Abstract:
Apparatus for exposing reference calibration patches onto photosensitive medium, includes: a light source; a plurality of optical fibers, one fiber for each element to be exposed; a light collector having an input port for receiving light emitted by the light source and an output port for delivering light to one end of the optical fibers; a plurality of light attenuators located with respect to the optical fiber for individually attenuating the light transmitted by each fiber; a projection print head located at the other end of the optical fibers for directing light from the fiber onto the photosensitive medium; and a controller connected to the light source for measuring and controlling the light output of the light collector.

Description:
FIELD OF THE INVENTION 
     The present invention relates to sensitometry and more particularly to apparatus for exposing sensitometric and bar code data onto photosensitive media in a manufacturing environment. 
     BACKGROUND OF THE INVENTION 
     The use of a sequence of reference calibration patches exposed on a roll of film to enable better exposure control during optical printing is known in the art. See for example U.S. Pat. No. 5,767,983 issued Jun. 16, 1998 to Terashita. The use of reference calibration patches has also been shown to be useful in determining correction values for scanned film data used in digital printing. See for example U.S. Pat. No. 5,667,944 issued Sep. 16, 1997 to Reem et al. and U.S. Pat. No. 5,649,260 issued Jul. 15, 1997 to Wheeler et al. 
     U.S. Pat. No. 5,075,716 issued Dec. 24, 1991 to Jehan et al. shows apparatus for exposing reference calibration patches on photosensitive media that includes a light source, and a bundle of optical fibers for transporting light from the light source to the photosensitive medium. The exposures to the photosensitive medium are controlled by providing groups of fibers having different numbers of fibers in each group and by apparatus for adjusting the spacing between the fiber bundles and the exposure plane. Furthermore, the exposure is accomplished by contacting the surface of the photosensitive medium with the print head of the apparatus to precisely locate the exposure plane and minimize flare. 
     There are many problems experienced with the use of conventional sensitometric apparatus to apply reference calibration patches to film. One problem is that contact exposures are not desirable in the manufacturing environment, since the surface of the film can be damaged or contaminated by contact with the print head of the sensitometer. Another problem is in exposing film at 4log E levels using a non-contact exposure apparatus without causing excessive image flare. Another problem is in providing a high enough exposure to expose the reference calibration patches in a short enough time (e.g. less than 100 milliseconds) to be compatible with the dwell time available for printing during the manufacturing process. An example of film manufacturing apparatus is described in U.S. Pat. No. 5,461,450 issued Oct. 24, 1995 to Long, et al. The film is transported in the apparatus using an intermittent motion that constrains the dwell time (the time that the film is stationary and the perforator punches are engaged with the film) as described above. A further problem relates to the size of both the conventional sensitometric apparatus and the size of the exposures produced thereby. It would be desirable to locate the sensitometer for exposing reference calibration patches into the manufacturing equipment of the photosensitive materials, where space is at a premium, to provide the most accurate placement of the patches and maximize the manufacturing system performance. It is also desirable to locate the sensitometric exposure device along with a barcode exposure device for the purpose of printing associated metadata and controlling both devices with a central control system There is also a need for a sensitometer that is easy to set up, reliably maintains its calibration in the manufacturing environment, and can automatically setup to meet the exposure needs of various product types without interrupting the process flow. A further need is to provide a sensitometer that is capable of reliably providing millions of exposures without failure or adjustment. 
     There is a need therefore for an improved apparatus for exposing sensitometric and meta data onto photosensitive media that avoids the problems noted above. 
     SUMMARY OF THE INVENTION 
     The need is met according to the present invention by providing an apparatus for exposing reference calibration patches onto photosensitive medium, including: a light source; a plurality of optical fibers, one fiber for each element to be exposed; a light collector having an input port for receiving light emitted by the light source and an output port for delivering light to one end of the optical fibers; a plurality of light attenuators located with respect to the optical fiber for individually attenuating the light transmitted by each fiber; a projection print head located at the other end of the optical fibers for directing light from the fiber onto the photosensitive medium; and a controller connected to the light source for measuring and controlling the light output of the light collector. 
     According to a further aspect of the invention, the apparatus includes a data printer having: a second light source; a two dimensional liquid crystal light modulator for modulating the light from the second light source; optics for projecting an image of the light modulator onto the photosensitive medium; and the controller being connected to the light modulator and the light source for applying a two dimensional bar code image signal to the light modulator and activating the light source for exposing the two dimensional bar code onto the photosensitive medium. 
     The apparatus operates as a system that prints both barcode data and sensitometric information on the photosensitive medium transported under the print heads located on a web transport of a photosensitive medium manufacturing machine. 
     ADVANTAGES 
     The apparatus of the present invention has the advantage of providing: a broad dynamic exposure range of up to 4 Log E; rapid exposure times regardless of film type; non-contact printing, whereby no part of the apparatus contacts the photosensitive and fragile film surface; precise, controllable, adjustable exposures; a reference calibration patch profile with a substantially flat profile shape at peak values along with a minimal flare skirt; and a precision of exposure of better than 1% over an 8× range of film speeds and product sensitivities. 
     In the preferred embodiment, the apparatus is located on a perforation/printing station of a film manufacturing machine at a specific location where a predetermined frame stops, regardless of film length, thus allowing one fixed location printer system to generate various film lengths without need for operator intervention or setup for film length changes on the station. Physically printing the reference calibration patches and the barcode data in the same frame location (frame 0) during the same machine index dwell, allows for the most accurate placement of each printed image relative to the other, resulting in minimal dimensional variation between the two image geometries. 
     The printer control system allows for more efficient and reliable data transfer from the reference calibration patch printer to the bar code data printer. This allows the barcode data printer the capability of reporting on certain characteristics of the reference calibration patch printer and including that info in the data printed by the bar code printer. 
     Minimum space is required for implementation on a production manufacturing machine and a minimum impact on present spooler control system during printing, and can be configured for projection printing on a planar or radiused film surface. Its modular design provides for minimized setup and install time. The preferred XENON illumination sources provide long life, stable and high reliability compared to tungsten or other sources. 
     The use of optical fibers allows for the transport of precise signals through an electromagnetically noisy machine space. The small footprint, very fast cycle, and ease of maintenance, result in a significant improvement in overall performance compared to standard sensitometers. Separating light source from the print head and joining them with optical fibers allows for flexible placement of the print head on the machine, and easy replacement of the light source or print head. 
     Communications between the printer control system with the web transport control system allows for filmstrips with the same data message to be identified by cartridge ID and other specific data. The identification information can be stored in the factory. This identification can be used to provide data corrections or updates by communicating the updates to the photofinisher and using the identification information printed in the data and located on the cartridge to identify the affected filmstrips. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of apparatus for exposing reference calibration patches according to the present invention; 
     FIG. 2 is a diagram showing a reference calibration target which includes an array of reference calibration patches and an array of 2-D bar code symbols produced by the apparatus of the present invention; 
     FIG. 3 is perspective view of the print head shown in FIG. 1; 
     FIG. 4 is a perspective view of the filter plug shown in FIG. 1; 
     FIG. 5 is a cross sectional view of the filter plug shown in FIG. 1; 
     FIG. 6 is a schematic diagram of the data printer according to one aspect of the present invention; 
     FIG. 7 is a schematic diagram of the overall control system of the apparatus of the present invention; 
     FIG. 8 is a schematic diagram of the sensitometric exposure control system shown in FIG. 7; 
     FIG. 9 is a flow chart showing the method of driving the flash lamps for exposing sensitometric data; 
     FIG. 10 is a graph useful in describing the method shown in FIG. 9; 
     FIG. 11 is a perspective view showing a moveable cap for the print head shown in FIG. 3; 
     FIG. 12 is a partial view showing a fixed transparent protective cap over the print head shown in FIG. 3; 
     FIG. 13 is a partial view of a pressurized print head; 
     FIG. 14 is a schematic diagram showing the location of the apparatus of the present invention on a film perforation/printing machine; and 
     FIG. 15 is a partial view showing a moveable color temperature filter on the filter plug that could be moved automatically. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, apparatus for exposing reference calibration patches to form a latent image onto photosensitive medium, generally designated  10 , includes a light collector such as an integrating sphere  12 , having a plurality of apertures. A pair of flash lamps  14  and  16 , preferably Xenon flash lamps, are located in two of the apertures, and an attenuator filter plug  18  is located in another of the apertures. Each flash lamp  14  and  16  is connected to a power supply  43  and  42  respectively and can be caused to emit one pulse of light when triggered by controller  20 . Attenuator filter plug  18  captures light exiting integrating sphere  12  and transfers it into multiple reference calibration patch optical fibers  23 , as well as multiple exposure control optical fibers  38 . A spectrophotometer  17  is inserted into an additional aperture in integrating sphere  12  to collect information on the spectral energy distribution of the exposure light and relay it to controller  20 . Exposure control optical fibers  38  sample the exposure light and transfer it to exposure integrator circuit  40  which interfaces with controller  20  to control the exposure level as will be detailed later. 
     Optical fibers  23  transmit the light from integrating sphere  12  to projection printhead assembly  26  which can be located distant from the rest of reference calibration patch exposure apparatus  10 . Optical fibers  23  are preferably multimode optical fibers such as 2 mm diameter PMMA (poly-methyl-methyl acrylate) plastic fibers manufactured by Mitsubishi Rayon and known as type ESKA™. Projection printhead assembly  26  is located in a fixed location relative to photosensitive media  34  which is in contact with photosensitive media transport and indexing drum  36 . Projection printhead assembly  26  consists of projection printhead body  27  into which optical fibers  23  enter. The end of optical fiber  23  is polished and held a fixed distance from the surface of media  34  by projection printhead body  27 . Projection printhead lens  30  focuses an inverted image of the end of optical fiber  23  onto media  34  at substantially 1:1 magnification. Lens  30  is preferably a simple symmetric bi-convex lens of BK-7 glass with a first surface radius of 1.5 mm, a second surface radius of −1.5 mm and a thickness of 3-mm. Lens  30  is also preferably coated with an anti-reflection coating optimized for broadband white light in the 400-700 nm region. Between the end of fiber  23  and lens  30  is located a projection printhead input baffle  28  whose function is to trap non-image light rays and stop them from creating flare light at the image plane. Baffle  28  is formed by steps  25  that are provided with a non-reflective surface such as black anodization or light absorbing paint that assists in trapping non-image light rays. Between lens  30  and the image plane on the surface of media  34  is a projection printhead glare stop aperture  32 . The function of glare stop aperture  32  is to stop any non-image light from forming glare around the exposed image. A hollow projection printhead output chamber  31  is formed between the second surface of lens  30  and glare stop aperture  32 . 
     This invention can be used to expose different film formats. One example is the film format known as the Advanced Photographic System (APS) which is documented in published system specifications, known as the Redbook. FIG. 2 illustrates an arrangement of latent image exposures on an APS format photographic element. The APS system reserves specific areas on the photographic element for use by photofinishing apparatus. These areas can be used for exposing reference calibration patches, and other data used in the photofinishing process. Referring to FIG. 2, an APS format photographic element  70 , comprising a strip of photosensitive media  34 , according to the Redbook specification, is shown. The film strip includes a first reserved frame  72  (known as “Frame 0”) reserved for use in photofinishing apparatus and outside the customer image area. Perforation  84  is provided adjacent to frame 0  72  on the film strip  70  and locates the position of frame 0  72  along the filmstrip. According to a preferred embodiment of the present invention two latent images are exposed in frame 0  72 . These are a reference calibration patch array  76  consisting of a plurality of reference calibration patches  82 , and a 2D Barcode symbol array  74  consisting of an arrangement of 2D barcode symbols  78 . Both arrays  76  and  74 , are arranged as shown in FIG. 2 within a second reserved area  80 , located within frame 0  72 . Other arrangements of the arrays are possible. 
     FIG. 3 shows a perspective view of the projection printhead assembly  26 . Printhead assembly  26  consists of a printhead body  27  connected to a plurality of optical fibers  23 . The optical fibers  23  are collected into optical fiber bundle  50 . Light energy transmitted through an optical fiber  23  into the printhead body  27  passes through the body  27  to exit the head via a projection printhead glare stop aperture  32  and on to the photosensitive media  34  (not shown). An antireflective surface  48  on the printhead body  27  reduces reflections of the light energy between the media  34  and the opposing surfaces of printhead body  27 . An example of how this is achieved would be to apply a surface coating, such as a Sherwin Williams Co Flat Black E61 Series Epoxy enamel with 0-5% Gloss, alternatively or in combination with a diffuse surface texture, such as resulting from bead blasting the surface. 
     FIG. 4 illustrates the attenuation filter plug assembly  18 . Plug assembly  18  consists of a attenuation filter plug body  19  connected to a plurality of reference calibration patch optical fibers  23  and exposure control optical fibers  38  with the optical fibers  23  collected into optical fiber bundle  50 . Light energy collected in the integrating sphere  12  (not shown) passes into the filter plug assembly  18  through the optical color correction filter  24  and through aperture mask  54  and into the individual attenuation filters  22  before passing finally into the fiber optics  23 . Aperture mask  54  is aligned with the plurality of individual attenuation filters  22  such that each attenuation filters  22  is aligned with an individual aperture in the aperture mask  54  to insure that light does not leak around the edges of the attenuation filters  22 . The attenuation filters  22  are preferably a stable optical neutral density filter such as Inconel™ on glass, or other material as known in the art. Color correction filter  24  is also preferably a stable optical filter material such as a Schott FG type glass or similar material as known in the art. Retaining ring  52  holds filter  24  and mask  54  in place in a recess formed in plug body  19 . 
     FIG. 5 is a partial cross sectional view further describing the filter plug assembly  18  described in FIG.  4  and showing its internal construction. Light energy collected in the integrating sphere  12  passes into the filter plug assembly  18  through optical color correction filter  24  located on one end of the plug body  19 . Optical correction filter  24  is used to adjust the spectrum of light passed through individual attentuation filters  22  by attenuating particular undesirable wavelengths such that a desired color spectrum is achieved. This color corrected light then passes through aperture mask  54  and through the array of individual attenuation filters  22  and into optical fiber  23 . Each attenuation filter  22  has a unique optical neutral density or color resulting in a unique latent image exposure level for each reference calibration patch  82  as shown in FIG.  2 . The reference calibration patches produced by this system can be neutral, colored or any combination thereof. 
     Referring to FIG. 6, a data printer, generally designated  100 , for exposing bar code data symbols onto photosensitive medium, includes illumination source  108 , preferably a Xenon flash with suitable reflector (not shown), driven by power supply  112  further controlled by a controller  20 . The controller  20  uses various control inputs in its operation, including those from overall machine controller  134 . For example, the machine controller  134  sends timing information to trigger the flash as well as apparatus calibration and setup information to controller  20 . The illumination source  108  directs uniform illumination into a fiber optic bundle  114 . 
     The fiber optic bundle  114  directs the illumination to pass through color correction filter  118  housed in housing  116 . Housing  116  contains a plurality of filters arranged in a manner that allows them to be individually introduced in front of the fiber optic bundle  114  by rotation of housing  116 . Housing  116  is attached at its center to the shaft of motor  120  allowing it to be rotated by motor  120 . Motor  120  is controlled by signals from controller  20 . 
     Illumination passing through filter  118  passes through condenser optics  124  and toward light valve array  126 , preferably a liquid crystal device (LCD) array. Light valve array  126  has a plurality of individually addressable pixels for selectively blocking or transmitting illumination to form characters and specific geometry in response to the address and energization of the individual pixels. The light valve array  126  is driven by video driver  125  and the driver  125  driven by controller  20  via control line  132 . 
     Illumination passing light valve array  126  forms an image that passes further through focusing optics  128  to be focused down to the imaging position  130  on the photosensitive medium  34  forming a latent image. Photosensitive media  34  is supported and transported on the photosensitive media transport and indexing drum  36  of a web transport device. The photosensitive media is held to the indexing drum  36  by means of a suitable traction inducing device (not shown), for example a vacuum generated between the media and drum or a nip roll compressing the media against the drum  36   
     In operation, the printer receives setup information from machine controller  134  that is passed to the controller  20 . This information, for example, film strip length and film product code, is used to select the correct color correction filter  116  and rotate it into place via motor  120  as well as set up the proper level and duration of illumination source  108 . The indexing drum  36  moves photosensitive media  34  into the proper location along the media to the imaging position  130  shown in FIG.  6 . Indexing drum  36  is then directed to stop motion by machine controller  134 . Machine controller  134  then recognizes that photosensitive media  34  is in position and directs controller  20  to flash illumination source  108  via power supply  112 . The illumination passes through the system, generating an image at light valve  126  that is focused onto the photosensitive media at imaging position  130  and completing the cycle. Indexing drum  36  is then directed by machine controller  134  to begin the next cycle of operation and move to the next filmstrip position. 
     Referring now to FIG. 7 the interconnection of both the reference calibration patch printer  10  and data printer  100  is illustrated. Note that not all parts are shown for both printers; refer to FIGS. 1 and 6 for full details. Power supply  112 , triggered by a signal from controller  20 , flashes illumination source  108  whose light is collected by condenser optics  124  and modulated by light valve array  126 . The spatial pattern used to modulate the light is generated by controller  20  in response to data from machine controller  134 . Focusing optics  128  images the modulated light from light valve  126  onto photosensitive media  34  held on photosensitive media transport and indexing drum  36  forming 2D barcode symbol array  74 . Adjacent to symbol array  74  is reference calibration patch array  76  formed by reference calibration patch printer  10 . Controller  20  commands power supplies  42  and  43  to activate flash lamps  14  and  16  as will be described in detail later. Controller  20  uses photosensitive media sensitivity data from machine control  134  as well as data from exposure integrator circuit  40  to build an accurate latent image exposure through integrating sphere  12  and projection printhead assembly  18 . Both reference calibration patch printer  10  and data printer  100  are commanded to make exposures when photosensitive media  34  and media transport and indexing drum  36  are substantially stopped as communicated by machine control  134 . 
     Illustrated in FIG. 8 is a more detailed description of the exposure integrator circuit  40 . Optical fibers  38  deliver light energy from integrating sphere  12  to photosensors  136  and  138 . Photosensors  136  and  138  are preferably silicon photodiodes. Exposure integrator circuit  40  contains two redundant channels labeled “A” and “B”. To enhance reliability, photosensors  136  and  138  are preferably of similar functional capabilities, but from different manufacturers, thus reducing the probability of both failing or degrading at the same rate. As light energy is captured by the photodiodes an electrical current is produced and integrated by analog integrator circuits  140  and  142 . Analog integrator circuits are well known in the art and one example is Burr Brown Part #IVC102, Tucson Ariz. The output of the integrator circuits is applied to the input of analog to digital converters  144  and  146 . Analog to digital converters  144  and  146  are shown as having 16 bit parallel digital data outputs, but converters with different resolution and/or serial outputs may be made to work as well. A 16 bit bi-directional digital data bus  152  connects the converters with controller  20  shown in FIG. 1. A control signal bus  150  connects controller  20  with converters  144  and  146 , and integrators  140  and  142 . Individual control signals are provided to reset integrators  140 ,  142  and to enable the output of converters  144 ,  146 . Also present on the exposure integrator circuit  40  is a nonvolatile memory  148 . This device could be an EEPROM, battery backed up SRAM, or any other non-volatile digital memory device. Non-volatile memory  148  is connected to controller  20  via data bus  152  and control signal bus  150 . Read and write control lines connect non-volatile memory  148  with CPU  20  via signal bus  150 . 
     Also present on exposure integrator circuit  40  is a temperature compensation mechanism comprised of temperature sensor  154 , temperature controller  156 , heater  158 , and heatsink  160 . Photosensors  136  and  138 , and temperature sensor  154  are tightly coupled thermally to heatsink  160  such that they are all at substantially identical temperatures. Temperature controller  156  senses this temperature via temperature sensor  154  and applies power as necessary to heater  158  to maintain a constant temperature just slightly above the ambient temperature. This mechanism corrects for the temperature-induced drift in the sensitivity of photosensors  136  and  138 . 
     Referring now to FIGS. 9 and 10, the sequence of operation of the flash lamps  14  and  16  will be described. Starting at step  162  the second step is to retrieve a target exposure value from non-volatile memory  148  (shown in FIG.  8 ), as shown in step  164 . Different target exposure values will be determined by calibration and stored in memory  148 , one target value for each film speed. The next step in the sequence consists of resetting the integrator circuits  140  and  142  in FIG. 8, as shown in step  166 . Next a “major” flash pulse is generated by triggering flash lamp power supply  43  in FIG. 1, as shown in step  168 . In step  170  a reading is made by transferring the digital data from analog to digital converter “A”  144  in FIG. 8 to controller  20  in FIG.  1 . Step  172  illustrates the calculation of an intermediate variable “stepsize” by dividing the reading from the analog to digital converter by the target value. The next step, shown in step  174  is to cause another major flash lamp pulse to be generated. This is followed in step  176  by reading the analog to digital converter value. A decision is made in step  178  by comparing the current analog to digital converter value to the target value minus 1.5 times the stepsize variable. As long as the current analog to digital converter reading is less than this calculated value the sequence continues by looping back to box  174  and generating additional Major flash pulses. Once the analog to digital converter reading exceeds the calculated value the sequence continues on to box  180 . At this point the majority of the integrated exposure energy has been created and delivered to the film. 
     FIG. 10 illustrates graphically one method of building the integrated exposure. The target value (which is fixed), the integrated exposure (equivalent to the analog to digital converter output), and the individual major and trimming flashes (equivalent to the photosensor output) are plotted versus time. As the sequence proceeds as described above the integrated exposure increases in large steps to quickly approach the final target. From here on, the exposure increases slowly in smaller steps to achieve very fine accuracy of exposure. 
     Referring again to FIG. 9, the sequence continues in step  180  by causing a trimming flash to be generated by flash lamp power supply  42  and flash lamp  16 . In step  182  the output of the analog to digital converter is read. Step  184  shows the comparison of the latest reading to the target value, as long as the reading is less than the target the sequence returns to step  180  and continues to flash. After the reading exceeds the target value, flashing stops and the sequence proceeds to step  186 . It can be seen that by adjusting the trimming flash level it is possible to achieve the integrated exposure level within a resolution of ±1 trimming flash energy unit. Now in step  186  the value generated by the second or “B” channel is read. By reading the output from analog to digital converter  146  and subtracting it from the target value in step  188  an error value is generated. Next the absolute value of the error value is formed in step  190 . In step  192  the error value is compared to a predetermined tolerance and the sequence ends in either success or failure in steps  196  and  194  respectively. Alternatively, the large and small exposures can be performed simultaneously to reduce the exposure time. 
     A concern in the manufacturing environment is that of contamination entering the glare stop aperture  32  and settling on the printhead lens  30  in the projection printer assembly  26  of the reference calibration patch Printer  10  effectively blocking or degrading the projected illumination. This contamination may consist of chips or flakes of photosensitive media  34  generated as the result of the perforating process, or other cutting processes not illustrated here, and left loosely attached to the media  34 . Interactions between the media  34  and a perforator/printer station of a web transport  240  (see FIG. 14) may cause this loosely attached contamination to become dislodged from media  34  and thrown into the glare stop aperture  32 . Another source of contamination is from maintenance activities in the area near the printhead assembly  26 . Cleaning solvents, and other contaminates used during maintenance may be inadvertently directed toward the glare stop aperture  32  possibly blocking or degrading the projected image. 
     In either case, the contamination may be very difficult to clean away due to the plurality of apertures  34  and general construction of the printhead body  27 . A printhead apparatus that allows for easy removal of contamination would be desirable. An apparatus for protecting the glare stop aperture  32  and printhead lens  30  from being contaminated is also desirable. 
     To address this problem, as shown in FIG. 11, a moveable cover  96  is supported by cover bearing  90  attached to the projection printhead body  27 . Moveable cover  96  is retracted into a position exposing the plurality of glare stop apertures  32  by cover actuator  97  connected to support  94 . In this position the printhead assembly  26  is configured to expose the photosensitive media  34 . Cover actuator  97  may be an electrical solenoid or similar device activated by the overall machine controller  134 . A cover return spring  92  urges the moveable cover  96  into the extended position covering the plurality of glare stop apertures  32  when the actuator  97  is de-energized, thus providing contamination protection by shielding the plurality of glare stop apertures  32  from the environment. 
     An alternative arrangement is shown in FIG. 12 where a fixed transparent cover  98  with antireflective surfaces is attached to the front of the printhead body  27  in a position that covers the plurality of glare stop apertures  32 . This cover remains in place at all times shielding the plurality of glare stop apertures  32  from the environment and providing a front surface that can be easily cleaned if contaminated. 
     Another alternative arrangement is shown in FIG. 13 where the contamination is prevented from entering the plurality of glare stop apertures  32  by means of a continuous flow of pressurized air exiting from each aperture  32 . Projection printhead body  27  containing the plurality of optical fibers  23 , input baffle  28 , lens  30 , and glare stop aperture  32  are configured as shown in FIG. 13. A small output chamber  31  is formed between aperture  32  and lens  30  by the assemblage of the components as shown. One end of delivery channel  204  is ported into the sidewall of the chamber  31  as shown, and the other end is connected to delivery tube  202 . Tube  202  is further connected to a pressurized air source  200  which supplies a constant flow of clean pressurized air to tube  202 . Air flowing through tube  202  and channel  204  enters chamber  31  as shown, pressurizing chamber  31  and then exiting glare stop aperture  32  along the airflow path  206 , exhausting to the environment. Connections between the plurality of glare stop apertures  32  allow for the plurality of chambers  31  to be similarly pressurized, exhausting air along similar air flow paths  206 . 
     The air continuously flowing out of glare stop aperture  32  and along air flow path  206  effectively prevents typical environmental contamination from entering the plurality of glare stop apertures  32 , maintaining the imaging performance of printhead assembly  26   
     FIG. 14 illustrates the arrangement of the entire printing system consisting of the perforator/printer station of a web transport  240 , the reference calibration patch printer  10 , and data printer  100  as well as associated control connections. Printers  10  and  100  are designed to produce the reference calibration patch array  76  and 2D barcode symbol array  74  in frame 0  72  relative to perforation  84  in a photographic element  70  as shown in FIG.  2 . 
     Media  34  is supported by web transport rollers (not shown) and rotatable indexing drum  36  such that it passes between fixed perforator die  232  and moveable perforator punch support  226  of perforator assembly  238 . Support  226  moves in a linear fashion and contains a plurality of punches  224  that are used to generate perforations in the film, such as perforation  84 , when the punch  224  is moved into engagement with the fixed perforator die  232  through the motion of support  226 . The support  226  is moved linearly by actuator link  228  that is attached to actuator  230 . Actuator  230  may, for example, be a servo motor driving an eccentric linkage connected to support  226 . Actuator  230  receives signals from overall machine controller  134  to start and stop a cycle of motion that corresponds to a perforation cycle where punch  224  and fixed perforator die  232  operate to form a perforation or plurality of perforations in the media  34 . 
     Media  34  supported on the rotatable indexing drum  36 , passes by printers  100  and  10  and then into a suction box  220  and eventually over idler roller  234  and continuing to further process steps not shown. The purpose of the suction box  220  is to tension the film invariantly regardless of media  34  velocity and acceleration through the station  240 . Suction box  220  operates under sub-atmospheric pressure generated by a vacuum source (not shown) drawing air through exhaust pipe  222 . 
     Data printer subsystem  100  mounted on the station  240  in a position radially and circumferentially located over indexing drum  36 , is actuated by a power supply  112  further controlled by a controller  20 . Reference calibration printer  10 , mounted on the station  240  in a position radially and circumferentially located over indexing drum  36  is actuated by a power supply  43  and  42  and further controlled by controller  20 . Printers  10  and  100  are further mechanically located with respect to each other to assure precise placement of the reference calibration patch array  76  and the 2-D barcode data symbol array  74 . 
     Perforator/printer station common exposure location  236  represents a location whereby frame 0  72  and adjacent perforation  84  are located for any filmstrip length of an APS photographic element  70  consisting of media  34  supported on indexing drum  36  during operation of the station  240 . Location  236  further represents the printing location on media  34  for printers  10  and  100  regardless of filmstrip length. It further represents the position where the indexing velocity of indexing drum  36  supporting media  34  is zero during the time in the perforation cycle when the punch  224  is engaged in the media  34 . 
     A strip of photosensitive media  34  is converted to a useable format by adding perforations and edge printing. This may be done on a perforator/printer station of a web transport  240  as shown in FIG.  14 . An example is the perforation  84  found on APS format photographic element  70  and shown in FIG.  2 . The perforation  84  is provided adjacent to frame 0  72  on the film strip  70  and locates the position of frame 0  72  along the filmstrip. The intention of this apparatus is to provide capability to add two additional features to frame 0  72 . These are a sensitometric exposure element array  76  consisting of a plurality of reference calibration patches  82  and a 2D barcode symbol array  74  consisting of an arrangement of 2 D barcode symbols  78 . Both arrays  76  and  74  are arranged as shown in FIG. 2 within a second reserved area  80 , located within frame 0  72 . 
     The perforation of the filmstrip can be generated using an indexing, incremental motion perforator as is know in the art. A punch and die combination generates a perforation pattern in the film, such as media  34 , by a series of incremental punching operations where the film is perforated to form a first set of perforations, the punches retract from engagement in the film, the film is indexed ahead to the next perforation position, the film forward velocity is reduced to zero, and the punches engage in the film to begin a new perforating cycle and form a second set of perforations adjacent to the first. The film is typically indexed to subsequent positions by a rotatable support device that engages the film in some manner. For example, using a nip roller or vacuum drum to generate a temporary attraction between the support device and film. A continuous series of perforations can be generated in this manner as well as a discontinuous series of perforations. An example of a discontinuous series of perforations is found on the APS filmstrip, well known in the art, where no perforations are present at the leader and trailer positions along the filmstrip. 
     The cycle of operation commences with the media  34  supported on the station  240  is first perforated by the punch  224  while the media is at rest during the dwell time between indexes. The punch  224  disengages the media  34  by the action of actuator  230  controlled by controller  134 . Controller  134  then commands a servo indexing motor (not shown) attached to Indexing Drum  36  to rotate and transport the media  34  out of the perforator assembly  238  until frame 0  72  is located in position on the drum  36  that corresponds to location  236 . Controller  134  commands the servo indexing motor rotation driving drum  36  to stop rotation and reduce the media  34  velocity to zero. The controller  134  then signals the controller  20  of printers  10  and  100  to begin operation while the media  34  is not in motion. The printing operation must subsequently complete during the dwell time between indexes, typically less than 100 msec. Controller  134  simultaneously signals the actuator  230  to begin a perforation cycle to generate a second series of perforations adjacent to the first on the same filmstrip. Alternatively the perforation cycle could be the start of a new filmstrip. Controller  20  operates subsystems  10  and  100  and then signals controller  134  when the printing operation is completed. Actuator  230  also signals controller  134  once the perforation cycle is complete. Controller  134  then completes the peroration cycle by commanding the indexing drum  36  servo motor to rotate the drum  36  transporting the media into the next perforation position. 
     The printing positional variation for printers  10  and  100  is generally a function of the highly accurate positioning capability of the drum  34  servo motor, resulting in accurate placement of arrays  74  and  76  within second reserved area  80 . This setup results in a station  240  with the capability of printing to media  34  with highly accurate positioning, during a short (&lt;100 msec) duration and with one printer  10  and  100  machine position that can accommodate all filmstrip lengths. 
     FIG. 15 is a partial view further describing the attenuation filter plug assembly  18  described in FIG.  5  and further illustrating an alternative apparatus that allows for automatic optical color correction filter adjustment in response to signals from controller  20 . Light energy collected in the integrating sphere  12  passes into the filter plug assembly  18  through the optical color correction filter  24  located on one end of the plug body  19 . The correction filter  24  is used to adjust the spectrum of light passed through to the individual attentuation filters  22  by attenuating particular undesirable wavelengths such that a desired color spectrum is achieved. This color corrected light then passes through the array of individual attenuation filters  22  and into fiber optics  23 . It may be desirable to provide automatic adjustment of the correction filter  24  in response to changes in illumination color temperature measured by the spectrophotometer  17  inserted into integrating sphere  12  and analyzed by controller  20  as shown in FIG.  1 . Color temperature may change for example due to typical aging characteristics of flashlamps  14  and  16  shown in FIG. 1. A rotatable color correction filter wheel  60  contains a plurality of correction filters  24  each with individual color correction characteristics interacting with the filter plug assembly as shown in FIG.  15 . The wheel  60  is attached to the center shaft of rotatable motor  62  that is actuated by controller  20  in response to measurements from spectrophotometer  17 . The wheel  60  places an individual color correction filter  24  in front of the of aperture mask  54  and individual optical attenuation filters  22  in the filter plug body  19  of plug assembly  18  as shown in FIG. 15 achieving the desired automatic adjustment of color temperature of the illumination from integrating sphere  12 . This example illustrates one apparatus for achieving automatic color temperature correction, other arrangements are possible. 
     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  reference calibration patch printer 
       12  integrating sphere 
       14  major output flash lamp 
       16  trimming output flash lamp 
       17  spectrophotometer 
       18  attenuation filter plug assembly 
       19  attenuation filter plug body 
       20  controller 
       22  individual optical attenuation filters 
       23  optical fibers 
       24  optical color correction filter 
       25  steps 
       26  projection printhead assembly 
       27  projection printhead body 
       28  projection printhead input baffle 
       30  projection printhead lens 
       31  projection printhead output chamber 
       32  projection printhead glare stop aperture 
       34  photosensitive medium 
       36  transport and indexing drum 
       38  exposure control optical fibers 
       40  exposure integrator circuit 
       42  major flash lamp power supply 
       43  trimming flash lamp power supply 
       48  antireflective surface 
       50  optical fiber bundle 
       52  retaining ring 
       54  aperture mask 
       60  color correction filter wheel 
       62  motor 
       70  APS format photographic element 
       72  frame 0 
       74  2D barcode data symbol array 
       76  reference calibration patch array 
       78  2D barcode symbols 
       80  second reserved area 
       82  reference calibration Patches 
       84  perforation 
       90  cover bearing 
       92  cover return spring 
       94  spring support 
       96  movable cover 
       97  cover actuator 
       98  transparent cover 
       100  data printer 
       108  illumination source 
       112  power supply 
       114  fiber optic bundle 
       116  housing 
       118  color correction filter 
       120  motor 
       124  condenser optics 
       125  video driver 
       126  light valve array 
       128  focusing optics 
       130  imaging position 
       132  control line 
       134  overall machine controller 
       136  photosensor A 
       138  photosensor B 
       140  analog integrator circuit A 
       142  analog integrator circuit B 
       144  analog to digital converter A 
       146  analog to digital converter B 
       148  non-volatile memory 
       150  digital control signal bus 
       152  digital data signal bus 
       154  temperature sensor 
       156  temperature controller 
       158  heater 
       160  heatsink 
       162 - 196  operational sequence flow chart steps 
       200  pressurized air source 
       202  delivery tube 
       204  delivery channel 
       206  air flow path 
       220  suction chamber 
       222  exhaust pipe 
       224  perforator punch 
       226  movable perforator punch support 
       228  actuator link 
       230  actuator 
       232  fixed perforator die 
       234  idler roller 
       236  perforator/printer station common exposure location 
       238  perforator assembly 
       240  perforator/printer station of a web transport