Abstract:
The present invention discloses a proofing head apparatus and a proofing printer for generating a proof. The proofing head assembly comprises a color light analyzer and a color printhead joined by a housing to align the color light analyzer and to direct both the printhead and the color light analyzer at a media. In certain embodiments a controller is provided to drive the color light analyzer to make color measurements of an image and to instruct the printhead to render images on a receiver media. The controller can adjust the colors printed by the printhead so that an image printed by the printhead will match the appearance of the same image as printed by another printer. The proofing printer assembly of the present invention incorporates the proofing head with a media advance and translation mechanism.

Description:
FIELD OF THE INVENTION 
   This invention relates to image proofing systems, more particularly to a proofing apparatus and a proofing head assembly used to prepare color correct samples of printed materials. 
   BACKGROUND OF THE INVENTION 
   In the printing industry, it is common to provide a sample of an image to the customer for approval prior to printing a large number of copies of the image using a high volume output device such as a printing press. The sample image is known as a “proof”. The proof is used to ensure that the consumer is satisfied with the contents, composition and color gamut and tone characteristics of the image. 
   It is not, however, cost effective to print the proof using high volume output devices of the type used to print large quantities of the image. This is because it is expensive to set up high volume output devices to print an image. Accordingly, it has become the practice in the printing industry to use digital color printers to print proofs. Digital color printers render color prints of images that have been encoded in the form of digital data. This data includes code values indicating the colors to be printed in an image. When the 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 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. One reason for this is that variations in ink, paper and printing conditions can cause a digital color printer to generate images with colors that do not match the colors produced by a high volume output device using the same values. Therefore, a proof printed by a digital color printer may not have colors that match the colors that will be printed by the high volume output device. 
   Accordingly, digital color printers have been developed that can be color adjusted so that they can mimic the performance of high volume output devices. Such adjustable color printers are known in the industry as “proofers”. Two types of adjustments are commonly applied to cause proofers to produce visually accurate proofs of an image: color calibration adjustments and color management adjustments. 
   Color calibration adjustments are used to modify the operation of the proofer so that the proofer prints the colors called for in the code values of the images to be printed by the proofer. These adjustments are necessary to compensate for the variations in ink, paper and printing conditions that can cause the colors printed by the proofer to vary from the colors called for in the code values. To determine what color calibration adjustments must be made, it is necessary to determine how the proofer translates code values into colors on a printed image. This is done by asking the proofer to print a calibration test image. The calibration test image consists of a number of color patches. Each color patch contains the color printed by the proofer in response to a particular code value. The stand-alone calibration device measures the colors in the test image. The color of each color patch is compared to code values associated with that patch and the comparisons are used to determine what adjustments must be made to the proofer to cause the proofer to print desired colors in response to particular color code values. 
   Color management adjustments are used to modify the operation of the proofer so that an image printed by the proofer will have an appearance that matches the appearance of the same image as printed by a high volume output device. The first step in color management is to determine how the high volume output device converts color code values into printed colors. This is known as characterization. To characterize a high volume output device it is necessary to obtain a characterization test image. The characterization test image can be printed by the high volume output device. However, if it is known that the high volume output device converts code values into printed colors in accordance with an industry standard proofing system such as MatchPrint ™ or Cromalin ™, then a test image printed in accordance with that standard can be used for characterization purposes. 
   In either case, the characterization test image is submitted to the stand-alone color management device. The color patches on the characterization test image are compared to the color code values associated with the patches. This comparison is used to determine the adjustments that must be made to cause the proofer to print images having the same color gamut and tone characteristics as the images printed by the high volume output device. The proofer is then adjusted accordingly. 
   In this manner, the proofer is adjusted so that the proofer is properly calibrated to render images having the colors called for in the code values in the image to be proofed and is also adjusted to modify the code values in the image to be proofed in accordance with the profile for the output device. Thus, the proofer renders images having the colors that will appear the same as the colors in the images printed by output device. 
   It will be recognized that both calibration adjustments and color management adjustments are based upon objective measurements of the color gamut and tone characteristics of the test images printed by the proofer and by the high volume output device. 
   Various devices are used to measure the color content of an image. The most common devices are the densitometer and the color scanner. These devices typically analyze the color content of the light reflected by an image by dividing light into a set of primary colors, such as red, green and blue. These devices divide light into primary colors by passing the light through a set of colored filters. By measuring the intensity of the light in each primary color, it is possible to objectively measure the color content of an image. 
   A special form of densitometer, the colorimeter, can also be used to objectively measure the color gamut and tone characteristics of an image. Colorimeters are designed to objectively measure the color of a sample in a way that approximates human visual response. This is accomplished by the use of filters that are chosen to mimic human visual response. 
   A more accurate device for measuring color for calibration and color management purposes is the spectrophotometer. The spectrophotometer measures the reflectance or transmittance of an object at a number of wavelengths throughout the visible spectrum. More specifically, a spectrophotometer exposes a test image to a known light source and then analyzes the light that is reflected by the test image to determine the spectral intensity of the sample. A typical spectrophotometer is capable of measuring a group of pixels in an image and includes an apparatus that measures the light that is reflected by a portion of an image at a number of wavelengths throughout the visible spectrum to obtain data that reflects the true spectral content of the reflected light. Because the spectrophotometer measures color with greater accuracy than do the other measurement devices discussed above, the spectrophotometer is preferred. 
   Thus, densitometers, colorimeters, color scanners, and spectrophotometers can be used for color measurement. However, these are typically stand-alone devices and the use of such devices during proofing is very costly. Part of this cost is created by the inherent redundancy of many of the systems used in these devices. For example, a stand-alone spectrophotometer, has an “X-Y” table to move the test image relative to the spectrophotometer. A digital color printer or proofer also contains an “X-Y” displacement mechanism for moving the paper and printing element or printhead. Similarly, both the spectrophotometer and the proofer contain separate electrical control systems, motors and other components. Thus, the total cost of the proofing system including a separate stand-alone color measurement device and a proofer is high and can be in excess of more than U.S. $10,000.00. 
   Installation and maintenance costs are also high because two separate devices, typically manufactured by different vendors, must be separately purchased, installed, and maintained. Finally, there is a significant labor cost associated with making calibration and color management adjustments to the proofer using a stand-alone color measurement device. 
   Accordingly, there are substantial cost and efficiency penalties associated with stand-alone proofing combinations and what is needed is an integrated proofing apparatus. 
   Special printers having integrated color scanners or densitometers for color calibration purposes exist. Examples of color calibration and correction systems of this type can be found in commonly assigned U.S. Pat. Nos. 5,053,866, and 5,491,586. These patents show specially designed printing systems for generating a color image and adjusting the color content of subsequent images based upon the colors printed in the color image. However, these specially designed systems also use redundant structures for printing and color measurement and do not teach or suggest color management capabilities. 
   It will also be recognized that many high quality color digital printers exist. However, these printers are not designed with integral proofing capabilities. Thus, what is also needed is a proofing head having calibration and color management capabilities and that can be readily integrated into an existing printer. 
   Accordingly, it is an object of the present invention to provide a proofer that is low in cost and is easily maintained. 
   It is also an object to provide a proofer that substantially automates the proofing process. 
   It is also an object of the present invention to provide a proofing head that can be readily incorporated into a printer of conventional design to permit the printer to act as a proofer. 
   SUMMARY OF THE INVENTION 
   The present invention resides in a proofing printer for generating a proof and a proofing head assembly. The proofing head assembly comprises a color light analyzer and a color printhead joined by a housing that directs the color light analyzer and the printhead at a media. A controller is provided to drive the color light analyzer to make color measurements of an image and to instruct the printhead to render images on a receiver media. The controller can adjust the colors printed by the printhead so that an image printed by the printhead will match the appearance of the same image as printed by another output device. The proofing printer assembly of the present invention combines the proofing head with a media advance and translation mechanism. Certain embodiments of the proofing printer self-calibrate and automatically characterize another output device. One embodiment of the proofing head of the present invention is adapted to be incorporated into color printers without color calibration and color management capabilities. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a drawing of the proofing process using a stand-alone color measurement device according to the prior art. 
       FIG. 2  shows a schematic diagram of a proofer of the present invention. 
       FIG. 3  shows an expanded view of the proofer of  FIG. 1  with various components exhibited in cross section. 
       FIG. 4  shows a detailed view of a portion of the proofer of  FIGS. 2 and 3 . 
       FIG. 5  shows a diagram of another embodiment of the present invention. 
       FIG. 6  shows an embodiment of the proofing head of the present invention for use with a conventional printer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a drawing of the proofing process using a stand-alone color measurement device according to the prior art. The process of making calibration adjustments to the proofer  10  begins when the proofer  10  renders a calibration test image  16 . Calibration test image  16  contains a multiplicity of color patches  17 . Each of color patches  17  contains the color printed by proofer  10  in response to a particular color code value. The color content of the color patches  17  of test image  16  are measured using stand alone color measurement device  12 . The color measurements are compared to the code values associated with the color patches  17 . A set of calibration adjustments is determined using these comparisons. The operation of the stand-alone proofer  10  is then adjusted so that the stand-alone proofer  10  renders a proof having the colors called for in the color code values for the proof. 
   The process of making color measurement adjustments to proofer  10  begins by obtaining a characterization test image  18 . Characterization test image  18  is printed by high volume output device  14  or otherwise printed in accordance with a standard color proofing system such as MatchPrint ™. Characterization test image  18  also contains a set of color patches  19 . Each of color patches  19  is associated with a color code value. The location of each of patches  19  on characterization test image  18  are defined by convention or by an industry standard e.g. American National Standards Institute standard IT8.7/3. 
   Characterization test image  18  is submitted to color measurement device  12 . The color content of color patches  19  are measured and compared to the color code values associated with color patches  19 . Comparison of the color code values to the colors printed in color patches  19  forms the foundation for building a mathematical model that predicts the color that high volume device  14  will print as a function of input code values. This mathematical model is inverted to allow prediction of image code values as a function of colorimetric values. These two mathematical models relating code values to the color output of high volume output device  14  comprise the primary elements in what is known as a device profile. The device profile for high volume output device  14  is used to adjust proofer  10  to convert the code values in the image to be proofed into modified code values. Proofer  10  prints the proof using the modified code values. 
   It will be appreciated that substantial operator involvement is required to make calibration and color management adjustments using the stand alone devices. For example, an operator using a stand-alone color measurement device  12  is required to cause the high volume output device  14  to print test image  18 . The operator must then wait for the test image  18  to be printed and convey test image  18  from the high volume output device  14  to the stand-alone color measurement device  12 . The operator must then insert the characterization test image  18  into the color management device  12  to initiate the color measurement. Then the operator must wait for stand-alone color measurement device  12  to complete making the color measurements. Finally, the operator must adjust proofer  10  using the information from stand-alone color management device  12  to determine the adjustments that must be made to the proofer and to make those adjustments. 
     FIG. 2  shows a proofer  26  according to a preferred embodiment of the present invention. Proofer  26  comprises a proofing head  50  having a color light analyzer  20 , a color printhead  56  and a housing  40  which joins light analyzer  20  to printhead  56 . Printhead  56  may use any of several known technologies, such as, for example, ink jet, laser, impact, etc. 
   Housing  40  can comprise any of a box, closed frame, continuous surface or any other enclosure defining an interior chamber  41 . In the embodiment of  FIGS. 2 and 3 , housing  40  comprises a housing that holds both color light analyzer  20  and printhead  56 . Housing  40  directs printhead  56  so that a donor material such as an ink  52  ejected by printhead  56  is directed onto media  30 . Housing  40  also directs the light analyzer  20  so that it receives light reflected by media  30 . 
   The proofing head  50  is advanced along an X-axis by a translation unit  60 . In the embodiment shown in  FIG. 2 , translation unit  60  comprises a motor  62  and a belt  64 . Belt  64  is aligned along an X-axis relative to the media and supported at one end by a freely rotating support pinion  66  and a drive pinion  68 . Drive pinion  68  is operated by motor  62 . Housing  40  of proofing head  50  is fixed to belt  64  and moves in accordance with the motion of belt  64 . Y-axis displacement of media  30  relative to proofing head  50  is provided by media advance  70 . Media advance  70  can comprise any number of well-known systems for moving media  30  within a printer including but not limited to a motor  72  driving pinch rollers  74 , a motorized platen roller (not shown). Of course, other mechanical arrangements may be used to provide relative translation of proofing head  50  and media  30 . 
   A controller  80  is provided and, as will be discussed in greater detail below, controller  80  drives the operation of printhead  56 , light analyzer  20 , translation unit  60 , and media advance  70  during calibration, color management and printing operations. Controller  80  can comprise any of a programmable digital computer, a programmable logic controller, a series of electronic circuits or a series of electronic circuits reduced to the form of an integrated circuit. 
     FIG. 3  shows another view of proofer  26  with proofing head  50  shown in partial cross section. As is seen in this view, housing  40  comprises an interior chamber  41  that contains both color light analyzer  20  and printhead  56 . An opening  42  in housing  40  permits ink  52  to flow from printhead  50  during printing operations to form an image on a media  30  positioned in a media plane  37 . 
   Opening  42  in housing  40  also permits light to pass between a media  30  positioned in a media plane  37  and color light analyzer  20  during color management and calibration operations. In one embodiment, housing  40  directs the printhead  56  so that ink ejected by the print head flows onto one portion of a media. In this embodiment, the housing  40  directs the color light analyzer to collect light reflected by a second portion of the media  30 . The first portion is adjacent to the second portion. However, in an alternative embodiment the first and second portion are separate. 
   Printhead  56  preferably comprises ink jet nozzles  54  for ejecting colored ink droplets  52  onto media  30 . In such a design, colored ink is supplied to the printhead  50  by a suitable reservoir (not shown). Printhead  56  may be caused to eject droplets of ink  52  by a thermal mechanism or by an electro-mechanical mechanism. Printhead  56  may also use continuous ink flow technology. 
   Color light analyzer  20  preferably includes a light source  22  that emits a light beam  24  having a known spectral composition. Light beam  24  is directed at media  30  and is reflected by the media. Color light analyzer  20  receives the reflected light via sensor  28 . The color content of the reflected light is then measured and a signal representing the color content is transmitted from color light analyzer  20  to controller  80 . The color light analyzer  20  can be a densitometer, calorimeter, color scanner or spectrophotometer. In the embodiment of  FIG. 3 , color light analyzer  20  comprises a spectrophotometer. 
   The process of making calibration and color management adjustments to proofer  26  will now be described with reference to  FIGS. 2 and 3 . 
   In the first step of the calibration process, controller  80  causes media advance  70  to position media  30  into position for printing. Controller  80  then accesses an electronic representation of a test image used for calibration. This electronic representation is stored in a controller memory  82 . This electronic representation contains particular code values defining the colors to be printed at particular X-Y positions on media  30  to form test image  32 . Alternatively, the electronic representation of test image  32  to be used for calibration can be stored on a device such as a data disk (not shown) or a computer network (not shown) and accessed by way of communication interface  84 . Controller  80  positions printhead  56  at particular X-Y coordinates on media  30  by the action of translation unit  60  and media advance  70 . The controller  80  causes printhead  56  to eject ink droplets  52  to form the color patches  34  on the test image  32  in accordance with the code values in the electronic representation of the calibration test image  32 . 
   In the second step of the calibration process, controller  80  actuates the media advance  70  and translation unit  60  so that the color light analyzer  20  can scan each of the color patches  34 . The color light analyzer  20  measures the spectral reflectance of each of the patches  34 . Controller  80  receives the measurement data from each of the color patches  34 . Controller memory  82  contains code values associated with each of the patches of the characterization test image. Controller  80  then compares the color measured at each of patches  34  against the color code values associated with each of patches  34 . From this comparison controller  80  then determines the adjustments that must be made to cause printhead  56  to generate a particular color on media  30 . Controller  80  then makes the calibration adjustments so that the printhead  56  renders images having the colors associated with the code values for the images. 
   Color management adjustments are made to the operation of proofer  26  using a characterization test image (not shown). The characterization test image can be printed by the high volume output device or printed in accordance with a standard color proofing system. In either case, the characterization test image contains a number of color patches with each patch associated with a particular code value. The characterization test image is inserted into the media advance  70 . Controller  80  then advances the color light analyzer  20  to each of the color patches and measures the color of each patch. 
   Controller memory  82  contains code values associated with each of the patches of the characterization test image. The colors measured at each of the patches by color light analyzer  20  are transmitted to controller  80  and compared to the code values associated with the patches. Controller  80  uses these comparisons to build a device profile that predicts how the high volume output device will convert code values to colors on a printed image. Controller  80  then makes the color management adjustments in accordance with the profile. 
   To print the proof using proofer  26 , the data representing an image, Ir, to be proofed is provided to interface  84  which converts this data into a form that is usable by controller  80 . Controller  80  receives this data and modifies this data to reflect calibration adjustments and profile adjustments. Controller  80  then transmits printing instructions to the printhead  56  in accordance with the adjusted data so that so that an image printed by the printhead  56  will visually match the appearance of the same image as printed the high volume output device. 
   It will be understood that it is also possible to accomplish the same result by using the calibration data and color adjustments to modify the way in which controller  80  transforms color code values into printing instructions or by using calibration and color management adjustments to modify the way in which the printhead  56  transforms printing instructions into the release of ink  52 . 
   It will also be understood that the time required to perform color calibration measurements can be reduced by using color light analyzer  20  to measure the color patches  34  of test image  32  during the printing of test image  32 . 
   Accordingly, both calibration and characterization of the proofer  26  is accomplished in the present invention with greatly reduced operator involvement and equipment cost as compared to the stand-alone color proofer arrangement of  FIG. 1 . 
     FIG. 4  shows a detailed embodiment of controller  80  of the present invention. In this embodiment, independent processors are used for image processing ( 120 ), color management ( 130 ), calibration ( 150 ), and control purposes ( 160 ). Each of the independent processors of  FIG. 4  can comprise any of a programmable digital computer, a programmable logic controller, a series of electronic circuits or a series of electronic circuits reduced to the form of an integrated circuit. It will readily be understood that it is possible to practice the present invention using other combinations of processors and electrical circuits to perform the required functions. 
   In the embodiment of  FIG. 4 , a media advance  70  and translation unit  80 , as generally described above, are provided for maneuvering proofing head  50  and media  30 . Controller  160  operates media advance  70  and translation unit  60  to position the proofing head  50  at particular X-Y co-ordinates relative to media  30 . 
   To make calibration adjustments, a test image  32  is generated by the proofer  26 . Controller  160  maneuvers color light analyzer  20  into position to measure the color content of the color patches  34  of calibration test image  32 . The measurements are provided to a color calibrator  150 . Color calibrator  150  calculates color density at particular patches  34  and compares these densities to the color densities that the printhead  56  was instructed to print. From this, the color calibrator  150  generates a calibration look up table (CaLUT). The CaLUT correlates color code values in the electronic image data to the color code values that must actually be used during printing to cause the printhead  56  to generate the desired colors in the printed image. During printing, color calibrator  150  modifies the code values in the data representing the image to be printed in accordance with the CaLUT. 
   To make color management adjustments, a characterization test image (not shown) having color patches printed by the high volume output device or printed in accordance with an industry standard, is inserted into the media advance  70 . Controller  160  causes media translation unit  60  to color light analyzer  20  into positions to measure color content of the color patches of the characterization test image. The measurements are provided to color image processor  130 . Color image processor  130  generates a color profile of the data measured from the test image using one or more profiling techniques known in the art. Examples of software embodying these techniques include CompassProFile ™ software sold by Color Savvy Systems, Ltd. of Springboro, Ohio, and KODAK COLORFLOW ICC Profile Editor sold by Eastman Kodak Company of Rochester, N.Y. The profile takes the form of a three or four dimensional Look Up Table (ChLUT), depending upon the number of color channels in the image. The color image processor  130  can comprise a trilinear or quadlinear interpolation processor (not shown) to modify the color code values in the electronic data representing an image in accordance with the ChLUT. 
   During proofing operations, electronic data representing the image to be proofed is transmitted to the proofer  26 . This data, Ir, is accepted by the proofer  26  by way of an image source  110 . Image source  110  can comprise any convenient interface for accepting Ir from an external source and making Ir available for processing and printing by the proofer  26 . Image source  110  can include systems for receiving and decoding magnetic or optical disk drives and flash memory cards. Image source  110  can also include systems for receiving electronic signals from computers, computer networks, and other devices. These signals may take the form of raster image data, outline image data in the form of a page description language or other forms of digital representation. 
   Image source  110  is coupled to an image processor  120  that converts the image data Ir from image source  110  into a pixel-mapped page image Ipm. Color image processor  130  processes the pixel-mapped image Ipm, using the ChLUT to form a processed image Ip. This modifies the image, Ip, so that the color gamut and tone characteristics of the code values in the processed image Ip match the color gamut and tone characteristics of the output of the high volume output device that has been profiled. After processing, the processed image Ip is stored in memory  140  until the processed image, Ip, is needed for printing. 
   To print the proof, processed image Ip is fed from memory  140  to previously mentioned calibrator  150 . Calibrator  150  modifies the processed image Ip using the CaLUT to produce a calibrated image Ic. This calibrated image Ic is then fed to the printer controller  160 . Printer controller  160  determines, from this data, the colors to be used in the image, and where these colors are to be deposited on a receiver media  30 . Controller  160  advances the printhead  56  and media  30  to any X-Y coordinate by operation of the translation unit  60  and media advance  70 . Printer controller  160  then applies a time-varying electrical pulse to the printhead  56  to eject a combination of ink droplets  52  from printhead  56  in accordance with the calibrated image Ic. 
   The proofer  26  of  FIG. 4 , therefore, modifies image data twice before printing: once to ensure that the colors of the printed image properly reflect the calorimetric characteristics of a high volume output device and once to ensure that the printhead  56  creates the desired colors on a particular receiver media  30 . 
   It will also be appreciated that proofer  26  can be configured to automatically execute both calibration adjustments and color management adjustments with a minimum of operator involvement. In the system shown in  FIG. 5 , the media advance  70  can be supplied by a media supply source such as a tray  78 . Tray  78  is configured to contain more than one sheet of media  30 , and to supply the media  30  to the media advance  70  in an orderly fashion. With this arrangement, a user can insert a receiver media  30  and a second media  31  having a test image  33  printed by a high volume output device into the tray  78 . Controller  80  is programmed to execute both calibration and color management adjustments using these images. After calibration and color management adjustments, the proofer  26  is ready to generate a visually accurate proof. 
   It will be understood that printing conditions can change during the printing of the proof. These changes can alter the color content of an image printed by printhead  56  on a receiver media  30 . To prevent this, proofer  26  of the present invention can be configured so that the light reflecting from colors printed by printhead  56  on a media  30  is measured by the color light analyzer  20  during printing. Controller  80  can then make printer calibration adjustments in response to real-time color measurements. 
   It will also be understood that circumstances may arise wherein the printhead  56  cannot be made to print the desired colors on the media  30 . For example, this can occur because a supply of an ink is exhausted or because the printhead  56  is clogged or damaged. In such circumstances, no adjustment of the calibration can compensate for the problem, thus, controller  80  can be programmed to stop printing or to provide the user with a warning that calibration errors occurred during printing. This warning can comprise a written warning printed on the image, an interruption of the printing process or other forms of aural or visual notification. 
   As is shown in  FIG. 6 , one particularly valuable application of the proofing head  50  of the present invention is for a proofing head  50  that can be installed into a conventional printer  200 , having a predefined printhead mounting area  210 . Printer controller  212  controls the operation of printer media advance  230  and printhead translation unit  220 . An electrical connection  214  is also defined between printer controller  212  and printhead mounting area  210  to allow the printer controller  212  to govern the operation of a conventional printhead to  216  (not shown). Media advance  230  comprises a media roller  232  and pinch roller  234 . A motor  236  drives the operation of roller  232  to advance a sheet of media  240  along a Y-axis. Translation unit  220  can movably position the mounting area  210  relative to the media along an X-axis by rotating drive pinion  268  to drive belt  264  and pinion  266 . The printer  200  operates as does any conventional printer and, does not have any inherent structure for performing calibration or characterization operations. 
   Proofing head  50  is installed in the predefined printhead mounting area  210 . To accommodate this, housing  40  is shaped to fit into printhead mounting area  210 . In this embodiment, housing  40  comprises an inner chamber  41  that contains controller  80 , printhead  56  and color light analyzer  20 . In this embodiment, the controller  80  is electrically connected to controller  212  by way of the electrical connection  214 . In this manner, the printing instructions transmitted by the printer controller  212  are received by the controller  80  of the proofing head  52 . 
   Once installed into the printhead mounting area  210 , proofing head  50  is used to execute printer calibration and characterization adjustments. In this respect, controller  80  of proofing head  50  is connected to printer controller  212  to cause printer controller  212  to operate translation unit  220  and media advance  230  to allow for the creation of a calibration test image and to allow for the color measurement of calibration and characterization test images as generally described above. Alternatively, printer  200  can be connected to an external computer  250 , which directs printer controller  212  to maneuver proofing head  50  to particular locations in order to allow the proofer to perform calibration and characterization operations, as generally described above. 
   During printing, the printer controller  212  transmits printing instructions to controller  80 . Controller  80  modifies the printing instructions in accordance with color calibration and color management adjustments so that an image printed by printer  200  will have the same visual appearance as the same image when printed by a high volume printer or output device. In one embodiment of the present invention, controller  80  uses color light analyzer  20  to ensure that the colors that are printed by printhead  56  onto a media  240  during printing match the colors that the controller  80  has instructed the printhead  56  to print. If these colors do not match, controller  80  modifies the operation of the printhead  56 . 
   Thus, as is shown and described, the proofing head  56  can be incorporated into a conventional printer to provide calibration and proofing capabilities to such a printer  210  without substantial modification to the existing printer design. 
   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. 
   PARTS LIST 
   
       
         10  stand-alone proofer 
         12  stand-alone color measurement device 
         14  high volume output device 
         16  calibration test image 
         17  color patches 
         18  characterization test image 
         19  color patches 
         20  color light analyzer 
         22  light source 
         24  light beam 
         26  proofer 
         28  sensor 
         30  media 
         31  second Media 
         32  calibration test image 
         33  characterization test image 
         34  color patches 
         37  media plane 
         40  housing 
         42  opening in housing 
         50  proofing head 
         52  ink 
         56  printhead 
         60  translation unit 
         62  motor 
         64  belt 
         66  support pinion 
         68  drive pinion 
         70  media advance 
         72  motor 
         74  pinch rollers 
         76  media supply source 
         78  tray 
         80  controller 
         82  controller memory 
         84  controller interface 
         110  image source 
         120  image processor 
         130  color image processor 
         140  image memory 
         150  color calibrator 
         160  printhead controller 
         200  conventional printer 
         210  predefined printhead mounting area 
         212  printer controller 
         214  electrical connection 
         216  conventional printhead 
         220  translation unit 
         230  media advance 
         232  media roller 
         234  pinch roller 
         236  motor 
         250  conventional computer 
         264  belt 
         266  support pinion 
         268  drive pinion