Abstract: A thermal printer is disclosed which includes a plurality of thermal print heads, each of the plurality of thermal print heads being operable to print a distinct one of a plurality of colors. The plurality of thermal print heads may print output at a plurality of spatial resolutions. The thermal printer may include dot size varying means for varying perceived levels of color printed by the thermal printer by varying sizes of dots printed by the plurality of thermal print heads. The printer may perform various image processing steps on an image to be printed, such as tone scale adjustment, thermal history control, and common mode voltage correction, to improve the perceived quality of the printed image. The thermal printer may be incorporated into a digital photo-printing vending machine for printing images provided by a customer.

Abstract: Described herein are methods, devices and reagents for direct thermal imaging and, more particularly, for multicolor direct thermal imaging, wherein a direct thermal imaging member comprising different image-forming compositions is imaged at different speeds by a source of heat to form a multicolored image.

Abstract: A printing device that includes a platen for supporting an imaging member during a printing operation and at least one print head subassembly for direct thermal printing on the imaging member. The print head subassembly is configured to be movable independently of the platen for printing on a first surface of the imaging member in a first transport path and on a second surface of the imaging member in a second transport path. The printing device also includes at least one driving roller for driving the imaging member during the printing operation that is configured to drive the imaging member through a driving nip created by the driving roller with a substantially constant degree of wrap wherein the distance of transport of said imaging member for a given angular rotation of said driving roller is substantially the same for the first transport path and the second transport path.

Abstract: A multicolor direct thermal imaging method wherein a multicolor image is formed in a thermal imaging member comprising at least first and second different image-forming compositions and a thermal printer for use in practicing the method. Heat is applied to at least the second image-forming composition while the first image-forming composition is at a first baseline temperature (T1) to form an image in at least the second image-forming composition, and heat is applied to at least the first image-forming composition while it is at a second baseline temperature (T2) to form an image in at least the first image-forming composition, wherein T1 is different from T2.

Abstract: In one aspect of the invention there is disclosed a multicolor thermal imaging system wherein different heating elements on a thermal print head can print on different color-forming layers of a multicolor thermal imaging member in a single pass. The line-printing time is divided into segments, each of which is divided into a plurality of subintervals. All of the pulses within the segments have the same energy. In one embodiment, every pulse has the same amplitude and duration. Different colors are selected for printing during the different segments by varying the fraction of subintervals that contain pulses. This technique allows multiple colors to be printed using a thermal print head with a single strobe signal line. Pulsing patterns may be chosen to reduce the coincidence of pulses provided to multiple print head elements, thereby reducing the peak power requirements of the print head.

Abstract: Techniques are disclosed for stitching images printed by a multi-head printer in a manner that is relatively insensitive to misregistration of the image segments. When a pair of overlapping print heads print a pair of adjacent image segments which meet in a stitching region, printing at each location in the stitching region is accomplished by both print heads with a weighting that depends on the location being printed within the stitching region. In one embodiment, for example, the output of each print head is weighted by a linear function of horizontal pixel position. Techniques are also disclosed for selecting screening patterns for use when stitching is performed with variable-dot printers. Such screening patterns are selected to minimize variations in density that may arise as the result of cross-web and/or down-web misregistration.

Abstract: The present invention provides a thermal printer in which the temperature of the thermal printing head can be modulated by means of an auxiliary heat sink, and methods for printing using such a thermal printer.

Abstract: A multicolor direct thermal imaging method wherein a multicolor image is formed in a thermal imaging member comprising at least first and second different image-forming compositions and a thermal printer for use in practicing the method. Heat is applied to at least the second image-forming composition while the first image-forming composition is at a first baseline temperature (T1) to form an image in at least the second image-forming composition, and heat is applied to at least the first image-forming composition while it is at a second baseline temperature (T2) to form an image in at least the first image-forming composition, wherein T1 is different from T2.

Abstract: Techniques are disclosed for stitching images printed by a multi-head printer in a manner that is relatively insensitive to misregistration of the image segments. When a pair of overlapping print heads print a pair of adjacent image segments which meet in a stitching region, printing at each location in the stitching region is accomplished by both print heads with a weighting that depends on the location being printed within the stitching region. In one embodiment, for example, the output of each print head is weighted by a linear function of horizontal pixel position. Techniques are also disclosed for selecting screening patterns for use when stitching is performed with variable-dot printers. Such screening patterns are selected to minimize variations in density that may arise as the result of cross-web and/or down-web misregistration.

Abstract: Techniques are disclosed for performing thermal history control in a thermal printer in which a single thermal print head prints sequentially on multiple color-forming layers in a single pass. Each pixel-printing interval may be divided into subintervals, which may be of unequal duration. Each sub-interval may be used to print a different color. The manner in which the input energy to be provided to each print head element is selected may be varied for each of the subintervals. For example, although a single thermal model may be used to predict the temperature of the print head elements in each of the subintervals, different parameters may be used in the different subintervals. Similarly, different energy computation functions may be used to compute the energy to be provided to the print head in each of the subintervals based on the predicted print head temperature.

Abstract: A model of a thermal print head is provided that models the thermal response of thermal print head elements to the provision of energy to the print head elements over time. The amount of energy to provide to each of the print head elements during a print head cycle to produce a spot having the desired density is calculated based on: (1) the desired density to be produced by the print head element during the print head cycle, (2) the predicted temperature of the print head element at the beginning of the print head cycle, (3) the ambient printer temperature at the beginning of the print head cycle, and (4) the ambient relative humidity.

Abstract: A model of a thermal print head is provided that models the thermal response of thermal print head elements to the provision of energy to the print head elements over time. The thermal print head model generates predictions of the temperature of each of the thermal print head elements at the beginning of each print head cycle based on: (1) the current ambient temperature of the thermal print head, (2) the thermal history of the print head, (3) the energy history of the print head, and (optionally) (4) the current temperature of the print medium. The amount of energy to provide to each of the print head elements during a print head cycle to produce a spot having the desired density is calculated based on: (1) the desired density to be produced by the print head element during the print head cycle, and (2) the predicted temperature of the print head element at the beginning of the print head cycle.

Abstract: A multicolor imaging system is described wherein at least two, and preferably three, different image-forming layers of a thermal imaging member are addressed at least partially independently by a thermal printhead or printheads from the same surface of the imaging member by controlling the temperature of the thermal printhead(s) and the time thermal energy is applied to the image-forming layers. Each color of the thermal imaging member can be printed alone or in selectable proportion to the other color(s). Novel thermal imaging members are also described.

Abstract: We disclose an electronic imaging method and apparatus capable of effectively and accurately sensing and interpolating color image data received from a two-dimensional array of discrete image sensing elements, particularly, from a so-called “Bayer Pattern” array. In operation, the method and apparatus both extract one-color image data from the two-dimensional array and generate therefrom fully color-recovered image data by a combination of interpolation and non-linear filtering. Efficiency is accomplished, without departure from good accuracy, by performing two one-dimensional color recovery applications and essentially incrementally combining the results thereof. The first one-dimensional color recovery application generates a partially color-recovered image in which, for each row in that dimension, values are recovered for all of the colors present in that row. The second one-dimensional color recovery application then generates all the remaining colors at each pixel by operating along a second dimension.

Abstract: A technique for optimizing or enhancing color images. Embodiments are disclosed for creating an enhanced color image, including the enhancement of perceived color uniformity. In a “dot-on-dot” registration scheme for producing color images, the dots need to be precisely superimposed on each other to provide optimum or enhanced images. The dot-on-dot registration produced by a single head thermal printer is generally acceptable, but a single head machine is very slow because multiple passes (reciprocation) are required to lay down multiple colors of dots. In a much faster multi-head or tandem thermal imaging system a serious problem of dot misalignment may cause moire patterns or other visual artifacts in the color images produced by dot patterns. A solution to this problem is disclosed herein which intentionally misregisters superimposed dots in a novel and particular manner to achieve image optimization.

Abstract: A multicolor imaging system is described wherein at least two, and preferably three, different image-fonning layers of a thermal imaging member are addressed at least partially independently by a thermal printhead or printheads from the same surface of the imaging member by controlling the temperature of the thermal printhead(s) and the time thermal energy is applied to the image-forming layers. Each color of the thermal imaging member can be printed alone or in selectable proportion to the other color(s). Novel thermal imaging members are also described.

Abstract: A thermal printer is disclosed which includes a plurality of thermal print heads, each of the plurality of thermal print heads being operable to print a distinct one of a plurality of colors. The plurality of thermal print heads may print output at a plurality of spatial resolutions. The thermal printer may include dot size varying means for varying perceived levels of color printed by the thermal printer by varying sizes of dots printed by the plurality of thermal print heads. The printer may perform various image processing steps on an image to be printed, such as tone scale adjustment, thermal history control, and common mode voltage correction, to improve the perceived quality of the printed image. The thermal printer may be incorporated into a digital photo-printing vending machine for printing images provided by a customer.

Abstract: A model of a thermal print head is provided that models the thermal response of thermal print head elements to the provision of energy to the print head elements over time. The thermal print head model generates predictions of the temperature of each of the thermal print head elements at the beginning of each print head cycle based on: (1) the current ambient temperature of the thermal print head, (2) the thermal history of the print head, and (3) the energy history of the print head. The amount of energy to provide to each of the print head elements during a print head cycle to produce a spot having the desired density is calculated based on: (1) the desired density to be produced by the print head element during the print head cycle, and (2) the predicted temperature of the print head element at the beginning of the print head cycle.

Abstract: A thermal printer is disclosed which includes a plurality of thermal print heads, each of the plurality of thermal print heads being operable to print a distinct one of a plurality of colors. The plurality of thermal print heads may print output at a plurality of spatial resolutions. The thermal printer may include dot size varying means for varying perceived levels of color printed by the thermal printer by varying sizes of dots printed by the plurality of thermal print heads. The printer may perform various image processing steps on an image to be printed, such as tone scale adjustment, thermal history control, and common mode voltage correction, to improve the perceived quality of the printed image. The thermal printer may be incorporated into a digital photo-printing vending machine for printing images provided by a customer.

Abstract: A model of a thermal print head is provided that models the thermal response of thermal print head elements to the provision of energy to the print head elements over time. The amount of energy to provide to each of the print head elements during a print head cycle to produce a spot having the desired density is calculated based on: (1) the desired density to be produced by the print head element during the print head cycle, (2) the predicted temperature of the print head element at the beginning of the print head cycle, (3) the ambient printer temperature at the beginning of the print head cycle, and (4) the ambient relative humidity.