Abstract:
Systems and methods are disclosed for positioning or storing an electro-optical instrument (e.g., spectrophotometer) within a printing device to facilitate calibration or maintenance of the instrument. In various embodiments, the electro-optical instrument may be pivoted or moved to an inclined position to facilitate calibration of the instrument relative to one or more calibration references. The electro-optical instrument may also be moved or inclined along a travel path in the printing device to a position or positions adjacent to various calibration references.

Description:
CROSS REFERENCE TO RELATED APPLICATION/PRIORITY CLAIM 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/794,606, filed on Apr. 24, 2006, the entirety of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This application is directed generally and in various embodiments to calibration, maintenance, and storage of electro-optical instrumentation, and more particularly, to automatic calibration and storage of electro-optical instrumentation within printing devices. 
     BACKGROUND 
     Digital printing presses and other digital printing devices (hereinafter “printing devices”) may incorporate an electro-optical instrument, typically a reflection spectrophotometer, for automatically controlling print attributes.  FIG. 1  illustrates a conventional arrangement of a reflection spectrophotometer  15  within a printing device  10 . As shown, the spectrophotometer  15  may be oriented above a media guide  20  and include an illumination source  25  (e.g., an LED or lamp) for illuminating print media  30  (e.g., paper) via a first guide aperture  35  as the media  30  is passed through the guide  20 . Although depicted as a slotted guide, the guide  20  may alternatively be a roller or other device for suitably directing the media  30 . Light reflected from the media  30  is received by a sensor module  40  within the spectrophotometer  15  via an aperture  45 . Although not shown for the sake of clarity, the sensor module  40  may include optics (e.g., lens, mirrors, etc.), light detectors (e.g., CCD sensors), and various electronics configured for processing the reflected light and generating spectral data therefrom. The spectral data may be communicated to a print engine (not shown) within the printing device  10  and used, for example, to control colors printed by the printing device  10  in accordance with a color desired standard. In order to ensure that the spectral data accurately represents the color characteristics of the media  30 , the orientation of the spectrophotometer  15  is required to be such that its “read plane” (i.e., a plane parallel to the illuminating/detecting face of the spectrophotometer  15  corresponding to optimal illumination and light detection) precisely coincides with the upper surfaces of the media  30 . Typically, the surfaces of the media  30  must be within several thousandths of an inch of a known read plane or at a known offset in order to obtain suitably accurate spectral data. Repeatability of such tolerances may be maintained, for example, by providing a reference surface (not shown) that contacts a portion of the illuminating/detecting face of the spectrophotometer  15  or reference features. 
     It is necessary to periodically calibrate the spectrophotometer  15  using a calibration reference. Typically, the calibration reference is matched to the spectrophotometer  15  and comprises a white source (e.g., a white ceramic disc) having a color characteristic traceable to a suitable color standard, such as that established by the National Institute of Standards and Technology. Non-white (e.g., red, green, and/or blue) calibration references may also be used. During calibration, spectral data generated by the spectrophotometer  15  using the calibration reference is compared to spectral data corresponding to the calibration reference that has been previously stored within the spectrophotometer  15 . Based upon this comparison, a color transform curve for suitably compensating spectral data of subsequent measurements may be generated using known methods. 
     For the printing device  10  of  FIG. 1 , automatic calibration of the spectrophotometer  15  may be problematic due to the orientation of the spectrophotometer  15  relative to the guide  20 . In particular, the structure of the guide  20  generally precludes physical placement of the calibration reference at the read plane, particularly in cases where the guide  20  is a roller. 
       FIG. 2  illustrates an alternative placement of a calibration reference  50  as is known in the art. As shown, the calibration reference  50  is placed below a second guide aperture  55  aligned with first guide aperture  35  such that that calibration reference  50  is illuminated through the guide  20 . This arrangement may not be satisfactory, however, as placement of the calibration reference  50  outside of the read plane may degrade the accuracy of the resulting spectral data, thus degrading the calibration accuracy. 
       FIGS. 3   a - 3   c  illustrate sequential operation of an alternative arrangement known in the art for automatically calibrating the spectrophotometer  15 . In  FIG. 3   a , a top view of the spectrophotometer  15  and guide  20  in the normal operating position is shown. The calibration reference  50  is positioned adjacent to a side of the guide  20 . During calibration, the spectrophotometer  15  is taken offline and mechanically translated such that its read plane coincides with the upper surface of the calibration reference  50 , as shown in  FIG. 3   b . The spectrophotometer  15  is re-translated to its normal online position subsequent to calibration, as shown in  FIG. 3   c . Translation of the spectrophotometer  15  between the measurement and calibration positions requires the use of a full-length translation system (not shown). The internal space required for accommodating such a system may result in an unacceptable enlargement of the printing device  10 . 
     As an alternative to the automatic calibration arrangements described above, media for which spectral data has been obtained a priori (e.g., by performing offline measurements) may be manually fed through the printing device  10 . The resulting spectral data generated by the spectrophotometer  15  may then be compared to the previously-obtained spectral data in order to determine the appropriate transform curve. This calibration technique, however, is time-consuming and requires a substantial amount of manual intervention. 
     Because use of the spectrophotometer  15  in the measurement and calibration modes is typically intermittent, it is generally desirable to automatically store the spectrophotometer  15  within the printing device  10  during periods of nonuse such that contamination of its optical surfaces is minimized. Storage of the spectrophotometer  15  in this manner within the limited internal space of a conventional printing device is problematic and may be exceedingly difficult in cases where a large portion of the available space is allocated to spectrophotometer  15  calibration features. 
     In view of the problems described above, there is a need for more efficient and effective systems and methods for calibrating and maintaining electro-optical instruments within printing devices. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates a side view of a conventional spectrophotometer arrangement within a printing device; 
         FIG. 2  illustrates a side view of a conventional spectrophotometer calibration arrangement within a printing device; 
         FIGS. 3   a - 3   c  illustrate sequential top views of a conventional spectrophotometer calibration arrangement within a printing device; 
         FIGS. 4   a - 4   c  illustrate sequential side views of a system for calibrating and storing a spectrophotometer within a printing device according to various embodiments of the present invention; 
         FIG. 4   d  illustrates a side view of the system of  FIGS. 4   a - 4   c  when the spectrophotometer is inclined in a maintenance position according to various embodiments of the present invention; 
         FIGS. 5   a - 5   b  illustrate top views of trays and arrangements of calibration references thereon for use in the system of  FIGS. 4   a - 4   c  according to various embodiments of the present invention; 
         FIGS. 5   c - 5   d  illustrate side views of reference surfaces of the tray of  FIG. 5   b  according to various embodiments of the present invention; 
         FIGS. 6   a - 6   b  illustrate sequential side views of a system for calibrating and storing a spectrophotometer within a printing device according to various embodiments of the present invention; 
         FIG. 6   c  illustrates a top view of a tray and an arrangement of a calibration reference thereon for use in the system of  FIGS. 6   a - 6   b  according to various embodiments of the present invention; 
         FIG. 7   a  illustrates a side view of a system for calibrating and storing a spectrophotometer within a printing device according to various embodiments of the present invention; and, 
         FIG. 7   b  illustrates a top view of a tray and an arrangement of calibration references thereon for use in the system of  FIG. 7   a  according to various embodiments of the present invention. 
     
    
    
     DESCRIPTION 
       FIG. 4   a  illustrates a side view of a system  60  for calibrating and storing a spectrophotometer  65  within a printing device  10  according to various embodiments of the present invention. As shown, the spectrophotometer  65  comprises components similar to those described above in connection with  FIG. 1  and is oriented such that its read plane corresponds to the upper surfaces of media  30  passing through the guide  20 . In addition to the spectrophotometer  65 , the system  60  may comprise pivot  70  attached to the spectrophotometer  65  such that spectrophotometer  65  (and its read plane) may be inclined at an angle relative to the guide  20 . Although the pivot  70  is shown attached to the bottom left corner of the spectrophotometer  65 , it will be appreciated that other suitable mounting locations may be employed. It will also be appreciated that the mounting location may be dictated by, among other things, the geometry, physical configuration, weight, and/or materials of the spectrophotometer  65 . According to various embodiments and as shown, the pivot  70  may be implemented as a hinge, although any device or structure that enables one device to be repositioned (e.g., rotated, translated, etc.) relative to another device may generally be used. 
     The system  60  further comprises an actuator  75  pivotably attached to the spectrophotometer  65  for generating a mechanical force necessary to incline the spectrophotometer  65  about the pivot  70 . According to various embodiments, the actuator  75  may be implemented using any suitable mechanical actuator, electromechanical actuator (e.g., a stepper motor, solenoid, etc.), hydraulic actuator, or pneumatic cylinder actuator. 
     The system  60  further comprises a calibration module  80  disposed adjacent to the spectrophotometer  65 . As shown, the calibration module  80  comprises a calibration reference tray  85  on which one or more calibration references  90  ( FIGS. 5   a - 5   b ) are arranged. As discussed below, the calibration module  80  may be configured to extend the tray  85  into the read plane of the spectrophotometer  65  when the spectrophotometer  65  is in the inclined position. The tray  85  may further include a reference surface  95  for engaging the illuminating/detecting surface of the spectrophotometer  65  when the tray  85  is extended such that the upper surface of the calibration reference(s)  90  is maintained precisely within the read plane. Other alignment features (e.g., alignment pins/sockets, etc.) may also be employed. 
     The system  60  further comprises a controller  100  in communication with the spectrophotometer  65 , the actuator  75 , and the calibration module  80 . Although the controller  100  is shown separately in the embodiments of  FIGS. 4   a - 4   c , the controller  100  may be integral to the spectrophotometer  65  in other embodiments. The controller  100  may be implemented using a programmable microprocessor, for example, and in one embodiment may be configured to perform independent and fully automatic control of the system  60  responsive to one or more commands received from a printing device  10  within which the system  60  is integrated. The commands may include, for example, commands for calibrating or storing the spectrophotometer  65 . In other embodiments, one or more components of the system  60  may be externally controlled by the printing device  10 . The controller  100  may also read data (analog or digital) from the spectrophotometer  65 , the actuator  75 , and the calibration module  80 . Such data may include, for example, position data (e.g., spectrophotometer  65  position data, actuator  75  position data, tray  85  position data), as well as data relating to any error conditions (e.g., position errors, mode errors, etc.). Errors may be reported by the controller  100  to a host processor (not shown) of the associated printing device  10 , for example. 
     As shown in  FIG. 4   a , the spectrophotometer  65  is in a position corresponding to the measurement mode of the system  60 .  FIG. 4   b  illustrates the system  60  subsequent to initiation of the calibration or storage modes in response to a command received by the controller  100 . In response to an output from the controller  100 , the actuator  75  applies mechanical force to the spectrophotometer  65  such that the spectrophotometer  65  is inclined at a predetermined angle about the pivot  70 . 
     Subsequent to the inclination of the spectrophotometer  65  and as shown in  FIG. 4   c , the tray  85  of the calibration module  80  is extended responsive to a controller  100  output such that a calibration reference  90  contained on the tray  85  is introduced into the read plane of the spectrophotometer  65 . In various embodiments, tray  85  may be linearly extended into position using any suitable actuator (e.g., stepper motor, solenoid, etc.). According to certain embodiments, an actuator may be used to rotate/spin the tray  85  into position. Positioning of the tray  85  further results in the contact of the reference surface  95  with the illuminating/detecting face of the spectrophotometer  65  such that upper surface of the calibration reference  90  is accurately maintained within the read plane. Calibration of the spectrophotometer  65  may be automatically commenced after a properly extended tray  85  position is detected by controller  100 . Subsequent to calibration, the tray  85  may be retracted and the spectrophotometer  65  declined by the actuator  75  to its normal operating position ( FIG. 4   a ). 
       FIG. 5   a  illustrates a top view of the tray  85  and an arrangement of a calibration reference  90  thereon according to various embodiments of the present invention. Although only one calibration reference  90  is depicted, it will be appreciated that the tray  85  may instead comprise one or more additional calibration references  90  that may be positioned within the read plane by suitably controlling the linear extension of the tray  85 . The tray  85  may further include a seal  105 , such as, for example, a rubber seal, disposed about a periphery of the calibration reference  90 . The seal  105  may be configured to contact the illuminating/detecting face of the spectrophotometer  65  such that the illumination source  25  (see, e.g.,  FIG. 1 ) and sensor module  40  optics are sealably contained and protected from external contaminants. Accordingly, the calibration position of the spectrophotometer  65  ( FIG. 4   c ) may also correspond to its position when in the storage mode. It will be appreciated that in other embodiments, the seal  105  may be positioned on the tray  85  separately from the calibration reference  90  such that the tray  85  is positioned differently when in the calibration and storage modes. 
       FIG. 5   b  illustrates a top view of the tray  85  and an arrangement of calibration references  90  thereon according to various embodiments of the present invention. As shown, the tray  85  may be circular in shape and may comprise a plurality of calibration references  90  symmetrically disposed about a peripheral portion thereof. Subsequent to the extension of the tray  85 , the calibration module  80  may be configured to rotate the tray  85  such that a selected one of the calibration references  90  is introduced into the read plane. The tray  85  may further comprise a reference surface  110  (see, e.g.,  FIG. 5   d ) for contacting the illuminating/detecting surface of the spectrophotometer  65  as the tray  85  is rotated. The calibration references  90  may include different calibration colors (e.g., white, red, green, and blue), for example. Although four calibration references  90  are shown in  FIG. 5   b , it will be appreciated that a different number of calibration references  90  may be used instead. The tray  85  may further include a seal  105  disposed about each calibration reference in a manner similar to that described above in connection with  FIG. 5   a . Accordingly, any of the calibration references  90  may be placed into the read plane to enable storage of the spectrophotometer  65  (see, e.g.,  FIGS. 4   a - 4   d ). 
     According to other embodiments, a seal  105  may be assigned to a unique position on the periphery of the tray  85  separate from that of the calibration references  90  such that no calibration reference  90  is within the read plane during storage of the spectrophotometer  65 . Calibration references not located within the read plane (either during calibration or storage) can still be protected by the contact of their corresponding seals  105  with an outer-portion of the illuminating/detecting face of the spectrophotometer  65 . 
       FIG. 5   c  illustrates a side view of the reference surface  110  of the tray  85  of  FIG. 5   b  according to various embodiments of the present invention. As shown, the reference surface  110  may be contoured such that the spectrophotometer  65  is raised and lowered in accordance with the rotational position of the tray  85 . This may be useful, for example, where the read plane must be adjusted to accommodate calibration references  90  of different thicknesses. Alternatively, as shown in  FIG. 5   d , the reference surface  110  may be uniform such that the read plane is constantly maintained. 
     In addition to the measurement, calibration, and storage positions of the spectrophotometer  65 , embodiments of the present invention may further include a maintenance position whereby the inclination of the spectrophotometer  65  is increased past that corresponding to the calibration mode.  FIG. 4   d  depicts the system  60  in which the spectrometer  60  in inclined in the maintenance position. Advantageously, the increased inclination of the spectrophotometer  60  permits the manual insertion of an external calibration reference (not shown). Additionally, the inclination may be sufficiently steep in certain embodiments such the illumination source  25  and optics of sensor module  40  may be visually inspected and/or cleaned. 
       FIG. 6   a  illustrates a side view of a system  115  for calibrating and storing a spectrophotometer  65  within a printing device  10  according to various embodiments of the present invention. As shown, the spectrophotometer  65  can be oriented such that its read plane corresponds to the upper surfaces of media  30  passing through the guide  20 . In addition to the spectrophotometer  65 , the system  115  may comprise a set of guide features  120  attached to the spectrophotometer  65  and configured for receipt within a contoured cam path  125 . According to various embodiments, the guide features  120  may be wheels, for example. It will be appreciated, however, that the guide features  120  may instead be implemented using non-rotating devices, such as, for example, pins. It will further be appreciated that the number and position of the guide features  120  of  FIG. 6   a  is provided by way of example only and may be varied as needed. 
     The system  115  may further comprise an actuator  75  pivotably attached to the spectrophotometer  65  for generating the mechanical force necessary for causing the guide features  120  (and thus the spectrophotometer  65 ) to traverse the cam path  125 . According to various embodiments, the actuator  75  may be implemented as an electromechanical actuator (e.g., a stepper motor, solenoid, etc.) or a pneumatic cylinder actuator, for example. 
     The system  115  may further comprise a tray  130  disposed adjacent to one end of the cam path  125  upon which one or more calibration references  90  ( FIG. 6   c ) are arranged. 
     The system  115  further comprises a controller  100  in communication with the spectrophotometer  65  and the actuator  75 . The controller  100  may be similar to that described above in connection with  FIGS. 4   a - 4   c  and may be configured to respond to one or more externally-provided commands by calibrating or storing the spectrophotometer  65 . The controller  100  may also read data from the spectrophotometer  65  and the actuator  75  as described above to determine their respective positions and the presence of any error conditions. 
     As shown in  FIG. 6   a , the spectrophotometer  65  is in a position corresponding to the measurement mode of the system  115 .  FIG. 6   b  illustrates the system  115  subsequent to initiation of the calibration or storage modes responsive to a command received by the controller  100 . In response to an output from the controller  100 , the actuator  75  applies mechanical force to the spectrophotometer  65  such that the spectrophotometer  65  traverses the cam path  125 . Traversal of the cam path  125  by the spectrophotometer  65  causes the spectrophotometer  65  to be elevated above the tray  130  such that the calibration reference  90  is within the read plane. According to one embodiment, a reference surface (not shown) may be provided for engaging the transmitting/detecting face of the spectrophotometer  65  such that the calibration reference  90  is accurately maintained within the read plane. Calibration of the spectrophotometer  65  may automatically commence after the position of the calibration source  90  within the read plane is determined by the controller  100 . Subsequent to calibration, the actuator  75  may cause the spectrophotometer  65  to re-traverse the cam path  125  such that it again assumes a measurement position ( FIG. 6   a ). 
       FIG. 6   c  illustrates a top view of a tray  130  and an arrangement of a calibration reference  90  thereon according to various embodiments of the present invention. The tray  130  may be similar to the tray  85  described above and comprise a seal  105  for protecting the illumination source  25  and sensor module  40  optics from external contaminants. Accordingly, the calibration position of the spectrophotometer  65  ( FIG. 6   b ) may also correspond to its position when in the storage mode. To protect the calibration reference  90  from contaminants, the tray  130  may further comprise a spring loaded cover (not shown) configured to extend over the calibration reference  90  when the spectrophotometer  65  is in the measurement position. The cover may be configured such that it is forcibly retracted by the spectrophotometer  65  when in the calibration position. Although only one calibration reference  90  is depicted, it will be appreciated that the tray  130  may instead comprise one or more additional calibration references  90  that may be positioned within the read plane by suitably adjusting the tray  130  position. Circular tray geometries suitable for presenting a number of calibration references  90  by rotating the tray, such as described above in connection with  FIG. 5   b , may also be employed. 
       FIG. 7   a  illustrates the system  115  according to another embodiment of the present invention in which the cam path  125  has been extended. According to such embodiments, multiple calibration positions may be realized by varying the position of the spectrophotometer  65  such that one of a plurality of calibration sources  90  arranged on the tray  130  ( FIG. 7   b ) is within the read plane. According to various embodiments, one of the positions obtained by extending the cam path  125  may also be utilized to provide a maintenance mode in which the light source, optics, and other features of the spectrophotometer  65  are physically accessible for visual inspection, cleaning, and/or troubleshooting. Such troubleshooting may include, for example, manually presenting a calibration reference into the read plane. 
     In other embodiments, systems of the present invention may incorporate features of both systems  60 ,  115  described above. In certain embodiments, for example, a cam path may be provided such that traversal of the spectrophotometer  65  therethrough results in the inclination of the spectrophotometer  65  similar to that shown in  FIGS. 4   b - 4   c . A calibration module having features similar to those of the calibration module  80  may then be employed for enabling calibration or storage modes. 
     In still other embodiments, systems of the present invention may utilize an actuator (e.g., a screw shaft) for elevating the spectrophotometer  40  in a vertical fashion such that the read plane is maintained in a horizontal orientation. Such systems may include a calibration module similar to the calibration module  80  described above, with the exception that the tray is configured to extend horizontally into the read plane. 
     The examples presented herein are intended to illustrate potential and specific implementations of the present invention. It can be appreciated that the examples are intended primarily for purposes of illustration of the invention for those skilled in the art. No particular aspect or aspects of the examples is/are necessarily intended to limit the scope of the present invention. 
     It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, other elements. Those of ordinary skill in the art will recognize, however, that these and other elements may be desirable. However, because such elements are well known in the art and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein. 
     Any element expressed herein as a means for performing a specified function is to encompass any way of performing that function including, for example, a combination of elements that perform that function. Furthermore the invention, as defined by such means-plus-function claims, resides in the fact that the functionalities provided by the various recited means are combined and brought together in a manner as defined by the appended claims. Therefore, any means that can provide such functionalities may be considered equivalents to the means shown herein. 
     In general, it will be apparent to one of ordinary skill in the art that various embodiments described herein may be implemented in, or in association with, many different embodiments of software, firmware, and/or hardware. The actual software code or specialized control hardware used to implement some of the present embodiments is not limiting of the present invention. For example, certain aspects of embodiments described herein may be implemented in computer software using any suitable computer software language type such as, for example, C or C++ using, for example, conventional or object-oriented techniques. Such software may be stored on any type of suitable computer-readable medium or media such as, for example, a magnetic or optical storage medium. Thus, the operation and behavior of the embodiments may be described without specific reference to the actual software code or specialized hardware components. The absence of such specific references is feasible because it is clearly understood that artisans of ordinary skill would be able to design software and control hardware to implement the embodiments of the present invention based on the description herein with only a reasonable effort and without undue experimentation. 
     Moreover, the processes, systems and devices associated with the present embodiments may be executed by, or in operative association with, programmable equipment, such as computers, computer systems, and spectrophotometer processor systems. Software that causes programmable equipment to execute the processes may be stored in any storage device, such as, for example, a computer system (non-volatile) memory, an optical disk, magnetic tape, or magnetic disk. Furthermore, the processes may be programmed when the computer system is manufactured or via a computer-readable medium. Such a medium may include any of the forms listed above with respect to storage devices and may further include, for example, a carrier wave modulated, or otherwise manipulated, to convey instructions that may be read, demodulated/decoded and executed by a computer. 
     It can also be appreciated that certain process aspects described herein may be performed using instructions stored on a computer-readable medium or media that direct a computer system to perform the process aspects. A computer-readable medium may include, for example, memory devices such as diskettes, compact discs of both read-only and read/write varieties, optical disk drives, and hard disk drives. A computer-readable medium may also include memory storage that may be physical, virtual, permanent, temporary, semi-permanent and/or semi-temporary. A computer-readable medium may further include one or more data signals transmitted on one or more carrier waves. 
     A “computer” or “computer system” may be, for example, a wireless or wireline variety of a microcomputer, minicomputer, server, mainframe, laptop, personal data assistant (PDA), wireless e-mail device (e.g., “BlackBerry” trade-designated devices), cellular phone, pager, processor, fax machine, scanner, or any other programmable device configured to transmit and receive data over a network. Computer systems disclosed herein may include memory for storing certain software applications used in obtaining, processing and communicating data. It can be appreciated that such memory may be internal or external to the disclosed embodiments. The memory may also include any means for storing software, including a hard disk, an optical disk, floppy disk, ROM (read only memory), RAM (random access memory), PROM (programmable ROM), EEPROM (electrically erasable PROM), and other computer-readable media. 
     In various embodiments of the present invention disclosed herein, a single component may be replaced by multiple components, and multiple components may be replaced by a single component, to perform a given function or functions. Except where such substitution would not be operative to practice embodiments of the present invention, such substitution is within the scope of the present invention. 
     While various embodiments of the invention have been described herein, it should be apparent that various modifications, alterations and adaptations to those embodiments may occur to persons skilled in the art with the attainment of some or all of the advantages of the present invention. The disclosed embodiments are therefore intended to include all such modifications, alterations and adaptations without departing from the scope and spirit of the present invention.