Self calibrating media edge sensor

Abstract

Various edge detection arrangements are disclosed, including an edge detection method and arrangement that utilizes outputs of commonly illuminated reference and edge sensors as the inputs for a comparator. The reference sensor is configured to have a wide field of view and the edge sensor is configured to have a narrow, high gain, field of view. Therefore, the reference sensor has a broad signal response to an edge passage and the edge sensor a steep and narrow signal response. When the two signals are biased to cross each other, the comparator output changes state, indicating passage of an edge. Because the reference sensor provides a base signal level directly related to the real time illumination level that the edge sensor also receives, the reference sensor provides a switch point along the transition ramp of the edge sensor that integrates a majority of the random error sources.

1 . An apparatus comprising:
 a printhead for printing on a media, wherein the media comprises a label supported by a liner;   a platen disposed adjacent to the printhead for advancing the media past the printhead; and   a peel assembly disposed adjacent to the platen for separating the label from the liner; and   a sensor disposed adjacent to the peel assembly for sensing the media.   
     
     
         2 . An apparatus according to  claim 1 , further comprising a print controller, the print controller configured to receive a signal from the sensor indicating whether the label has been separated from the liner. 
     
     
         3 . An apparatus according to  claim 1 , wherein the peel assembly comprises a peel bar for separating the labels from the liner and wherein the platen is configured to drive the media to engage the peel bar such that the label is separated from the liner. 
     
     
         4 . An apparatus according to  claim 3 , wherein the sensor comprises:
 a first sensor disposed adjacent to the peel bar for sensing the media in a first sensing area; and   a second sensor disposed adjacent to the peel bar for sensing the media in a second sensing area.   
     
     
         5 . An apparatus according to  claim 4 , wherein the first and second sensing areas are disposed downstream of the peel bar, and wherein the label is fed into the first sensing area while the liner is fed into the second sensing area. 
     
     
         6 . An apparatus according to  claim 5 , further comprising a print controller configured to receive a first sensor signal from the first sensor indicating whether the label has been fed into the first sensing area. 
     
     
         7 . An apparatus according to  claim 5 , wherein the apparatus further comprises a print controller configured to receive a second sensor signal from the second sensor indicating whether the media disposed in the second sensing area defines a first opacity associated with the liner having no label supported thereon or a second opacity associated with the liner having the label supported thereon. 
     
     
         8 . An apparatus according to  claim 5 , wherein the apparatus further comprises a print controller configured to receive a second sensing signal from the second sensor indicating whether the liner is present within the second sensing area for determining whether the apparatus is in a peel mode. 
     
     
         9 . An apparatus according to  claim 5 , wherein the first sensor is disposed proximate an opening. 
     
     
         10 . An apparatus according to  claim 4 , wherein the first sensor is an edge sensor and the second sensor is a reference sensor, the reference sensor defining a broader sensing area than the edge sensor. 
     
     
         11 . An apparatus according to  claim 4 , wherein the second sensor defines a broader sensing area than the first sensor and the apparatus further comprises a comparator in communication with the first sensor and the second sensor for receiving respective signals therefrom and determining transition edges of the media from the signals. 
     
     
         12 . An apparatus according to  claim 3 , wherein the sensor is configured to detect information included on the media and further configured to communicate a signal associated with the information to a print controller. 
     
     
         13 . An apparatus according to  claim 12 , wherein the information on the media is disposed on a back surface of the label;
 wherein the sensor detects the information disposed on the back surface of the label, the information being exposed to the sensor after the media engages the peel bar and the label is separated from the liner; and   wherein the print controller is configured to receive a signal from the sensor, the signal being associated with the information disposed on the back surface of the label.   
     
     
         14 . An apparatus according to  claim 12 , wherein the information on the media is disposed on a top surface of the liner;
 wherein the sensor detects the information disposed on the top surface of the liner, the information being exposed to the sensor after the media engages the peel bar and the label is separated from the liner; and   wherein the print controller is configured to receive a signal from the sensor, the signal associated with the information disposed on the top surface of the liner.   
     
     
         15 . An apparatus according to  claim 1  further comprising a light source for emitting energy directed at the media, wherein the emitted energy is at least one of passed through or reflected by the media and received by the sensor. 
     
     
         16 . An apparatus according to  claim 15 , wherein said light source emits a collimating light. 
     
     
         17 . A method comprising:
 advancing a media between a platen and a printhead toward a peel assembly, wherein the media comprises a label supported by a liner;   separating, at least partially, the label from the liner;   sensing the media via a sensor, the sensor at a location proximate to the peel assembly.   
     
     
         18 . A method according to  claim 17 , wherein sensing further includes determining a characteristic of the media. 
     
     
         19 . A method according to  claim 17 , wherein the peel assembly includes a peel bar; and
 wherein separating includes separating the label from the liner, the label being separated as the media engages the peel bar.   
     
     
         20 . A method according to  claim 19 , wherein sensing includes sensing the label in a sensing area, the sensing areas being disposed adjacent to the peel bar such that the label enters the first sensing area as the label is being separated from the liner. 
     
     
         21 . A method according to  claim 19 , wherein sensing includes sensing whether the media disposed in a sensing area defines a first opacity associated with the liner having no label supported thereon or a second opacity associated with the liner having the label supported thereon, the sensing area being disposed at a location where the liner passes after engaging the peel bar; and
 wherein the method further comprises receiving a signal from a sensor indicating whether the media defines the first opacity or the second opacity.   
     
     
         22 . A method according to  claim 19 , wherein sensing includes:
 sensing the label in a first sensing area, the first sensing are being disposed adjacent to the peel bar such that the label enters the first sensing area as the label is being separated from the liner, and sensing whether the media disposed in a second sensing area defines a first opacity associated with the liner having no label supported thereon or a second opacity associated with the liner having the label supported thereon, the second sensing area being disposed at a location where the liner passes after engaging the peel bar.   
     
     
         23 . A method according to  claim 22 , further comprising:
 receiving a first sensor signal from a first sensor indicating the presence of a label in the first sensing area; and   receiving a second sensor signal from a second sensor indicating whether the media defines the first opacity or the second opacity.   
     
     
         24 . A method according to  claim 19 , wherein sensing further comprises receiving a sensor signal from a sensor indicating that an apparatus is operating in a peel mode, the sensor detecting the absence of the media in the peel assembly. 
     
     
         25 . A method according to  claim 19 , wherein sensing includes sensing information included on the media; and
 wherein the method further comprises receiving a signal from a sensor based on the information.   
     
     
         26 . A method according to  claim 25 , wherein the information is disposed on a back surface of the label;
 wherein sensing includes sensing the information on the back side of the label after the label has been separated from the liner; and   wherein receiving includes receiving a signal from a sensor associated with the information on the back surface of the label.   
     
     
         27 . A method according to  claim 25 , wherein the information is disposed on a top surface of the liner, the information being detectable when the label is separated from the liner;
 wherein sensing includes sensing the information on a top surface of the liner after the label is separated from the liner, and wherein receiving includes receiving a signal from a sensor associated with the information on the top surface of the liner.   
     
     
         28 . A method according to  claim 17 , wherein sensing includes sensing an area disposed at a location proximate the opening. 
     
     
         29 . A method according to  claim 17 , further comprising emitting energy directed at the media, wherein the emitted energy is at least one of passed through or reflected by the media. 
     
     
         30 . A method according to  claim 29 , wherein emitting energy includes emitting collimating light.