Abstract:
A message display that produces a visible message by projecting an image on a surface such as a wall or floor. A bright light source is provided, preferably including an array of light emitting diodes (“LED&#39;s”). The light from this bright source is passed through one or more lenses in a condenser assembly to make it more uniform. The light then passes through an image plate that contains a small version of the image to be displayed. Once the light passes through the image plate it next passes through a focusing assembly. The focusing assembly creates a desired projected image on a target surface such as a wall or floor. The projected image is a representation of the image contained on the image plate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to the field of display technology. More specifically, the invention comprises a projection system for projecting an illuminated image on a surface such as a floor or wall. 
         [0003]    2. Description of the Related Art 
         [0004]    Message display devices assume a wide variety of forms. Hazard warning signs used in industrial facilities are a simple example. These use a static display of a predefined message, often including both graphical and textual elements. Many different messages are presented by such signs. Typical prior art signs include messages such as “HARD HAT AREA” and “SAFETY GLASSES MUST BE WORN.” 
         [0005]    Some prior art displays are more sophisticated in that they are only illuminated some of the time. As an example, a display presenting the message “TEST IN PROGRESS” would only be visible when a test is in fact in progress. These more sophisticated displays are often internally illuminated by an incandescent bulb or an array of light emitting diodes. The display is simply a dark “box” on the wall when it is not illuminated. Once the internal light is switched on, however, the message becomes clear. 
         [0006]    Prior art displays tend to be as large as the message being displayed. In other words, if the message needs to be 36 inches by 36 inches, then the display device needs to be at least that large. For an illuminated sign on a wall, the display itself often becomes bulky and heavy. 
         [0007]    The placement of a display device on a floor surface is known in the prior art—messages painted on a road surface being one example—but for obvious reasons these tend to be static messages (“RIGHT TURN ONLY” etc.). While it is possible to place a changeable message on a floor surface, the display must be quite durable and it consequently tends to be rather expensive. 
         [0008]    It would be advantageous to provide a display device that does not need to be as large as the message it displays. It would also be advantageous to provide a relatively inexpensive display device that can display a message on a floor surface. The present invention provides these advantages, among others. 
       BRIEF SUMMARY OF THE PRESENT INVENTION 
       [0009]    The present invention comprises a message display that produces a visible message by projecting an image on a surface such as a wall or floor. A bright light source is provided, preferably including an array of light emitting diodes (“LED&#39;s”). The light from this bright source is passed through one or more lenses in a condenser assembly to make it more uniform. The light then passes through an image plate that contains a small version of the image to be displayed. The image plate may be a static image or an active device such as an LCD. 
         [0010]    Once the light passes through the image plate it next passes through a focusing assembly. The focusing assembly preferably includes a compensator lens, a variator lens, and a moveable objective lens. The focusing assembly preferably allows the zoom, collimation, focal length, and focus of the image to be adjusted. These features are used to create a desired projected image on a target surface such as a wall or floor. The projected image is a representation of the image contained on the image plate. 
         [0011]    The present invention allows the creation of an image that is much larger than the device creating it. It also allows the projection of an image on a floor surface. The device may also be switched on and off or otherwise altered in order to alter the message in the display. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view, showing an embodiment of the present invention oriented to project a message on a floor. 
           [0013]      FIG. 2  is a perspective view, showing how the present invention may be mounted to a column. 
           [0014]      FIG. 3  is a perspective view, showing how the present invention may be oriented to project an image on a vertical surface such as a wall. 
           [0015]      FIG. 4  is a perspective view, showing the projection of an image on a vertical wall. 
           [0016]      FIG. 5  is an elevation view, showing details of an exemplary condenser assembly. 
           [0017]      FIG. 6  is a sectional elevation view, showing details of an exemplary focusing assembly. 
           [0018]      FIG. 7  is an elevation view, showing the light source, condenser assembly, image plate, and focusing assembly. 
           [0019]      FIG. 8  is an elevation view, showing the components of  FIG. 7  enclosed within a simple depiction of the housings used to contain the components. 
           [0020]      FIG. 9  is a sectional elevation view, showing a representative embodiment of the electronics housing, the image module housing, and the focusing module housing. 
           [0021]      FIG. 10A  is a perspective view, showing the housing embodiments of  FIG. 9  attached to a mounting bracket. 
           [0022]      FIG. 10B  is a perspective view, showing the components of  FIG. 10A  attached to a mounting flange rather than a mounting bracket. 
           [0023]      FIG. 11  is a perspective view, showing the use of an LCD as the image plate. 
       
    
    
     REFERENCE NUMERALS IN THE DRAWINGS 
       [0024]      
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 10 
                 message projector 
                 12 
                 image footprint 
               
               
                 14 
                 message 
                 16 
                 column 
               
               
                 18 
                 mounting bracket 
                 20 
                 wall 
               
               
                 22 
                 door 
                 24 
                 floor 
               
               
                 26 
                 condenser assembly 
                 28 
                 image plate 
               
               
                 30 
                 projection axis 
                 32 
                 focusing assembly 
               
               
                 34 
                 focus lens 
                 36 
                 compensator lens 
               
               
                 38 
                 variator lens 
                 40 
                 rear objective lens 
               
               
                 42 
                 front objective lens 
                 44 
                 first condenser lens 
               
               
                 46 
                 second condenser lens 
                 48 
                 light source 
               
               
                 50 
                 mounting plate 
                 52 
                 electronics module 
               
               
                 54 
                 image module 
                 56 
                 focusing module 
               
               
                 58 
                 electronics housing 
                 60 
                 image module housing 
               
               
                 62 
                 focusing module housing 
                 64 
                 connection 
               
               
                 66 
                 connection 
                 68 
                 compensator lens carrier 
               
               
                 70 
                 compensator lens lock screw 
                 72 
                 variator lens carrier 
               
               
                 74 
                 variator lens lock screw 
                 76 
                 front objective lens carrier 
               
               
                 78 
                 threaded connection 
                 80 
                 vent 
               
               
                 82 
                 pivot 
                 84 
                 LCD display 
               
               
                 86 
                 electrical connector 
                 88 
                 mounting flange 
               
               
                 90 
                 fan 
                 92 
                 circuit board 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIGS. 1-4  show typical uses for the present invention, while the subsequent drawing views show internal details for some of the representative embodiments.  FIG. 1  shows an application where the desire is to project an image on a floor surface. Message projector  10  is secured in an elevated position. It is oriented to project a focused image on floor  24 . The projected image lies within image footprint  12 . In the particular example shown, the message “HARD HAT AREA” is projected. 
         [0026]    The brightness of the projected image may be configured for the particular application. For example, in a factory having little external illumination, moderate brightness will allow the image to easily capture the attention of persons walking in the area. If on the other hand solar illumination is present, the brightness may need to be increased. 
         [0027]    Suitable mounting hardware is preferably provided for the image projector.  FIG. 2  shows an embodiment in which mounting bracket  18  is provided for message projector  10 . Mounting bracket  18  is used to connect the message projector to a vertical column  16 . The mounting bracket preferably allows the angle of the message projector to be adjusted.  FIG. 3  shows an embodiment where message projector  10  is reoriented to project a message in a horizontal direction (in order to project the message on a vertical surface such as a wall). 
         [0028]      FIG. 4  shows the projection of a message on a vertical wall  20 . The message “TEST IN PROGRESS DO NOT ENTER” is projected over door  22 . This message alerts an approaching person of the fact that the area has been secured and should not be entered. 
         [0029]    The message projector is able to replace conventional signage, and may provide additional features. Embodiments of the message projector may contain one or more of the following features: 
         [0030]    (1) The ability to turn a message on and off; 
         [0031]    (2) The ability to alter the brightness of a message in response to changing ambient conditions or other conditions; 
         [0032]    (3) The ability to project a message in one or more colors; 
         [0033]    (4) The ability to project a message on a surface that is not purely perpendicular to the axis of projection, including oblique and curved surfaces; and 
         [0034]    (5) The ability to switch a message on or otherwise alter a message in response to an environmental condition—such as a proximity sensor sensing the approach of a factory worker. 
         [0035]    Having gained an understanding of the invention&#39;s applications, the reader may wish to know some internal details of some exemplary embodiments.  FIG. 5  shows the basic components of a preferred embodiment. Light travels through the assembly from left to right in the view. 
         [0036]    Light source  48  preferably provides illumination over a significant area. In the embodiment shown, an array of bright light emitting diodes (“LED&#39;s”) is used. A suitable array is the CSM 360 LED marketed by Luminus Devices, Inc., of Billerica, Mass., U.S.A. The CSM 360 includes an array of LED&#39;s mounted on a single chip. The array is capable of producing 6,000 lumens with a color spectrum from 3,000 K to 6,500 K. The input power is typically 40 to 80 W using a 12 V source. 
         [0037]    Condenser assembly  26  is positioned to collect the diverging light from light source  48  and create a roughly parallel light source. First condenser lens  44  and second condenser lens  46  focus parallel light rays through image plate  28 . Image plate  28  contains the image of the message that is to be projected. It may be relatively small—such as 8 mm by 8 mm. Once the light rays pass through image plate  28  they enter focusing assembly  32 . The focusing assembly adjusts the optical path in order to project an image along projection axis  30  and focus that image on a target surface. 
         [0038]      FIG. 6  shows a representative embodiment of focusing assembly  32  (in a sectioned view). From left to right, the assembly includes: focus lens  34 , compensator lens  36 , variator lens  38 , rear objective lens  40 , and front objective lens  42 . All the lenses are centered on projection axis  30 . Light passing through image plate  28  travels through the focusing assembly and out along projection axis  30 . 
         [0039]    While a discussion of optical design is beyond the scope of this disclosure, the reader may wish to understand the general function of the lenses in the embodiment presented. The light rays converge as they pass into image plate  28  from the left and diverge as they pass out to the right. Focus lens  34  reduces the angle of divergence. Compensator lens  36  further reduces the angle of divergence. The double-headed arrow shown in conjunction with compensator lens  36  is intended to indicate that its position along projection axis  30  is preferably adjustable. This allows for collimation adjustment. 
         [0040]    The position of variator lens  38  is preferably also made adjustable. As will be understood by those knowledgeable in the field, the motion of a variator lens alters the focal length of the lens assembly (and therefore the “zoom”). In the embodiment shown, the variator lens provides a “zoom” adjustment between 1:1 and 2.7:1. 
         [0041]    Rear objective lens  40  is fixed in position for the embodiment shown. Front objective lens  42 , however, is preferably made adjustable. Adjusting the separation between the two objective lenses varies the projection distance for the assembly (the distance between the front objective lens and a focused image projected on a surface). In the embodiment shown, the projection distance may be varied between 15 feet and 40 feet (4.6 m and 12.3 m). A simpler lens assembly can certainly be used. A more complex one could be used as well. However, the embodiment shown provides good flexibility in terms of the projection distance and the projected image size. 
         [0042]      FIG. 7  shows the entire optical path from light source  48  to front objective lens  42 . In sequence, the components are as follows: light source  48 , first condenser lens  44 , second condenser lens  46 , image plate  28 , focus lens  34 , compensator lens  36 , variator lens  38 , rear objective lens  40 , and front objective lens  42 . 
         [0043]    The reader may wish to know some specific examples for the lenses used in the assembly. All the lenses in the exemplary embodiment are marketed by Thorlabs, Inc., of Newton, N.J., U.S.A. First condenser lens  44  is an aspheric condenser lens having model number ACL 4532. It has an overall diameter of 45 mm and a focal length of 32 mm. Second condenser lens  46  is a Thorlabs model number ACL 7560. It has an overall diameter of 75 mm and a focal length of 60 mm. 
         [0044]    The components within the zoom lens assembly may be any suitable combination of convex and variator lenses. In the preferred embodiments, these lenses will be made of glass. However, for less expensive embodiments, the lenses may be made of plastic. 
         [0045]    The image plate may assume a wide variety of forms. In its simplest form it may be a “Gobo” mask. Such masks are used in theatrical lighting and may assume many forms. A simple one-color Gobo may be an image cut into a thin steel plate. A more complex Gobo may include multiple layers of glass plates. A multi-layer Gobo is often used to produce a full-color image. A Gobo mask creates a projected image by passing light through a pattern lying in the focal plane. More complex embodiments are possible, including the use of a computer-controlled LCD panel to create a changeable mask. The image plate includes a clear area corresponding to the message, with the balance of the area being opaque. The term “clear area” is not limited to a 100% transmission of light. In an LCD display—for example—the “clear area” may only correspond to a transmissibility of about 60%. As long as there is a significant difference in transmissibility between the clear and non-clear areas the functional purpose of the image plate will be met. 
         [0046]    The description of the “clear area” corresponding to the message means that the clear area will define a small version of the message that is to be projected on the target surface. The clear area may assume a complex form such as text (“HARD HAT AREA”) or a simple form such as a graphical arrow. 
         [0047]      FIG. 8  shows a simplified view of a combined housing that may be used to contain the light source, the condensing lenses, and the focusing lenses. Electronics module  52  contains the circuitry providing power to the light source and mounts the light source itself. Image module  54  contains the condensing lenses and the image plate. Focusing module  56  contains the lenses used to project and focus the desired image. 
         [0048]    The assembly shown includes three separate modules that are linked together. Other embodiments may include only two separate modules, while still other embodiments may use a single module to contain all the components. 
         [0049]      FIG. 9  shows a sectioned elevation view taken through a completed assembly in which representative housings for each of the modules are depicted in a simplified fashion. In the embodiment shown, most of the housing components are made of molded plastic. Electronics housing  58  is joined to image module housing  60 . Image model housing  60 , in turn, is joined to focusing module hosing  62 . 
         [0050]    In the embodiment shown, electronics housing  58  is made of molded plastic but includes an integral metal plate. Light source  48  is attached to the metal plate. Circuit board  92  is also attached to the metal plate, using conventional standoffs to provide a separation for cooling. Fan  90  may be attached to the housing, to the circuit board, or to the metal plate. 
         [0051]    Circuit board  92  includes the electronics necessary to drive light source  48  and fan  90 . For embodiments using an active image plate, it may also include the circuitry to control the image. Fan  90  draws air into the housing through one or more vents  80 . The air is preferably circulated around the circuit board and around light source  48 . A suitable gap is preferably provided between light source  48  and the first of the condenser lenses so that air can circulate around the light source. The heated air is exhausted from the housing as shown. 
         [0052]    In the version of  FIG. 9 , image module housing  60  is attached to electronics housing  58  via connection  64 , which may assume any suitable form. The image module housing contains the two condenser lenses and image plate  28 . The housing is preferably made from molded plastic. It preferably includes internal fixtures for receiving and holding the lenses in the desired position. The housing depicted may be molded in two halves. If this approach is used, the lenses are then placed in one of the two halves and the other half is secured in place to complete the assembly. 
         [0053]    Another alternative is to use a one-piece housing that includes flexible features to hold the optical components. As an example, thin and flexible annular ribs can be positioned to snap over the perimeter of each lens. Each lens in pushed into place and a flexible rib snaps over the lens&#39; perimeter to secure it in position. 
         [0054]    In the embodiment of  FIG. 9 , the housing is molded in two halves. A series of retention ribs  88  are provided. These include annular recesses designed to receive the outer perimeter of each lens. The lenses are placed in one of the two halves. The other half is then mated in position, at which point the annular recesses completely encircle and capture the lenses. Of course, one could also use a series of posts and snaps that grip only a portion of each lens. However the attachment is made between the lenses and the image module housing, the lenses should be held securely in place. 
         [0055]    Focusing module housing  62  is connected to image module housing  60  by threaded connection  66  in the particular version shown. The image module housing may also be made as one or more injection molded parts. Retention features are provided for holding focus lens  34  and rear objective lens  40  in fixed positions. However, if an embodiment having movable lenses is desired, features for facilitating the movement of the movable lenses must be incorporated. In the version shown, compensator lens  36 , variator lens  38 , and front objective lens  42  are all movable. 
         [0056]    Compensator lens carrier  68  holds the compensator lens. It slides along the projection axis. Compensator lens lock screw  70  is tightened in order to lock the compensator lens in a desired position. Likewise, the variator lens is carried in variator lens carrier  72 . Variator lens lock screw  74  it tightened to lock the variator lens in position. The two lock screws pass through slots in the exterior of the focusing module housing so that they are externally accessible. 
         [0057]    The front objective lens is connected to front objective lens carrier  76 . The front objective lens carrier is connected to the focusing module housing via threaded connection  78 . The distance between the two objective lenses is therefore adjusted by rotating front objective lens carrier  76 . 
         [0058]    The housing embodiments are depicted in a simplified fashion and the invention is by no means limited to the embodiments shown. Those skilled in the art will know that many different types of housing could be used. Suitable housings can be constructed to provide the following features, among others: 
         [0059]    (1) weather resistance for outdoor applications using cast zinc or other materials; 
         [0060]    (2) a hermetically-sealed enclosure in order to minimize condensation and fogging; 
         [0061]    (3) an electrically-insulated enclosure; 
         [0062]    (4) a one-piece construction that resists tampering and disassembly; and 
         [0063]    (5) a modular construction that allows the substitution of different image and focusing modules. 
         [0064]    The assembly of  FIG. 9  must be mounted to a wall, ceiling, or other support to operate. Electronics housing  58  itself may serve as a mounting bracket. Alternatively, external mounting features may be added.  FIGS. 10A and 10B  show embodiments in which additional mounting features have been added. In  FIG. 10A , mounting bracket  18  is connected to electronics housing  58 . A locking pivot  82  is preferably provided so that the angle between the mounting bracket and the rest of the assembly may be adjusted. In use, mounting bracket  18  may be attached to a ceiling, a wall, or some other structure. Message projector  10  is then attached to the mounting bracket. 
         [0065]    Several other significant features are seen in  FIG. 10A . The reader will observe how compensator lens lock screw  70  and variator lens lock screw  74  protrude out of the slots in the focusing module housing. To adjust the position of one of these lenses, the user loosens the lock screw, slides the lens to a new location, and tightens the lock screw again. The reader will also observe that front objective lens carrier  76  includes gripping features around its perimeter. These allow a user to easily grasp and rotate the front objective lens carrier in order to change the separation distance between the two objective lenses. 
         [0066]    The adjustments to the lens locations will ordinarily be made with the light source switched on (and in the case of an active image plate the image may be active or a test pattern may be active). The user will ordinarily make the adjustments by observing the projected image itself. 
         [0067]      FIG. 10B  shows an alternate mounting bracket. In this embodiment, mounting flange  88  has been added to the base of electronics housing  58 . The mounting flange may incorporate holes or other features that facilitate its attachment to an external object. For example, if message projector  10  is to be placed on a ceiling, mounting flange  88  may include openings arranged to facilitate attachment of the flange to an electrical junction box. Many types of mounting features could be added and the invention is in no way limited to any particular feature or features. 
         [0068]      FIG. 11  shows one embodiment of an “active” image plate  28 . The term “active” is used to indicate that the image plate is not limited to a static image (such as a metal “Gobo” plate). In the embodiment shown, the light path is directed through LCD display  84 . Electrical connector  86  connects the LCD display to suitable electronics located in the electronics housing. In other embodiments, the electronics may be located with the LCD display. 
         [0069]    The LCD display will typically create a “negative” image, meaning that the desired message will be presented as a clear area and the rest of the display will be dark. Light will be transmitted through the clear area in order to form the projected image. 
         [0070]    Those skilled in the art will realize that many other display technologies could be substituted for the LCD display shown. Any existing or future technology used in flat-screen displays could likely be applied, and the invention is by no means limited to any particular technology. 
         [0071]    The use of an “active” display allows additional possibilities for the projected message, including: 
         [0072]    (1) the use of a variety of colors; 
         [0073]    (2) the use of animation; 
         [0074]    (3) the use of different messages, possibly in response to different conditions; and 
         [0075]    (4) the use of time-driven messages (such as “45 DAYS WITHOUT A LOST-TIME ACCIDENT”). 
         [0076]    The lens adjustment embodiments shown in  FIGS. 6 and 9  should properly be viewed as simplistic embodiments. In particular, the sliding carriages shown in  FIG. 9  would likely be replaced by more sophisticated in some embodiments. Mechanisms similar to those used in camera lenses may be employed. For instance, the variator and objective lens adjustment features can be combined in one external grip that can be moved along the projection axis and also turned (in the manner of a camera zoom lens where a single device controls focus and zoom). 
         [0077]    Focusing features may be automated using the focusing technology found in present day cameras. Zoom may be controlled remotely if a drive system is installed in the focusing module. Remote control of the zoom feature allows the projected image to shrink and grow on command. This could be useful. Assume, for example, the presence of a “TEST IN PROGRESS—DO NOT ENTER MESSAGE.” This could be presented in a modest size. If a control system detects a person continuing to walk toward the secured area, the controller could command the message projector to simultaneously enlarge and flash the projected image. All these possibilities will be understood by those knowledgeable in the field. 
         [0078]    In a typical installation, the installer will mount the image projector and then switch the light source on in order to adjust the projected image. One of the objectives may be to correctly adjust the “depth of field.” This is significant factor when the image is projected on a surface that is not wholly perpendicular to the projection axis (such as a curved or oblique surface). A greater depth of field allows more of an image to be in focus when it is projected on a non-perpendicular surface. 
         [0079]    Adjusting the lenses themselves can increase the depth of field. Other features may be added if needed. For example, an adjustable iris can be provided to increase the depth of field, albeit at the expense of overall brightness. 
         [0080]    Although the preceding description contains significant detail, it should not be construed as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention. Those skilled in the art will know that many other variations are possible without departing from the scope of the invention. Accordingly, the scope of the invention should properly be determined with respect to the following claims rather than the examples given.