Patent Application
20070019216
The present invention relates to proofing systems and more particularly to novel methods for providing press sheets for use in proofing.
In the printing industry, it is common to provide a physical sample of a printed image to a client for approval prior to printing a large number of copies of the image. One type of sample print is known in the industry as a press sheet. The press sheet is an image printed by a printer that will be used to print the large number of copies of a printed output. The press sheet is evaluated by the client and/or the printer to determine whether the printer is set up to print an output that has a desirable/acceptable appearance. One limitation of this process is that the client and/or printer must physically review the press sheet to make this determination. However, it is often difficult to present such a press sheet to a client, particularly, when a great distance separates the printer and the client. Further, it is expensive to print one press sheet or a small number of press sheets using high volume output devices of the type used to print large quantities of an image.
Alternatively, a physical sample can be provided in the form of a proof. A proof is an image printed by a printer other than the high volume output device and is intended to have an appearance that matches the appearance of a printed output of the same image as printed by the high volume output device. Typically, such proofs are printed by digital color printers. Such digital color printers print color prints of images that have been encoded in the form of digital data. This digital data includes code values indicating the colors to be printed in an image. When a digital color printer generates the printed output of an image, it is intended that the image recorded on the printed output will contain the exact colors called for by the code values in the digitally encoded data. In theory, such an image should also have an appearance that matches the appearance of the image printed by a high volume output device.
However, in practice, it has been found that the colors in the images printed by digital color printers do not always match the colors printed by high volume output devices. Such color variations can be caused by difference in the ink/toner, substrate/paper and printing techniques used in the digital printer and in the high-volume output device. Accordingly, special digital color printers have been developed that can be color adjusted so that they can mimic the performance of high volume output devices. Such specially adjusted color printers are known in the industry as “proofers”. An example of such “proofer” is the Approval NX Digital Halftone Proofing System developed and manufactured by Kodak and sold by Kodak Polychrome Graphics, Rochester, N.Y., U.S.A. The Approval NX Digital Halftone Proofing System is specially designed so that it prints images that have an appearance that precisely mimics the appearance of a digital image that will be printed using a high volume output device using agreed upon settings. In this way, a consumer can be provided with a proof that reliably represents the appearance of the same image, as it will appear when printed by a high volume output device.
It will be appreciated however that this system, while commercially successful and highly valuable, does not enable a consumer to evaluate an actual image printed by the actual high volume printer that will print the job. Accordingly, day-to-day variations that might arise in the operation of such a high volume printer are not always accounted for. Further, this also requires that the proof printed by the proofer is manually delivered to the consumer for evaluation and that the consumer manually provide some form of authorization in response thereto. This can introduce the risk of unnecessary delays and communication errors. These factors can also lead to consumer dissatisfaction and extra expenses.
One approach to solving this problem is described in U.S. Pat. No. 6,707,931, entitled “Remote Print Press Proofing System” filed by Herbert on Apr. 26, 2002. In the '931 patent, a system for image sharing is described that has two embodiments. In one embodiment, a physical sample is printed by the high volume output device, removed therefrom, and taken to a digitizing device which can be a scanner, camera, camera scan back, or other digitizer. For example, FIG. 1 of the '931 patent provides a digitizer in the form of a stand-alone flat bed scanner that is a component of a scanning and image sharing system. The scanning and image sharing system is adapted to color correct the scanned image and to share the scanned image with a remote display device to allow a remote user to determine whether the physical sample has a desirable appearance. In the first example of the '931 patent, the user manually reviews the image and provides audio or verbal feedback to the printer who makes modifications to the digital image and provides a revised digital image to the consumer for review. Thus, in this approach, the consumer cannot judge the actual impact that the requested changes will have on the printed image.
In an alternative approach described in the '931 patent, the remote user is provided with an electronic image that is intended to represent what will be printed by the high volume printer based upon known color printing characteristics of the high volume printer. When the electronic image is transmitted to a remote user for presentation on a soft display, such as a CRT or LCD, the image is color corrected so that the image presented to the remote user has an appearance that corresponds to the predicted appearance of the image as it will be printed by the high-volume printer. If the remote user desires changes, the remote user can send signals to the image server requesting such changes and the remote server will simulate the effects of such changes and return a second electronic image to the remote user. This process can be iteratively repeated allowing the remote user to make any number of modifications to the image. When the user transmits an acceptance, the printing device will then print an image in accordance with the electronic image.
A central limitation of such a system is that it requires visual analysis of each image by a user and, of course, such analysis can be subject to human error. A further central limitation of such systems is that there is no inherent integration between the operation of the press and the scanning, evaluation, and feedback process, thus increasing the amount of time required to generate, share, evaluate, and make changes to a press sheet and to make corrections, or adjustments to the operation of the press of the '931 patent.
Accordingly, what is needed in the art is a more integrated system that enables rapid, accurate and automatic evaluation of an image printed by a high-volume output device to facilitate the process of detecting conditions in the printed image that do not conform to conditions called for by data in digital image data upon which the printed image is based that are of interest, so that proper adjustments can be made in the operation of the high-volume output device in a cost efficient and timely fashion.
In one aspect of the invention, a method for printing an image on a receiver medium is provided. In accordance with the method digital image data representing an image to be printed is received and a print engine is used to print an image on the receiver medium based upon the digital image data and initial printing settings. A press sheet image is captured of the image printed on the receiver medium and a virtual press sheet image is generated based upon the press sheet image said generating including the step of adapting the press sheet image to remove any artifacts induced by the manner in which the press sheet image is captured. The digital image data to form a virtual proof image having an appearance that reflects the anticipated appearance of an image printed on the receiver medium by the print engine based upon the digital image data and, automatically comparing the appearance of the virtual press sheet image and the appearance of the virtual proof image to detect differences.
In another aspect of the invention, a method for printing an image on a receiver medium is provided. In accordance with the method, digital image data representing an image to be printed is received and, a print engine is used to print an image on the receiver medium based upon the digital image data and initial printing settings. A press sheet image is captured of the image printed on the receiver medium and the press sheet image is automatically compared to the digital image data to detect differences between the appearance of the image represented by the digital image data and the appearance of the press sheet image. Differences are identified that reflect at least one of the presence of an image artifact introduced by the process used to capture the press sheet image, any detected difference introduced by the way in which a properly operating print engine converts digital image data into a printed image on a reference receiver medium or any detected difference introduced by a difference in the way in which a particular type of receiver medium responds to printing by the print engine and the way in which the reference receiver medium reacts to the same printing by the print engine. An output signal is generated based upon the detected differences and the identified differences.
In still another aspect of the invention, a system for printing images on a receiver medium is provided. The system comprises: a print engine to print an image on the receiver medium based upon digital image data, said printing being performed in accordance with initial printing settings; an image capture system adapted to capture a digital image of the receiver medium after an image has been printed thereon, and to generate captured image data reflecting the appearance of the image on the receiver medium; a processor adapted to cause the print engine to print the image on the receiver medium, to cause the image capture system to capture an image of the press sheet, and to convert captured image data into a virtual press sheet image by adapting captured image data to remove any artifacts introduced by the image capture system; a source of a virtual proof, said virtual proof being formed by adapting the digital image data to reflect known characteristics of the way in which the print engine converts digital image data into images to be formed on a receiver medium and by further adapting the digital image data to reflect known characteristics of a receiver medium upon which a press sheet is to be printed using the digital image data; and a comparator adapted to compare the appearance of virtual press sheet image and the appearance of virtual proof image to detect differences therebetween.
A medium advance 26 is used to position a receiver medium 24 and/or print engine 22 relative to each other to facilitate recording of an image on receiver medium 24. Medium advance 26 can comprise any number of well-known systems for moving receiver medium 24 within printer 20, including motor 28 driving pinch rollers 30, a motorized platen roller (not shown) or other well-known systems for the movement of paper or other types of receiver medium 24. Medium advance 26 is also used to position a receiver medium 24 relative to an image capture system 32 after an image has been printed on the receiver medium 24 by print engine 22.
Print engine 22, medium advance 26 and image capture system 32 are operated by a processor 34. Processor 34 can include but is not limited to a programmable digital computer, a programmable microprocessor, a programmable logic processor, a series of electronic circuits, a series of electronic circuits reduced to the form of an integrated circuit, or a series of discrete components. Processor 34 operates printer 20 based upon input signals from a user input system 36, sensors 38, a memory 40 and a communication system 54.
User input system 36 can comprise any form of transducer or other device capable of receiving an input from a user and converting this input into a form that can be used by processor 34. For example, user input system 36 can comprise a touch screen input, a touch pad input, a 4-way switch, a 6-way switch, an 8-way switch, a stylus system, a trackball system, a joystick system, a voice recognition system, a gesture recognition system or other such systems.
Sensors 38 are optional and can include light sensors and other sensors known in the art that can be used to detect conditions in the environment surrounding image capture system 32 and to convert this information into a form that can be used by processor 34 in governing operation of print engine 22, image capture system 32 and/or other systems of print 20. Sensors 38 can include audio sensors adapted to capture sounds. Sensors 38 can also include positioning and other sensors used internally to control printer operations.
Memory 40 can include conventional memory devices including solid state, magnetic, optical or other data storage devices. Memory 40 can be fixed within printer 20 or it can be removable. In the embodiment of
In the embodiment shown in
It will be appreciated that, in other embodiments, local display 66 can communicate with processor 34 without involvement of communication system 54. Similarly, local input 68 can be a component of user input system 36 and can also provide signals to processor 34 without involvement of communication system 54.
Each print order generally provides information from which processor 34 can determine what image is to be printed, how the image is to be printed and the quantity of the images that are to be printed. The typical print order will provide digital image data representing the image to be printed, however, the job order may include more. Processor 34 then begins to process the digital image data by converting the digital image data into a form that can be used by print engine 22 (step 72). This typically involves converting the digital image data into code values (or other data types) that represent specific colors to be printed on receiver medium 26 to form an image.
A press sheet 64 is then formed by printing a press sheet image 62 on receiver medium 24 (step 74) using initial printing settings. Generally, such printing settings can help to govern the way in which print engine 22 converts code values into colors in an image, or other aspects of the printing process, such as printing speed. However, such printing settings can also dictate aspects of maintenance of the printing process, such as when and how print engine 22 is to be adjusted and/or maintained. In the embodiment of
Processor 34 then operates medium advance 26 to move press sheet 64 to a position where press sheet 64 confronts image capture system 32 so that image capture system 32 can capture an electronic image of press sheet 64. Processor 34 then causes an image to be captured of press sheet 64 in the form of image data representing the appearance of image 62 on press sheet 64 (step 76). It will be appreciated that image capture system 32 can comprise any of a number of conventional image capture sensors (not shown) and associated control and image processing circuits that are adapted to sense a pattern of light reflected or passed through receiver medium 24. In this regard, image capture system 32 can comprise a charge couple device (CCD), a complimentary metal oxide sensor (CMOS), or any other electronic image sensor known to those of ordinary skill in the art.
In the embodiment of
There are a variety of image capture strategies that can be used to capture image information from press sheet 64. In one embodiment, each press sheet 64 is fully captured at the best available image capture resolution. In other embodiments, images are captured of each press sheet 64, however, certain portions of each press sheet 64 are captured differently. For example, images can be captured of press sheet 64 with certain areas captured greater resolution or with specific image capture goals in mind. In one embodiment of this type, regions of interest (ROI) can be defined within press sheet image 62 and an image captured of press sheet 64 in such regions can be performed in a manner that allows for better discrimination of features therein. This can be done by increasing resolution within such areas or by otherwise altering the scanning process so that a desired level of image detail will be available within the region of interest. In another embodiment, specialized target scanning can be used that defines a special target such as a particular text, image portion or combination of colors that should be found within a region of press sheet image 62, and image capture of that region can be performed with special emphasis to provide a level of image information that is high enough to allow a determination to be made as to whether the target area has an appropriate appearance while also providing less image information captured from other portions of press sheet image 62.
Processor 34 adapts the image of press sheet 64 to form a virtual press sheet image having an appearance that accurately represents the appearance of press sheet 64 (step 78). This step can involve any of a number of adjustments to the captured image of press sheet 64. A principal purpose of such adaptations is to remove any image artifacts induced by the manner by which an electronic image of press sheet 64 is captured. For example, depending on the way in which the press sheet image was captured, it may be necessary to correct the image to compensate for conditions in the image capture system 32, the light used to capture the image, or any number of other factors that can influence the accuracy with which image capture system 32 captures an image of press sheet 64. In particular, it will be appreciated that using certain types of image capture and, in particular, using high-speed line scanning, moiré effects can create significant artifacts that should be addressed. In one embodiment, this problem is addressed by sub-sampling in the direction of travel of receiver medium 24. Such sub-sampling can be performed during capture using a TDI camera or it can be performed during post-capture processing by processor 34.
A virtual proof image is then obtained. In the embodiment of
Alternatively, the virtual proof can be formed by adapting in like fashion the data transferred from processor 34 to print engine 22 during printing of the press sheet which, as noted above, is ultimately based upon the digital image data.
Similarly, it will be appreciated that print engine 22 and receiver medium 24 can interact in other ways to form an image on receiver medium 24, and that receiver medium 24 can interact with the dye, ink, or other colorant that will be applied by print engine 22 in various ways that will impact the apparent color of the printed image such as where receive medium 24 is adapted to form an image when subject to image exposure to light, heat, impact, or other forms of energy. For example, receiver medium 24 can, itself, be colored and/or textured in ways that will impact apparent color of any dyes, inks, or other colorants applied thereto by print engine 22. Such effects can be anticipated and can be used to modify the digital image data to form a virtual proof image so that a virtual press sheet image and virtual proof image can be compared accurately.
The virtual press sheet image is then automatically compared to the virtual proof image so that any differences between the appearance of the virtual press sheet image (step 82) and the appearance of the virtual proof image can be detected. One or both of the images can be normalized as necessary for this comparison. In one embodiment, this can be done by comparing the data representing the virtual press sheet image to the data representing the virtual proof image. Such comparisons can include comparing the code values in each image to detect any variation in color in the images. Other types of color analysis can be performed, for example, color differences can be detected by comparing colors and print characteristics in the image, such as solid ink density (SID), trapping, dot gain, Lab data, hue, saturation, print contrast, and/or gray balance. Other comparisons could comprise conducting a frequency analysis of the data in the images to identify areas of high-resolution image content and low-resolution image content so that the extent of the sharpness of the image recorded on the press sheet can be verified. Such comparisons can also include comparing the expected content and shapes found in the images so that printing errors, such as failing to update text or printing improperly, can be detected.
The automatic comparison step (step 82) can also be used to detect image artifacts in the virtual press sheet image that are indicative of printing process anomalies including, but not limited to, unintended ink drops, line thickness variations, line sharpness, pin cushion effects, and other variations that can occur in the printing process. Such a comparison can be employed to detect conditions that are specific to certain print engine types. For example, where print engine 22 is an inkjet print engine, comparison of the virtual proof image against the virtual press sheet image can be used to detect image artifacts in the virtual press sheet that are indicative of conditions caused by non-uniform operation of inkjet heads such as:
1. Airflow problems—
2. Dark Defect—
3. Satellite Drops on Text/Line art—
4. Pic-Out—
5. Streakers—
6. Clogged Jets—
7. Crooked Jets—
8. “Frowning” Serifs
9. Sync Bands—
Other problems that can be automatically detected by comparison of the virtual press sheet and virtual proof image include:
1. Density Shifts—
2. Print engine Stitching Defect—
3. Color Mis-registration—
4. Color-to-Color Bleed—
Still other conditions that could be detected in one or more embodiments of the invention during the comparison step (step 82) include but are not limited to problems that can arise because of the way in which the printing job has been set up, which yield the following characteristics that can be detected by way of this comparison:
1. Font artifacts—
2. Trap Errors—
3. Knockout Errors—
4. Color contamination in highlights and primaries—
5. Plugged shadows—
6. Image Sharpness—
7. Diffusion problems—
Revised printing settings can then be optionally determined based upon the detected differences for use in subsequent prints by the print engine (step 84). These revised print settings can be determined automatically based upon the type of difference detected where there are known revisions to image rendering settings that can address to a particular type of difference such as for example, changes to the code values, printing speed or other characteristics of the process of printing an image. In the above-described embodiment, problems can be resolved by automatically adjusting the printing settings.
Some problems may require revised printing settings that cause processor 34 to initiate or request maintenance or service procedures, such as a nozzle cleaning process or that adjust the operation of various nozzles or other printer surfaces to correct for detected problems. Accordingly, as used herein the term printing settings includes data or other electronic signals that can be used to signal a need to initiate such maintenance or service procedures or cause such adjustments to be made to the operation of the nozzles.
Optionally, a client, pressroom manager, or other person can be involved in the process of determining revised printing settings. In the embodiment shown in
Where this is done, it is useful to adapt the virtual press sheet image so that the colors in the virtual press sheet image have a displayed appearance that matches the appearance of the colors printed in the press sheet image 62 (step 86). It will be appreciated however, that differences in operating systems, dyes or other colorants used in a display and settings for a display can greatly influence the manner in which the display converts code values into colors. This can cause different displays to present the same image having substantially different colors. Accordingly, a process of color profiling can be performed for each display upon which a virtual press sheet image is to be presented in order to carefully build an association between the colors that the display generates in response to selected code values. By adapting the virtual press sheet image using such color profiling a virtual press sheet image can be formed that, when presented on the display, has colors that have the same appearance as colors on the press sheet. Where a virtual press sheet is to be presented on more than one display, such as where the virtual press sheet is transmitted to multiple users for review, each display can be separately profiled with the separate profiles for each display being used to form a version of the virtual press sheet image adapted for presentation on the display. In this way, each display receives a virtual press sheet image that will accurately represent the appearance of the printed press sheet 64 when presented on the display.
In certain embodiments, printer 20 is adapted for use with a class of displays that are certified to operate within a range of parameters so that only one version of the virtual press sheet image need be generated with that version being shared with any of the displays of the class. In other cases, the printer has profiles for more than one display type stored in memory 40, with processor 34 determining a display type and forming a variety of virtual press sheet images for distribution, with each virtual press sheet being adapted for presentation according to the display profile for the display to which the image is being sent.
Each virtual press sheet image is then transmitted to the one or more display (e.g. remote display 56 or local display 66) for which the virtual press sheet image has been adapted and is then presented thereon (step 88).
Similarly, the virtual proof image can also be adapted for presentation on a display for comparison with the virtual press sheet image 62, such as remote display device 56 or local display device 66 as is described above (step 90) and provided to the display for presentation thereon (step 92). Depending on the preferences of the reviewer(s) the virtual proof can be presented for side-by-side comparison with the virtual press sheet. Alternatively, the virtual proof can be available for alternate presentation with the virtual press sheet, superimposed presentation or other comparative presentation with the virtual press sheet image in a manner that is useful for a user.
As shown in
Thus, a client and/or a pressroom manager can review the quality of press sheet image 62 printed on receiver medium 24 without actually viewing press sheet 64 and can indicate whether the client and/or pressroom manager approves or requires changes (step 96). Such indications can be made electronically, by providing a remote user input system 58 at remote display 56 and a local user input system 68 at local display 66 that allows a user to make a response and cause a responsive signal to be transmitted to communication system 54 of printer 20. For example, as shown in
It will be appreciated that using this approach, the remote user has an opportunity to view a virtual press sheet image that has been printed in accordance with each requested change. This approach is made feasible, convenient and reliable in the present invention by incorporation of image capture system 32 into printer 20 so that a virtual press sheet image can be captured of the entire press sheet almost immediately after printing of press sheet image 62.
As is noted above, the appearance of the press sheet image 62 on press sheet 64 can vary depending upon the interaction of print engine 22, receiver material 26 and any printing materials such as colorants, donors or other material transferred to receiver material 26 by print engine 22. However, the prior art approach of digitally simulating the effect of requested changes to a printed image fails to consider that such digital simulations do not compensate for the effects of such interaction, and thus the method described herein provides a more accurate representation of the effect of a requested change than the prior art which does not even suggest simulating such effects.
In certain embodiments of the invention, the virtual press sheet may be printed as a part of an initial subset of images intended to satisfy the print order. For example, where a print order comprises 2000 copies of a print, it may be more efficient to obtain a virtual press sheet from an initial batch of 500 images. Because image capture system 32 of the present invention is incorporated into printer 20 and is capable of scanning full pages, a set of virtual press sheet images can be obtained based upon one, some, or all of the initial batch of images.
Similarly, as illustrated in
Where this is done, the virtual press sheet images can be compared to the virtual proof to detect conditions that may vary during a print job. For example, where a serialized number of prints are printed, the quality and correctness of the serialization data and the quality of the printing of the same can be verified throughout the batch. Similarly, conditions that can vary during the printing of the print job, such as conditions that drift or that otherwise can vary over time can be detected.
As noted above, when a difference is detected by comparing the virtual press sheet image to a virtual proof image, the display of the virtual press sheet can be made in a manner that underscores the existence of the condition to a reviewer of the virtual press sheet. This can be done in a variety of ways such as by: presenting graphical information indicating the identified differences, such as text 126 shown in
In this embodiment, the press sheet image and the image represented by the digital image data are compared to detect differences between the appearance of the image represented by the digital image data and the appearance of the press sheet image (step 140). Such a comparison can be performed in a manner similar to that described above with respect to the step of comparing the virtual press sheet and the virtual proof (e.g. step 82).
It will be appreciated, however, that this comparison may detect differences that reflect the presence of image artifacts introduced by the process used to capture the press sheet image. Examples of detected differences that reflect the presence of an image artifact introduced by the process used to capture the press sheet image include those differences that are created by an artifact caused by image capture conditions used in capturing the press sheet image, characteristics of an image sensor used to capture the press sheet image, image processing of the captured press sheet image, or other characteristics of the process used to capture, process or store the press sheet image.
Similarly, such a comparison may also detect differences introduced by the way in which a properly operating print engine converts digital image data into a printed image on a reference receiver. Examples of such differences include differences that are introduced by a change in image resolution, image color content or image size that are not called for in the digital image data but necessary for the printer engine 22 to print the image.
Further, such comparisons may detect differences introduced by a difference in the way in which a particular type of receiver medium responds to printing by print engine 22 and the way in which the reference receiver medium reacts to the same printing by the print engine. Examples of this include differences caused by the texture of the receiver medium, a difference caused by the color of the receiver medium or a difference in the surface finish of the receiver medium.
Because these types of detected differences do not accurately reflect differences between the desired appearance of an image, as indicated by the digital image data and the actual appearance of the press sheet image printed by print engine 22 in on receiver medium 24, there is a need to ensure that such differences are not used as a basis for correcting the printing process or for determining whether to authorize execution of a print job.
In the embodiment of
Accordingly, in the embodiment of
An output signal is then generated based upon the detected differences and the identified differences. This can be done in a variety of ways (step 144). The output signal can be generated to include detected differences other than the identified differences. The output signal can alternatively identify both the identified and detected differences. The output signal can also be used as a basis for generating a user perceptible signal that indicates which of the detected differences is among the identified differences.
In the embodiment shown, the output signal is also used for automatically determining revised printing settings (step 146). This can be done in a similar fashion to the step of automatically determining revised image printing settings described with reference to
Also optionally, the digital image data can be adapted for presentation on a display for user consideration (step 152) and can be presented thereon (step 151). These steps can also be performed in generally the same manner that is described above for adapting the virtual press sheet image for presentation. Difference information can then be presented to help an observer of a displayed press sheet image and/or a displayed image representing the digital image data to better appreciate the differences between the images. This information can be based upon the output signal and can comprise text or graphic information as is described above with respect to
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
