Direct thermal media and registration sensor system and method for use in a color thermal printer
An example disclosed media processing device includes an image processing unit; a first optical registration sensor; and a second optical registration sensor spaced apart from the first optical registration sensor along a first axis by a first distance associated with a gap between media units on a web.
1. A system in a thermal printer, the system comprising:
an optical registration system configured to detect optical properties of media having a repeating pattern of a first set of stripes that changes to a first color in response to heat and a second set of stripes that changes to a second color in response to heat, the second color being different from the first color, wherein the second set of stripes includes a fluorophore carrying stripe that is fluorescent under excitation light of a defined wavelength range, and the optical registration system comprises a confocal excitation light source, an anamorphic optical system, and an array sensor, wherein the excitation light source is configured to cause the second set of stripes to fluoresce, and where the anamorphic optical system filters and focuses a fluorescence light pattern emitted by the second set of stripes as an image on the array sensor; and
an image processing unit configured to determine a position of the second set of stripes on the array sensor and to output a signal when a stripe of the second set of stripes is detected at a predetermined position on the array sensor.
2. The system as defined in claim 1 , wherein the excitation light source is a solid state laser or light emitting diode with an emission wavelength below 400 nm.
3. The system as defined in claim 1 , wherein the array sensor is a solid state sensor for edge position detection.
4. The system as defined in claim 3 , wherein the solid state sensor is a linear CMOS or a CCD imaging sensor having at least 128 pixels.
5. The system as defined in claim 3 , wherein the optical registration system is configured with a first magnification in a first axis along the solid state sensor >1.00 in absolute value and a second magnification in a second sensor axis <1.00 in absolute value, wherein the second sensor axis is orthogonal to the first axis.
6. The system as defined in claim 1 , wherein two optical registration systems are utilized in tandem with the image processing unit, and the two optical registration systems are spaced apart both along and across the media.
7. The system as defined in claim 6 , wherein the two optical registration systems are configured to measure media skew, and the system is configured to use the measure of the media skew to rotate a thermal printhead to eliminate the media skew by aligning the thermal printhead with the second set of stripes.
8. The system as defined in claim 6 , wherein the two optical registration systems are configured to measure media skew, and the system is configured to use the measure of the media skew to rotate a media transport system to eliminate the media skew by aligning the second set of stripes with a thermal printhead.
9. The system as defined in claim 6 , wherein:
the two optical registration systems are configured to measure media skew, and
the system is configured to use the measure of the media skew to delay firing a thermal printhead element until a skewed stripe is near or directly under the thermal printhead element.
10. The system as defined in claim 1 , where the system is configured to use information regarding a bitmap to be printed to control printing of barcodes.
11. The system as defined in claim 1 , where the optical registration system comprises two cylindrical lenses and a dichroic beam splitter.