Abstract:
Devices and methods for providing sensor indication are disclosed. The sensor device includes utilizing the signal to activate a light source, transmitting light into a first indicator layer with the light source, and the first indicator layer optionally includes a fluorophore. The indicator layer provides visibility of light around the sensor device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to application entitled “METHOD AND DEVICE FOR ENHANCING SENSOR INDICATION” having Ser. No. 13/360,367, filed Jan. 27, 2012, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to the field of sensors and, more particularly, to methods and devices for enhancing the visibility of sensor indicators. 
       TECHNICAL BACKGROUND 
       [0003]    Industrial sensors are commonly used in a wide variety of applications and environments. Industrial sensors, such as proximity, optical and photoelectric sensors, can be used to detect the presence or absence of targets on a conveyor belt. In addition, industrial sensors can be used to monitor various components of process machinery. Industrial sensors often use one or more light sources that serve as indicators to convey a status signal, such as power, output, or margin, to an end user during set-up and operation. Light from the light source is often conveyed through a light pipe or similar optical structure serving to guide the light to the external environment. The light source is often colored or projected through a colored lens to emit colored light, often green, yellow, orange, or red. The visibility of these light-guide-coupled light sources is often poor, particularly when viewed from a large off-center angle, such as when the sensor is mounted above a viewing angle of the end-user. With the light source typically mounted on a PCB inside the sensor enclosure, much of the light source&#39;s light intensity is either reflected, scattered, or absorbed before it makes its way to the external environment to be viewed. The result is that the sensor&#39;s indicator lights appear relatively dim and so for proper viewing an end-user may desire to move close to the sensor to view the indicators. Additionally, achieving a uniform illumination that is visible from all around the perimeter of the sensor is also problematic. 
         [0004]    Furthermore, some industrial sensors, such as proximity sensors, often have a light source that is encapsulated in an epoxy potting material within the sensor housing. The light that is visible from the light source embedded in the potting is often faint as the majority of the light that is produced by the light source is either scattered or absorbed by the potting, preventing that light from escaping to the external environment where it can be viewed. 
         [0005]    Various solutions have been tried to address poor sensor indicator visibility, such as selecting brighter (and possibly larger) light source components, increasing the electrical current supplied to the light source, and using physical optical structures such as prisms, light pipes, textured surfaces, polished surfaces, and facets. Although the aforementioned methods can increase indicator visibility, they include various drawbacks, such as more expensive parts, additional part processing, increased electric load on a base circuit, and increased housing size to accommodate larger parts or additional structures. 
         [0006]    Therefore, it would be advantageous if an improved device or method for enhancing the visibility of sensor indicators could be developed that would allow one or more of the drawbacks discussed above and/or one or more other drawbacks to be entirely or at least partly overcome. 
       SUMMARY 
       [0007]    In at least some embodiments, a sensing device with enhanced sensor indication includes, a first indicator layer including a substrate having a top surface, a bottom surface, and end walls situated at least partially between the perimeters of the top surface and the bottom surface, wherein the first indicator layer is at least one of transparent and translucent, one or more fluorophores embedded in the indicator layer, a first light source for transmitting light into the indicator layer, wherein the transmitted light is reflected inside the indicator layer and absorbed by the fluorophore to generate enhanced light that is emitted from the end walls, wherein the enhanced light includes the light transmitted from the first light source with at least one characteristic modified by the fluorophore, a sensing circuit, and a housing for at least partially enclosing the first light source, the sensing circuit, and the first indicator layer. 
         [0008]    In at least some other embodiments, a sensing device with enhanced sensor indication includes, a first indicator layer including a substrate having a first top surface, a first bottom surface, and first end walls situated at least partially between the perimeters of the first top surface and the first bottom surface, wherein the first indicator layer is at least one of transparent and translucent, a second indicator layer including a substrate having a second top surface, a second bottom surface, and second end walls situated at least partially between the perimeters of the second top surface and the second bottom surface, wherein the second indicator layer is at least one of transparent and translucent. The sensing device further includes, a center barrier positioned between the first indicator layer and the second indicator layer, wherein the center barrier at least partially limits the passage of light between the first and second indicator layers, one or more fluorophores embedded in the first and second indicator layers, a first light source for transmitting light into the first indicator layer wherein the light is transmitted inside the first indicator layer and absorbed by the fluorophore to generate first enhanced light that is emitted from the first end walls, wherein the first enhanced light includes the light transmitted from the first light source with at least one characteristic modified by the fluorophore. The sensing device still further includes, a second light source for transmitting light into the second indicator layer wherein the light is transmitted inside the second indicator layer and absorbed by the fluorophore to generate second enhanced light that is emitted from the second end walls, wherein the second enhanced light includes the light transmitted from the second light source with at least one characteristic modified by the fluorophore, a passage extending through at least the first indicator layer, a sensing circuit, and a housing for at least partially enclosing the first and second light sources, the sensing circuit, and the first and second indicator layers. 
         [0009]    In at least yet some other embodiments, a method of providing a sensor indication includes, sensing an operational status at a sensor circuit, generating a signal at the sensor circuit based on the sensed operational status, utilizing the signal to activate a light source, transmitting light into a first indicator layer with the light source, wherein the first indicator layer includes a fluorophore embedded within a substrate, and wherein the fluorophore modifies at least one characteristic of the transmitted light from the light source, and emitting the modified transmitted light from an end wall of the first indicator layer. 
         [0010]    In one or more embodiments, a sensing device includes at least one indicator layer including a first indicator layer having a top surface, a bottom surface, and one or more end walls at least partially between the perimeters of the top surface and the bottom surface, and the end wall circumnavigates the housing such that the indicator layer is viewable 360 degrees around the housing. A first light source disposed near the indicator layer, and a housing is at least partially enclosing the first light source, and the first indicator layer. In one or more embodiments, the at least one indicator layer extends along an edge of at least one of a top, bottom, side surface of the housing and transitions away from the edge and toward an intermediate portion of the outer housing. 
         [0011]    In one or more embodiments, a sensing device includes a housing having an outer perimeter, a first indicator layer including a substrate having a first top surface, a first bottom surface, and first end wall is at least partially between the perimeters of the first top surface and the first bottom surface. The first indicator layer is at least partially disposed within the housing, the first end wall substantially disposed around the housing outer perimeter. The sensing device further includes a second indicator layer including a substrate having a second top surface, a second bottom surface, and one or more second end walls is at least partially between the perimeters of the second top surface and the second bottom surface. A center barrier is positioned between the first indicator layer and the second indicator layer, wherein the center barrier at least partially limits the passage of light between the first and second indicator layers, and a light source is disposed near the first indicator layer and the second indicator layer. 
         [0012]    In one or more embodiments, a method of providing indication for a sensing device includes sensing an operational status at a sensor circuit, generating a signal at the sensor circuit based on the sensed operational status, utilizing the signal to activate a light source, transmitting light into a first indicator layer with the light source, emitting light from an end wall of the first indicator layer, the end wall disposed along a perimeter of the sensing device, and is viewable around a perimeter of the sensing device. 
         [0013]    Other embodiments, aspects, features, objectives, and advantages of the present invention will be understood and appreciated upon a full reading of the detailed description and the claims that follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Embodiments of the invention are disclosed with reference to the accompanying drawings and are for illustrative purposes only. The invention is not limited in its application to the details of construction or the arrangements of components illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various other ways. Like reference numerals are used to indicate like components. In the drawings: 
           [0015]      FIG. 1  is a perspective view of an exemplary sensor with an indicating capability; 
           [0016]      FIG. 2  is a perspective view of one exemplary embodiment of an indicator layer and a light source; 
           [0017]      FIG. 3  is a perspective view of another exemplary embodiment of an indicator layer and a light source; 
           [0018]      FIG. 4A  is a perspective view of an exemplary printed circuit board with a light source and another exemplary embodiment of an indicator layer; 
           [0019]      FIG. 4B  is a perspective view of the printed circuit board and an indicator layer of  FIG. 4A , subsequent to installation of the former into the latter; 
           [0020]      FIG. 4C  illustrates a cross-section of the printed circuit board and indicator layer of  FIG. 4B  taken along line  4 C- 4 C thereof; 
           [0021]      FIG. 5  is a perspective view of yet another exemplary embodiment of a printed circuit board and indicator layer; 
           [0022]      FIG. 6A  is a side view of a portion of an exemplary indicator layer, 
           [0023]      FIG. 6B  is a top view of an indicator layer that includes the portion of  FIG. 6A ; 
           [0024]      FIG. 7A  is a partially cut-away perspective view of an exemplary sensor; 
           [0025]      FIG. 7B  is a partially cut-away perspective view of the sensor of  FIG. 7A , with a printed circuit board installed in an indicator layer; 
           [0026]      FIG. 7C  illustrates a cross-section of the sensor of  FIG. 7B , taken along line  7 C- 7 C thereof; 
           [0027]      FIG. 8  is a partially cut-away perspective view of a cross-section of another exemplary embodiment of the sensor; 
           [0028]      FIG. 9  is a partial view of yet another embodiment of a sensor, shown in cross-section; 
           [0029]      FIG. 10  is a partial view of still another embodiment of a sensor, shown in cross-section; 
           [0030]      FIG. 11  is a partial view of still yet another embodiment of a sensor, shown in cross-section; 
           [0031]      FIG. 12A  is a perspective view of a further embodiment of a sensor; 
           [0032]      FIG. 12B  is a cross-sectional view of the sensor of  FIG. 12A , taken along line  12 B- 12 B thereof; 
           [0033]      FIG. 13A  is a perspective view of another embodiment of a sensor, configured as a proximity sensor; 
           [0034]      FIG. 13B  is a partial top view of the sensor of  FIG. 13A ; 
           [0035]      FIG. 13C  is a cross-sectional view of the sensor of  FIG. 13B , taken along line  13 C- 13 C thereof; 
           [0036]      FIG. 14  is a perspective view of another embodiment of a sensor, configured as a photoelectric sensor; 
           [0037]      FIG. 15  is a perspective view of an exemplary sensor in a thin-profile embodiment; 
           [0038]      FIG. 16  is a perspective view of an exemplary sensor in a large-profile embodiment; 
           [0039]      FIG. 17A  is a perspective view of an exemplary sensor with limited-view indicator layers; 
           [0040]      FIG. 17B  is a partial cross-sectional view of  FIG. 17A  taken along line  17 B- 17 B thereof; 
           [0041]      FIG. 17C  is another partially cut-away, cross-sectional view of the sensor of  FIG. 17A ; 
           [0042]      FIG. 18  is an isometric view of a sensor device in accordance with one or more embodiments; 
           [0043]      FIG. 19  is an isometric view of a sensor device in accordance with one or more embodiments; 
           [0044]      FIG. 20  is a side view of a sensor device in accordance with one or more embodiments; 
           [0045]      FIG. 21  is a side view of a sensor device in accordance with one or more embodiments; 
           [0046]      FIG. 22  is an exploded view of a sensor device in accordance with one or more embodiments; 
           [0047]      FIG. 23  is an exploded view of a sensor device in accordance with one or more embodiments; 
           [0048]      FIG. 24  is an exploded view of an indicator component in accordance with one or more embodiments; and 
           [0049]      FIG. 25  is a cross-sectional view of an indicator component in accordance with one or more embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0050]      FIG. 1  depicts an exemplary sensor  100  having an indicating ability. The sensor  100  includes a housing  102 , an indicator layer  104 , and a mounting portion  106 . The housing  102  is configured to at least partially enclose the indicator layer  104  and a light source  107 . The light source  107  provides light to illuminate the indicator layer  104  to provide an indication based on the sensing of an event at the sensor  100 . The sensor  100  can include one of various types of sensing circuits  108  for providing an output to energize the light source  107  when desired conditions are met. Such sensing circuits  108  are commonly found, for example, in proximity sensors and photosensors. 
         [0051]    Referring to  FIG. 2 , one exemplary embodiment of the indicator layer  204  and the light source  207  are shown. The light source  207  serves to provide illumination to the indicator layer  204  and can include one or more of various source of light, for example, an incandescent light bulb, an LED, and an OLED. The indicator layer  204  includes a substrate having a top surface  210 , a bottom surface  212 , and a plurality of end walls  214  forming a layer perimeter  215 . The indicator layer  204  includes, in at least some embodiments, a substrate with embedded and/or enclosed fluorophores, as discussed further below. The fluorophore may consist of a fluorescent dye, nano-phosphor, or quantum dot. As seen in  FIG. 2 , the light source  207  can be positioned to direct light through the top surface  210  of the indicator layer  204 . Light received into the top surface  210  of the indicator layer  204  is reflected and affected by the fluorophore to establish enhanced light  216 . More particularly, the fluorophore absorbs the light received from the light source  207  and, upon absorption, the wavelength of the light is both shifted along the electromagnetic spectrum from a higher energy, shorter wavelength to a lower energy, longer wavelength and scattered in many directions to increase the visibility of the light to the human eye from various observation directions. Furthermore, the overall size of the surfaces  210 ,  212  is greater than the height of the end walls  214  such that the enhanced light  216  produces an intensified image along the perimeter  215  of the end walls  214  as it is emitted from the indicator layer  204 . 
         [0052]    As the top surface  210  and/or bottom surface  212  of the indicator layer  204  can be at least partially enclosed by a housing, such as housing  102 , to maximize visibility the enhanced light  216  is directed to the typically exposed end walls  214  forming the layer perimeter  215 . Depending on the surface configuration used for the indicator layer  204 , the amount of enhanced light  216  (after being established within the indicator layer) that passes through the top surface  210  and the bottom surface  212 , and therefore does not reach the end walls  214  (i.e., light losses), can be minimized. For example, when the indicator layer  204  is configured in a sheet or sheet-like form where the top and bottom surfaces  210 ,  212  are highly polished, such as to an SPI-A3 or better finish, so as to produce internal reflections, the enhanced light  216  is predominantly reflected internally towards the end walls  214  of the indicator layer  204 . In addition, as the enhanced light  216  is internally reflected within (e.g., internally reflected off the top and bottom surfaces  210 ,  212 ) the indicator layer  204  and communicated to the end walls  214 , it becomes more concentrated and thereby produces a bright glowing effect along the end walls  214  as the enhanced light  216  is emitted from the indicator layer  204 . This glowing effect is known as an “edge-glow” effect. 
         [0053]    The end walls  214  are shown orthogonal to the plane of the top surface  210  and bottom surface  212 , which are parallel to one another, to maximize illumination from the end walls  214 , although the end walls  214  can be positioned at various other angles relative to the top surface  210  and/or bottom surface  212  (which need not always be parallel to one another), as discussed below. To maximize the “edge-glow” effect, the indicator layer  204  can be comprised of a transparent material to maximize internal reflections. In at least some embodiments, the indicator layer  204  can include a transparent, semi-transparent, and/or translucent material, such as acrylic (PMMA), polycarbonate (PC), styrene-acrylonitrile (SAN), or polystyrene (PS), although other materials with varying transparency levels can be used as well, such as glass. In other embodiments where nano-phosphors or quantum dots are used, the indicator layer  204  can include these compounds in its bulk, embodied in an attached or applied layer at least partially covering the outer surface around the indicator layer  204 . The nano-phosphors and quantum dots are fluorophores that absorb energy emitted by the light source  207  and re-emit that energy at random angles and at specified wavelengths defined by the fluorophore&#39;s size. One benefit of using nano-phosphors or quantum dots is their inherent efficacy in wavelength conversion between the emission of the light source  207  and the desired output color. Another benefit is that a sensor can be standardized in form and function and then specialized by the addition of the nano-phosphor or quantum dot layers and surfaces. Yet another benefit is that the nano-phosphor or quantum dots can be spatially constructed to impart information about a sensor such as a logo, part number, and operational-state data, without having to add these features into the molded part. In this regard, the indicator layer  204  and/or a display layer  110  (see  FIG. 1 ) can be utilized in one or more embodiments to display the sensor information, wherein the display layer  110  would be visible through a sensor housing, such as housing  102 , and sized to accommodate the information as necessary and/or desired. 
         [0054]    Further, to increase the uniformity of illumination along the end walls  214 , a diffuse light source can be employed as the light source  207 . Also, applying a texture, such as a Charmilles #30 or Mold-Tech® MT-11520, to the end walls  214  can assist with producing a generally uniform and diffuse “edge-glow” effect. The fluorophore can be of any conventional, commercially-available fluorescent dye, nano-phosphor, or quantum dot that is suitable for absorbing and enhancing light and capable of being embedded in the indicator layer  204 . 
         [0055]    Referring to  FIG. 3 , an LED-based light source  307  is depicted emitting light into an indicator layer  304  through an end wall  314 , as opposed to through a top surface  310 , as discussed above. The use of an LED-based light source provides a powerful, yet efficient light source. In addition, an LED-based light source can allow for various options for coloring the light prior to entering the indicator layer  304 , and therefore changing the color of resultant enhanced light  316 . However, the use of fluorophores in the indicator layer  304  allows for a variety of color choices for the enhanced light  316  without requiring a light source  307  that emits a specific color. For example, a white, blue, or UVLED can be used as the light source  307  with an appropriate fluorophore to produce a desired color. By utilizing different fluorophores in an indicator layer  304  or multiple indicator layers  304 , a pair of LEDs having the same color can be used as light sources  307  to generate different color indications that are illuminated from the end walls  314 . In this manner, various types of sensors  300  can be mass-produced using a single color LED to supply all the light sources  307 , thus avoiding the need to stock and install various different light source parts. Furthermore, in some cases, if a longer wavelength, lower energy LED, such as an orange LED, were used to illuminate an indicator layer  304  consisting of a fluorophore that is excited by longer wavelength, higher energy light than is emitted by the orange LED, such as a yellow fluorophore for example, the result would be that the orange LED would not excite the yellow fluorophore and the indicator layer would appear to be a hue of orange. By combining this approach with the use of two LED&#39;s, one that excites the yellow fluorophore, such as a blue LED, and one that does not, such as an orange LED, it is possible to obtain the emission of two distinct colors from a single indicator layer  304  provided that the LED&#39;s are turned on individually and not at the same time. 
         [0056]    Referring now to  FIGS. 4A-4C , another embodiment of the indicator layer  404  is depicted. The indicator layer  404  includes a recess  420  forming a plurality of inner walls  422  about a center portion  424 . Although the recess  420  is depicted as extending through the top surface  410  and not through the bottom surface  412 , in at least some embodiments, the recess  420  can be an orifice that extends through the bottom surface  412  as well. Light sources  407  are provided on each of a first side  426  and second side  428  of a printed circuit board (PCB)  430 . The light sources  407  are in at least some embodiments surface mounted LED&#39;s and are positioned on the PCB  430  to fit at least partially inside the recess  420  formed in the indicator layer  404 . The PCB  430  includes a light source driver circuit (not shown) configured to illuminate one or both of the light sources  407 . 
         [0057]    As seen in  FIGS. 4B and 4C , with the PCB  430  installed in the recess  420  the light sources  407  are positioned to transmit a substantial portion of their light directly into the indicator layer  404 . As discussed above, light emitted from the light sources  407  is passed through the inner walls  422  and absorbed by the fluorophore in the indicator layer  404  to generate enhanced light  416  that is transmitted through the indicator layer  404  and emitted out of the end walls  414  of the indicator layer  404 . In addition, with the light sources  407  positioned in the center portion  424  and on the first and second sides  426 ,  428  of the PCB  430 , enhanced light  416  can be effectively emitted from each of the end walls  414  that surround the indicator layer  404  to provide light that is visible from all sides. Alternatively, only one light source  407  can be used to provide illumination along a first side  434  of the indicator layer  404 . 
         [0058]    In at least some embodiments, the recess  420  can be at least partially filled with a transparent or translucent potting material  438 , such as epoxy, to help couple the light from the light sources  407  into the inner walls  422  of the indicator layer  404 . The use of potting material  438  can reduce light losses and/or reduce or eliminate visible “hot-spots” created by the intensity of the light sources  407 . 
         [0059]    Referring to  FIG. 5 , yet another embodiment of the indicator layer  504  is depicted. It should be appreciated that, depending upon the embodiment, the indicator layer  504  can be configured to include various shapes and sizes to provide an indicator layer  504  that is shaped and sized to accommodate various types of sensors. For example, as seen in  FIG. 5 , the indicator layer  504  in one embodiment is configured to include a first portion  540  connected to a second portion  542  that ramps up to a third portion  544 . The PCB  530  includes a single LED light source  507 , although other types and quantities of light sources  507  can be provided in this embodiment, as well as other embodiments discussed herein. 
         [0060]    Once the PCB  530  is inserted into the recess  520  of the indicator layer  504  and the light source  507  is energized, light is passed into the indicator layer  504  through the inner walls  522  and reflected inside the indicator layer  504  as enhanced light  516 . The enhanced light  516  is reflected inside the indicator layer  504  so as to proceed through each portion  540 ,  542 ,  544  and so as to be emitted from each of the end walls  514 , although not equally, to provide a sensor indicator with illumination substantially along all of the end walls  514  to provide visibility around the perimeter of the sensor. Visibility could be enhanced by providing an additional light source  507  on the opposite side of the PCB  530 . 
         [0061]    Referring now to  FIG. 6A , a portion of an indicator layer  604  (such as shown in  FIG. 2 ) is shown with an end wall  614  at an angle β that is not orthogonal to a top surface  610  of the indicator layer  604 . As noted above, maximum light is emitted from the end walls  614  when they are orthogonal to the top surface  610 . By positioning the end wall  614  at a non-orthogonal angle, enhanced light  616  is emitted from both the end wall  614  and an end portion  646  of the top surface  610 . More particularly, because of the angle of the end wall  614 , at least a portion of the enhanced light  616  that contacts the end wall  614  is reflected upwards to the end portion  646  to provide a partial illumination of the top surface  610 . Referring to  FIG. 6B , with each of the end walls  614  having an angle β that is at about 135 degrees, a top surface perimeter  648  that includes the end portions  646  is illuminated, while an interior portion of the top surface  610  bounded by the top surface perimeter includes minimal or no illumination. Although the indicator layer  604  is shown in  FIG. 6B  as a square with equal angles β for each end wall  614 , in at least some embodiments, other indicator layer shapes and angles β can be provided (e.g., such that the top surface perimeter need not have a uniform width). 
         [0062]    Referring to  FIGS. 7A-7C , a partial view of another exemplary sensor  700  is shown with an indicator layer  704  secured to a housing  702 .  FIG. 7B  illustrates the PCB  730  and indicator layer  704  subsequent to installation of the former into the latter. As shown, the sensor  700  includes a bottom surface barrier  750  that is positioned at least partially under a bottom surface  712  of the indicator layer  704 . The bottom surface barrier  750  can include one or more of various materials configured to limit or prevent the loss of enhanced light  716  through the bottom surface  712 , thereby increasing the light intensity emitted from a plurality of end walls  714  of the indicator layer  704 . In at least some embodiments, the bottom surface barrier  750  can include an opaque, reflective substrate, while in other embodiments, the bottom surface barrier  750  can include a reflective coating applied to the bottom surface  712 . Similarly, in the present embodiment, a top surface  710  of the indicator layer  704  also includes a top surface bather  752  to limit or prevent the loss of enhanced light  716  through the top surface  710 . In at least one embodiment, the housing  702  of the sensor  700  extends at least partially across the top surface  710  to serve as the top surface bather  752 , although in other embodiments, the top surface bather  752  can be provided as a separate element from the housing  702 , similar to the bottom surface barrier  750 . Further, in at least some embodiments, the top surface bather  752  can include a reflective coating applied to the top surface  710 . Although both a top surface bather  752  and a bottom surface bather  750  are shown, in at least some embodiments only one or the other is provided. 
         [0063]    As shown in  FIG. 7C  (a cross-section of  FIG. 7B ), the light sources  707  mounted on the PCB  730  are positioned inside the recess  720  to transmit light into the inner walls  722 . When the light sources  707  are energized and light is transmitted through the inner walls  722 , the resultant enhanced light  716  is reflected within the indicator layer  704  towards the end walls  714 . Loss of the enhanced light  716  through the top surface  710  and the bottom surface  712  is limited by the bottom surface bather  750  and top surface bather  752 , which reflect the enhanced light back into the indicator layer  704 . Further as seen in  FIG. 7C , the housing  702  also includes a hole  756  for allowing the PCB  730  to pass therethrough. The recess  720 , as well as the hole  756 , can be filled with a transparent or translucent material, such as epoxy potting  738 , to help couple the light from the light sources  707  through the inner walls  722  and into the indicator layer  704 . 
         [0064]    Referring to  FIG. 8 , a partial view of another embodiment of the sensor  800  is shown in cross-section. The sensor  800  includes two indicator layers  804 , namely, a first indicator layer  860  having a first top surface  862  and a first bottom surface  864 , and a second indicator layer  866  having a second top surface  868  and a second bottom surface  870 . The first top surface  862  is secured to a housing  802 , which in this embodiment provides a top surface barrier  852 . A bottom surface barrier  850  is adhered to the second bottom surface  870 . In addition, a center barrier  872  is provided between the first bottom surface  864  of the first indicator layer  860  and the second top surface  868  of the second indicator layer  866 . The center barrier  872  is provided to limit or prevent first enhanced light  876  that is passed through the first indicator layer  860  from entering the second indicator layer  866 . Similarly, the center barrier  872  limits or prevents second enhanced light  878  that is passed through the second indicator layer  866  from entering the first indicator layer  860 . In this manner, the illumination of indicator layers  860 ,  866  can be independent of each other. The center barrier  872  can include a substrate comprised of an opaque metallized plastic, a metallic foil, reflective in-mold-label, or other suitable material that serves to limit or prevent the transmission of light therethrough. In addition to or in place of a substrate, the center barrier  872  can be comprised of a reflective coating that is applied to one or both of the first bottom surface  864  and the second top surface  868 . 
         [0065]    Light sources  807 , namely, upper light sources  880  and lower light sources  882  are positioned on a PCB  830  to direct light from the upper light sources  880  into the first indicator layer  860  and light from the lower light sources  882  into the second indicator layer  866 . One or more light source barriers  884  can be provided between the upper light sources  880  and the lower light sources  882  to prevent the passage of light therebetween. The light source barriers  884  in the present embodiment extend between the PCB  830  and the center barrier  872 , and can include foam or another suitable material to limit or prevent the transmission of light. 
         [0066]    Utilizing the configuration shown in  FIG. 8 , a single sensor  800  can provide multiple indications to an observer. For example, each indicator layer  860 ,  866  can be illuminated independently by energizing the upper light sources  880  and the lower light sources  882 , respectively, based on different criteria. In addition, the first indicator layer  860  can incorporate a fluorophore that is different in color from the fluorophore that is incorporated into the second indicator layer  866 , thereby providing additional discriminating indications, such as a green light source to indicate a machine is “on” and a red light source to indicate the machine is “off.” In addition, the light sources  880 ,  882  can be of a single color, while the color of the fluorophores in the indicator layers  860 ,  866  can be varied. In addition, in at least some embodiments, more than one light source  807  can be provided on each side of the PCB  830  for each indicator layer  804 . 
         [0067]    Further, although only one center barrier  872  is shown with two indicator layers  804  and four light sources  807 , multiple center barriers  872  and/or multiple light sources  807  can be provided and positioned between two or more indicator layers  804  to provide a greater quantity of indications for view by an observer. This holds true for various other embodiments described herein. 
         [0068]    Referring to  FIG. 9 , a partial view of yet another embodiment of the sensor  900  shown in cross-section is provided. The sensor  900  in  FIG. 9  is similar to the sensor  800  shown in  FIG. 8 , with the exception that the center barrier  972  does not extend to the end walls  914  of each of the first and second indicator layers  960 ,  966 . This allows the center barrier  972  to be completely encapsulated by the first and second indicator layers  960 ,  966  at the end walls  914 . Such a configuration is particularly advantageous in industrial settings, when the material composition of the center barrier  972  is less chemically resistant than the material composition of the first and second indicator layers  960 ,  966 . Furthermore, sealing the center barrier  972  and both of the first and second indicator layers  960 ,  962  adjacent the end walls  914  can be less efficient and less durable than forming a hermetic joint  973  by joining the materials that make up the first and second indicator layers  960 ,  966  (which can be similar or identical). A hermetic joint can be achieved between the first and second indicator layers  960 ,  966  using any of a variety of methods, such as overmolding, two-shot molding, solvent bonding, adhesive bonding, laser welding, and ultrasonic welding. 
         [0069]    Joining the first and second indicator layers  960 ,  966  at the end walls  914  can allow for some crosstalk of light therebetween, although minimizing the distances between the outer ends of center barrier  972  and the end walls  914  can maintain an acceptable level of light intrusion. 
         [0070]    Referring to  FIG. 10 , a partial view of still another embodiment of the sensor  1000  is shown. In this embodiment, an indicator layer  1004  is positioned at least partially between a housing  1002  and a bottom surface barrier  1050 . A PCB  1030  with a light source  1007  mounted thereon is provided. The light source  1007  is positioned in a housing interior cavity  1074  as opposed to a recess, as discussed above. When the light source  1007  is energized, light from the light source  1007  enters the indicator layer  1004  and enhanced light  1016  is generated that reflects to the end walls  1014  to produce an “edge-glow” effect. The housing interior cavity  1074  can be filled partially or in its entirety with a transparent/translucent material such as an epoxy potting  1038  as is common practice for many types of sensors. 
         [0071]    Referring to  FIG. 11 , a partial view of still yet another embodiment of the sensor  1100  is shown. In this embodiment, first and second indicator layers  1160 ,  1166  are situated between a housing  1102  and a bottom surface barrier  1150 . The indicator layers  1160 ,  1166  are separated by a center barrier  1172 . A pair of light sources  1107 , namely a first light source  1180  and a second light source  1182 , are mounted on a cover portion  1190  that is part of or connected to a PCB  1130 . The cover portion  1190  is positioned in the housing  1102  such that it rests against the first top surface  1162 . 
         [0072]    The first light source  1180  is positioned by the PCB  1130  to provide illumination to a first cavity  1192  formed at least in part by the first indicator layer  1160 , the center barrier  1172 , and the cover portion  1190 . The configuration of the first cavity  1192  allows for light from the first light source  1180  to illuminate the first indicator layer  1160  (generating first enhanced light  1176 ) without illuminating the second indicator layer  1166 . A second cavity  1194  is formed at least in part by the second indicator layer  1166 , the cover portion  1190 , and one or more wall barriers  1196  extending therebetween. The wall bathers  1196  can include an opaque material, such as plastic, metal, or foam. 
         [0073]    As seen in  FIG. 11 , the first indicator layer  1160  and the center barrier  1172  do not extend into the second cavity  1194  and they are at least partially blocked from receiving light from the second light source  1182  by the wall barriers  1196 . This configuration allows light from the light source  1182  to illuminate the second indicator layer  1166  (generating second enhanced light  1178 ) while limiting or preventing this light from illuminating the first indicator layer  1160 . 
         [0074]    Referring now to  FIGS. 12A and 12B , a further embodiment of the sensor  1200  is shown, wherein the sensor  1200  is an inductive proximity sensor. The sensor  1200  includes a housing  1202 , a first and second indicator layer  1260 ,  1266 , and a mounting portion  1206 . Similar to the indicator layer  504  in  FIG. 5 , the first and second indicator layers  1260 ,  1266  include multi-planar portions. Also similar to the embodiment of  FIG. 9 , the first and second indicator layers  1260 ,  1266  are partially separated by the center barrier  1272  and include multiple first and second light sources  1280 ,  1282  positioned on a PCB  1230  to allow for substantially independent illumination of the layers  1260 ,  1266 . As discussed above, this configuration provides a sensor that is capable of multiple indications that are visible to an observer from multiple viewing positions. In addition, the end walls  1214  of the first and second indicator layers  1260 ,  1266  are joined to at least partially encapsulate the center barrier  1272 . Also, the PCB  1230  is shown secured to a coil assembly  1231 . 
         [0075]    Referring to  FIGS. 13A-13C , another embodiment of the sensor  1300  is depicted, wherein the sensor  1300  is a proximity sensor having an elongate cylindrical housing  1302  with external threads  1303  to which complementary mounting nuts (not shown) can be threaded. A sensing face  1305  is located at a first end  1301  of the housing  1302  to permit the associated circuitry (not shown) within the housing  1302  to perform a proximity sensing function through the sensing face  1305 , as is known in the art. An annular indicator layer  1304  is provided to convey a status indication, such as to indicate “power on” or “object sensed.” A connector port  1309  is located opposite the sensing face  1305  to provide a means for powering the sensor  1300 . 
         [0076]    In at least some embodiments, the indicator layer  1304  is positioned adjacent to the connector port  1309 . The housing  1302 , indicator layer  1304 , and connector port  1309  are secured together, for example, by means of a press fit or adhesive. A PCB  1330  is situated inside the housing  1302  and includes a light source  1307  mounted thereon. Connector pins  1311  situated inside the connector port  1309  are connected to the PCB  1330  by wires  1313 . When energized, light from the light source  1307  enters the indicator layer  1304  to produce enhanced light  1316  that is emitted from the circumferential end wall  1314  of the indicator layer  1304  to provide an “edge-glow” effect that can be viewed radial-symmetrically around the sensor  1300 . A housing interior  1315  of the housing  1302  can be filled with a transparent or translucent potting compound  1336 . Although this embodiment is shown with a single light source  1307  and a single indicator layer  1304 , more than one indicator layer  1304  and light source  1307  can be provided utilizing at least some configurations of the various embodiments described above. 
         [0077]    Referring to  FIG. 14 , still another embodiment of the sensor  1400  is depicted, wherein the sensor  1400  is a photoelectric sensor. The sensor  1400  includes a housing  1402  with sensing optics  1417  and associated circuitry (not shown) to perform a photoelectric sensing function through the optics  1417 , as is known in the art. The housing  1402  has integral mounting holes  1419 . The mounting holes  1419  can be internally threaded and can take the form of slots. Although depicted as being located adjacent the optics  1417 , it should be noted that the mounting holes  1419  can be located in various locations about the sensor  1400  and can vary in quantity. First and second indicator layers  1460 ,  1466  can be provided. In at least some embodiments, the indicator layers  1460 ,  1466  are configured similar to as shown and described with reference to  FIG. 9 . Light losses from the indicator layers  1460 ,  1466  can be limited or prevented by a top surface barrier  1452 . Further, back corners  1423  of the housing  1402  can be chamfered to allow for light from the end walls  1414  to be viewable from above as well as around the sensor  1400 . A cable  1425  or other power connection can be provided to supply power to the sensor  1400 . 
         [0078]    Referring to  FIGS. 15 and 16 , a thin-profile embodiment of the sensor  1500  and a large-profile embodiment of the sensor  1600 , respectively, are shown. As illustrated, the size of the sensors can vary to accommodate a particular application. Further, referring to  FIGS. 17A-17C , in at least some embodiments, end walls  1714  of indicator layers  1704  can be partially blocked by a housing  1702 . This configuration can serve to increase the intensity of the enhanced light emitted from the exposed end walls  1714 . In addition, the indicator layers  1704  can be used to convey light from a light source  1707  that is not or cannot be positioned close to the desired portion of the housing  1702  to provide sufficient illumination to be accurately detected by an observer. 
         [0079]    Further, the indicator layer  1704  in at least some embodiments can include standard fluorophores, such as nanophosphors or quantum dots in high volumes positioned close to the exterior surface  1714  of the indicator layers  1704 , by applying them onto the exterior surface  1714 , such as by painting. In other embodiments, an inner groove  1709  can be situated inside the indicator layer  1704  and in close proximity to a layer perimeter  1715  of the indicator layer  1704 . Groove side walls  1711  can be deposited with the nanophosphor or quantum dot material to illuminate the layer perimeter  1715  through the end walls  1714 , without exposing the nanophosphor or quantum dot material to the external environment. Situating the nanophosphor or quantum dot material in high volumes close to the exterior surface  1714 , as described, can be performed on other indicator layers discussed herein as well. This placement of the nanophosphor or quantum dot material allows for a conduction of light from the light source to the fluorescent volume where the emission of the desired color is generated with the added benefit of scattering light into higher angles to improve visual output of the indicator layer. For example, when a sensor incorporates the nanophosphor or quantum dot material in high volumes close to the exterior surface  1714  and the sensor is mounted at a height that exceeds the eye level of an end user, such that the end user has to look up at an angle to view the end wall  1714  of the sensor  1700 , for example, an angle greater than about 45 degrees but less than about 90 degrees relative to horizontal, the added brightness produced by the higher volume close to the exterior surface provides improved visibility of the illumination of the indicator layer  1704 . In addition to improved visibility, color differentiation between multiple indicator layers can be improved as well. 
         [0080]      FIGS. 18-21  illustrate a sensing device  1800 , such as a proximity sensor, that includes one or more indicators, as constructed in one or more embodiments. The sensing device includes a housing  1810  with one or more indicator layers  1820 , where the housing  1810  is configured to at least partially enclose the indicator layers  1820  and a light source  1808 . In one or more embodiments, the sensing device  1800  includes an indicator component  1818  with two or more indicator layers  1820 , such as a first indicator layer  1830  ( FIG. 24 ), and a second indicator layer  1832  ( FIG. 24 ).  FIGS. 22 and 23  illustrate exploded views of examples of the sensing device  1800  according to one or more embodiments. The sensing device  1800  further includes one or more of a shield  1802 , bobbin  1804 , PCB  1806  including a sensing circuit, light source  1808 , indicator component  1818 , potting plug assembly  1819 , mounting structure  1850 , fasteners  1851 , or connector assembly  1816 . 
         [0081]    The light source  1808  ( FIG. 24 ) provides light to illuminate the indicator layers  1820  to provide an indication based on the sensing of an event by the sensing device  1800 . The sensing device  1800  can include one of various types of sensing circuits for providing an output to energize the light source  1808  when desired conditions are met. Such sensing circuits are commonly found, for example, in proximity sensors and photo sensors. 
         [0082]    Referring to  FIGS. 23-25 , an indicator layer  1820  and the light source  1808  ( FIG. 23 ) are shown. The light source  1808  serves to provide illumination to the indicator layers  1820  and can include one or more of various source of light, for example, an incandescent light bulb, an LED, and an OLED. The indicator layer  1820  has a top surface  1834 , a bottom surface  1836 , and one or more end walls  1838  forming a layer perimeter. 
         [0083]    The indicator layer  1820  includes, in one or more embodiments, a substrate with embedded and/or enclosed fluorophores. The fluorophore may consist of a fluorescent dye, nano-phosphor, or quantum dot. The light source  1808  can be positioned to direct light through the top surface  1834  of the indicator layer  1820 . Light received into the top surface  1834  of the indicator layer  1820  is reflected and affected by the fluorophore to establish enhanced light. In one or more embodiments, the fluorophore absorbs the light received from the light source  1808  and, upon absorption, the wavelength of the light is both shifted along the electromagnetic spectrum from a higher energy, shorter wavelength to a lower energy, longer wavelength and scattered in many directions to increase the visibility of the light to the human eye from various observation directions. In one or more embodiments, the overall size of the surfaces  1834 ,  1836  is greater than the height of the end wall  1838  such that the enhanced light produces an intensified image along the perimeter of the end wall  1838  as it is emitted from the indicator layer  1820 . 
         [0084]    As the top surface  1834  and/or bottom surface  1836  of the indicator layers  1820  can be at least partially enclosed by a housing, such as housing  1810 , to maximize visibility the enhanced light is directed to the typically exposed end walls  1838  forming the layer perimeter. In one or more embodiments, depending on the surface configuration used for the indicator layer, the amount of enhanced light (after being established within the indicator layer) that passes through the top surface and the bottom surface, and therefore does not reach the end walls (i.e., light losses), can be minimized. For example, when the indicator layer is configured in a sheet or sheet-like form where the top and bottom surface are highly polished, such as to an SPI-A3 or better finish, so as to produce internal reflections, the enhanced light is predominantly reflected internally towards the end walls of the indicator layer. In addition, as the enhanced light is internally reflected within (e.g., internally reflected off the top and bottom surfaces) the indicator layer and communicated to the end walls, it becomes more concentrated and thereby produces a bright glowing effect along the end walls as the enhanced light is emitted from the indicator layer. This glowing effect is known as an “edge-glow” effect. 
         [0085]    The end walls  1838  are shown orthogonal to the plane of the top surface and bottom surface, which are parallel to one another, to maximize illumination from the end walls, although the end walls can be positioned at various other angles relative to the top surface and/or bottom surface, which need not always be parallel to one another. To maximize the “edge-glow” effect, the indicator layer can be comprised of a transparent material to maximize internal reflections. In at least some embodiments, the indicator layer can include a transparent, semi-transparent, and/or translucent material, such as acrylic (PMMA), polycarbonate (PC), styrene-acrylonitrile (SAN), or polystyrene (PS), although other materials with varying transparency levels can be used as well, such as glass. In other embodiments where nano-phosphors or quantum dots are used, the indicator layer can include these compounds in its bulk, embodied in an attached or applied layer at least partially covering the outer surface around the indicator layer. The nano-phosphors and quantum dots are fluorophores that absorb energy emitted by the light source and re-emit that energy at random angles and at specified wavelengths defined by the fluorophore&#39;s size. One benefit of using nano-phosphors or quantum dots is their inherent efficacy in wavelength conversion between the emission of the light source and the desired output color. Another benefit is that a sensor can be standardized in form and function and then specialized by the addition of the nano-phosphor or quantum dot layers and surfaces. Yet another benefit is that the nano-phosphor or quantum dots can be spatially constructed to impart information about a sensor such as a logo, part number, and operational-state data, without having to add these features into the molded part. In this regard, the indicator layer and/or a display layer can be utilized in one or more embodiments to display the sensor information, wherein the display layer would be visible through a sensor housing, such as housing, and sized to accommodate the information as necessary and/or desired. 
         [0086]    Further, to increase the uniformity of illumination along the end walls, a diffuse light source can be employed as the light source. Also, applying a texture, such as a Charmilles #30 or Mold-Tech® MT-11520, to the end walls can assist with producing a generally uniform and diffuse “edge-glow” effect. The fluorophore can be of any conventional, commercially-available fluorescent dye, nano-phosphor, or quantum dot that is suitable for absorbing and enhancing light and capable of being embedded in the indicator layer. 
         [0087]    Referring to  FIG. 25 , a view of the indicator component  1818  is shown in cross-section. The indicator component  1818  includes at least two indicator layers  1820 , namely, a first indicator layer  1830  having a top surface  1834  and a bottom surface  1836 , and a second indicator layer  1832  having a top surface  1834  and a bottom surface  1836 . The top surface  1834  of the first indicator layer  1830  is secured to the housing  1810 . In one or more embodiments, a center barrier  1870  is provided between the first indicator layer  1830  and the second indicator layer  1832 . The center barrier  1870  is provided to limit or prevent enhanced light that is passed through the first indicator layer  1830  from entering the second indicator layer  1832 . Similarly, the center barrier  1870  limits or prevents second enhanced light that is passed through the second indicator layer  1832  from entering the first indicator layer  1830 . The center barrier  1870  allows for the illumination of indicator layers  1830 ,  1832  to be independent of each other. 
         [0088]    In one or more embodiments, the center barrier  1870  can include a substrate comprised of an opaque metallized plastic, a metallic foil, reflective in-mold-label, or other suitable material that serves to limit or prevent the transmission of light therethrough. In addition to or in place of a substrate, the center barrier  1870  can be comprised of a reflective coating that is applied to one or both of the bottom surface  1836  and the top surface  1834 . In one or more embodiments, the center barrier includes an in-mold label. In at least one embodiment, the in-mold label is made of transparent acrylic and consists of a white ink layer printed over an opaque silver ink layer printed over a white ink layer (white-silver-white) on one side of the acrylic label. The white ink layer produces a lambertiant scattering of the light that serves to increase the intensity of the light conveyed by the status indicators while the opaque silver layer prevents light from bleeding through the label to the other side. In one or more embodiments, the center barrier has cut outs which correspond to components inserted therethrough, or with openings in the indicator component  1818 . In one or more embodiments, the center barrier is approximately 0.010″ shorter along the edges than the finished part in order to prevent the edges of the label from being exposed to the outside environment. 
         [0089]    In one or more embodiments, the indicators layers  1820  have a non-planar overall shape, for example as shown in  FIGS. 22 and 25 . In one or more embodiments, the indicator layer  1820  has a first portion  1842  that is aligned with a first edge of the housing, for example as shown in  FIG. 18 ,  25 . In one or more embodiments, the indicator layer  1820  has a second portion  1844  that is angled relative to the first portion  1842 , for instance at an angle of 45 degrees relative to the edge of the housing, as shown in  FIG. 22 . The angled indicators layers  1820  assist with the visibility of the indicators of the sensing device such that they can be easily viewed 360 degrees around the sensing device regardless as to what orientation the sensing device is mounted in. Other angles that allow sufficient viewing of the indicator layer around the sensing device are contemplated herein as well. 
         [0090]    In one or more embodiments, the at least one indicator layer  1820  extends along an edge of at least one of a top, bottom, side surface of the housing and transitions away from the edge and toward an intermediate portion of the outer housing. In one or more embodiments, the end wall portion of the indicator layer substantially circumnavigates a housing perimeter. In one or more embodiments, the indicator layer  1820  circumnavigates the housing such that the indicator layer is visible 360 degrees around the housing, optionally the end wall of the indicator layer completely circumnavigates the housing. In one or more embodiments, the housing has two or more side planes, and the end wall is disposed along a portion of each of the side planes. 
         [0091]    In one or more embodiments, a cross-section of one or more of the indicator layers has an overall non-linear shape. The indicator layers  1820 , in one or more embodiments, have an overall structure that is non-planar, and portions of the indicator layer  1820  can be planar, for example, as shown in  FIG. 25 . 
         [0092]    The sensing device  1800  further includes mounting structure  1850  which is detachably coupled with the sensing device  1800 , where  FIGS. 18 ,  20 - 21  show the sensing device  1800  with the mounting structure  1850 , and  FIG. 19  illustrates the sensing device  1800  without the mounting structure  1850 . The mounting structure  1850  includes an angled portion  1852 , for example a 45 degree angle relative to an outer wall  1854  of the mounting structure  1850 . The angle portion  1852  is disposed adjacent to an angled portion  1812  of the sensing device  1800 , as shown in  FIG. 19 . In one or more embodiments, the angled portion  1812  of the sensing device  1800  is disposed at a 45 degree angle relative to a top sensing surface or plane  1814 . 
         [0093]    The angled surfaces allow for the mounting structure  1850  in multiple orientations relative to the sensing device, allowing for the sensing device to be mounted in multiple orientations. For example,  FIGS. 18 and 20  illustrates the mounting structure  1850  mounted to the sensing device  1800  in a first orientation. The mounted structure can be rotated 90 degrees as shown in  FIG. 21 . The indicator layers  1820  are visible in 360 degrees of the device  1800  regardless of the orientation of the sensing device. However, depending on the desirability of the location of the various indicator layers, various rotations and types of mounting structure  1850  can be used. 
         [0094]    To assemble to the sensing device, referring to  FIG. 24 , the indicator layer  1830  is overmolded with a barrier  1870  in a first stage of assembly  1888 . This assembly is overmolded with the second indicator layer  1832  at a second stage of assembly  1889 , to create an indicator component  1818 . The housing  1810 , shield  1802 , bobbin  1804 , PCB  1806  and light source  1808  are assembled (see  FIGS. 22 ,  23 ). Potting material is disposed through the filling ports or potting ports  1817 . A sealing member, such as a sphere, for example, an acrylic ball, is disposed within the port, and an insert is disposed in the port. The insert is shaped and/or sized to trap the sealing member or sphere within the port. In one or more embodiments, the insert is sized such that the sphere seals against the insert, and the insert is interference fitted within the port. The sealing member is sized and/or shaped to prevent exit of potting material from the sensing device. A connector assembly  1816  is further assembled to the sensing device. 
         [0095]    Although the above description discloses in at least some embodiments sensors for use in industrial controls, such as proximity and photoelectric sensors, it should be understood that other non-industrial and industrial sensing and indicating products can also be included, for example, illuminating cord-sets, light curtains, safety products, PLC&#39;s, motor drives, Through-Beam sensors, Transceiver sensors, Color Contrast sensors, Time-Of-Flight sensors, and stack lights. 
         [0096]    Various types of sensors can include the indictor layers as discussed herein, and can further include multiple center barriers, light sources, and indicator layers, as desired to provide varying levels of indication. Further, in at least some embodiments, the material used for the indicator layers can be different, even when the indicator layers are hermetically joined together. Sensing circuits can be mounted on the PCB or on another circuit board in the housing. Alternatively, the sensing circuit can be located separate from the housing. The sensing circuit can vary among the embodiments and is selected based on the particular type of sensor used and its intended use. 
         [0097]    Notwithstanding the above examples, the present invention is intended to encompass numerous other embodiments and/or applications, and/or to satisfy a variety of other performance levels or criteria in addition to or instead of the above examples. It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.