Abstract:
An invisible scanning safety system for use with laser projection systems that includes sensors monitoring less than the entire laser accessible region such that the region monitored is reduced to almost the absolute minimum, to thereby prevent unwarranted stoppages or disturbances in projection. The system may also monitor a 360 degree region around the lens of the laser projector, a wedge-shaped region, a pyramid-shaped region or a chimney-shaped region.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/931,321, filed May 21, 2007, which is hereby incorporated by reference herein in its entirety, including but not limited to those portions that specifically appear hereinafter, the incorporation by reference being made with the following exception: In the event that any portion of the above-referenced provisional application is inconsistent with this application, this application supercedes said above-referenced provisional application. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    1. The Field of the Invention 
         [0004]    The present disclosure relates generally to safety systems for use with laser-based projection systems. 
         [0005]    2. Description of Background Art 
         [0006]    Lasers produce coherent light which, when looked at, appears to the eye to have come from a very distant source. Consequently, the image formed on the retina by a laser beam is always incredibly small and therefore of very high power density. Most lasers that are used in entertainment, theater and public exhibitions have outputs high enough to pose a significant risk of eye injury. If the laser output power is greater than about 0.5 watts, burning a person&#39;s skin may also be a significant risk. Laser powers of just a few milliwatts can damage the retina long before natural aversion responses such as blinking can take place. By contrast, a non-coherent source of radiation, such as a light bulb, is less hazardous to view because it forms an extended image, rather than a point image, when focused by the eye. The power density of non-coherent light at the retina is therefore lower than that produced by a laser of equivalent radiant power. 
         [0007]    Eye-injury thresholds depend upon a number of factors such as wavelength, exposure duration and viewing situation. Injury severity following overexposure depends upon the part of the retina that is overexposed and the extent of any bleeding within the eye. Effects range from partial blindness to total loss of sight in the affected eye. Eye damage caused by exposure to laser radiation is generally permanent. 
         [0008]    As image projection systems advance, the desire for a higher lumen output grows. Higher output systems are especially desirable when large surfaces are being projected upon, such as in dome-style theaters. The greater the number of lumens produced by a projection system, the greater the contrast ratio that can be produced (contrast is a measure of a system&#39;s darkest and brightest levels). Thus, higher lumen output systems inherently increase the potential for eye damage to human beings. 
         [0009]    To reduce the risk of potential injury, often times barriers of some sort are put into place to limit human interaction with the projected light. Such barriers may include walls, railings, or other physical means to inhibit the public from placing themselves in danger. Non-physical barriers may also be used, and usually include invisible scanning systems that are attached to domes, walls, and other fixed stands. 
         [0010]    The available scanning systems may include one or more sensors for receiving a stimulus from a monitored region. The stimulus may include reflected light beams from light that is directed into the monitored region. When a human or other foreign object crosses into a monitored region, the projection system may automatically switch to a safe mode of operation before any potential harm can occur. 
         [0011]    The proposed new system and method of this application combines an scanning safety system with an image projection system and has particular use with image projection systems utilizing lasers which are powerful enough to cause damage to the human visual anatomy. The scanning safety system is relatively imperceptible to the vision of human beings and in most applications will be invisible to the vision and other senses of human beings. Thus, the new system and method may form an invisible barrier over the most critical areas of a laser projection system so there is no need for an external barrier or any additional safety components to prevent harmful human interaction with the laser light being projected. 
         [0012]    The unobtrusive, and in most applications invisible, barrier of the present system and method may extend along an outermost boundary of a laser accessible region for the laser projection system. The barrier may also take the form of a wedge shape, pyramid shape or a chimney shape. Again, according to one aspect of the present disclosure, if the unobtrusive barrier is crossed by a foreign object, the laser projection system will automatically shut off, reduce laser power to a safe level, or blank out the area where the foreign object is located, all preventing harm to the foreign object such as a human being. 
         [0013]    Another proposed feature of the present system and method is that it can exist with several warning layers that can initiate a temporary reduction in power and/or an audible warning as part of an additional safety zone if a foreign object comes near a location where action will be taken regarding the power of the projected laser light, that is the actual cut off point. 
         [0014]    The present system and method is particularly suited for use with laser projection systems such as the Evans &amp; Sutherland Laser Projector (“ESLP”) which incorporate coherent light sources with Grating Light Valve™ (“GLV”) light modulators. GLV based systems work by scanning a narrow column of pixels across a screen using a column-based architecture. The amount of concentrated light in the narrow width can potentially be dangerous if scanned across a human eye at a close distance, however, the column-based architecture is inherently safer at larger distances than raster-based architecture using a beam in which all of the beam&#39;s energy is focused onto a single point. But, the distances for potential damage still vary with intensity and size of the original source even for laser projection systems with column-based architectures. 
         [0015]    In view of the dangers posed from laser radiation, industry guidelines and governmental regulations dictate safety rules to prevent injury to the public. Furthermore, many previously available devices have been developed to prevent accidental exposure to laser radiation all of which have problems and disadvantages addressed by the system and method of the present disclosure. 
         [0016]    The features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of this disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The features and advantages of the disclosure will become apparent from a consideration of the subsequent detailed description presented in connection with the accompanying drawings in which: 
           [0018]      FIG. 1  is a perspective view of a laser projector with scanners; 
           [0019]      FIG. 2  is a view of the laser projector shown in  FIG. 1  and the region accessible by the projection lasers; 
           [0020]      FIG. 3  is a view of the laser projector shown in  FIG. 1  with the region accessible by the projection lasers and a monitored region of one of the scanners; 
           [0021]      FIG. 4  is a view of the laser projector shown in  FIG. 1  and the full monitoring range of one of the scanners; 
           [0022]      FIG. 5  is a view of the laser projector shown in  FIG. 1  and an unobtrusive safety barrier; 
           [0023]      FIG. 6  is a block diagram of a laser safety system in accordance with an embodiment of the present disclosure; 
           [0024]      FIG. 7  is a perspective view of a laser projector with a wedge-shaped invisible safety barrier; 
           [0025]      FIGS. 8A-8C  are a front view, side view, and a top view, respectively, of the laser projector and the wedge-shaped safety barrier shown in  FIG. 7 ; 
           [0026]      FIG. 9  is a side view of the laser projector and the wedge-shaped safety barrier shown in  FIG. 7  in relation to a projection cone; 
           [0027]      FIG. 10  is a front view of the laser projector and the wedge-shaped safety barrier shown in  FIG. 7  in relation to a projection cone; 
           [0028]      FIG. 11  is a perspective view of a laser projector and a chimney-shaped safety barrier; 
           [0029]      FIG. 12  is a front view of the laser projector and the chimney-shaped safety barrier shown in  FIG. 11  in relation to a projection cone; 
           [0030]      FIG. 13  is a side view of the laser projector and the chimney-shaped safety barrier shown in  FIG. 11  in relation to a projection cone; and 
           [0031]      FIG. 14  is a view of the laser projector shown in  FIG. 11  and the full scanning range of the scanners. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure claimed. 
         [0033]    In describing and claiming the present disclosure, the following terminology will be used in accordance with the definitions set out below. As used herein, the terms “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps. 
         [0034]    Referring now to  FIG. 1 , there is illustrated a perspective view of a laser projector  10 . The projector  10  includes a boxed enclosure  12  which contains the laser projection components. These components may include one or more light modulation devices, lasers, scanning mirror, power supply, optics, and control circuitry. The lasers and light modulation devices may be under the control of a control unit. The control unit may be able to control the laser output as well as the intensity of the light exiting the projector  10 . 
         [0035]    The laser projector  10  shown in  FIG. 1  is suitable for use in dome-style theaters. The laser projector  10  is mounted on the floor (or ground) at approximately the middle of the dome. The laser projector  10  projects upwardly, to thereby generate an image on the inner surface of the dome. 
         [0036]    The enclosure  12  is mounted on a frame  14  having four (4) legs  16 . The enclosure  12  serves as a housing for the components of the projector  10 . In particular, the enclosure  12  sits on a horizontal platform  15  that is secured to sidewalls of the legs  16  by a plurality of horizontal members  17 . In particular, the horizontal members  17  are attached to the lower portions of the legs  16 . The legs  16  continue extending vertically upwards from the points where the horizontal members  17  are attached. A top end  16 A of each of the legs  16  terminates at approximately the same height as the top  12 A of the enclosure  12 . 
         [0037]    Mounted on the top end  16 A of each of the legs  16  is an infrared (“IR”) scanner  18 . Each of the IR scanners  18  may include a sensor that receives a stimulus from an area proximate the projector  10 . The sensor may be an optical sensor that detects a light stimulus. The IR scanners  18  may further include a laser that sends out a very short pulse of light. At the same time the light is sent out by one of the IR scanners  18 , an electronic timer internal to the IR scanner  18  is started. When pulsed light from the IR scanner  18  is incident on an object, it is reflected and received back at the sensor in the IR scanner  18 . By measuring the time (Δt) between the transmission of the light pulse and its reception by the sensor, an IR scanner  18  may calculate the distance to the detected object. 
         [0038]    The IR scanners  18  may each include a rotating scanning mirror that deflects light pulses from its laser such that the IR scanner  18  may potentially monitor an arc of approximately 190 degrees. An IR scanner  18  may not only determine the distance to an object, but the direction of the object relative to the IR scanner  18  may be determined from the angle of the scanning mirror at which the light pulse was initially transmitted. Thus, from the measured distance and the direction of the object, an IR scanner  18  may determine the exact position of the object relative to the IR scanner  18 . 
         [0039]    The IR scanners  18  may each include an input/output module for receiving necessary programming. It should be further understood that the laser radiation emitted by the IR scanners  18  is harmless to a person. Desirably, the radiation emitted by the IR scanners  18  is relatively imperceptible by a human and in most instances will be completely invisible to a human. Thus, the system and method of the present disclosure will, in nearly all instances, provide its advantages in an invisible and imperceptible manner to humans. It will be appreciated that many different devices and portions of the electromagnetic or acoustic spectrum can be used to perform the same and equivalent functions carried out by the IR scanners  18 . 
         [0040]    Referring now to  FIG. 2 , there is illustrated a side view of the laser projector  10 . A laser accessible region  20  is depicted in  FIG. 2  as the inverted cone extending upwardly from the projector  10 , or more specifically, from a projection lens. It will be understood that the laser accessible region  20  is that region through which the laser projector  10  scans or sweeps light from the projection lasers to thereby generate an image on a dome (not explicitly shown). The laser accessible region  20  includes a boundary  22 , which are the sidewalls of the inverted cone. The boundary  22  defines where the laser accessible region  20  terminates. 
         [0041]    Because the laser projector  10  is typically mounted on the floor, the ground, or on a small pedestal, in the center of a theater, a person  23  may be able to intrude past the boundary  22  and enter into the laser accessible region  20 . For example, a person  23  may climb a barrier or stand on a theater seat. Such an intrusion into the laser accessible region  20  would be undesirable because of the potential harm from the laser radiation emitted from the laser projector  10 . As will be explained in further detail below, the IR scanners  18  are operable to detect a person  23  before the person  23  crosses the boundary  22  into the laser accessible region  20 . Once detected, the projector  10  may automatically employ safety measures to ensure that the person  23  is not harmed by the projection lasers. 
         [0042]    Referring now to  FIG. 3 , there is depicted a side view of the laser projector  10  and the laser accessible region  20 . In addition, there is shown a side view of a monitored region  24  for one of the IR scanners  18 . The monitored region  24  from the IR scanner  18  is spaced apart from the boundary  22  of the laser accessible region  20  to thereby provide advanced warning of an intrusion. In this regard, the monitored region  24  shown in  FIG. 3  forms part of an unobtrusive, and in nearly all practical applications invisible, barrier. Typically, the spacing between the monitored region  24  and the boundary  22  of the laser accessible region should be adequate to allow the laser projector  10  to switch to a safe operating mode prior to the actual intrusion of the boundary  22  by an object or person  23 . 
         [0043]    In one exemplary embodiment, the spatial distance between the monitored region  24  and the boundary  22  of the laser accessible region  20  is in the range from about 5 inches to about 18 inches. In another exemplary embodiment, the spatial distance between the monitored region  24  and the boundary  22  of the laser accessible region  20  is about 7 inches. It will be appreciated that the above discussion regarding a single IR scanner  18  is applicable to all four (4) IR scanners  18  of the projector  10 . 
         [0044]    Referring now to  FIG. 4 , there is depicted a view of the laser projector  10  and the full monitoring range  25  of one of the IR scanners  18 . As explained previously, the monitored region  24  ( FIG. 5 ) of an IR scanner  18  represents an area swept by an IR laser internal to the IR scanner  18  using a scanning mirror. The monitored region  24  ( FIG. 5 ) of an IR scanner  18  may comprise only a portion of the full monitoring range  25  of the IR scanner  18 . 
         [0045]    Still referring to  FIG. 4 , the full monitoring range  25  of the IR scanner  18  may be substantially planar and include boundaries  25 A,  25 B and  25 C. The boundaries  25 A and  25 B represent the left and right scanning limits of the IR scanner  18 . The boundary  25 C is arcuate and may be determined by the maximum scanning distance of the IR scanner  18 . However, as will be shown in relation to  FIG. 5 , it may be undesirable to use the full monitoring range  25  of the IR scanners  18 . 
         [0046]    Referring now to  FIG. 5 , there is depicted all four (4) IR scanners  18  and the laser projector  10 . The monitored regions  24  of each of the IR scanners  18  intersect along lines  28 . The cross-hatched regions  26 , while within the full monitoring range  25  of the IR scanners  18 , are not monitored for foreign objects. That is, the IR scanners  18  are programmed or otherwise configured not to monitor the cross-hatched regions  26 . Alternatively, the IR scanners  18  are programmed to ignore foreign objects in the cross-hatched regions  26 . 
         [0047]    As seen in  FIG. 5 , the combined monitored regions  24  of each of the four (4) IR scanners  18  form a continuous invisible barrier  29  adjacent the boundary  22  of the laser accessible region  20  (not explicitly shown in  FIG. 5  for convenience purposes). Thus, as best represented in  FIG. 2 , it is very unlikely, and perhaps virtually impossible, for a person  23  to penetrate into the laser accessible region  20  without detection because of the contiguous barrier  29  formed by the IR scanners  18 . 
         [0048]    Referring now to both  FIGS. 2 and 5 , in the event that a person  23  or other foreign object is detected to enter any one of the monitored regions  24 , the IR scanner  18  that detects the intrusion will transmit a signal to the projector  10 . This detection will occur due to reflected light from the IR laser in the IR scanners  18  stimulating the sensors in the IR scanners  18 . The IR scanners  18  may calculate the exact position of the intruding object by angle and distance, or the IR scanners  18  may simply recognize that an intrusion has occurred. In response to the intrusion, the applicable IR scanners  18  will transmit a signal, such as a warning signal, to the laser projector  10 . This signal may contain position information on the foreign object. Multiple signals may be sent in order to keep the laser projector  10  updated as to the position of the foreign object. 
         [0049]    In response to the signal, the laser projector  10  may automatically switch to a safe operating mode. In one exemplary embodiment, the safe operating mode involves the laser projector  10  to cease projecting an image such that no laser light is emitted from the laser projector  10 . In another exemplary embodiment, the safe operating mode involves the laser projector  10  blanking out an area surrounding the intruding object. This is possible because the IR scanners  18  are able to report the location of the foreign object as well as changes in the position of the foreign object. In still another exemplary embodiment, the safe operating mode involves the laser projector  10  reducing the power of the projection lasers such that their laser radiation is at a safe level for incidence upon a human. This may be a localized reduction in power around the intruding object. Alternatively, the laser projector  10  may use the light modulating device to vary the intensity. 
         [0050]    Referring now to  FIG. 6 , there is depicted a block diagram of a safety system in accordance with an exemplary embodiment of the present disclosure. An IR scanner  18  includes at least one sensor and at least one IR laser. The at least one sensor is able to monitor a monitored region for intrusions. This region may encompass any of the monitored regions described herein. 
         [0051]    In particular, the IR scanner  18  receives a stimulus, e.g., a reflected beam of IR light, when an object, such as a person, enters the monitored region. The IR scanner  18  generates a warning signal in response to the stimulus received from the region monitored by the at least one sensor when a foreign object is detected. The warning signal is sent to, and received by, the projector control unit  100 . The projector control unit  100  then controls the projection lasers  102 , or other appropriate device, to render the projection lasers  62  to an appropriate safe level. It will be appreciated that the system described in  FIG. 6  may be utilized with any of the embodiments described herein. 
         [0052]    Referring now to  FIG. 7 , there is depicted another exemplary embodiment of the present invention. A laser projector  30  is mounted in an enclosure  32 . It will be noted that the particular shape of the enclosure  32  illustrated in  FIG. 7  and  FIGS. 8A-C  is not crucial and the particular shape of the enclosure  32  shown in these figures may be adapted for a particular installation and the shape of the enclosure may vary to meet the requirements of any specific installation. 
         [0053]    Continuing to refer to  FIG. 7 , four (4) IR scanners  34 A,  34 B,  34 C and  34 D are mounted to the enclosure  32  and around a projection lens  36  of the laser projector  30 . In a particular, the IR scanners  34 A,  34 B,  34 C and  34 D are mounted in a box configuration around the projection lens  36 . Stated another way, an IR scanner is located above, below and on either side of the projection lens  36  of the projector  30 . Stated still another way, the IR scanners  34 A,  34 B,  34 C and  34 D are mounted proximate the projection lens  36 . 
         [0054]    The IR scanners  34 A and  34 B monitor planar and predefined regions that extend upwardly from the enclosure  32  and that are substantially parallel to each other. The IR scanners  34 C and  34 D monitor planar and predefined regions that extend upwardly from the enclosure  32  and that are non-parallel to each other. The predefined regions monitored by IR scanners  34 C and  34 D intersect along an intersection  38  above the lens  36 . 
         [0055]      FIGS. 8A ,  8 B and  8 C each illustrate different views of the system shown in  FIG. 7 , where like reference numerals indicate like components. It will be noted that the predefined monitored regions of the IR scanners  34 A,  34 B,  34 C and  34 D form roughly a wedge-shaped or triangularly-shaped invisible safety barrier  40  around an area in front of the projection lens  36 . The invisible barrier  40  has two substantially parallel and planar monitored regions and two planar monitored regions, which converge above the projection lens  36 . 
         [0056]    Referring now to  FIGS. 9 and 10 , where like reference numerals depict like components, a projection cone  42  from the lens  36  is shown in relation to the safety barrier  40 . In particular, the predefined monitored regions of the four (4) IR scanners  34 A,  34 B,  34 C and  34 D surround the harmful region  44 , indicated by the diagonally-lined area in the figure, of the laser projector  30 . It will be noted, however, that the four (4) IR scanners  34 A,  34 B,  34 C and  34 D scan an area less than the area accessible by the projection lasers of the projector  30 . That is, the safety barrier  40  does not monitor the entire area accessible by the projection lasers of the projector  30  and the IR scanners  34 A,  34 B,  34 C and  34 D monitor less than all of the area of the projection cone  42  for an intrusion. 
         [0057]    Further, it will be noted that the region inside of the invisible barrier  40  is not necessarily directly monitored. However, it will be observed that it is very unlikely, and perhaps virtually impossible, for a person or other foreign object to enter into the harmful region of the projector  30  without passing through one or more of the predefined monitored regions of the IR scanners  34 A,  34 B,  34 C and  34 D. Again, when an intrusion of the unobtrusive barrier  40  is detected, the laser projector  30  may switch to one of a number of safe operating modes as explained above. It will be noted that the intersection  38  is within the laser accessible region  42  and is the furthermost point of the invisible barrier  40  from the projection lens  36 . 
         [0058]    Another embodiment of the present disclosure may include three or more IR scanners forming a pyramid-shaped unobtrusive/invisible barrier around the hazardous region. The pyramid-shaped unobtrusive/invisible barrier may comprise three or more planar scanning fields that converge at a single point, typically above the projection lens of a laser projector. Likewise, it will be noted that the region inside of the pyramid-shaped barrier is not directly monitored. However, it is very unlikely, and perhaps virtually impossible, for a person to enter into the harmful region of the laser projector without passing through one or more of the predefined fields forming the wall of the pyramid-shaped barrier around the harmful region. Again, when an intrusion is detected, the laser projector  30  may switch to one of a number of safe operating modes as explained above. 
         [0059]    Referring now to  FIGS. 11-14 , there is depicted another illustrative embodiment of the present disclosure.  FIG. 11  illustrates a perspective view of an exemplary laser projector  50  mounted in an enclosure  52  (as indicated above the particular shape and configuration of the enclosure is not crucial to the operation of the present system and method). The laser projector  50  includes a projection lens  54 . Four (4) IR scanners  56 A,  56 B,  56 C and  56 D are disposed around the lens  54 . 
         [0060]    Still referring to  FIGS. 11-14 , each of the IR scanners  56 A,  56 B,  56 C and  56 D monitor a region comprising four (4) predefined monitored regions. In particular, each of the predefined monitored regions of the IR scanners  56 A,  56 B,  56 C and  56 D are substantially rectangular in shape and extend upwardly and parallel to a central axis of the projection path of the laser projector  50 . The predefined monitored regions for the IR scanners  56 A,  56 B,  56 C and  56 D roughly form a four-walled unobtrusive/invisible barrier  60  around the lens  54  in the form of a “chimney.” Each of the “walls” of the “chimney” is formed by one of the predefined monitored regions, and extends upwardly from the enclosure  52  and towards the projection screen. Each of the “walls” of the chimney may be substantially parallel to an opposing “wall” and substantially perpendicular to an adjacent “wall.” It will be noted that the top end of the four-walled unobtrusive/invisible barrier  60  formed by the predefined monitored regions of the IR scanners  56 A,  56 B,  56 C and  56 D may be open or unmonitored. But again, it is unlikely that a person or object will enter from the direction of the dome screen or other surface upon which an image is projected. 
         [0061]    It will be understood that the monitored regions of the IR scanners  56 A,  56 B,  56 C and  56 D may extend to a height greater than the harmful region of the laser projector  50 , but not all of the way to the surface upon the image is projected, such as the dome. Alternatively, the height of the monitored region formed from the four (4) monitored regions may only extend to that height necessary to ensure protection from harmful exposure to laser radiation. 
         [0062]    As mentioned, the monitored regions of the IR scanners  56 A,  56 B,  56 C and  56 D may roughly form a chimney shape with an unmonitored interior. Again, it will be understood that the laser accessible region (taking the form of a cone—see  FIGS. 12-13 ) may be larger than the region monitored by the IR scanners  56 A,  56 B,  56 C and  56 D. In fact, it is entirely possible, and intentional, that a person is able to come into direct contact with laser light from the projection system  50  without triggering a switch to safe mode. When any of the IR scanners  56 A,  56 B,  56 C and  56 D detect an intrusion into a monitored region, however, the laser projector  50  may immediately and automatically switch to one of the safe operating modes as previously described. 
         [0063]    Referring now to  FIGS. 11 and 12 , where like reference numerals depict like components, a projection cone  64  from the lens  54  is shown in relation to the unobtrusive/invisible barrier  60 . In particular, the predefined monitored regions of the four (4) IR scanners  34 A,  34 B,  34 C and  34 D completely enclose a harmful region  62 , indicated by the diagonally lined area, of the laser projector  50 . It will be noted, however, that the four (4) IR scanners  56 A,  56 B,  56 C and  56 D scan an area less than the area accessible by the projection lasers of the projector  50 . That is, the barrier  60  does not monitor the entire area accessible by the projection lasers of the projector  50  and the IR scanners  56 A,  56 B,  56 C and  56 D monitor less than all of the area of the projection cone  64  for an intrusion. 
         [0064]    Further, it will be noted that the region inside of the invisible barrier  60  is not necessarily directly monitored. However, it will be observed that it is very unlikely, and perhaps virtually impossible, for a person or other object to enter into the harmful region  62  of the projector  50  without passing through one or more of the predefined monitored regions of the IR scanners  56 A,  56 B,  56 C and  56 D. Again, when an intrusion of barrier  60  is detected, the laser projector  50  may switch to one of a number of safe operating modes as explained above. 
         [0065]      FIG. 14  illustrates the full scanning ranges of the IR scanners  56 A,  56 B,  56 C and  56 D in relation to the laser projector  50 . As seen in  FIG. 11 , the full scanning ranges of the IR scanners  56 A,  56 B,  56 C and  56 D are purposely limited to only the predefined monitored regions as shown in  FIGS. 11-13 . 
         [0066]    It will be noted that the barriers  40  and  60  described above define three-dimensional shapes formed by the planar regions scanned by IR scanners. These three-dimensional shapes extend into the laser accessible regions of a laser projection system, but do not encompass all of the laser accessible regions. It will be appreciated that the invisible safety barrier may take the form of any three-dimensional shape in accordance with the present disclosure. A suitable invisible barrier in accordance with the present disclosure need not completely enclose a harmful region formed by projection lasers, but may only bound the harmful region on at least three sides. Indeed, a safety barrier in accordance with the present disclosure extends into a laser accessible region for a laser projection system and bounds a harmful region in the laser accessible region on at least three sides. It will be further appreciated that a safety barrier in accordance with the present disclosure may not monitor the entire laser accessible region for a projection laser. Instead, some of the laser accessible region may be unmonitored. 
         [0067]    It will be noted that in the exemplary embodiments of the present disclosure described herein, that is that it is very unlike, and perhaps virtually impossible, for a person to enter the hazardous area created by the projection lasers from behind the laser projector due to the placement of the IR scanners. The enclosure or housing for the laser projector may serve as a physical barrier to prevent such an intrusion. Furthermore, other physical barriers may be utilized to prevent a person from crawling or otherwise entering the hazardous area. 
         [0068]    The IR scanners discussed herein may take the form of programmable IR laser scanners. One suitable commercially available IR scanner can be selected from the S3000 family of Safety Laser Scanners manufactured by SICK AG, Erwin-Sick-Str. 1, D-79183 Waldkirch, Germany. Further information regarding the S3000 family of Safety Laser Scanners can be found at the following universal resource locator addresses all of which are incorporated herein by this reference in the form they exist as of May 19, 2008: 
         [0000]    
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/en.html 
               
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/s3000/en.html 
               
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/s3000/s3000professional/en.html 
               
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/s3000/s3000advanced/en.html 
               
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/s3000/s3000standard/en.html 
               
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/s3000/s3000remote/en.html 
               
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/s3000/s3000professionalcms/en.html 
               
               
                   
                 http://www.sick.com/home/factory/catalogues/safety/espe 
               
               
                   
                 /laserscanner/s30000/en.html 
               
               
                   
                 http://www.mysick.com/saqqara/view.aspx?id=IM0012598 
               
               
                   
                   
               
             
          
         
       
     
         [0069]    It will be appreciated that scanners other than the IR scanners disclosed herein may be used in accordance with the present invention and that any number of different devices, now know or know in the future, used to detect the presence of an object within a predefined field can also be used within the scope of the present invention. In particular, such scanner or detectors may operate using any number of different wavelengths of energy, or any combinations thereof, including ultrasonic energy. 
         [0070]    In the foregoing Detailed Description, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this Detailed Description of the Disclosure by this reference, with each claim standing on its own as a separate embodiment of the present disclosure. 
         [0071]    It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present disclosure and the appended claims are intended to cover such modifications and arrangements. Thus, while the present disclosure has been shown in the drawings and described above with particularity and detail, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.