Abstract:
A thermostat is provided with an image projection capability that allows images concerning the operation of the thermostat to be projected onto a surface in the vicinity of the thermostat. The image projection is preferably accomplished by directing an internally generated image to an image enlargement device which thereafter projects an enlarged image onto the surface in the vicinity of the thermostat. The surface that receives the projected image is preferably defined by a screen affixed to the wall that the thermostat is mounted to.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to programmable thermostats and in particular to the display capabilities of such thermostats. 
     Programmable thermostats have heretofore included alphanumeric displays located within the thermostat. These displays are typically located on the front of the thermostat so as to be viewable by a person making selections as to set point temperatures that are to occur at various times of the day or night. The size of these displays is constrained by virtue of the limited space available for such displays on the front panel of the thermostat. As a result, the displays are relatively small resulting in only limited information being displayed. There is no room for on-screen instructions as to how to program the thermostat. 
     What is needed is a thermostat with a capability to legibly display more information than is permitted on the front face of the thermostat. 
     SUMMARY OF THE INVENTION 
     A thermostat is provided with an image projection capability that allows images concerning the operation of the thermostat to be projected onto a surface in the vicinity of the thermostat. The image projection is preferably accomplished by directing an internally generated image to an image enlargement device which thereafter projects an enlarged image onto the surface in the vicinity of the thermostat. The image is preferably generated by a microprocessor and displayed on an internal image forming device located within the body of the thermostat. One or more mirrors or prisms located within the body of the thermostat transfer the image to the image enlargement device which is preferably a convex mirror. The enlargement device is preferably mounted within a housing located on a top front portion of the thermostat so as to maximize the projection length onto the surface in the vicinity of the thermostat. The surface that receives the projected image is preferably defined by a screen affixed to the wall that the thermostat is mounted to. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more apparent by reading a detailed description thereof in conjunction with the following drawings in which: 
     FIG. 1 is a side view of a thermostat having a projection device mounted to the top of the thermostat; 
     FIG. 2 is a front view of the thermostat of FIG. 1 illustrating the projection of an image above the thermostat; 
     FIG. 3 illustrates a processor and associated display device for generating and image that is thereafter transferred by certain apparatus so as to produce the image of FIG. 2; 
     FIG. 4 illustrates a processor with an alternative image display device and alternative image transfer apparatus to that of FIG. 3; and 
     FIG. 5 is a schematic illustration of a program resident in the processor of FIGS. 3 and 4 which generates exemplary display images that are to be projected. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a programmable electronic thermostat  10  is seen to include a backend portion  12  that is normally attached to a wall  14 . The thermostat  10  includes a projection device  16  preferably mounted to the top of the thermostat so as to project an image onto a screen  18  affixed to the wall  14  above the thermostat. It is however to be understood that the projection may be directly onto the wall  14  without the need for the screen  18 . Referring to FIG. 2, the front side of the thermostat  10  is seen to include a set of four depressible keys,  20 ,  22 ,  24  and  26 . While the number of such keys may vary, the preferred embodiment will preferably have four such depressible keys. The thermostat  10  may include a viewable display  28  on the front side of the thermostat. The display  28  is not however required and would merely be in addition to the projected display from the projection device  16 . An image  30  projected by the device  16  appears above the thermostat  10 . The exemplary display is of various set point temperatures occurring at identified times of the day. There is furthermore instructions provided as to how to manipulate the depressible keys so as to change the selected setpoint temperatures and associated times at the bottom of the display. In particular, the up/down keys  22  and  26  are used to scroll to a time or temperature that is to be changed whereas the keys  20  and  24  are to be used to increment a selected time or temperature either up or down. 
     Referring to FIG. 3, the internal structure of the thermostat which produces the projected image  30  is illustrated. In particular, a processor  32  is connected to a display driver  34  which in turn is connected to a display device  36 . The display device  36  in FIG. 3 is preferably a raster scanned laser light emitting diode device which produces a sufficiently illuminated image that can be directed onto a mirror  38 . Such display devices are available in sizes constrained by the internal dimensions of a thermostat. It is however to be understood that other miniature display devices producing a sufficiently illuminated image may also be used. The mirror  38  projects the image onto an image enlargement device such as a convex-shaped mirror  40 . The convex shaped mirror is preferably mounted within the projection device  16 . The position of the convex shaped mirror is preferably adjustable so as to appropriately direct the image onto the screen  18  which may vary in location above the thermostat. 
     Referring to FIG. 4, an alternative internal structure is shown for generating and thereafter projecting an image onto the screen  18 . In particular, the processor  32  is connected to a display driver  41  which is in turn connected to a transparent liquid crystal display  42 . A projection lamp  44  projects light through the image formed on the transparent liquid crystal display  42 . The illuminated image is magnified by an inverting lens  46  before passing to a mirror  48  which redirects the image on to a convex-shaped mirror  49  and hence onto the screen  18 . The convex shaped mirror  49  is preferably mounted within the projection device  16 . The position of the convex shaped mirror is preferably adjustable so as to appropriately direct the image onto the screen  18  which may vary in location above the thermostat. 
     It is to be appreciated that FIGS. 3 and 4 merely show two possible image projection systems. Other types of miniature display devices in conjunction with other combinations of lenses and mirrors may be used to produce an appropriate image on the mirror  18 . 
     Referring now to FIG. 5, a process executable by the processor  32  so as to project particular images onto the screen  18  is shown. The process begins with a step  50  wherein a menu of control and display features of the thermostat  10  is provided to a display driver such as the display driver  34  in FIG. 3 or the display driver  41  in FIG.  4 . The respective display drivers cause a predefined image of the menu to be formed on a display device, such as display device  36  in FIG. 3 or display device  42 , in FIG.  4 . The formed menu image is thereafter projected on to the screen  18 . The thus projected menu preferably allows the viewer to make a selection between setting temperatures, setting modes of operation, setting the fan speed, or editing the schedule for any of the above features. The projected menu preferably includes instructions as to how to make a selection using the arrow keys. 
     The processor proceeds to a step  52  and reads the status of the arrow keys  20  through  26 . The processor then proceeds to a step  54  and uses the read status of the arrow keys to determine which, if any, of the programmable features of the thermostat has been selected for display. The appropriate image for setting temperature, mode of operation, and fan speed is displayed in either step  56 ,  58  or  60 . Any changes to the displayed images is noted by the processor through a check of the status of the arrow keys after a reasonable time has elapsed following the initial image display. If an edit feature has been selected, then the processor proceeds to call for an image of an editing menu in a step  62 . The image could for instance be a programming schedule such as shown in FIG.  2 . In the event an edit menu such as shown in FIG. 2 is selected, then the processor will proceed through steps  64 ,  66 , and  68  so as to allow the user to scroll through, for instance, days of the week. The processor looks at the status of the arrow keys to determine whether the user has first selected a period during the day that is to be edited and to thereafter edit the time and date for that selected period pursuant to the status of the arrow keys. The processor then proceeds to a step  70  to inquire whether or not the particular displayed image is to be entered or cancelled. This latter determination is made by reading the status of normally one of the arrow keys that would signify what the user wished to do. In the event that an entry has been signaled by an appropriately depressed key, then the processor would proceed to step  72  and save any changes noted in editing the temperature setpoint schedule in steps  62  through  68  or any changes made to any of the other displayed images formed in steps  56 ,  58 , or  60 . This is done in step  72 . It is to be noted that the processor proceeds from either step  70  or step  72  back to step  50  and again implements a projection of a menu of control and display features for the thermostat. 
     It is to be appreciated that preferred embodiments of a thermostat having an image projection capability have been disclosed. Alterations and modifications to the thus disclosed thermostat may occur without departing from the scope of the invention. In particular, the type of display device may vary as well as the arrangement of mirrors and lenses downstream of the display without departing from the scope of the invention. Moreover, the projection device  16  may either be totally within the body of the thermostat or it could be an affixed or foldout device relative to the thermostat. 
     Accordingly, the foregoing description of the invention is by way of example only, and the invention is to be limited by the following claims and equivalents thereto.