Abstract:
One aspect of the invention involves a thermal image generation device comprising a casing forming an interior cavity. One surface of the casing includes a screen with thermochromic material attached to a bottom surface of the screen. The casing houses at least one thermal transfer element movable over regions of the thermochromic material to alter a temperature at the regions from a steady-state, ambient temperature. Such temperature alterations temporarily cause a color variation to the thermochromic material until the regions of the thermochromic material return to the ambient temperature.

Description:
FIELD 
   The invention generally relates to the field of thermal image generation. In particular, one embodiment of the invention relates to a system and technique for altering a surface of a thermochromic film to form graphical representations that are temporarily visible until the thermochromic film returns to its normal, ambient temperature. 
   GENERAL BACKGROUND 
   Over the past few decades, efforts have been made to conserve our national resources. While it is now commonplace for residential communities to participate in recycling programs, greater strides in conservation are now necessary for businesses. For example, in order to reduce wasteful usage of paper and other costly office supplies, more and more businesses are providing employees with erasable illustrative aids such as blackboards and whiteboards. However, these illustrative aids require a person to manually write or draw an image directly on to the illustrative aid. 
   Currently, printers normally use ink or toner cartridges that permanently print a graphical representation on paper or plastic slides. Even thermal printers generate graphical representations that a permanent until erased by a thermal heating process. These printing mechanisms are unable to temporarily produce a graphical representation (e.g., text or image) on a surface without user activity and that automatically fades away after a prescribed period of time. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the invention will become apparent from the following detailed description of the invention in which: 
       FIG. 1  is an exemplary block diagram of a first embodiment of a thermal image generation device operating as a distributed node of a network. 
       FIG. 2  is an exemplary block diagram of a second embodiment of the thermal image generation device operating as a dedicated output device of a computing unit. 
       FIGS. 3A and 3B  are exemplary block diagrams of a detailed embodiment of the thermal image generation device of  FIG. 1  or  2  with a thermochromic film positioned adjacent to a cover. 
       FIG. 4  is an exemplary block diagram of an embodiment of logic employed within the thermal image generation device of  FIGS. 3A and 3B . 
       FIG. 5  is an exemplary block diagram of an embodiment of a thermal transfer element of the thermal image generation device of  FIG. 1 . 
       FIG. 6  is an exemplary block diagram of another detailed embodiment of the thermal image generation device of  FIGS. 1  or  2  with thermochromic micro-capsules embedded into the material forming the cover. 
       FIG. 7  is an exemplary block diagram of an embodiment of a product adapted to receive an external add-on device made in part with thermochromic micro-capsules to represent different operational states of the product. 
       FIG. 8  is an exemplary flowchart of the operations of the invention. 
   

   DETAILED DESCRIPTION 
   In general, one embodiment of the invention relates to a thermal image generation device and its associated method for visually altering a thermochromic material (e.g., a thermochromic film) in response to a change in temperature until the thermochromic material returns to its ambient temperature. For one embodiment, the visual alteration causes graphical representations, namely text and/or images, to be temporarily visible on the thermochromic material. 
   Herein, certain details are set forth in order to provide a thorough understanding of the invention. Of course, it is contemplated that the invention may be practiced through many embodiments other that those illustrated. Well-known circuits and operations are not set forth in detail in order to avoid unnecessarily obscuring the present invention. 
   Referring to  FIG. 1 , an exemplary block diagram of a first embodiment of a thermal image generation device operating as a distributed node of a network is shown. One example of the thermal image generation device includes a writing tablet of any size or configuration. Of course, this embodiment is for illustrative purposes and other embodiments may incorporate the inventive aspects described herein. 
   Configured as a local area network (LAN) or as a wide area network (WAN), the network  100  comprises a link  110  interconnecting one or more (N≧1) computers  120   1 – 120   N  (e.g., desktop, a laptop, a hand-held, a server, a workstation, etc.). The link  110  is an information-carrying medium (e.g., electrical wire, optical fiber, cable, bus, or air in combination with wireless signaling technology) that is adapted to establish communication pathways between the computers  120   1 – 120   N  and a thermal image generation device  130 . 
   As shown, the thermal image generation device  130  operates as a centralized output device, which is adapted with logic, namely hardware, firmware, software module(s) or any combination thereof. Herein, a “software module” is a series of code instructions that, when executed, performs a certain function. Examples of such code include an operating system, an application, an applet, a program or even a subroutine. Software module(s) may be stored in a machine-readable medium, including but not limited to an electronic circuit, a semiconductor memory device, a read only memory (ROM), a flash memory, an erasable ROM (EROM), a floppy diskette, a compact disk, an optical disk, a hard disk, a fiber optic medium, a radio frequency (RF) link and the like. 
   Referring now to  FIG. 2 , an exemplary block diagram of a second embodiment of the thermal image generation device  130  operating as a dedicated output device such as a writing tablet is shown. The thermal image generation device  130  is coupled to a computer  200  over a dedicated link  210 . This enables information to be downloaded from the computer  200  to the thermal image generation device  130 . As an alternative, the thermal image generation device  130  may be configured as an input/output (I/O) device for uploading information to the computer  200  as represented by a dashed arrow. This may be accomplished by implementing the thermal image generation device  130  with a touch screen, keypad or another input mechanism. 
   Referring to  FIGS. 3A and 3B , exemplary block diagrams of a detailed embodiment of the thermal image generation device  130  of  FIG. 1  or  2  is shown. The thermal image generation device  130  comprises a casing  300  made of a rigid material such as hardened plastic. The casing  300  provides a cavity for housing logic (e.g., thermal transfer element(s), processor, thermal sensor(s), etc.) and protecting such logic from damage caused by environmental conditions. One surface  310  of the casing  300  features a screen  320  made of a semi-opaque material having a transparent or translucent quality (e.g., glass, plastic, etc.). 
   A thermochromic film  330  is attached to the screen  320 . As shown in  FIG. 3B , for this embodiment, the thermochromic film  330  is applied to a bottom surface  325  of the screen  320  by a lamination process. Of course, other application techniques may be utilized. 
   Referring back to  FIG. 3A , a side surface  315  of the casing  300  enables a connector port  340  to be accessible through the casing  300 . For instance, in one embodiment, the connector port  340  may be configured to receive an adapter to the link  110  (e.g., Ethernet adapter) that enables communications over the network  100  as shown in  FIG. 1 . Alternatively, the connector port  340  may include a serial port, a parallel port or a Universal Serial Bus (USB) port for communications with the computer  200  of  FIG. 2  or even a wireless receiver or transceiver (e.g., light emitting diode “LED” detector, a radio frequency “RF” receiver or transceiver, etc.). Of course, multiple connector ports may be provided to support different types of adapters. 
   In response to applying a temperature to a region  335  of the thermochromic film  330 , this temperature differing from its ambient temperature (Ta) by a temperature difference (T 1 ), the thermochromic film  330  within the region  335  experiences a color variation. The color variation may be applied in any chosen pattern to represent an image, alphanumeric character, a reference point or any other graphical representation, depending on the manner in which changes in temperature (Ta±T 1 ) are applied to the thermochromic film  330 . For instance, the temperature difference T 1  may be greater than or equal to one degree Celsius (≧1° C.) 
   Referring to  FIG. 4 , an exemplary block diagram of an embodiment of logic within the casing  300  of the thermal image generation device  130  of  FIGS. 3A and 3B  is shown. The logic  400  comprises a processor  410 , a driver circuit  420 , a thermal transfer element  430  and a sensor  440 . In response to information downloaded from a remote source (e.g., computer) or retrieved from internal memory situated within the casing  300 , the processor  410  controls the driver circuit  420 . The driver circuit  420  activates and controls the thermal transfer element  430  so as to alter the temperature of certain regions of the thermochromic film from its ambient temperature (Ta) to a resultant temperature (Ta±T 1 ). 
   Herein, for one embodiment, the driving circuit  420  may be a light source (e.g., light emitting diode, laser, etc.). For this embodiment, the heat transfer element  430  is generally a light beam produced by the light source and a combination of filters and lenses, which adjust the light beam. 
   Alternatively, the driving circuit  420  may be a voltage and/or current regulator to adjust the voltage and/or current realized by the thermal transfer element  430 . For this embodiment, the thermal transfer element  430  may be adapted as a single thermal element such as a semiconductor or an impedance component (e.g., a resistor, inductor, potentiometer, capacitor, etc.). 
   Where the thermal transfer element  430  is effectively a light beam produced by a combination of filters (e.g., Fresnel lens) and lenses, the adjustment of the light beam may be controlled by mechanical logic  435 . For this embodiment, the mechanical logic  435  includes, but is not limited or restricted to mirror(s) controlled by galvanometers. Also, the mechanical logic  435  may provide feedback regarding the direction of the light beam deflected by the positioning of the mirror(s) over link  450 . 
   Where the thermal transfer element  430  is employed as an impedance component, the mechanical logic  435  enables placement of the thermal transfer element  430  along an X, Y axial region bounded by the perimeter of thermochromic film proximate to the screen  320  of  FIGS. 3A and 3B . For instance, the mechanical logic  435  may be a roller assembly having an array of thermal elements (see  FIG. 5 ) that controls Y-axis placement of the array along the thermochromic film  330 . Alternatively, the mechanical logic  435  may be an assembly that enables one or more thermal elements to be independently positioned anywhere along the thermochromic film  330 . The mechanical logic  435  provides feedback regarding the X and/or Y-axis screen position of the thermal transfer elements. 
   The sensor  440  regulates the temperature applied to the region  335  and provides such information to the processor  410  over link  460 . Upon receipt of the feedback information from the sensor  440 , the processor  410  responds accordingly by controlling the mechanical logic  435  to alter placement of the thermal transfer element  430 , the driver circuit  420  to activate/deactivate the thermal transfer element  430  or a combination thereof. 
   Referring to  FIG. 5 , an exemplary block diagram of an embodiment of the thermal transfer element utilized within the thermal image generation device  130  is shown. The thermal transfer element  430  includes an array of thermal elements  500  that are laterally spaced apart (X-axis) and adjacent to the thermochromic film  330 . Namely, the array  500  forms a single row of thermal elements  510   1 – 510   c  (where “C”≧1). Such spacing is static in nature and may extend across the entire width of the thermochromic film  330  or along a particular region  335  as illustrated in  FIGS. 3A and 3B . 
   The mechanical logic  435  adjusts the longitudinal (Y-axis) placement of the array of thermal elements  500 . While the mechanical logic  435  controls the longitudinal movement, each thermal element  510   1 – 510   c  is discreetly controlled by the driving circuit  420 . The combination of mechanical movement and thermal element control will enable a graphical representation (e.g., text, image, etc.) to be displayed temporarily on the thermochromic film  330 . In addition, one or more thermal sensors (e.g., sensors  520   1 – 510   c ) may be employed to regulate the temperature of a corresponding thermal elements  510   1 – 510   M . 
   Another embodiment may include a static array of thermal elements (not shown). The array may be arrange to form a numbers of rows (R, R≧1) and columns (C, C≧1). Each thermal element  510   1 – 510   c  may have a corresponding thermal sensor  520   1 – 520   c . Each thermal element  510   1 – 510   c  would be under discreet control. This implementation would not have any mechanical assembly to control placement of a single array of thermal elements as described above. 
   It is contemplated that a thermal removing device (e.g., a heat sink)  530  may be coupled as part of the logic  400  of  FIGS. 4 and 5  to assist in returning thermochromic film  330  back to ambient room temperature. This will assist the thermochromic film  330  in changing back to ambient color state in a timely fashion. 
   Referring now to  FIG. 6 , an exemplary block diagram of another detailed embodiment of the thermal image generation device  130  of  FIG. 1  or  2  is shown. In lieu of a screen/film combination  320 ,  330  of  FIGS. 3A and 3B , material forming the screen  600  is also embedded with thermochromic micro-capsules  610 . In response to a region  620  of the screen  600  experiencing a change in temperature (T 1 ) from its ambient temperature (Ta), namely the application of a resultant temperature (Ta±T 1 ) to the region  620 , the thermochromic micro-capsules  610  within that region  620  experience a color variation. The color variation experienced by these thermochromic micro-capsules  610  is temporary and returns to its normal color as the resultant temperature returns to the ambient temperature (Ta). 
   Referring now to  FIG. 7 , an exemplary block diagram of an embodiment of a product adapted with integrated components and/or with attachable components made in part with thermochromic micro-capsules is shown. For instance, the integrated component  700  and/or attachable component  710  are injected molded plastic elements formed with a thermal transfer element  720  and  730 , respectively. Each of the thermal transfer elements  720  and  730  may be one or more impedance elements. 
   In one embodiment, in response to a certain condition (e.g., power up, correct depression of a button, etc.), the thermal transfer element  720  is configured to receive current from internal logic  740  within the product  750 . This causes the thermal transfer element  720  to generate additional thermal heat, which results in the thermochromic material within the integrated component  700  changing color. The same or even a different event may cause the internal logic  740  to apply current to the thermal transfer element  730  of the attachable component  710 . 
   Of course, in response to a certain condition (e.g., power-off, incorrect depression of a button, etc.), the internal logic  740  may discontinue current supplied to the thermal transfer elements  720  and/or  730 , which returns the thermochromic material within the components  700  and/or  710  to its ambient temperature and color. 
   Referring now to  FIG. 8 , an exemplary flowchart of the operations of the invention is shown. In response to a condition (e.g., power up, depression of a button, etc.), a thermal transfer element is activated to alter the temperature of thermochromic material (blocks  800  and  810 ). The thermochromic material may be an entire sheet of thermochromic film or a particular region, thermochromic material mixed with other material as a composite and the like. 
   One or more sensors are used to monitor the temperature of the thermochromic material in order to determine whether it has experienced a sufficient temperature difference to alter the color of the thermochromic material (blocks  820  and  830 ). For example, for this embodiment, the sensor(s) may be used to determine if the temperature of the thermochromic material has risen above or fallen below its ambient temperature (Ta) by a selected temperature difference (T 1 ) causing the thermochromic material to change color (block  840 ). 
   The sensor(s) also periodically monitor if the temperature of the thermochromic material has risen above a maximum temperature or fallen below a minimum temperature (block  850 ). Also, the sensor(s) monitor whether temperature of the thermochromic material has remained at this temperature for a prescribed period of time (block  860 ). Upon confirming that at least one of these events has occurred, the thermal transfer element may now be deactivated (block  870 ). This would allow gradual fading of the displayed graphical representation as the thermochromic material returns to its ambient temperature. 
   Such deactivation may be to substantially reduce current applied to and/or voltage realized by one or more thermal elements being impedance elements. Where the thermal transfer element is a light beam, deactivation is accomplished by discontinuing or deflecting the light beam. 
   Alternatively, if the maximum or minimum temperature has not been met or exceeded, the thermal transfer element may continue to be activated or periodically throttled between an activated and deactivated state in order to retain the displayed graphical representation. The thermal transfer element may be deactivated in response to an affirmative action by the user (e.g., depress button, power-off, etc.). It is contemplated that a thermal removing device may be used in combination to more quickly return the thermochromic material back to its approximate ambient temperature. 
   While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described. For example, it may be possible to implement the invention or some of its features in hardware, firmware, software or a combination thereof.