elements may be tangible devices (e.g., EP exposure LEDs or EP exposure lasers) that determine the location of toner particles printed on the print medium. Pel forming elements may be grouped into one or more print heads 162. Pel forming elements 165 may be stationary (e.g., as part of a static print head 162) or movable (e.g., as part of a print head 162 that moves across print medium 180) as a matter of design choice. Pel forming elements 165 may be assigned to one of one or more color planes corresponding to each of one or more types of marking materials (e.g., the primary colors cyan, magenta, yellow, and black (CMYK)).

[0010]

[0024] In further embodiments, printer 160 is a multi-pass printer (e.g., dual-pass, three-pass, four-pass, etc.), where multiple sets of pel forming elements 165 print the same area of ​​the printed image on print medium 180. The sets of pel forming elements 165 may be located on the same physical structure (e.g., an array of nozzles on an inkjet printhead 162) or on separate physical structures. The resulting print medium 180 can be printed in color and / or in any number of shades of gray, including black and white (e.g., cyan, magenta, yellow, and black (CMYK)). Host system 110 could include any computing device, such as a personal computer, a server, or even a digital imaging device, such as a digital camera or scanner.

[0011]

[0025] Sheet image 120 may be any file or data that describes how an image on a sheet of print media 180 should be printed. For example, sheet image 120 may include PostScript data, Printer Command Language (PCL) data, and / or any other printer language data. Print controller 140 processes the sheet image to generate bitmap 150 for transmission. Bitmap 150 includes instructions (e.g., commanded ink drop size and / or commanded pel formation element position) for one or more printheads 162 and pel formation elements 165. Bitmap 150 may be a halftoned bitmap (e.g., a compensated halftone bitmap generated from compensated halftones or an uncompensated halftone bitmap generated from uncompensated halftones) for printing on print media 180. Printing system 130 may be a high-speed printer capable of operating at a relatively high volume (e.g., greater than 100 pages per minute).

[0012]

[0026] Print medium 180 may be continuous form paper, cut-sheet paper, and / or any other tangible medium suitable for printing. In a generalized form, printing system 130 includes printer 160 that presents (e.g., with toner, ink, etc.) a bitmap 150 based on sheet image 120 onto print medium 180. While shown as a component of printing system 130, other embodiments may characterize printer 160 as a separate device communicatively coupled to print controller 140.

[0013]

[0027] The print controller 140 may be any system, device, software, circuitry, and / or other suitable component operable to transform the sheet image 120 to generate a bitmap 150 for printing on the print medium 180. In this regard, the print controller 140 may have processing and data storage capabilities. In one embodiment, a measurement module 190 is implemented as part of a compensation system that obtains measurements of the print medium 180. The measurements are communicated to the print controller 140 for use in the compensation process. The measurement system may be a stand-alone process or may be integrated into the print system 130.

[0014]

[0028] According to one embodiment, measurement module 190 may be an image sensor that performs measurements of the printed image on print medium 180. Measurement module 190 may generate and transmit measurement data (e.g., print response measurement data). The measurement data may be OD (e.g., optical density), perceived lightness (e.g., L* in the CIELAB color plane L*a*b*), and / or scanned image (e.g., RGB) data corresponding to the printed image. In one embodiment, measurement module 190 may include one or more sensors that individually or collectively obtain measurements of the printed markings generated for all or some of pel forming elements 165. In another embodiment, measurement module 190 may be a camera system, an in-line scanner, a densitometer, or a spectrophotometer.

[0015]

[0029] 2A shows a generalized form of print controller 140 (e.g., DFE or digital front end) that includes an interpreter module 212, a halftoning module 214, and a compensation module 230. These individual components may represent hardware used to implement print controller 140. Alternatively, or additionally, the individual components may represent logic blocks that are implemented by executing software instructions within a processor of printer controller 140.

[0016] 2B shows an alternative embodiment having print controllers 140A and 140B. In this embodiment, print controller 140A includes an interpreter module 212 and a halftoning module 214, and print controller 140B includes a compensation module 230. Print controllers 140A and 140B may be implemented within the same printing system 130 (as shown) or may be implemented separately.

[0017]

[0030] The interpreter module 212 is operable to interpret, render, rasterize, or otherwise convert print job images (e.g., raw sheetside images, such as sheet image 120) into sheetside bitmaps. The sheetside bitmaps generated by the interpreter module 212 for each primary color are each a two-dimensional array of pels representing the print job image (e.g., a Continuous Tone Image (CTI)) and are also referred to as full sheetside bitmaps. A two-dimensional pel array is considered a “full” sheetside bitmap because the bitmap contains the entire set of pels for the image. The interpreter module 212 is operable to interpret or render multiple raw sheetside images simultaneously, so that the rendering speed substantially matches the image processing speed of the production print engine. In one embodiment, the transfer function is implemented by the print controller 140 and may be applied directly to the image data as part of pre-press image processing. In that case, contone image data (e.g., CTI data) is transformed by applying a transfer function to the CTI data before halftoning. The transfer function involves mapping input digital counts of the system to output digital counts, where the digital counts are gray levels or color values ​​that represent pels in bitmap 150 (FIG. 1). The transfer function may be used to calibrate printing system 130.

[0018]

[0031] The halftoning module 214 can operate to represent a sheet surface bitmap as an ink halftone pattern. For example, the halftoning module 214 can convert pels (also known as picture elements) into a CMYK ink halftone pattern for application to paper. The halftone design can include a predefined mapping of input pel gray levels to output drop sizes (e.g., commanded ink drop sizes delivered to the printhead) based on pel location.

[0019]

[0032] In one embodiment, the halftone design may include a finite set of transition thresholds (e.g., zero, small, medium, and / or large) among a finite set of successively larger drop sizes, starting with zero and ending with the largest drop size. The halftone design may be implemented as a threshold array (e.g., halftone threshold array), such as a single-bit threshold array or a multi-bit threshold array. In another embodiment, the halftone design may be implemented as a three-dimensional look-up table with all encompassed gray level values.

[0020]

[0033] In a further embodiment, the halftoning module 214 performs multi-bit halftoning using a halftone design that includes a set of thresholds for each pel in the sheet plane bitmap, one threshold for each non-zero ink drop size. A pel is halftoned with the drop size that corresponds to that pel's threshold. The set of thresholds for a halftone design is called a multi-bit threshold array (MTA).

[0021]

[0034] Multi-bit halftoning is a halftone screening operation whose end result is the selection of a specific drop size available from the entire set of drop sizes the print engine can use for printing. Drop size selection based on the contone value of a single pel is referred to as "point operation" halftoning. Drop size selection is based on the contone level for each pel in the sheet surface bitmap. This is in contrast to "neighborhood operation" halftoning, in which multiple pels neighboring the printed pel are used to determine the drop size. An example of neighborhood operation halftoning is the well-known error diffusion method.

[0022]

[0035] Multi-bit halftoning is an extension of binary halftoning, which uses a single threshold array combined with logical operations to determine whether a drop is printed based on the contone level of a pel. Binary halftoning uses one non-zero drop size plus a zero drop size (e.g., no drop size, in which case no ink is ejected). Multi-bit halftoning extends the concept of a binary threshold array to more than one non-zero drop size.

[0023]

[0036] Multi-bit halftoning may use multiple threshold arrays (e.g., multi-bit threshold arrays), one for each non-zero drop size. The point operation logic may be extended to more, fewer, or the same number of operation sets to determine drop size by comparing a threshold value or thresholds to the image contone data for each pel. Multi-bit defines a set of drop sizes that are a power of two (e.g., a 2-bit halftone design has a total of four drops, including the zero drop size). While it is possible to define the number of drops using a power of two, a system that does not follow this rule, such as a system with a total of three drops, may be used and still be considered multi-bit.

[0024]

[0037] For multi-bit halftoning, the MTA is a three-dimensional array containing one two-dimensional array for each drop size (e.g., commanded ink drop size) transition. Thus, the MTA contains a set of two-dimensional arrays of thresholds for transitions between drop sizes: the first plane (or plane 1) provides the threshold for the large-power level, while the second plane (or plane 2) and third plane (or plane 3) provide the thresholds for the medium-power and small-power levels, respectively, for a system with three drop sizes that does not include the zero drop size (none or off). In other embodiments, the correspondence between the number of planes and drop sizes is a matter of design choice, and a different one-to-one relationship may be used.

[0025]

[0038] To use these threshold arrays for halftoning, each multi-bit threshold array is tiled over the contone image data provided by the sheet plane bitmap, providing a set of threshold values ​​for each pixel in the sheet plane bitmap. The contone image data (e.g., digital counts, gray level data) is logically compared to the threshold data on a pixel-by-pixel basis. Large droplets are generated by halftoning when the image contone data is greater than the respective large-threshold value in plane 1.

[0026]

[0039] A medium drop is generated if the image contone data is greater than the medium drop threshold for plane 2 and the image contone data is less than or equal to the large drop threshold for plane 1. A small drop is generated if the image contone data is greater than the small drop threshold for plane 3 and the image contone data is less than or equal to the medium drop threshold for plane 2.

[0027]

[0040] Finally, an off / no-drop size occurs if the contone image data is below the small-drop threshold for plane 3. In this embodiment of a 2-bit to multi-bit printing system, this set of four logical equations used in conjunction with the threshold values ​​from each plane of the multi-bit threshold array allows each print drop size to be defined based on the contone value.

[0028]

[0041] It is also possible to define alternative versions of the halftoning formulas. An example of an alternative set of halftone logical expressions is replacing the "less than or equal to" operation with a "less than" operation and replacing the "greater than" operation with a "greater than or equal to" operation. A further variation begins by testing for the largest drop size first, using the "less than or equal to" and "greater than" logical expressions. If no drop size is found, the process continues with the logical expression for the next smaller drop size. If a drop size is not found with the sequential testing of each drop size, no drop size is assumed. The threshold array for each different set of halftoning formulas varies, and therefore, a threshold array is generated assuming a given set of formulas.

[0029]

[0042] In other embodiments, the number of planes of threshold data can be expanded to handle any number of drop sizes. These two-dimensional arrays of data can be segmented into separate memory areas and stored in any convenient order. For example, the thresholds for each drop size transition can be stored consecutively in memory, and it is often advantageous to do so.

[0030]

[0043] The compensation module 230 performs a compensation process on the uncompensated halftones 218 received by the print controller 140, or previously generated uniform compensated halftones, to generate one or more compensated halftones (compensated halftones) 220. A compensated halftone is a halftone adjusted to achieve a target output response. The compensated halftones 220 are then received by the halftoning module 214 along with the sheet surface bitmap. In one embodiment, the uncompensated halftones 218 represent a reference halftone design that is modified to create compensated halftones based on measured OD data 501 (e.g., print response measurement data) and target OD data 502 (e.g., target response data). In such an embodiment, system response measurements (e.g., measured optical density (OD) data 501) are received via the measurement module 190 using the uncompensated halftones 218 to print a test chart.

[0031]

[0044] Alternatively, compensation module 230 can perform a compensation process to generate a compensated transfer function (compensation transfer function) 225 based on measured OD data 501 and target OD data 502. The measurement units of measured OD data 501 have the same units as target OD data 502. In such an embodiment, measurements of the system response (e.g., measured optical density (OD) data 501) are received via measurement module 190 using compensation halftoning 220 to print a test chart. Compensation transfer function 225 is then received by transfer function application module 235. Transfer function application module 235 applies the received compensation transfer function 225 to print image data received from interpreter module 212 before halftoning is performed by halftoning module 214. As described above, the transfer function involves mapping input digital counts (or tints) for the system to output digital counts, where the digital counts are gray levels or color values ​​representing pels in bitmap 150 (FIG. 1). A transfer function can be received or generated (eg, generated based on target OD vs. input digital count data and measured OD vs. output digital count data).

[0032]

[0045] The compensation module 230 is further implemented to perform a calibration process to maintain optical density (OD) within the printer 160 to compensate for OD differences from the target OD. According to one embodiment, a calibrated printing system is a printing system that achieves a first target response while printing on a first print substrate using a first halftone design and a first printer transfer function. M1 is a measured response corresponding to the target printing system printing on the first print substrate using the first halftone design and a none or an identity transfer function (e.g., digital counts output = digital counts input). The measured response M1 has the same units of measure as the target response T1. M2 is a measured response corresponding to the calibrated printing system printing on a second print substrate using the first halftone design and the first printer transfer function. T2 is a second target response when printing on the second print substrate using the first halftone design and the first printer transfer function. The measured response M2 has the same units of measure as the target response T2.

[0033]

[0046] FIG. 3 illustrates one embodiment of the compensation module 230, including a calibration generator 305, a chart generator 310, and a calibration engine 320. The calibration generator 305 facilitates the calibration process in the printing system 130 by directing the calibration process. In one embodiment, the calibration process is performed to generate or update a printing system (or printer) transfer function (e.g., for short-term printer OD variation compensation), a print substrate transfer function, and / or a composite transfer function. In such an embodiment, each calibration is based on a calibration performed using a print substrate (e.g., print media or customer paper) implemented for a print job in the printing system 130. In a further embodiment, each calibration may be initiated by a system operator via a graphical user interface (GUI 330) in the printing system 130.

[0034]

[0047] As used herein, a printer transfer function (e.g., printerTF, first printer transfer function) is a mapping of input digital counts of a printing system to output digital counts to achieve a first target response (e.g., T1, reference ink deposition, OD target) while printing on a first substrate (e.g., S1 or reference substrate) using a first halftone design (e.g., reference halftone design). When the printer transfer function is applied to a printing system, the printing system becomes a calibrated printing system. A substrate transfer function (e.g., substrateTF) is a mapping of input digital counts of a calibrated printing system to output digital counts to achieve a second target response (e.g., T2) while printing on a second substrate (e.g., S2, customer substrate) using the first halftone design and first printer transfer function. A composite transfer function (CTF) is a transfer function that is a composite of the printer transfer function and the substrate transfer function.

[0035]

[0048] The chart generator 310 prints a test chart at the beginning of the calibration process. In one embodiment, the chart generator 310 generates an image (e.g., a printed image for the test chart) including a test pattern corresponding to one or more print heads 162, which is then processed by the measurement module 190 to generate OD measurement data. In a further embodiment, first measurement data is generated associated with an image printed during a first calibration process using an identity transfer function and an initial print substrate (e.g., a first print substrate). Similarly, second measurement data is generated by printing an image during a subsequent calibration process on a subsequent print substrate (e.g., a second print substrate) using the printer transfer function derived for the first print substrate. Third measurement data is generated by printing an image during a verification process on the subsequent print substrate using the print substrate transfer function and the printer transfer function associated with the print substrate. In one embodiment, the print substrate used during the subsequent print substrate calibration may be the same or different from the initial print substrate.

[0036]

[0049] The calibration engine 320 receives the first and second measurement data and generates a print substrate transfer function. In an embodiment, the print substrate transfer function is implemented to generate a composite transfer function (CTF). The third measurement data can be used to verify the accuracy of the composite printer transfer function and the print substrate transfer function.

[0037] 4 illustrates one embodiment of calibration engine 320, including substrate calibration logic 410 and printer calibration logic 420. Substrate calibration logic 410 and printer calibration logic 420 receive measured OD data 501.

[0038]

[0050] The substrate calibration logic 410 may be implemented to generate a substrate transfer function for each customer paper used in the printing system 130. The printer calibration logic 420 is implemented to generate a printer transfer function. The composite transfer function generation logic 430 generates a composite transfer function based on a mathematical function composition of the printer transfer function and the substrate transfer function.

[0039]

[0051] In one embodiment, the print substrate calibration logic 410 generates an updated (or corrected) print substrate transfer function to compensate for variations to the printer transfer function or variations to the print substrate measurement response. In such an embodiment, the print substrate calibration logic 411 first generates a first print substrate transfer function based on the current printer transfer function (e.g., PTF_k, where k represents the printer transfer function index). Thus, PTF_k is used to print a test chart on a customer paper, and its associated measurement data is used to determine a print substrate transfer function (e.g., substrateTF_i_j, where i is the index of a different paper and j is the index of a repeat (e.g., iterative) print substrate transfer function for the same paper).

[0040]

[0052] In a further embodiment, the print substrate calibration logic 410 generates a new print substrate transfer function (e.g., substrateTF_i_j+1) based on an updated printer transfer function (e.g., PTF_k+1). In this embodiment, the print substrate calibration logic 410 generates substrateTF_i_j+1 using measurements made with PTF_k+1. The latest version of PTF and substrateTF is used for printing on the print substrate associated with substrateTF.

[0041]

[0053] FIG. 5 illustrates one embodiment of print substrate calibration logic 410. As shown in FIG. 5, print substrate calibration logic 410 includes a full-range print substrate transfer function generation engine 520 that receives measured OD data 501 (associated with printing using customer paper and a printer transfer function) and target OD data 502 from measurement module 190. In one embodiment, full-range print substrate transfer function generation engine 520 generates a full-range print substrate transfer function based on the measured OD data 501 and the target OD data 502 using the printer transfer function used. As used herein, a full-range transfer function has a number of digital count values ​​calibrated to achieve the target OD 502, and the maximum target optical density (e.g., maximum target, DDMax) is the maximum optical density of the measured OD data 501 acquired using a substrate by an image processing system (e.g., printing system 130).

[0042]

[0054] FIG. 6 illustrates one embodiment for generating transfer functions (e.g., printer transfer functions and / or print substrate transfer functions) for all digital count levels (e.g., gray levels). Target OD data T(g) (e.g., target OD data 502) is used as the target for the current halftone applied with the identity transfer function, or the current halftone with the current printer transfer function applied. The measured response (measured response) is given by M(g) (e.g., measured OD data 501). The measured response is determined by printing a single color corresponding to the ink. Given a known response, at gray level g1, the target OD is OD1. To achieve OD1, print level g2 is printed. For example, using 0:255 for g1, the set of g2 values ​​defines the transfer function. Expressed as a continuous function, the transfer function is: g_output=TF(g_input) The transfer function equation is given by the target T and the inverse measured response M -1 In terms of, it can be written as: g_output=M-1 (T(g_input))=TF(g_input) By using the g_output values ​​as substitution values ​​for the corresponding g_input values, the calibrated target response is achieved for all levels. The transfer function can be generated as a look-up table (e.g., LUT) or a mathematical curve. The transfer function curve may be generated by mathematical curve fitting (e.g., using a cubic spline, a smoothing spline curve, or other known mathematical approximation techniques). The transfer function curve can then be evaluated using the input values ​​to determine the output values ​​by direct calculation. A technical advantage of a look-up table (e.g., LUT) is that evaluating a look-up table reduces the computational burden compared to the often complex run-time calculations associated with evaluating a curve.

[0043]

[0055] 7 is a flow diagram illustrating one embodiment of a process 700 for generating a transfer function (e.g., a full-range print substrate transfer function). Process 700 may be performed by processing logic, which may include hardware (e.g., circuitry, dedicated logic, programmable logic, microcode, etc.), software such as instructions executing on a processing device, or a combination thereof. In one embodiment, process 700 is performed by calibration engine 320.

[0044]

[0056] Process 700 begins at process block 710, where measured OD data is received. At process block 720, target OD data is received. At process block 730, transfer functions are generated based on the measured OD data 501 and the target OD data 502. In one embodiment, process block 730 generates full-range print substrate transfer functions FRsubstrateTF_i_j. The transfer functions (e.g., LUTs representing the transfer functions), the OD targets associated with the transfer functions, and / or the measured OD data associated with the transfer functions may be stored in system memory for later access.

[0045]

[0057] The full range print substrate transfer function generation engine 520 may also use new test data for the print substrate to generate a print substrate transfer function (e.g., substrateTF_i+1_j) associated with a different print substrate according to process 700 using the corresponding measured OD data 501 and target OD data 502 for the new substrate.

[0046]

[0058] According to one embodiment, the above process is performed to generate a full-range print substrate transfer function lookup table (LUT) 530 (shown in FIG. 5 ) that includes a full-range print substrate transfer function (FRsubstrateTF_i_j) associated with each digital count for each color plane. In a further embodiment, the LUT 530 also includes multiple operating point parameters, including OD, ΔE, percent dot (PD) knockdown, etc. As used herein, ΔE is a measure of how perceptible a variation in the operating point is, while PD knockdown is the operating point defined by the percent dot reduction from a solid area (100% tint level).

[0047]

[0059] 5, the substrate calibration logic 410 also includes a sub-range substrate transfer function generation engine 540. In one embodiment, the sub-range substrate transfer function generation engine 540 receives the operating point data, receives a full-range transfer function (e.g., full-range substrate transfer function) corresponding to the image processing system, and generates a sub-block transfer function (e.g., sub-range substrate transfer function) corresponding to the image processing system for each of the plurality of digital count values ​​based on the operating point data and the full-range transfer function, where the full-range substrate transfer function generates a maximum OD (e.g., Dmax) equal to the maximum measured OD (e.g., Ddmax) at the end of the tonal range, and the sub-range substrate transfer function has a maximum OD less than DDmax OD.

[0048]

[0060] A resulting technical advantage is that the sub-range transfer function can be generated without acquiring new measured OD data 501 when a shift in the operating point is detected, which saves operator time and / or reduces system burden. Other data, such as DDmax and DDmin (discussed below), may also be received as needed. In a further embodiment, the input domain of the sub-range transfer function matches the input domain of the full-range transfer function, and the output range of the sub-range transfer function is a subset of the output range of the full-range transfer function.

[0049]

[0061] Matching the domains or ranges can be achieved by appropriate selection of data points or mathematical approximation. Typically, if the full-range transfer function is continuous, no approximation is required. If the full-range transfer function is discrete, an approximation may be required. A technical advantage of matching the input domains or ranges in this embodiment is that it ensures continuity when applying the sub-range transfer function in the image processing system. In yet another embodiment, the input domain of the sub-range transfer function matches the range of contone levels in the image processing path, and the output range of the sub-range transfer function matches the domain of the halftone thresholds used in the threshold array.

[0050]

[0062] As used herein, a sub-range transfer function includes a plurality of digital count values ​​calibrated to an optical density target value (e.g., a first optical density target value) indicated by operating point data 503, where the optical density target value indicated by operating point data 503 is less than a DDmax value (e.g., a second optical density target value). A technical advantage accrues with respect to a full-range transfer function calibrated to a maximum calibration optical density, as explained further below, is that such a full-range transfer function includes the data necessary to generate a sub-range transfer function calibrated to some optical density target less than the full-range maximum calibration optical density.

[0051]

[0063] In one embodiment, the sub-range substrate transfer function generation engine 540 receives the full-range substrate transfer function from the full-range substrate transfer function LUT 530 and receives operating point data 503 from the GUI 330. In such an embodiment, the GUI 330 displays the operating parameters stored in the LUT 530, where these LUT values ​​include measured OD vs. PD and ΔE vs. PD. DDmax corresponds to the OD measured at 100% tint level, and DDmin corresponds to the OD measured at 0% tint level. In a further embodiment, the system operator (or user) reviews multiple displayed options (e.g., operating parameters) and selects operating point data that achieves the desired result on the substrate based on the OD values, ΔE color difference, PD reduction, and additional data (e.g., ink drying ability).

[0052]

[0064] The compensation module 230 can convert operating point parameters to OD values ​​(e.g., from OD, PD knockdown, DeltaE, etc.) using known conventional image processing methods (e.g., look-up tables containing relationships between operating point parameters), with the technical advantage of allowing input of multiple operating point parameter types. In one embodiment, for each provisional user-defined operating point parameter selected in the GUI, two other values ​​are also displayed based on data from the LUT. In a further embodiment, an option to link different color plane selections is available to avoid the need to define each color plane separately. In yet another embodiment, the user can use the displayed information to trade off PQ parameters to make a final operating point decision.

[0053]

[0065] The Dmax target value associated with the selection, the DDmax value, and the minimum substrate OD (DDmin or minimum optical density) value are used to determine a digital count value (DC_1). In one embodiment, the DDmin value comprises the optical density value associated with the unprinted areas of the print substrate (e.g., blank paper OD), while the DDmax value comprises the optical density of the printed areas of the print substrate (e.g., printed using a maximum digital count such as DC=255). Thus, DDMax is the highest OD achievable using the full range TF, and DDmin is the blank paper OD. DC_1 is the value that achieves the target Dmax for a linear OD target response when used as an input to the full range TF, and is given by: DC_1=(((2^bitdepth)-1)*(Dmax-DDmin)) / (DDmax-DDmin) where DC_1 is a floating-point value in the domain (0,((2^bitdepth)-1)) and bitdepth is the input bit depth of the full-range TF.

[0054]

[0066] The sub-range print substrate transfer function (SRsubstrateTF_i_j_k) that generates a linear OD from DDmin to Dmax is generated by: SRsubstrateTF_i_j_k(DC)=FRsubstrateTF_i_j(DC_1*DC / ((2^bitdepth)-1)), where k is the index of sub-TFs with different Dmax target values ​​for the same substrate.

[0055]

[0067] As a result, a sub-range substrate transfer function can be generated for each DC value (e.g., 0-255 for a DC system with a bit depth of 8 bits). The sub-range substrate transfer function is generated for a particular substrate i based on the DDmax (e.g., second optical density target value) and minimum optical density value (e.g., DDmin) of the image processing system. A technical advantage resulting from generating a sub-range transfer function based on the minimum optical density value of the image processing system is that such a sub-range transfer function provides an OD range that includes the minimum optical density value (e.g., unprinted white paper). According to one embodiment, the sub-range substrate transfer function generation engine 540 generates a sub-range substrate transfer function look-up table (LUT) 550 (shown in FIG. 5 ) that includes a sub-range substrate transfer function (SRsubstrateTF_i_j_k) associated with each digital count of each color plane of the image processing system. The sub-range substrate transfer functions for each color plane may differ from each other because the full-range substrate transfer function and DDmax may differ for each color plane. A technical advantage resulting from generating a sub-range substrate transfer function for each color plane is improved density control when printing each color plane using its corresponding sub-range substrate transfer.

[0056]

[0068] 8 is a flow diagram illustrating one embodiment of a process 800 for generating sub-range print substrate transfer functions. The process 800 for generating printer transfer functions and print substrate transfer functions has been described above. The process 800 may be performed by processing logic, which may include hardware (e.g., circuitry, dedicated logic, programmable logic, microcode, etc.), software such as instructions executing on a processing device, or a combination thereof. In one embodiment, the process 800 is performed by the sub-range print substrate transfer function generation engine 540.

[0057]

[0069] Process 800 begins at process block 810, where operating point data 503 is received from GUI 330. At process block 820, a full-range substrate transfer function is received (e.g., from memory, from full-range substrate transfer function generation engine 520, and / or from outside compensation module 230). At process block 830, a sub-range substrate transfer function is generated based on the operating point data 503 and the full-range substrate transfer function. At process block 840, the sub-range substrate transfer function is stored in sub-range substrate transfer function LUT 550.

[0058]

[0070] Returning to FIG. 4, printer calibration logic 420 is implemented to generate a printer transfer function, and composite transfer function generation logic 430 generates a CTF based on the printer transfer function and the print substrate transfer function.

[0059] FIG. 9 illustrates one embodiment of the composite transfer function generation logic 430, which includes a composite transfer function generation engine 910 and compensation drift logic 920. The composite transfer function generation engine 910 generates a CTF based on a mathematical function composition of a printer transfer function and a substrate transfer function (e.g., a full-range or sub-range transfer function). The CTF is then sent to the transfer function application module 235 in the form of a LUT 237 (FIG. 2A) that is applied to the CTF data. In one embodiment, the range of the substrate transfer function is equal to the domain of the printer transfer function, having the aforementioned domain. Based on the above, the composite transfer function generation logic 430 generates CTF values ​​using a discrete composite transfer function.

[0060]

[0071] Compensation drift logic 920 is implemented to perform concentration drift calculations to facilitate the technical gains that result from generating an updated compensation transfer function.

[0061] 10 illustrates one embodiment of compensation drift logic 920. According to one embodiment, compensation drift logic 920 receives print response measurement data corresponding to a printed image printed on a print substrate using a transfer function applied to print image data defining the printed image, and generates a compensation transfer function based on the print response data and a target response upon a determination that the average print response data exceeds a first threshold. According to another embodiment, compensation drift logic 920 receives print response measurement data corresponding to each of a plurality of measurement samples of the printed image printed on a print substrate using a transfer function applied to print image data defining the printed image, generates average print response data based on the print response measurement data, and generates a compensation transfer function based on the average print response data and the target response upon a determination that the absolute value of the average print response data according to the applied transfer function exceeds a first threshold. A technical advantage resulting from generating a compensation transfer function based on the average print response data is that the effects of transient noise in the measurement data are minimized.

[0062]

[0072] As shown in FIG. 10 , compensation drift logic 920 includes OD prediction logic 1010, which receives recent measured OD data 501 (e.g., at the start of a calibration process in calibration generator 305) generated by applying an identity transfer function during print image processing. As described above, measured OD data 501 is generated from a print image that includes a test pattern corresponding to one of multiple print heads 162. In an embodiment, the printed test pattern is included as part of a production print job. In such an embodiment, a production print job data image is printed by applying the current compensation transfer function, while the test pattern image is printed by applying the identity transfer function. Technical advantages resulting from printing a test pattern with the identity transfer function applied to the test pattern image include computational efficiencies with respect to common processing with other test marks, other test patterns that are included as part of the test pattern image and require the identity transfer function for proper printing.

[0063]

[0073] In one embodiment, the compensation drift logic 920 generates processed printing response data (e.g., first processed printing response data or first predicted response data (predicted response data)). In such an embodiment, the processed printing response data is generated by applying a current compensation transfer function (e.g., a current composite transfer function) to the measured OD data 501 to determine a predicted OD response (predicted OD response). A technical advantage resulting from applying the compensation transfer function to measured response data corresponding to printing using an identity transfer function is that the compensation is used to determine a predicted response.

[0064]

[0074] The comparison logic 1020 compares the processed print response data with the target OD data 502 to determine if the difference exceeds a predetermined first threshold (e.g., |Predicted OD - Target OD| < 0.02 ). Correction logic 1030 corrects measured OD data 501 using printer TF to account for the fact that printer TF was not used to generate measured OD data 501. Correction logic 1030 stores the corrected measured OD data (also referred to herein as processed print response data, predicted OD response, or Pred OD) in measurement storage 1040. In one embodiment, measurement storage 1040 stores the corrected measured OD data for a predetermined number (e.g., three) of the most recent measured OD data 501 results. Weight generation logic 1050 generates weighted average measured print response data for each input DC level, expressed as follows:

[0065]

number

[0066]

[0075] According to one embodiment, the compensation drift logic 920 facilitates generation of an updated compensated full-range substrate transfer function based on the averaged measured print response data. In such an embodiment, the updated compensated full-range substrate transfer function is generated by the full-range print substrate transfer function generation engine 520 (e.g., using process 700 of FIG. 7 ) and the composite transfer function generation engine 910. For example, an intermediate compensation transfer function (e.g., full-range print substrate transfer function) is generated based on the averaged measured print response data, while an updated compensation transfer function (e.g., composite transfer function) is generated based on the intermediate compensation transfer function and the target response data.

[0067]

[0076] In a further embodiment, the updated compensation transfer function replaces the current compensation transfer function and is used to print the remainder of the print job. At the end of the print job, updated metadata is stored, including a new DDmax, DDmin, full-range substrate transfer function LUT 530, and updated operating point data 503. In such an embodiment, the metadata includes the identification of the print substrate and print settings (e.g., print speed, print resolution, etc.). In a further embodiment, the updated compensation transfer function can be later retrieved using the metadata (e.g., the modification logic 1030 retrieves the updated compensation transfer function by matching the associated metadata parameters). Technical advantages resulting from storing and retrieving the updated compensation transfer function in association with metadata include avoiding regeneration of the compensation transfer function (or intermediate compensation transfer functions) when the printing system metadata matches the previous metadata.

[0068]

[0077] The OD prediction logic 1010 is implemented to generate second processed print response data including a second predicted OD based on the updated compensation transfer function. The comparison logic 1020 then compares the second predicted OD with the target OD data 502 to determine whether the difference exceeds a user-defined threshold set by an operator using the GUI 330 (e.g., |New TF Pred OD - Target OD|< User-defined quality level ), where New TF Pred OD is the second processed measured print response; Target OD is the target OD data; and New TF Pred OD = Measured OD (current updated compensation transfer function (DC)). In one embodiment, if the comparison logic 1020 determines that the difference between the second processed print response data and the target OD data 502, e.g., the second OD response absolute difference, exceeds a user-defined threshold (e.g., the second threshold), it transmits an alert to the GUI 330 for display. However, the updated compensation transfer function is sent to the transfer function application module 235 for storage in the LUT 237 to be applied to the CTI data, and if it determines that the difference between the second processed print response data and the target OD data 502 does not exceed the user-defined threshold, the alert is bypassed. A technical advantage resulting from transmitting an alert when the second threshold is exceeded is to prompt a system or user response (e.g., initiate a full recalibration of the current substrate instead of using the updated transfer function). In one embodiment, the second threshold is greater than the first threshold, which provides the technical advantage of a different response to each threshold.

[0069]

[0078] 11 is a flow diagram illustrating one embodiment of a process 1100 for performing drift compensation. The process 1100 for generating the printer transfer function and the print substrate transfer function is described above. The process 1100 may be performed by processing logic, which may include hardware (e.g., circuitry, dedicated logic, programmable logic, microcode, etc.), software such as instructions executing on a processing device, or a combination thereof. In one embodiment, the process 1100 is performed by the compensation drift logic 920.

[0070]

[0079] At process block 1110, print job generation is performed. As described above, print job generation is performed by applying a current compensation transfer function to print image data defining the production print job. At process block 1120, a test pattern is printed by applying a transfer function (e.g., an identity transfer function) to print image data defining the test pattern. At process block 1130, measurement data corresponding to the printed test pattern (e.g., generated from measuring the printed test pattern) is received.

[0071]

[0080] At process block 1140, first processed printing response data (e.g., Pred OD) is generated by applying the current compensation transfer function to the first printing response measurement data. At decision block 1150, a determination is made as to whether the absolute difference between the processed printing response data and the target printing response (Target OD) exceeds a predetermined first threshold (e.g., |Predicted OD - Target OD| < 0.02 ). If no, control is returned to process block 1110 and process 1100 is repeated (e.g., bypassing generating an updated compensation transfer function and / or replacing the current compensation transfer function). Otherwise, in process block 1160, an updated compensation transfer function is generated.

[0072]

[0081] 12 is a flow diagram illustrating one embodiment of a process 1200 for generating updated compensation transfer functions. The process 1200 for generating the printer transfer function and the print substrate transfer function is described above. The process 1200 may be performed by processing logic, which may include hardware (e.g., circuitry, dedicated logic, programmable logic, microcode, etc.), software such as instructions executing on a processing device, or a combination thereof. In one embodiment, the process 1200 is performed by the full-range print substrate transfer function generation engine 520 and the composite transfer function generation engine 910 (e.g., using process 700 of FIG. 7).

[0073]

[0082] At process block 1210, average measured print response data is generated. At process block 1220, an intermediate compensation transfer function is generated based on the average measured print response data. At process block 1230, an updated compensation transfer function is generated based on the intermediate compensation transfer function and the target response data. At process block 1240, the updated compensation transfer function replaces the current compensation transfer function, such that the updated compensation transfer function is available for print image processing. At process block 1250, the updated compensation transfer function is saved. Technical advantages resulting from generating an updated compensation transfer function based on the intermediate compensation transfer function include eliminating the need to capture new measured OD data 501 as a result of modified operating point data 503, as discussed above with respect to the full-range and sub-range print substrate transfer functions.

[0074]

[0083] 11 , at process block 1170, second processed print response data is generated based on the updated compensation transfer function. At decision block 1180, a determination is made as to whether the absolute difference between the second processed print response data and the target OD data exceeds a second user-defined threshold set by an operator using GUI 330 (e.g., |New TF Pred OD - Target OD|< User-defined quality level ). If not, control is again passed back to process block 1110 to repeat process 1100. However, if at process block 1190 a determination is made that the difference between the second processed print response data and the target OD data exceeds a user-defined second threshold, an alert is generated and communicated (e.g., to GUI 330).

[0075]

[0084] Although shown as a component of print controller 140, other embodiments may feature compensation module 230 included in a separate device communicatively coupled to print controller 140. For example, FIG. 13 illustrates one embodiment of compensation module 230 implemented in network 1300. As shown in FIG. 13, compensation module 230 is included in computing system 1310 and communicates with print system 130 via cloud network 1350.

[0076]

[0085] 14 illustrates a computer system 1600 in which the printing system 130, the print controller 140, and the compensation module 230 may be implemented. The computer system 1600 includes a system bus 1620 for communicating information and a processor 1610 coupled to the bus 1620 for processing information.

[0077]

[0086] Computer system 1600 further includes a random access memory (RAM) or other dynamic storage device 1625 (referred to herein as main memory), coupled to bus 1620, for storing instructions and information executed by processor 1610. Main memory 1625 may also be used for storing temporary variables or other intermediate information during execution of instructions by processor 1610. Computer system 1600 may also include a read-only memory (ROM) and / or other static storage device 1626, coupled to bus 1620, for storing instructions and static information used by processor 1610.

[0078]

[0087] A data storage device 1627, such as a magnetic disk or optical disk, and its corresponding drive may also be coupled to the computer system 1600 for storing information and instructions. The computer system 1600 may also be coupled to a second I / O bus 1650 via an I / O interface 1630. Multiple I / O devices, including a display device 1624, input devices (e.g., an alphanumeric input device 1623, and / or a cursor control device 1622), may be coupled to the I / O bus 1650. The communication device 1621 is for accessing other computers (servers or clients). The communication device 1621 may include a modem, a network interface card, or other well-known interface device, such as one used to couple to an Ethernet, token ring, or other type of network.

[0079]

[0088] Embodiments of the present invention may include various steps, as described above. The steps may be embodied in machine-executable instructions. The instructions may be used to cause a general-purpose or special-purpose processor to perform particular steps. Alternatively, the steps may be performed by specific hardware components that contain hardwired logic for performing the steps, or by any combination of programmed computer components and custom hardware components.

[0080]

[0089] Elements of the present invention may be provided as a machine-readable medium for storing instructions executable by a machine. The machine-readable medium may include, but is not limited to, a floppy disk, an optical disk, a CD-ROM, a magneto-optical disk, a ROM, a RAM, an EPROM, an EEPROM, a magnetic or optical card, a transmission medium, or any other type of medium / machine-readable medium suitable for storing electronic instructions. For example, the present invention may be downloaded as a computer program, which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) via a communications link (e.g., a modem or network connection) by a data signal embodied in a carrier wave or other transmission medium.

[0081]

[0090] The following clauses and / or examples relate to further embodiments or examples. Details in the examples may be used in any one or more embodiments. Various features of different embodiments or examples may be combined in various ways, with some features being included and other features being excluded, as appropriate for a variety of different applications. Examples may include subject matter such as a method, means for performing the operations of the method, or at least one machine-readable medium containing instructions that, when executed by a machine, cause the machine to perform the operations of a method, device, or system according to the embodiments and examples described herein.

[0082]

[0091] Some embodiments relate to example 1, including a system, the system comprising: at least one physical memory device that stores compensation logic; one or more processors coupled to at least one physical memory device and executing compensation logic; and the compensation logic is: receiving print response measurement data corresponding to a print image printed on a print substrate using a transfer function applied to print image data defining the print image; generating first processed printing response data based on the printing response measurement data; determining whether an absolute difference between the first processed printed response data and the target response exceeds a first threshold; and Upon determining that the absolute difference exceeds the first threshold, generating an updated compensation transfer function based on the first processed printing response data and the target response.

[0083]

[0092] Example 2 includes the specific features of example 1, in which generating the first processed printing response data further includes applying a current compensation transfer function to the printing response measurement data.

[0084]

[0093] Example 3 includes the particulars of example 1 or 2, wherein the printing response measurement data includes data corresponding to each of the plurality of measurement samples; and generating the first processed printing response data further includes averaging the data corresponding to each of the plurality of measurement samples.

[0085]

[0094] Example 4 includes the specific features of Examples 1-3, and the compensation logic further comprises: generating second processed print response data by applying the updated compensation transfer function to the print response measurement data; determining a second response difference comprising an absolute value of the difference between the second processed printing response data and a second threshold value; generating an alert upon a determination that the second response difference exceeds a second threshold; and Bypassing the alert upon a determination that the second response difference does not exceed the second threshold.

[0086]

[0095] Example 5 includes the specific features of Examples 1-4, wherein generating the updated compensation transfer function comprises: generating an intermediate compensation transfer function based on the first processed printing response data; and Generating an updated compensation transfer function based on the intermediate compensation transfer function and the target response.

[0087]

[0096] Example 6 includes the specific features of Examples 1-5, wherein the compensation logic stores the updated compensation transfer function together with the compensation metadata.

[0088]

[0097] Example 7 includes the specifics of Examples 1-6, and the compensation logic further uses the compensation metadata to retrieve an updated compensation transfer function.

[0089]

[0098] Example 8 includes certain of examples 1-7, wherein the at least one memory device stores a graphical user interface (GUI), and one or more processors coupled to the at least one physical memory device operate the GUI to display the alert.

[0090]

[0099] Example 9 includes the specifics of examples 1-8, and further includes one or more print engines.

[0091]

[0100] Example 10 includes the specifics of Examples 1-9, where the print response measurement data includes optical density data.

[0092]

[0101] Some embodiments relate to Example 11 including at least one computer-readable medium having stored thereon instructions, which when executed by one or more processors, cause the processors to: receiving print response measurement data corresponding to a print image printed on a print substrate using a transfer function applied to print image data defining the print image; generating first processed printing response data based on the printing response measurement data; determining whether an absolute difference between the first processed printed response data and the target response exceeds a first threshold; and generating an updated compensation transfer function based on the first processed printing response data and the target response upon a determination that the absolute difference exceeds the first threshold; Execute the following.

[0093]

[0102] Example 12 includes the specific features of example 11, wherein generating the first processed printing response data further includes applying the current compensation transfer function to the printing response measurement data.

[0094]

[0103] Example 13 includes the particulars of Examples 11 and 12, wherein the print response measurement data includes data corresponding to each of the plurality of measurement samples; and generating the first processed print response data further includes averaging the data corresponding to each of the plurality of measurement samples.

[0095]

[0104] Example 14 includes the particulars of examples 11-13, storing instructions that, when executed by one or more processors, cause the processors to: generating second processed print response data by applying the updated compensation transfer function to the print response measurement data; determining a second response difference comprising an absolute value of the difference between the second processed printing response data and a second threshold value; generating an alert upon a determination that the second response difference exceeds a second threshold; and bypassing the alert upon a determination that the second response difference does not exceed a second threshold; is executed again.

[0096]

[0105] Example 15 includes the particulars of Examples 11-14, wherein generating the updated compensation transfer function comprises: generating an intermediate compensation transfer function based on the first processed printing response data; and Generating an updated compensation transfer function based on the intermediate compensation transfer function and the target response.

[0097]

[0106] Some embodiments relate to Example 16, which includes a method, the method comprising: receiving print response measurement data corresponding to a print image printed on a print substrate using a transfer function applied to print image data defining the print image; generating first processed printing response data based on the printing response measurement data; determining whether an absolute difference between the first processed printed response data and the target response exceeds a first threshold; and Upon determining that the absolute difference exceeds the first threshold, generating an updated compensation transfer function based on the first processed printing response data and the target response.

[0098]

[0107] Example 17 includes the specific features of example 16, in which generating the first processed printing response data further includes applying the current compensation transfer function to the printing response measurement data.

[0099]

[0108] Example 18 includes the particulars of Examples 16 and 17, wherein the print response measurement data includes data corresponding to each of the plurality of measurement samples; and generating the first processed print response data further includes averaging the data corresponding to each of the plurality of measurement samples.

[0100]

[0109] Example 19 includes the specifics of Examples 16-18, and further includes: generating second processed print response data by applying the updated compensation transfer function to the print response measurement data; determining a second response difference comprising an absolute value of the difference between the second processed printing response data and a second threshold value; generating an alert upon a determination that the second response difference exceeds a second threshold; and Bypassing the alert upon a determination that the second response difference does not exceed the second threshold.

[0101]

[0110] Example 20 includes the particulars of Examples 16-19, wherein generating the updated compensation transfer function comprises: generating an intermediate compensation transfer function based on the first processed printing response data; and Generating an updated compensation transfer function based on the intermediate compensation transfer function and the target response.

[0102]

[0111] Although many alternatives and modifications of the present invention will no doubt become apparent to those skilled in the art after reading the foregoing description, it should be understood that any particular embodiments shown and described by way of illustration are not intended to be considered limiting in any way. Accordingly, references to details of various embodiments are not intended to limit the scope of the claims, which in themselves recite only those features which are deemed essential to the invention.

Claims

1. at least one physical memory device that stores compensation logic; one or more processors coupled to the at least one physical memory device and configured to execute the compensation logic; wherein the compensation logic: receiving print response measurement data corresponding to a print image printed on a print substrate using a transfer function applied to print image data defining the print image; generating first processed printing response data based on the printing response measurement data; determining whether an absolute difference between the first processed printed response data and a target response exceeds a first threshold; and generating an updated compensation transfer function based on the first processed printing response data and the target response upon a determination that the absolute difference exceeds a first threshold; Including, the system.

2. 10. The system of claim 1, wherein generating the first processed printing response data further comprises applying a current compensation transfer function to the printing response measurement data.

3. 2. The system of claim 1, wherein the printing response measurement data includes data corresponding to each of a plurality of measurement samples; and generating the first processed printing response data further includes averaging data corresponding to each of the plurality of measurement samples.

4. 4. The system of claim 3, wherein the compensation logic further comprises: generating second processed printing response data by applying the updated compensation transfer function to the printing response measurement data; determining a second response difference comprising an absolute value of a difference between the second processed printing response data and a second threshold value; generating an alert upon a determination that the second response difference exceeds a second threshold; and bypassing the alert upon a determination that the second response difference does not exceed a second threshold; Including, the system.

5. 10. The system of claim 1, wherein generating the updated compensation transfer function comprises: generating an intermediate compensation transfer function based on the first processed printing response data; and generating the updated compensation transfer function based on the intermediate compensation transfer function and the target response; Including, the system.

6. 6. The system of claim 5, wherein the compensation logic stores the updated compensation transfer function along with compensation metadata.

7. 7. The system of claim 6, wherein the compensation logic further uses the compensation metadata to derive the updated compensation transfer function.

8. 5. The system of claim 4, wherein at least one memory device stores a graphical user interface (GUI), and wherein the one or more processors coupled to the at least one physical memory device operate the GUI to display the alert.

9. 10. The system of claim 1, further comprising one or more print engines.

10. 10. The system of claim 1, wherein the print response measurement data includes optical density data.

11. At least one computer-readable storage medium having stored thereon instructions that, when executed by one or more processors, cause the processors to: receiving print response measurement data corresponding to a print image printed on a print substrate using a transfer function applied to print image data defining the print image; generating first processed printing response data based on the printing response measurement data; determining whether an absolute difference between the first processed printed response data and a target response exceeds a first threshold; and generating an updated compensation transfer function based on the first processed printing response data and the target response upon a determination that the absolute difference exceeds a first threshold; A computer-readable storage medium that causes the

12. 12. The computer-readable storage medium of claim 11, wherein generating the first processed printing response data further comprises applying a current compensation transfer function to the printing response measurement data.

13. 12. The computer-readable storage medium of claim 11, wherein the print response measurement data includes data corresponding to each of a plurality of measurement samples; and generating the first processed print response data further includes averaging data corresponding to each of the plurality of measurement samples.

14. 14. The computer-readable storage medium of claim 13 having stored thereon instructions that, when executed by one or more processors, cause the processors to: generating second processed printing response data by applying the updated compensation transfer function to the printing response measurement data; determining a second response difference comprising an absolute value of a difference between the second processed printing response data and a second threshold value; generating an alert upon a determination that the second response difference exceeds a second threshold; and bypassing the alert upon a determination that the second response difference does not exceed a second threshold; A computer-readable storage medium further comprising:

15. 12. The computer-readable storage medium of claim 11, wherein generating the updated compensation transfer function comprises: generating an intermediate compensation transfer function based on the first processed printing response data; and generating the updated compensation transfer function based on the intermediate compensation transfer function and the target response; 1. A computer-readable storage medium comprising:

16. receiving print response measurement data corresponding to a print image printed on a print substrate using a transfer function applied to print image data defining the print image; generating first processed printing response data based on the printing response measurement data; determining whether an absolute difference between the first processed printed response data and a target response exceeds a first threshold; and generating an updated compensation transfer function based on the first processed printing response data and the target response upon a determination that the absolute difference exceeds a first threshold; A method comprising:

17. 17. The method of claim 16, wherein generating the first processed printing response data further comprises applying a current compensation transfer function to the printing response measurement data.

18. 17. The method of claim 16, wherein the print response measurement data includes data corresponding to each of a plurality of measurement samples; and generating the first processed print response data further includes averaging data corresponding to each of the plurality of measurement samples.

19. 20. The method of claim 18, further comprising: generating second processed printing response data by applying the updated compensation transfer function to the printing response measurement data; determining a second response difference comprising an absolute value of a difference between the second processed printing response data and a second threshold value; generating an alert upon a determination that the second response difference exceeds a second threshold; and bypassing the alert upon a determination that the second response difference does not exceed a second threshold; A method comprising:

20. 17. The method of claim 16, wherein generating the updated compensation transfer function comprises: generating an intermediate compensation transfer function based on the first processed printing response data; and generating the updated compensation transfer function based on the intermediate compensation transfer function and the target response; A method comprising:

Images