Patent Publication Number: US-6705698-B2

Title: Marking media using notches

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This is a continuation of copending application number 09/240,373 filed on Jan. 29, 1999 which is hereby incorporated by reference herein. 
    
    
     BACKGROUND AND SUMMARY 
     The present invention relates to printing devices. More particularly, the present invention relates to a print medium, detection system, and method for use in printing devices. 
     Printing devices, such as inkjet printers, use printing composition (e.g., ink or toner) to print text, graphics, images, etc. onto print media. The print media may be of any of a variety of different types. For example, the print media may include paper, transparencies, envelops, photographic print stock, cloth, etc. Each of these types of print media have various characteristics that ideally should be accounted for during printing, otherwise a less than optimal printed output may occur. Additional characteristics may also affect print quality, including print medium size and print medium orientation. 
     One way in which a printing device can be configured to a particular print medium is to have a user make manual adjustments to the printing device based upon these characteristics and factors. One problem with this approach is that it requires user intervention which is undesirable. Another problem with this approach is that it requires a user to correctly identify various characteristics of a particular print medium. A further problem with this approach is that a user may choose not to manually configure the printing device or may incorrectly manually configure the printing device so that optimal printing still does not occur in spite of user intervention. This can be time-consuming and expensive depending on when the configuration error is detected and the cost of the particular print medium. 
     Automatic detection of the different characteristics of various print media used in printing devices would be a welcome improvement. Accordingly, the present invention is directed to alleviating these above-described problems and is designed to help optimize printing on a variety of different types of print media under a variety of operating conditions and user inputs. The present invention accomplishes this without degrading the perceived finished output print quality. 
     An embodiment of a print medium in accordance with the present invention for use in a printing device includes a substrate that is configured to receive a printing composition from the printing device. The substrate has a first surface and an edge. The first surface has at least one characteristic and is configured to receive the printing composition from the printing device during printing. The substrate is further configured to define at least one notch in the edge. The at least one notch has a geometry configured to encode data representative of the at least one characteristic of the first surface. 
     The above-described print medium may be modified and include the following characteristics described below. The geometry may be configured to help minimize visual perceptibility of the at least one notch. The geometry of the notch may be substantially semicircular. 
     The substrate may define the at least one notch in a predetermined location along the edge. In such cases, the location of the notch encodes additional data representative of the characteristic of the first surface. 
     The substrate may define at least two notches in the edge. In such cases, the at least two notches are arranged in a pattern that encodes additional data representative of the at least one characteristic of the first surface. The print medium may be used in a printing device and may also be used in a print media detection system. 
     An embodiment of a print media detection system in accordance with the present invention for use in a printing device includes a source, sensor, controller, and substrate. The source is configured to transmit a light signal and the sensor is configured to detect the light signal from the source and convert the light signal into an electrical signal. The controller is coupled to the sensor and is configured to receive the electrical signal from the detector. Based at least in part on the electrical signal, the controller controls an operating parameter of the printing device. The substrate is configured to receive a printing composition from the printing device. The substrate has at least one characteristic and an edge. The substrate is further configured to define at least one notch in the edge. The at least one notch has a geometry selected to allow the light signal to travel from the source through the notch to the sensor. The geometry is configured to encode data representative of the characteristic of the substrate. 
     The above-described print media detection system may be modified and include the following characteristics described below. The geometry of the at least one notch may be configured to help minimize visual perceptibility of the at least one notch. The geometry of the notch may be substantially semicircular. 
     The substrate may be configured to define a plurality of notches in the edge. Each of the notches has a geometry selected to allow the light signal to travel from the source through the notches to the sensor. The geometry of notches is configured to encode data representative of the characteristic of the substrate. 
     The plurality of notches may be arranged in a pattern that encodes data representative of the characteristic of the substrate. The plurality of notches may be arranged in a predetermined location along the edge. In such embodiments, the location of the notches along the edge encodes additional data representative of the at least one characteristic of the first surface. 
     The substrate may define the at least one notch in a predetermined location along the edge. In such cases, the location of the notch along the edge encodes additional data representative of the characteristic of the first surface. The media detection system may be used in a printing device. 
     An alternative embodiment of a print media detection system in accordance with the present invention for use in a printing device includes structure for transmitting a light signal and structure for sensing the light signal and converting the light signal into an electrical signal. The print media detection system also includes structure, coupled to the detecting structure, for controlling an operating parameter of the printing device based at least in part on the electrical signal received from the detecting structure. The print media detection system additionally includes structure for receiving printing composition from the printing device. The structure for receiving printing composition has at least one characteristic, an edge, and defines, in the edge, structure for encoding data representative of the characteristic. 
     The above-described alternative embodiment of a print media detection system in accordance with the present invention may be modified and include the following characteristics described below. In such cases, the structure for receiving printing composition may include a substrate configured to receive a printing composition from the printing device. The substrate has a characteristic and an edge. The structure for encoding data representative of the characteristic includes at least one notch in the edge. The notch has a geometry selected to allow the light signal to travel from the structure for transmitting through the notch to the structure for sensing. The geometry is configured to encode data representative of the characteristic of the substrate. 
     The structure for receiving printing composition may include a substrate and the structure for encoding data representative of the characteristic may include a plurality of notches. In such cases, the notches each have a geometry selected to allow the light signal from the structure for transmitting to travel from the structure for transmitting through the notches to the structure for sensing. The notches are arranged in a pattern that encodes data representative of the characteristic of the substrate. 
     The print media detection system may be used in a printing device. 
     An embodiment of a method of detecting a characteristic of a substrate of print medium used in a printing device, the substrate of print media having at least one characteristic, an edge, and being configured to receive a printing composition from the printing device, in accordance with the present invention includes encoding data into the edge of the substrate of print medium, the data representing the at least one characteristic of the substrate of print medium. The method also includes transmitting a light signal through the encoded data in the edge of the substrate of print medium and detecting the light signal subsequent to transmission through the encoded data in the edge of the substrate of print medium. The method additionally includes converting the detected light signal into an electrical signal, the electrical signal having a pattern representative of the characteristic of the print medium. The method further includes controlling an operating parameter of the printing device based at least in part on the electrical signal. 
     The above-described method in accordance with the present invention may be modified and include the following characteristics described below. The data may be encoded into the substrate as at least one notch. The method may also include configuring a geometry of the at least one notch to encode data representative of the characteristic of the substrate of print medium. The geometry of the notch may be substantially semicircular. The method may additionally include configuring the geometry of the at least one notch to help minimize visual perceptibility of the at least one notch. 
     The data may be encoded into the substrate as a plurality of notches. The method may also include configuring a geometry of the notches to encode data representative of the characteristic of the substrate of print medium. The method may additionally include arranging the notches in a pattern that encodes additional data representative of the characteristic of the substrate. The geometry of the notches may be substantially semicircular. The method may further include configuring the geometry of the notches to help minimize visual perceptibility of the notches. 
     Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a printing device that includes an embodiment of the present invention. 
     FIG. 2 is a front, top view of a print media handing system of the printing device shown in FIG.  1  and an embodiment of a print media detector of the present invention, also shown in FIG. 1, with a partial sheet of print media of the present invention. 
     FIG. 3 is a front perspective view of the print media handling system, print media detector, and partial sheet of print media shown in FIG.  2 . 
     FIG. 4 is a schematic diagram of a print media detector of the present invention in use with a sheet of print media of the present invention. 
     FIG. 5 is a diagram of a voltage output waveform at a sensor of the embodiment of the print media detector shown in FIGS. 1-4 for the sheet of print media shown in FIGS. 2-4. 
     FIG. 6 is a diagram illustrating a geometry of a notch in an edge of a sheet of print medium in accordance with the present invention. 
     FIG. 7 is a diagram illustrating a geometry of a different notch in an edge of a different sheet of print medium in accordance with the present invention. 
     FIG. 8 is an exemplary alternative embodiment of a print medium of the present invention. 
     FIG. 9 is a diagram of a voltage output waveform at the sensor of the embodiment of the print media detector shown in FIGS. 1-4 for a set of notches defined by the print medium shown in FIG.  8 . 
     FIG. 10 is another exemplary alternative embodiment of a print medium of the present invention. 
     FIG. 11 is a diagram of a voltage output waveform at the sensor of the embodiment of the print media detector shown in FIGS. 1-4 for a set of notches defined by the print medium shown in FIG.  10 . 
     FIG. 12 is a diagram of a voltage output waveform at the sensor of the embodiment of the print media detector shown in FIGS. 1-4 for a different set of notches defined by the print medium shown in FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates an embodiment of an inkjet printing device  20 , here shown as an “off-axis” inkjet printer, constructed in accordance with the present invention, which may be used for printing business reports, correspondence, desktop publishing, and the like, in an industrial, office, home or other environment. A variety of inkjet printing devices are commercially available. For instance, some of the printing devices that may embody the present invention include plotters, portable printing units, copiers, cameras, video printers, and facsimile machines, to name a few, as well as various combination devices, such as a combination facsimile and printer. For convenience, the concepts of the present invention are illustrated in the environment of inkjet printer  20 . 
     While it is apparent that the printing device components may vary from model to model, the typical inkjet printer  20  includes a frame or chassis  22  surrounded by a housing, casing or enclosure  24 , typically made of a plastic material. Sheets of print media are fed through a printzone  25  by a print media handling system  26 . The print media may be any type of suitable material, such as paper, card-stock, transparencies, photographic paper, fabric, mylar, metalized media, and the like, but for convenience, the illustrated embodiment is described using paper as the print medium. Print media handling system  26  has an input supply feed tray  28  for storing sheets of print media before printing. A series of conventional print media drive rollers (not shown in FIG. 1) driven by a direct current (dc) motor and drive gear assembly (not shown) may be used to move the print media from the feed tray  28 , through the printzone  25 , and, after printing, onto a pair of extended output drying wing members  30 , shown in a retracted or rest position in FIG.  1 . Wings  30  momentarily hold a newly printed sheet of print media above any previously printed sheets still drying in an output tray portion  32 , then wings  30  retract to the sides to drop the newly printed sheet into the output tray  32 . Media handling system  26  may include a series of adjustment mechanisms for accommodating different sizes of print media, including letter, legal, A- 4 , envelopes, etc., such as a sliding length adjustment lever  34 , a sliding width adjustment lever  36 , and an envelope feed port  38 . Although not shown, it is to be understood that media handling system  26  may also include other items such as one or more additional print media feed trays. Additionally, media handling system  26  and printing device  20  may be configured to support specific printing tasks such as duplex printing and banner printing. 
     Printing device  20  also has a printer controller  40 , illustrated schematically as a microprocessor, that receives instructions from a host device, typically a computer, such as a personal computer (not shown). Many of the printer controller functions may be performed by the host computer, including any printing device drivers resident on the host computer, by electronics on board the printer, or by interactions between the host computer and the electronics. As used herein, the term “printer controller  40 ” encompasses these functions, whether performed by the host computer, the printer, an intermediary device between the host computer and printer, or by combined interaction of such elements. Printer controller  40  may also operate in response to user inputs provided through a key pad  42  located on the exterior of the casing  24 . A monitor (not shown) coupled to the computer host may be used to display visual information to an operator, such as the printer status or a particular program being run on the host computer. Personal computers, their input devices, such as a keyboard and/or a mouse device, and monitors are all well known to those skilled in the art. 
     A carriage guide rod  44  is supported by chassis  22  to slidably support an off-axis inkjet pen carriage system  45  for travel back and forth across printzone  25  along a scanning axis  46 . As can be seen in FIG. 1, scanning axis  46  is substantially parallel to the X-axis of the XYZ coordinate system shown in FIG.  1 . Carriage  45  is also propelled along guide rod  44  into a servicing region, as indicated generally by arrow  48 , located within the interior of housing  24 . A conventional carriage drive gear and dc (direct current) motor assembly (both of which are not shown) may be coupled to drive an endless loop, which may be secured in a conventional manner to carriage  45 , with the dc motor operating in response to control signals received from controller  40  to incrementally advance carriage  45  along guide rod  44  in response to rotation of the dc motor. 
     In printzone  25 , the media sheet receives ink from an inkjet cartridge, such as a black ink cartridge  50  and three monochrome color ink cartridges  52 ,  54  and  56 . Cartridges  50 ,  52 ,  54 , and  56  are also often called “pens” by those in the art. Pens  50 ,  52 ,  54 , and  56  each include small reservoirs for storing a supply of ink in what is known as an “off-axis” ink delivery system, which is in contrast to a replaceable ink cartridge system where each pen has a reservoir that carries the entire ink supply as the printhead reciprocates over printzone  25  along the scan axis  46 . The replaceable ink cartridge system may be considered as an “on-axis” system, whereas systems which store the main ink supply at a stationary location remote from the printzone scanning axis are called “off-axis” systems. It should be noted that the present invention is operable in both off-axis and on-axis systems. 
     In the illustrated off-axis printer  20 , ink of each color for each printhead is delivered via a conduit or tubing system  58  from a group of main ink reservoirs  60 ,  62 ,  64 , and  66  to the on-board reservoirs of respective pens  50 ,  52 ,  54 , and  56 . Stationary ink reservoirs  60 ,  62 ,  64 , and  66  are replaceable ink supplies stored in a receptacle  68  supported by printer chassis  22 . Each of pens  50 ,  52 ,  54 , and  56  has a respective printhead, as generally indicated by arrows  70 ,  72 ,  74 , and  76 , which selectively ejects ink to from an image on a sheet of media in printzone  25 . 
     Printheads  70 ,  72 ,  74 , and  76  each have an orifice plate with a plurality of nozzles formed therethrough in a manner well known to those skilled in the art. The illustrated printheads  70 ,  72 ,  74 , and  76  are thermal inkjet printheads, although other types of printheads may be used, such as piezoelectric printheads. Thermal printheads  70 ,  72 ,  74 , and  76  typically include a plurality of resistors which are associated with the nozzles. Upon energizing a selected resistor, a bubble of gas is formed which ejects a droplet of ink from the nozzle onto a sheet of print media in printzone  25  under the nozzle. The printhead resistors are selectively energized in response to firing command control signals delivered by a multi-conductor strip  78  (a portion of which is shown in FIG. 1) from the controller  40  to printhead carriage  45 . 
     To provide carriage positional feedback information to printer controller  40 , a conventional optical encoder strip  84  extends along the length of the printzone  25  and over the service station area  48 , with a conventional optical encoder reader being mounted on a back surface of printhead carriage  45  to read positional information provided by encoder strip  84 . Printer  20  uses optical encoder strip  84  and optical encoder reader (not shown) to trigger the firing of printheads  70 ,  72 ,  74 , and  76 , as well as to provide feedback for position and velocity of carriage  45 . Optical encoder strip  84  may be made from things such as photo imaged MYLAR brand film, and works with a light source and a light detector (both of which are not shown) of the optical encoder reader. The light source directs light through strip  84  which is received by the light detector and converted into an electrical signal which is used by controller  40  of printing device  20  to control firing of printheads  70 ,  72 ,  74 , and  76 , as well as carriage  45  position and velocity. Markings or indicia on encoder strip  84  periodically block this light from the light detector in a predetermined manner which results in a corresponding change in the electrical signal from the detector. The manner of providing positional feedback information via optical encoder reader may be accomplished in a variety of different ways known to those skilled in the art. 
     An embodiment of a print media detector  86  constructed in accordance with the present invention is attached to sidewall  88  of print media handling system  26 . As discussed more fully below, print media detector  86  is positioned in or adjacent the print media path to read encoded data regarding one or more characteristics of a print medium prior to printing on the print medium by pens  70 ,  72 ,  74 , and  76 . As can be seen in FIG. 1, print media detector  86  includes a source  90  configured to transmit a light signal and a sensor  92  configured to detect the light signal from source  90  and convert the light signal into an electrical signal. Sensor  92  is coupled to controller  40  and controller  40  is configured to receive the electrical signal from sensor  92  and, based at least in part on this electrical signal, control one or more operating parameters of printing device  20 . 
     A front, top perspective view of print media handing system  26  of printing device  20  and print media detector  86  are shown in FIG. 2. A stack of print media  94  is loaded in input supply feed tray  28  and aligned via sliding length adjustment lever  34  and sliding width adjustment lever  36 . Print media feed rollers  96 , only one of which is shown, are designed to select a single sheet of print media  98  from stack  94  and transport sheet  98  to printzone  25  for printing on first surface  100  of the substrate of sheet  98  by one or more of pens  50 ,  52 ,  54 , and  56 . This is known as “picking” by those skilled in the art. Print media feed rollers  96  are mounted on a shaft  102  (see FIG. 3) which is driven by a motor (not shown). This motor is controlled by printer controller  40 . As can be seen in FIG. 2, output drying wing members  30  support print media sheet  98  as it travels through printzone  25  during printing, as well as subsequent to printing to allow for drying, as discussed above. 
     A user may desire to produce a variety of different printed outputs with printing device  20 . For example, a user may want to produce letters, envelopes, glossy-finish photographs, overhead transparencies, etc. Each of these printed outputs resides on a different print medium. Each of these types of print media have various characteristics such as surface finish, dry time, print medium size, print medium orientation, color, printing composition capacity, etc. that ideally should be accounted for during printing, otherwise a less than optimal printed output may occur. 
     One way in which printing device  20  can be configured to a particular print medium is to have a user make manual adjustments to the printing device based upon these characteristics through, for example, keypad  42  and/or a computer (not shown) attached to printing device  20 . One problem with this approach is that it requires user intervention which is undesirable. Another problem with this approach is that it requires a user to correctly identify various characteristics of a particular print medium. A further problem with this approach is that a user may choose not to manually configure the printing device or may incorrectly manually configure printing device  20  so that optimal printing still does not occur in spite of user intervention. This can be time-consuming and expensive depending on when the configuration error is detected and the cost of the print medium. 
     As can be seen in FIG. 2, sheet  98  is configured to define a set of notches  104 ,  106 ,  108 ,  110 ,  112 , and  114  that extend between first surface  100  and second surface  116  (see FIG.  3 ). Notches  104 ,  106 ,  108 ,  110 ,  112 , and  114  have a geometry configured to encode data representative of one or more characteristics of sheet of print media  98 . As noted above, these characteristics include a variety of things such as the type of print media (e.g. paper, transparencies, envelops, photographic print stock, cloth, etc.), print medium size, print medium dry time, proper print medium orientation in input supply feed tray  28  or envelope feed port  38 , and optimal printing device driver selection which may vary with different types of print media. 
     The geometry includes things such as the shape of the notches (e.g., substantially parabolic, rectangular, triangular, etc.), the dimensions of the notches, and the positions of the notches relative to one another (i.e., patterns formed by notches  104 ,  106 ,  108 ,  110 ,  112 , and  114 ), as well as the positions of notches  104 ,  106 ,  108 ,  110 ,  112 , and  114  on print media sheet  98  (e.g., the positions of notches  104 ,  106 ,  108 ,  110 ,  112 , and  114  relative to intersecting edges  118  and  120  of sheet  98  which define corner  122 ). It should be noted that the use of the word substantially in this document is used to account for things such as engineering and manufacturing tolerances, as well as variations not affecting performance of the present invention. 
     Unlike barcodes or computer punch cards, the size of notches  104 ,  106 ,  108 ,  110 ,  112 , and  114  is designed to minimize or eliminate visual perceptibility. In fact, the size of notches  104 ,  106 ,  108 ,  110 ,  112 , and  114 , as well as all others shown in the additional drawings, is enlarged so that the notches may be seen and discussed In actual embodiments of the present invention, the notches defined by sheets of print medium are specifically designed to minimize or eliminate visual perceptibility so that perceived output print quality of printing device  20  is not degraded. For example, in one embodiment of the present invention, notches, such as notches  104 ,  106 ,  108 ,  110 ,  112 , and  114 , are configured to be substantially circular and each have a diameter substantially within a range of between 0.001 inches and 0.008 inches. 
     Thus, the present invention automatically detects different characteristics of various print media used in printing devices to help optimize output print quality of printing device  20 . The present invention also saves user time and money by eliminating time-consuming and expensive trial and errors to obtain such output print quality. The present invention accomplishes this without degrading perceived output print quality of the printing device by minimizing or eliminating visual perceptibility of the encoded data. 
     Notches  104 ,  106 ,  108 ,  110 ,  112 , and  114  defined by print media sheet  98 , as well as other notches in accordance with the present invention, may be placed in sheets of print media during manufacture of the print medium or afterwards as, for example, part of a sizing or branding process. One way in which the notches may be created is through the use of a rotary chem-milled die and anvil tooling process. A different die can be used for each type or size of print media. An second way in which notches may be created is through the use of a computer controlled laser drill. Changes in notch shape or location are effected via changes in the program controlling the laser. With laser drilling, special attention to notch shape and dimensions may be necessary for thicker print media. 
     Referring again to FIG. 2, an additional set of notches  124  defined by print media sheet  98  is generally represented by a rectangle. Set of notches  124  extends between first surface  100  and second surface  116  of print media sheet  98 . Although not shown, it is to be understood that up to six additional sets of notches may be defined by print media sheet  98 , two sets at each of the three additional corners, as shown below in connection with FIG.  10 . 
     A schematic diagram of source  90  and sensor  92  of print media detector  86  in use with a sheet of print media  126  is shown in FIG.  4 . As can be seen in FIG. 4, source  90  includes a light emitting diode (LED)  128  having a cathode  130  electrically connected to ground  132  and an anode  134  electrically connected to a current-limiting resistor  136 . Current-limiting resistor  136  is also electrically connected to a switch  138  that is electrically connected to a power source  140 . When switch  138  is closed, as, for example, when a sheet of print media is “picked” by print media feed rollers  96 , power is supplied to LED  128  via power source  140  to produce a light signal  142 . When switch  138  is open, no power is supplied to LED  128  and, as a consequence, no light signal is produced. Switch  138  is configured to be normally open so no light signal is produced. Switch  138  may be closed during “picking” of a sheet of print media by, for example, controller  40 . Alternatively, switch  138  may be positioned in input supply feed tray so that it closes during “picking” by physical contact between switch  138  and the “picked” sheet of print media. 
     As can also be seen in FIG. 4, sensor  92  includes a phototransistor  144  having a collector  146  electrically connected to current-limiting resistor  152  and an emitter  150  electrically connected to ground  148 . Current-limiting resistor  152  is also electrically connected to power source  154 . Although a different power source  154  is shown for sensor  92  than for source  90 , it is to be understood that in other embodiments of the present invention, source  90  and sensor  92  may use the same power source. Collector  146  of phototransistor  144  is also electrically connected to printer controller  40  via terminal  156 . Phototransistor  144  is configured to not conduct current to ground  148  through current-limiting resistor  152  in the absence of a predetermined value of light. Once this value is sensed at phototransistor  144 , it conducts current to ground  148 , producing a voltage drop across current-limiting resistor  152  which produces an electrical signal at terminal  156  that is received by printer controller  40 . The resistance of phototransistor  144  is configured to decrease as the magnitude of light illuminating it increases. As the resistance of phototransistor  144  decreases, the amount of current through pull-up resistor  152  increases, producing a greater voltage drop across pull-up resistor  152  and a lower magnitude electrical signal at terminal  156 . 
     As can additionally be seen in FIG. 4, sheet of print media  126  includes a substrate  127  having a first surface  158  shown facing source  90 . Substrate  127  also includes a second surface (not shown) opposite of first surface  158  and facing sensor  92 . Sheet of print media  126  defines a set of a plurality of notches  160  in edge  162  of sheet of print media Set of notches  160  is configured to encode data representative of one or more characteristics of sheet of print media  126 , as discussed above. 
     As can be further seen, set of notches  160  encodes this data in several ways. First, each notch has a substantially semicircular shape. Second, set of notches  160  is arranged in subsets of notches  164 ,  166 , and  168  that extend along edge  162  of sheet  126 . In the embodiment of print media sheet  126  shown there are three subsets: one of three notches, one of two notches, and one of a single notch. Third, each of the notches has dimensions, examples of which are shown and discussed below in FIGS. 6 and 7. 
     In operation, a sheet of print media of the present invention, such as sheet  126 , is “picked” by print media feed rollers  96  and transported to printzone  25 , as generally indicated by arrow  170  in FIG.  4 . As set of notches  160  passes between source  90  and sensor  92 , switch  138  of source  90  is closed so that current is conducted to ground  132  through LED  128  which produces light signal  142 . Light signal  142  passes through each of the notches of set  160  and triggers phototransistor  144  to conduct, producing a voltage waveform shown in FIG.  5 . Once set of notches  160  passes though print media detector  86 , light signal  142  is reflected off first surface  158  so that phototransistor  144  no longer conducts current. Switch  138  is then opened so that LED  128  no longer produces light signal  142 . 
     A diagram of a voltage output waveform at terminal  156  of sensor  92  versus time as sheet of print media  126  passes through print media detector  86  during a period of a little over fifty (50) milliseconds is shown in FIG.  5 . For a power source  154  of 5 volts, voltage signal  172  represents the output voltage at terminal  156  as a function of time with LED  128  of source  90  producing light signal  142  between a time zero (0) milliseconds and up to just after fifty (50) milliseconds. The periods where voltage signal  172  drops below the higher voltage level A to the lower voltage level B occur during those times when light signal  142  travels from LED  128  of source  90  through one or more of the notches of set  160  to phototransistor  144  of sensor  92 . The periods where voltage signal  172  is near five (5) volts at voltage level A occur during those times when light signal  142  is reflected from first surface  158  or print media sheet  126 . For example, the period substantially between zero (0) and twenty-five (25) milliseconds on voltage signal  172  where the voltage drops below voltage level A to voltage level B three times occurs when light signal  142  passes through one of the three notches in subset of notches  164 . Printer controller  40  is configured to receive signal  172  and, based at least in part on signal  172 , control one or more operating parameters of printing device  20 . 
     A diagram illustrating a geometry of a notch  173  in an edge  174  of a sheet of print medium  176  in accordance with the present invention is shown in FIG.  6 . As mentioned above, the notches of the present invention are configured to have dimensions that encode data representative of one or more characteristics of a print medium. As an example, notch  172  is configured to have a substantially semicircular shape. The dimensions of notch  172  are defined by a radius (R) that has a substantially uniform length such that radius (R) defines a substantially uniform radius of curvature  178 . 
     As another example, a diagram illustrating a geometry of a different notch  180  in an edge  182  of a different sheet of print medium  184  in accordance with the present invention is shown in FIG.  7 . As can be seen in FIG. 7, notch  180  is configured to have a substantially parabolic shape with a length (a) and a width (b). The geometries of notches  172  and  180  may produce differently shaped voltage waveforms at terminal  156  of sensor  92  when sheets  176  and  184  travel at the same speed through print media detector  86  depending on the values of (R), (a), and (b). For example, if (R) is substantially 0.002 inches and (b) is substantially 0.002 inches, then the voltage waveform at terminal  156  will drop below voltage level A to voltage level B approximately twice as long for notch  172  than for notch  180 . 
     An alternative embodiment of a print medium  186  constructed in accordance with the present invention is shown in FIG.  8 . Print medium  186  includes a substrate  187  having a first surface  188  and an opposite second surface (not shown). Print medium  186  also includes edges  190 ,  192 ,  194 , and  196 , pairs of which intersect to form corners  198 ,  200 ,  202 , and  204 , as shown. Notches  206 ,  208 , and  210  are formed in edge  190  adjacent corner  198  and notches  212 ,  214 , and  216  are formed in edge  194  adjacent corner  202 . Notches  206 ,  208 ,  210 ,  212 ,  214 , and  216  are configured to encode data representative of one or more characteristics of print medium  186 . As can be seen in FIG. 8, each of the notches has a substantially semicircular shape and notches  206 ,  208 , and  210  form one set of notches  218  while notches  212 ,  214 , and  216  form another set of notches  220 . As can also be seen in FIG. 8, set of notches  218  and set of notches  220  are arranged in the same pattern. The patterns are the same so that printer controller  40  and print media detector  86  can determine the orientation of print medium  186  in printzone  25  or inform a user of printing device  20  of any improper orientation so that neither print medium  196  nor user time are not wasted. In the case of print medium  186  only first surface  188  is to be printed on (e.g., it contains a special coating as with certain transparencies or photographic stock) so sets of notches  218  and  220  are arranged as shown. Controller  40  is configured to look for a changing voltage signal at terminal  156  during “picking” of print medium  186 . If the voltage signal remains constant, the user of printing device  20  is informed to reorient print medium  186  in input supply feed tray  28  for printing on first surface  188  instead of the second surface. 
     A diagram of a voltage output waveform at terminal  156  of sensor  92  versus time as set of notches  218  of print medium  196  pass through print media detector  86  during a period of a little over fifty (50) milliseconds is shown in FIG.  9 . For a power source  154  of 5 volts, voltage signal  222  represents the output voltage at terminal  156  as a function of time with LED  128  of source  90  producing light signal  142  between a time zero (0) milliseconds and up to just after fifty (50) milliseconds. The periods where voltage signal  172  drops below voltage level A to voltage level B occur during those times when light signal  142  travels from LED  128  of source  90  through one or more of the notches of set  218  to phototransistor  144  of sensor  92 . The periods where voltage signal  172  is near five (5) volts at voltage level A occur during those times when light signal  142  is reflected from first surface  188  of print media sheet  186 . For example, the period substantially between just after zero (0) and thirty (30) milliseconds on voltage signal  222  where the voltage drops below voltage level A to voltage level B three times occurs when light signal  142  passes through the notches  206 ,  208 , and  210 . Printer controller  40  is configured to receive signal  222  and, based at least in part on signal  222 , control one or more operating parameters of printing device  20 . Notches  212 ,  214 , and  216  of set of notches  220  will produce a voltage signal substantially identical to signal  222  when passing through print media detector  86 . 
     Another alternative embodiment of a print medium  224  constructed in accordance with the present invention is shown in FIG.  10 . Print medium  224  includes a substrate  225  having a first surface  226  and an opposite second surface (not shown). Print medium  224  also includes edges  228 ,  230 ,  232 , and  234 , pairs of which intersect to form corners  236 ,  238 ,  240 , and  242 , as shown. Sets of notches  244 ,  246 ,  248 ,  250 ,  252 ,  254 ,  256 , and  258  in edges  228 ,  230 ,  232 , and  234  are defined by print medium  224  and extend between first surface  226  and the second surface. Sets of notches  244 ,  246 ,  248 ,  250 ,  252 ,  254 ,  256 , and  258  are configured to encode data representative of one or more characteristics of print medium  224 . As can be seen in FIG. 10, each of the notches has a substantially semicircular shape and each set of notches  244 ,  246 ,  248 ,  250 ,  252 ,  254 ,  256 , and  258  is arranged in a different pattern. The patterns are different so that printer controller  40  and print media detector  86  can determine the orientation of print medium  224  in printzone  25  and make adjustments based on this orientation (e.g., print in landscape mode instead of portrait mode) or inform a user of printing device  20  of any improper orientation so that neither print medium  224  nor user time are not wasted. 
     A diagram of a voltage output waveform at terminal  156  of sensor  92  versus time as set of notches  244  of print medium  224  pass through print media detector  86  during a period of a little over fifty (50) milliseconds is shown in FIG.  11 . For a power source  154  of 5 volts, voltage signal  260  represents the output voltage at terminal  156  as a function of time with LED  128  of source  90  producing light signal  142  between a time zero (0) milliseconds and up to just after fifty (50) milliseconds. The periods where voltage signal  260  drops below voltage level A to voltage level B occur during those times when light signal  142  travels from LED  128  of source  90  through one or more of the notches of set  244  to phototransistor  144  of sensor  92 . The periods where voltage signal  244  is near five (5) volts at voltage level A occur during those times when light signal  142  is reflected from first surface  226  of print media sheet  126 . For example, the period substantially between zero (0) and twenty-five (25) milliseconds on voltage signal  260  where the voltage drops below voltage level A to voltage level B three times occurs when light signal  142  passes through the notches in subset of notches  262 . Printer controller  40  is configured to receive signal  260  and, based at least in part on signal  270 , control one or more operating parameters of printing device  20 . 
     A diagram of a voltage output waveform at terminal  156  of sensor  92  versus time as set of notches  246  of print medium  224  pass through print media detector  86  during a period of a little over fifty (50) milliseconds is shown in FIG.  12 . For a power source  154  of 5 volts, voltage signal  264  represents the output voltage at terminal  156  as a function of time with LED  128  of source  90  producing light signal  142  between a time zero (0) milliseconds and up to just before fifty (50) milliseconds. The periods where voltage signal  264  drops below voltage level A to voltage level B occur during those times when light signal  142  travels from LED  128  of source  90  through one or more of the notches of set  246  to phototransistor  144  of sensor  92 . The periods where voltage signal  264  is near five (5) volts at voltage level A occur during those times when light signal  142  is reflected from first surface  226  of print media sheet  224 . For example, the period substantially between zero (0) and fifteen (15) milliseconds on voltage signal  264  where the voltage drops below voltage level A to voltage level B two times occurs when light signal  142  passes through notches in subset of notches  266 . Printer controller  40  is configured to receive signal  264  and, based at least in part on signal  264 , control one or more operating parameters of printing device  20 . 
     As can be seen by comparing FIGS. 11 and 12, voltage signal  260  differs from voltage signal  264  even though both are generated as a result of “picking” of print medium  224  by print media feed rollers  96 . The differences result from orienting print medium  224  differently in input supply feed tray  28  of print media handling system  26 . These differences may or may not matter depending on the type of print medium and the print job. If these different print medium orientations do matter, controller  40  can pause printing and signal the user of printing device  20  to properly orient print medium  224  in input supply feed tray  28  before beginning printing or controller  40  can adjust printing by printing device  20  for the particular orientation, thereby avoiding waste of print medium  224 , as well as waste of time. 
     Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only, and is not to be taken necessarily, unless otherwise stated, as an express limitation. For example, although print media detector  86  is shown attached to sidewall  88  or print media handing system  26 , other locations are possible. For example, in alternative embodiments of the present invention, print media detector  86  may be located on input supply feed tray  28 . As another example, although notches have been shown as being configured to have a geometry that is substantially circular or parabolic, it is to be understood that other shapes (e.g., substantially rectangular, triangular, etc.) and are within the scope of the present invention. In addition, although specific dimensional measurements have been given for the notches, it is to be understood that other dimensions that still allow detection by print media detector  86  while minimizing or eliminating visual perceptibility are within the scope of the present invention. As a further example, the size and/or shape of notches on the same print media (e.g., semicircular) may be configured to be different. These differently sized and/or shaped notches encode additional data representative of one or more characteristics of a print medium by affecting the magnitude of a light signal passing through them differently. As yet a further example, the print media detector may be a contact-type detector rather than and optical-type detector, as shown in the drawings. Such a contact-type detector could physically engage each of the notches and thereby determine the number of notches as well as measure any differences between them such as size and shape. The spirit and scope of the present invention are to be limited only by the terms of the following claims.