Abstract:
A printhead cartridge identification system is disclosed which ensures that an ink jet printer operates only with ink jet cartridges compatible with the specific printer function. An ink container which supplies ink to an associated printhead has a light reflector incorporated into a transparent wall of the ink container housing. The cartridge, comprising the ink container and associated printhead, is mounted on a scan carriage. Periodically, the carriage is conveyed to an optical station comprising a light source and a photosensor. The light source is energized and a beam of light is directed towards the reflector.

Description:
BACKGROUND OF THE INVENTION AND MATERIAL DISCLOSURE STATEMENT 
     The present invention relates to ink jet recording devices and, more particularly, to a system for detecting and identifying the presence of a specific type of printhead cartridge. 
     Ink jet recording devices eject ink onto a print medium such as paper in controlled patterns of closely spaced dots. To form color images, multiple groupings of ink jets are used, with each group being supplied with ink of a different color from an associated ink container. 
     Thermal ink jet printing systems use thermal energy selectively produced by resistors located in capillary filled ink channels near channel terminating nozzles or orifices to vaporize momentarily the ink and form bubbles on demand. Each temporary bubble expels an ink droplet and propels it toward a recording medium. Most commercial printing systems utilize a carriage type printer which has a relatively small printhead containing the ink channels and nozzles. The printhead is usually sealingly attached to an ink supply container and the combined printhead and container, referred to as a printhead cartridge, is reciprocated to print one swath of information at a time on a stationarily held recording medium, such as paper. After the swath is printed, the paper is stepped a distance equal to the height of the printed swath, so that the next printed swath will be contiguous therewith. The procedure is repeated until the entire page is printed. 
     An important practical concern for application of commercial thermal ink jet printers is to insure that a particular printhead cartridge assembly that is to be used is compatible with the function desired; i.e., if the printer is set to print in a first (red) color, that a red, rather than say black, cartridge assembly is installed. Alternatively, it may be required that a particular cartridge even though having a “correct” ink color is also the proper cartridge configuration for the specific system. For example, many commercial ink jet printers have OEM brand configurations and/or follow on products with perhaps, increased resolution, which may require a change in cartridge configuration and function. It is therefore desirable to identify that the second updated cartridge is being used rather than the earlier cartridge. 
     It is known in the prior art to provide encoding information on a printhead relating to a printhead characteristic such as color or serial number. U.S. Pat. No. 5,049,898 discloses encoded information in the form of a magnetic media which can be read by a magnetic read/write head to provide outputs for further use or display. U.S. Pat. No. 4,872,027 discloses a resistor circuit formed on a printhead in encoded form. The encoded information is addressed from a microprocessor which reconfigures control functions to provide different processing capabilities such as text or graphics. Co-pending application USSN 08/650,149discloses a printhead identification system in which a unique digital code is formed on a printhead, or group of printheads. Print operation is enabled when a matching code signal from a system controller to the printhead is confirmed. Co-pending application Ser. No. 08/572,595 filed on Dec. 14, 1995 and assigned to the same assignee as the present invention, discloses a system and method for sensing the presence or absence of an ink jet cartridge combined with an ink level sensing function. 
     Those prior art references relying on printhead cartridge code formation and detection techniques can be relatively expensive. It would be desirable to have a detection system which provides an elegant, yet simple, method for identifying a small number of possible printhead cartridge types. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of invention to provide a printhead cartridge identification system which is adapted to include a relatively simple identification element associated therewith together with a single inexpensive sensing means for “reading” the identification element and producing an output signal representative of the specific type of printhead cartridge sensed. The cartridge signal is then used to prepare an ink jet printer for operation with the specific type of printhead cartridge identified. 
     In the present invention, and in an exemplary embodiment, a thermal ink jet printer is disclosed which includes a printhead cartridge for printing on a recording medium in response to image drive signals. Ink is supplied to a printhead from an ink container which is fluidly connected to the printhead. The printhead and container are mounted on a scanning carriage which moves back and forth across a print zone, the printhead ejecting ink droplets from nozzles to form an image on the recording medium. An optical system comprising a light source and a light detector is fixedly located along the path of travel of the carriage and positioned so that light from the light source is directed towards the ink container when it is positioned opposite the optical system. The ink container has an optical light directing element formed in a wall recess. Light from the light source is directed towards the light detecting element. In one embodiment, a cartridge reflector has a reflective surface whose reflective intensity varies according to the composition of a selected reflective material. Optical means include a light source for directing light towards the reflector and a sensor for sensing the intensity of the reflected light. Each level of detected intensity corresponds to a specific type of printhead cartridge with a predetermined set of printing characteristics. 
     According to a second embodiment of the invention, the relative location of the light source and light sensor of the optical assembly with respect to the cartridge reflector is set so that the reflected light from the light source is sensed only when a specific type of cartridge is in place. 
     More particularly, and in a first embodiment, the present invention relates to an ink jet printhead cartridge sensing system for identifying a specific type of cartridge, the sensing system comprising: 
     an optical assembly including a light source and a photosensor, 
     means for positioning a cartridge adjacent said optical assembly, said cartridge including at least one reflective member, 
     means for energizing said light source when said cartridge is adjacent said optical assembly, the light source emitting a beam of light which is directed generally towards said reflective member, said photosensor detecting the amount of light reflected from said reflective member and generating a signal indicative thereof and 
     cartridge identification means for processing the photosensor output signal and determining whether the signal corresponds to a predetermined signal representative of a specific type of cartridge. 
     The invention, in a second embodiment, relates to an ink jet printhead cartridge sensing system for identifying a specific type of cartridge, the sensing system comprising: 
     an optical assembly including a light source and a photosensor separated from each other by a set distance, 
     means for positioning said cartridge adjacent said optical assembly, said cartridge including at least one light reflective member comprising at least a first and second reflective member connected by a third surface, 
     meaning for energizing said light source when said cartridge is adjacent said optical assembly, the light source emitting a beam of light which is directed generally towards said reflective member and reflected therefrom towards said photosensor, said photosensor generating a high output when the separation distance between the light source and the photosensor is approximately equal to the length of the third surface connecting the first and second reflective surfaces and a low output signal when the separation distance and the third surface length are not approximately equal, and 
     cartridge identification means for processing the photosensor output signal and determining whether the signal corresponds to a predetermined signal representative of a specific type of cartridge. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a perspective view of an ink jet printer which incorporates the printhead cartridge identification system of the present invention. 
     FIG. 2 is a cross-sectional view through the printhead cartridge shown in FIG.  1 . 
     FIG. 3 is a block diagram of the control circuitry for controlling operation of the printhead cartridge identification system. 
     FIG. 4 is a schematic diagram of a comparator circuit used to correlate a sensed output signal to a specific cartridge. 
     FIG. 5 shows a cross-sectional view of a printhead cartridge of a first type aligned with a cartridge sensing assembly which provides a positive ID for that cartridge. 
     FIG. 6 shows a cross-sectional view of a printhead cartridge of a second type aligned with a cartridge sensing assembly which provides a positive ID for this cartridge. 
     FIG. 7 shows the cartridge of FIG. 4 aligned with the cartridge sensing assembly of FIG. 5 to demonstrate a negative ID. 
     FIGS. 8A and 8B show a test fixture for forming light reflecting surfaces built into the printhead cartridge. 
     FIG. 9 illustrates a perspective view of a color ink jet printer which incorporates the printhead cartridge identification system of the present invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a perspective view of a thermal ink jet printer  8  of the type disclosed in co-pending application U.S. Ser. No. 08/572,595, referenced supra, whose contents are hereby incorporated by reference. A preferred embodiment of the printhead cartridge identification system of the present invention is disclosed for use with the illustrated printer, but it is understood the invention can be practiced in other types of thermal ink jet printers as well as other reproduction devices such as piezoelectric printers, dot matrix printers and ink jet printers driven by signals from a document Raster Input Scanner. 
     Referring to FIG. 1, printer  8  includes an ink jet printhead cartridge  10  mounted on a carriage  12  supported by carriage rails  14 . The carriage rails are supported by a frame  15  of the ink jet printer  8 . The printhead cartridge  10  includes a container  16  shown in detail in FIG. 2, containing ink for supply to a thermal ink jet printhead  18  which selectively expels droplets of ink under control of electrical signals received from a controller  50  (FIG. 3) of the printer  8  through an electrical cable  20 . Container  16  comprises a housing  17  having a wall  17 A seating reflective element  22 , shown in further detail in FIG.  2 . Container  16  is fluidly, but detachably connected, to printhead  18  and can be replaced when the ink is depleted therefrom. Alternatively, the entire cartridge can be replaced upon each depletion depending upon the particular system requirements. The printhead  18  contains a plurality of ink channels which carry ink from the container  16  to respective ink ejecting orifices or nozzles. When printing, the carriage  12  reciprocates back and forth along the carriage rails  14  in the direction of the arrow  23 , the entire width traverse constitutes a scanning path. The actual printing zone is contained within the scanning path. As the printhead cartridge  10  reciprocates back and forth along a print path and past a recording medium  24 , such as a sheet of paper or a transparency, droplets of ink are expelled from selected ones of the printhead nozzles towards the sheet of paper. Typically, during each pass of the carriage  12  the recording medium  24  is held stationary. At the end of each pass, the recording medium  24  is stepped in the direction of the arrow  26 . 
     Also shown in FIG. 1 is an optical sensing assembly  30 . Referring to FIGS. 1 and 2, assembly  30  includes a housing  31  within which are mounted a light source  36  and a photosensor  38 . The light sources is electrically connected to a power source while the photosensor  38  output is electrically connected into the system controller circuits as will be seen. Container  16 , in a preferred embodiment, is designed as a two compartment unit. Assembly  30  is mounted in the carriage path so that, as container housing wall  17 A moves into a position opposite the assembly  30 , the light from light source  36  is directed toward light directing element  22  Photosensor  38  is positioned to detect light directed from element  22  in the manner described in further detail below. Optical assembly  30  can also include a second light source which can be used to direct light towards a second reflective member in container  16  to sense the level of ink in the container. This configuration is disclosed and claimed in the co-pending application and is not described here but it is understood that an ink sensing system could be used in combination with the cartridge identification methods of the present invention. 
     FIG. 2 includes a cross-sectional view of the printhead cartridge  10  along the line  2 - 2  of FIG.  1  and shows the housing  17  and the printhead  18  attached to the container. The printhead  18  is fluidly but detachably connected to the container  16 . The housing  17  is made of a lightweight but durable plastic, which in a preferred embodiment, is polypropylene. Housing  17  has an air inlet  31  and an ink outlet  34  formed within wall  17 B. The air inlet  31  provides for the transfer of air between the interior of housing  17  and the ambient. Ink outlet  34  provides for fluid transfer of ink contained in the ink container  16  from the interior of the housing  17  to the ink jet printhead  18 . Manifold  37  directs filtered ink from the ink outlet  34  into printhead  18  and to the ink ejecting orifices for ejecting ink onto the recording medium  24 . 
     Housing  17  defines an interior space partitioned into a first chamber  40  and a second chamber  42  by a dividing member  44 . The dividing member  44  extends from one side wall of the housing  17  to an opposite side wall of the housing and essentially divides the housing into the first chamber  40  and the second chamber  42  such that the second chamber  42  is larger than the first chamber  40 . 
     The first chamber  40  contains an ink retaining member  46  typically made of a foam material to hold liquid ink. Liquid ink  48 , stored in the second chamber  42 , is transferred from the second chamber  42 , which is substantially free of ink retaining material, to the ink retaining material  46  through an ink inlet  41  defined by the dividing member  44 . A fill port  49  allows for filling the cartridge with ink. The ink  48  passes into the ink retaining material  46  through the ink inlet  41  and ink is released through ink outlet  34  as necessary to supply the printhead  18  with ink for printing. To maintain a proper amount of ink in the ink retaining material  46  for supply to the printhead  18 , the housing  17  includes a mechanism for transferring ink from the second chamber  42  to the first chamber  40  by maintaining a proper amount of air pressure above the liquid ink  48  for filling the material  46  with ink when necessary. This mechanism includes a directing member  60 , which defines, with the dividing member  44 , an air transfer passageway  62  having a vent inlet  64  coupled to a vent outlet  66  for pressurizing the second chamber  42  to a static (no flow) condition. The directing member  60  does not extend from one sidewall to an opposite sidewall as does the dividing member  44 , but instead forms a vent tube. 
     The construction of the container  16  compartments as described to this point is exemplary. There are other known ways of constructing an ink supply container with dividing sections while maintaining an appropriate back pressure to the printhead nozzle. For purposes of the present invention, it is understood that the container is constructed so that, during operation, ink moves from chamber  42  to chamber  40  through the passageway between the two compartments under pressure conditions established by techniques well known to those skilled in the art. Of interest to the present invention is the modification made to the ink container  16  by the specific construction of element  22  as described below. 
     Referring particularly to FIG. 2, in a preferred embodiment, light reflecting element  22  is formed as part of wall  17 A. In the preferred embodiment, element  22  is a prism having two facet surfaces  22 A,  22 B extending into the interior of compartment  48  and angled towards each other and connected by surface  22 C. Element  22  is formed into a roof mirror by placing reflective tapes  22 D,  22 E on surfaces  22 A,  22 B, respectively. According to a first aspect of the invention, tapes  22 D,  22 E can be formed of a plurality of reflective materials whose reflective intensity is representative of a predetermined type of printhead cartridge. For example, it is desired to identify a first type of printhead cartridge (Cartridge A) having a first specific print characteristic (color/ink density, resolution) and a second type of printhead cartridge (Cartridge B) having a second specific set of print characteristics. For Cartridge A, tapes  22 D,  22 E are made of polished aluminized hot stamp foil of a first reflective level. For cartridge B, tapes  22 D,  22 E are made of a polished aluminum hot stamp foil of a second lower reflective level. 
     Operation of Sensing System 
     The sensing system of the present invention, which is considered to comprise the combination of reflective element  22 , the optical assembly  30 , and the controller  50  circuitry, is designed to be enabled to perform a printhead cartridge identification following a specific event such as the start of a print job. To perform the check, the printhead cartridge is positioned adjacent assembly  30  where the identification is accomplished by appropriate circuitry. FIG. 3 shows control circuitry in block diagram form for enabling the sensing system. FIG. 4 shows a schematic of the comparator circuit used to correlate the output of the photosensor. A main controller  50  conventionally includes a CPU, a ROM for storing complete programs and a RAM. Controller  50  controls the movement of carriage  12  as well as other printer functions described below. 
     When a line recording operation is performed, each resistor associated with a jet in printhead  18  is driven selectively in accordance with image data from a personal computer P/C  52  or other data source sent into controller  50 . Controller  50  sends drive signals to the printhead  18  heater resistors causing ink droplets to be ejected from the jets associated with the heated resistor thus forming a line of recording on the surface of the recording medium  24 . 
     For purposes of description, the sensing system will be considered as being activated at the beginning of a print job. 
     Operation at Start of Print Job 
     Referring to FIGS. 1-4, image signals from the P/C  52  to controller  50  initiate a start print sequence. Carriage  12  is moved to sensing station  41  so as to position housing wall  17 A of container  16  adjacent and facing the optical assembly  30 . Under control of controller  50 , a power source  56  energizes light source  36 . Source  36 , in a preferred embodiment, is an LED with a peak wavelength in the range of 880 to 940 nm. A beam of light is directed towards housing wall  17 A. Light is reflected from reflective surfaces  22 D,  22 E of roof mirror  22  and redirected so as to impinge on photosensor  38 . The two reflections allow the beam to be stepped vertically downward to avoid a higher than acceptable angle of incidence at the detector. The output signal from photosensor  38  is sent to logic circuitry within controller  50 . 
     As a first example, assume cartridge  10  is Cartridge A type having the polished aluminized tape  22 D,  22 E of a first reflective level. The light impinging on photosensor  38  results in an output current of, about 2700 μa to flow. An output signal, V out , is sent to printhead cartridge identification circuit  60  in controller  50 . Assuming a V out  of 3.0-5.0V, this circuit compares the photosensor output signal to signal levels stored in memory and finds a “match” confirming the presence of Cartridge A. Appropriate signals are sent to printhead drive circuit  61  as well as other appropriate timing circuits to cause the ensuing print function to accommodate the specific characteristics of the identified printhead Cartridge A. 
     As a second example, assume cartridge  10  is Cartridge B type having the polished aluminized tapes  22 D,  22 E of a second, lower, reflective level. The intensity of the reflected light impinging on photosensor  38  results in an output current of about 240 μa. Circuit  60  compares the V out  (assume a V out  of 0.6-3.0 volts) to signal levels stored in memory and finds a “match” confirming the presence of Cartridge B and prepares the printer for operation with a Printhead Cartridge B characteristic. 
     If the printer cannot identify the photosensor  38  signals as being either from Cartridge A or Cartridge B, further printing may be disabled and a warning sent to the user (at P/C Display  55 ) indicating the cartridge type is not compatible with the printer. It is understood that the term “cartridge” can indicate either the ink container or the printhead, or the combination of ink tank and printhead. Thus, it is possible that either the wrong ink container or the wrong printhead cartridge assembly has been identified as not compatible. 
     From the above two examples, it will be apparent that by simply changing the reflective material, any reflective intensity desired could be selected and the number of different types of printhead cartridges capable of being identified could be expanded accordingly. However, in order to maintain sufficient discrimination between intensity levels, it is believed that approximately three levels of intensity (e.g., three effective type of materials) may be optimum. 
     According to a second aspect of the invention, the printhead cartridge type can be identified by correlating the location of the light source  36  and light detector  38  in optical assembly  30  with the location of the reflector  22  in the ink container. FIGS. 5 and 6 show two cartridge ID sensing configurations which confirm a “correct” cartridge while, to demonstrate the principle, FIG. 6 shows the cartridge of FIG. 5 being “read” by the optical assembly of FIG. 5 resulting in identification of that cartridge as an “incorrect” cartridge. 
     Referring to FIG. 5, a printhead cartridge  70  has an ink container  71  with light directing element  72  formed as part of wall  71 A. Light detecting element  72  is a roof mirror having two facet surfaces  72 A,  72 B connected by surface  72 C having a length l. Surfaces  72 A,  72 B are made reflective by any known technique including one of the two previously described reflective tapes. Optical assembly  80  contains a light source  82  and a photosensor  84  separated vertically by a distance d. Distance d is approximately equal to the length l of surface  72 C. Assembly  80  is mounted in the path of the scanning carriage so that container  71  can be moved into position opposite the assembly  30 . When light source  82  is energized, light is reflected from surface  72 A to surface  72 B to impinge on photosensor  84 . A “high” output signal is sent from photosensor  84  to the cartridge identification circuit  60  in FIG. 3 which identifies the cartridge as, say a Cartridge Type C. The printer then prepares for a printing operation based on the characteristics of the Type C cartridge. 
     Referring to FIG. 6, a printhead cartridge  90  has an ink container  91  with light directing element  92  formed as part of wall  91 A. Light detecting element  92  is a roof mirror having two facet surfaces  92 A,  92 B connected by surface  92 C having a length 1′. Surfaces  92 A,  92 B are made reflective by any known technique including one of the two previously described reflective tapes. It is noted that element  92  is at a lower position in wall  91 A than the position of element  72  in FIG. 5 because of the shorter length of the surface between the two reflecting sensors; e.g., 1′ is shorter than 1′. Optical assembly  100  contains a light source  102  and a photosensor  104  separated by a distance d′ shorter than the distance d for the FIG. 5 embodiment. Distance d′ is approximately equal to the 1′ length of surface  92 C. Assembly  100  is mounted in the path of the scanning carriage so that container  91  can be moved into position opposite the assembly  100 . When light source  102  is energized, light is reflected from surface  92 A to surface  92 B to impinge on photosensor  104 . A “high” output signal is sent from photosensor  104  to the cartridge identification circuit  60  in FIG. 3 which identifies the cartridge as, say Cartridge Type D. The printer then prepares for a printing operation based on the characteristics of the Type D cartridge. 
     Referring next to FIG. 7, this shows cartridge  70  (Type C) inserted in the carriage and brought opposite optical assembly  100  which is configured to detect a Type D cartridge. When the light source  102  is energized, the light impinges on surface  72 C causing the light to scatter. Thus, almost no light reaches photosensor  104 , and the output is a “low” level signal which is recognized by circuit  60  as a “wrong cartridge” signal. (Circuit  60  has been waiting for a “high” signal indicating a Type C cartridge.) It is apparent that the same result will occur if optical assembly  80  (Type C) attempts to identify cartridge  90  (Type D); e.g., pulsing of light source  82  will result in a signal directed above the light directing element  92  resulting in no output signal from detector  84 . For the first case, the distance d′ is not approximately equal to 1′; for the second case d will not be approximately equal to 1′. 
     A preferred hot stamping method for attaching the reflective tapes  22 D,  22 E shown in FIGS. 1 and 3 embodiment will now be described with additional reference to FIGS. 8A,  8 B. In FIG. 8A, reflective element  22  is shown seated in a specially designed supporting member  110 . Member  110  has a semi-cylindrical shape with a cavity  112  having surfaces  112 A,  112 B,  112 C formed so as to conform to the surfaces  22 A,  22 B,  22 C, respectively. Element  22  is held in a seated position by a vacuum (not shown) applied to vents  114 ,  116 . Member  110  is pivoted to the position shown in FIG. 8A so as to bring surface  112 A to a horizontal position. A strip  120  of reflective tape is placed across the top of the cavity  112 . Hot stamping tool  118 , in one embodiment, has a flat silicone rubber bonding surface  121  having a width D approximately equal to the width of surfaces  22 A,  22 B. The tool is lowered into contact with tape  120  and forces a portion of the tape into heated compressive contact with surface  112 A bonding that portion of the tape (tape  22 A) to surface  112 A. The tool is withdrawn and member  110  pivoted to the position shown in FIG. 8B where surface  112 B is now brought to a horizontal orientation. Tape  22 B is formed in the same manner as tape  22 A. The ends of tape strip  120  is then cut, and element  22  is ready for mounting into container wall  17 A. 
     The hot stamping method is preferred over prior art techniques such as using a relatively expensive pressure sensitive tape or wherein reflective layers are vacuum deposited on the reflector surfaces. The use of a hot stamp tool whose bonding end has a surface orientation which conforms to the sloping surface of the cavity to which the tape is to be bonded is therefore preferred. Prior art hot stamp methods created shearing forces when the tool was removed resulting in a tool life less than 1,000 cycles. Print quality was also adversely affected by creating wrinkles and folds in the stamped material. The hot stamp method of the present invention, using compression forces, improves tool life to at least 20,000 cycles with improved print quality and enables the stamping process to become fully automated. 
     It is understood that these techniques have utility for bonding a variety of materials to cavity sloping walls. It will be appreciated that the cavity may have more than two sloping surfaces with the nesting fixture undergoing a plurality of incremental pivoting movements to accommodate the number of sloped surfaces to which the tape is to be bonded. 
     While the cartridge ID system has been disclosed in the context of identifying a single cartridge, the invention can be used to identify a plurality of cartridges; e.g., multiple cartridges used in a color printer. FIG. 9 shows a full color scanning type of printer. Referring to FIG. 8, a thermal ink jet printer  130  is shown. Several ink supply cartridges  132 ,  133 ,  134 ,  135 , each with an integrally attached thermal printhead  140  to  143 , are mounted on a translatable carriage  150 . During the printing mode, the carriage  150  reciprocates back and forth on guide rails  152  in the direction of arrow  154 . A recording medium  156 , such as, for example, paper, is held stationary while the carriage is moving in one direction and, prior to the carriage moving in a reverse direction, the the recording medium is stepped a distance equal to the height of the stripe of data printed on the recording medium by the thermal printheads. Each printhead has a linear array of nozzles which are aligned in a direction perpendicular to the reciprocating direction of the carriage. The thermal printheads propel the ink droplets  158  toward the recordings medium  156  whenever droplets are required, during the traverse of the carriage, to print information. The signal-carrying ribbon cables attached to terminals of the printheads have been omitted for clarity. The printer  130  can print in multiple colors, wherein each cartridge  132  to  135  contains a different color ink supply. For a representative color printer and additional control details, see for example, U.S. Pat. No. 4,833,491, the disclosure of which is incorporated herein by reference. 
     According to the invention, each of the ink containers forming part of cartridges  132 - 135  are of the same construction as the cartridge shown in FIGS. 1,  3 ; e.g., each cartridge has an ink container having a prism reflector formed in the wall facing outward. The reflector is associated with cartridge ID detection. Cartridge  132  is shown having an ink container  160  with reflective member  162 . Cartridges  133 - 135  have similar containers and reflective members not specifically called out for ease of description. As in the single cartridge embodiment, a sensing assembly  163  includes a housing  164  within which are mounted a light source  166  and a photosensor  168 . 
     In operation and referring to FIGS. 3 and 9, image signals from P/C  52  to controller  50  initiate a start print sequence. Carriage  150  is moved so as to position the cartridge  132  with first ink container  160  opposite the sensing assembly  162 . Under control of controller  50 , power source  54  is caused to sequentially energize light source  166  while measuring the output of photosensor  168 . The sequencing and detection operation for cartridge  132  is the same as that previously described for cartridge  10 . Source  166  is first energized to check that the cartridge is the correct type (reflections from member  162  reach the photosensor to provide an output within a predicted range). Once cartridge  132  ID is confirmed, carriage  150  is moved to position the next cartridge  133  in position to be sensed. The preceding process is enabled for each cartridge until all cartridges have been identified as being in the “correct” cartridge. Printing operations can then be instituted. After some period of operating time, one or more cartridges may become depleted of ink and have to be replaced. The cartridge ID sensing is repeated to insure that the replacement cartridge is of the required type for the specific printing system. It is noted that, for these and earlier embodiments, if a cartridge is inserted so it is not fully seated in its operative position (e.g., tilted upward), an incorrect reading will alert the operator to check the cartridge and, if the cartridge is skewed, proper seating can be implemented. 
     While the embodiment disclosed herein is preferred, it will be appreciated from this teaching that various alternative, modifications, variations or improvements therein may be made by those skilled in the art. For example, while the optical sensing assembly  30  has been shown in a fixed position with carriage  12  moved so as to present the ink cartridges in adjacency, the sensing assembly could be moved past stationary cartridges. Also, for the color configuration of FIG. 9, instead of the carriage being incrementally moved past the fixed optical assembly, four optical assemblies could be used with the carriage moved so as to align each cartridge with a separate sensing assembly and sequence the cartridges. As a further example, other materials could be used instead of the ones described for tapes  22 D,  22 E; including reflective metals, mirrors, pressure sensitive tapes, etc. 
     In another embodiment, light source  36  can emit light in wavelengths other than in the range of 880-940 nm.