Patent Publication Number: US-9835555-B2

Title: Sensor for sensing reflective material located on a surface having more than one of radiation emitters located on either side of a radiation detector

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present is a continuation application of pending U.S. patent application Ser. No. 13/507,956, filed Aug. 9, 2012 to which priority is claimed under 35 U.S.C. §120, the entire contents of which are hereby incorporated by reference 
     TECHNICAL FIELD 
     The present relates to material sensors, and more particularly to a sensor for sensing reflective materials. 
     BACKGROUND 
     Precipitation sensors have been developed to determine the presence of water in its vapor, liquid and solid forms, but usually the sensor is immersed in the material. Non-immersed sensing is a significant challenge. One example of a non-immersed sensor is the Bosch vehicle windshield rain sensor (Optical Sensor U.S. Pat. No. 6,376,824 by Michenfelder et al) used to operate windshield wipers. This sensor depends on the change in refraction of a reflected light beam against glass when water is on the outer glass surface. However, it has poor sensitivity for snow, unless the glass can be heated enough to melt the snow next to the glass. This would be difficult to facilitate without making the vehicle occupants too uncomfortable and initially, in cold environments, would not work at all until the heating reached an acceptable level for the sensor to be engaged. 
     BRIEF SUMMARY 
     We have invented a sensor that uses a reflective rather than refractive technique, and as such is very well suited to determining the presence of winter precipitation such as snow, sleet, frost, ice or ice pellets. A radiation source such as a LED is oriented to radiate through a transparent material such as glass, at an angle that does not cause a surface reflection back to the radiation sensor. When a reflective material such as winter precipitation is on the transparent material surface, a radiation sensor such as but not limited to a photo transistor, photo diode or light dependent resister adjacent to the radiation source senses the radiation reflection. 
     Accordingly, there is provided a sensor for sensing reflective material, the sensor comprising:
         a housing having a transparent window;   a sensor mount located in the housing and angled away from a housing wall;   a radiation emitter mounted in the sensor mount for emitting radiation along a first axis through the transparent window, the transparent window having an amount of the reflective material located thereon; and   a radiation detector mounted in the sensor mount and located adjacent the radiation emitter, the radiation detector being located to receive reflected radiation from the reflective material along a second axis, the first axis being angled towards the second axis.       

     In one example, the sensor includes two radiation emitters each located on either side of the radiation detector, the two radiation emitters being mounted to emit radiation along their respective first axes through the transparent window towards a common focal point on an outer surface of the transparent window. The sensor mount includes two spaced apart cavities aligned along the respective first axes in which the radiation emitters are located, and another cavity aligned along the second axis in which the radiation detector is located. 
     In one example, the sensor mount is located at a junction between the housing wall and a housing floor so that sensor mount is angled away from the housing wall. 
     In another example, a baffle extends into the housing from the housing wall. 
     In another example, a temperature sensor is located on a lower surface of the transparent window. 
     In yet another example, a baffle wall extends into the housing from the housing wall; and a temperature sensor is located on a lower surface of the transparent window. 
     In one example, the radiation emitter is a Light Emitting Diode (LED). 
     In one example, the radiation sensor is a photo transistor or photo diode located adjacent to the radiation emitter so as to detect reflected radiation. 
     In another example, the radiation emitter is disposed so that radiation is emitted through the transparent window at an angle that does not cause a surface reflection back to the radiation detector. A controller is located in the housing and is connected to a variable resistor, the radiation detector, the radiation emitter and the temperature sensor. A controller is located in the housing and is connected to a fixed resistor, the radiation detector, the radiation emitter and the temperature sensor. 
     In one example, the radiation detector is an integrated circuit having a photo transistor, a photo diode or a light dependent resister located adjacent to the radiation emitter so as to detect reflected radiation. 
     In another example, the reflective material is winter precipitation. The winter precipitation is snow, sleet, frost, ice or ice pellets. 
     In one example, the reflective material is non-winter precipitation: The non-winter precipitation is reflective liquids, dirt, or particulate material suspended in liquids. 
     In one example, the sensor is mounted for use on motorized transportation including trucks, cars, motor bikes, recreational vehicles, trains, or boats. 
     In another example, the sensor is mounted for use on solar panels and trough reflectors. 
     In yet another example, the sensor is mounted for use on sidewalks, driveways, walkways, roads, roofs, or infrastructure projects. 
     In another example, the sensor is mounted for use with greenhouses, atriums, windows, freezer glass doors, skylights; on planes, helicopters; food services, freezers/fridges, spacecraft, buildings; for landscaping such as grass and garden maintenance, crops; or for weather determination, climate, ecosystem preservation; or for medical applications and storage of tissues and cells, sterilizations; or for food preparation and preservation, and the like. 
     In another example, the sensor is used in solar applications for building materials including decking, walls or shingles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the discovery may be readily understood, embodiments are illustrated by way of example in the accompanying drawings. 
         FIG. 1A  illustrates top view of a sensor; 
         FIG. 1B  illustrates a side view of the sensor showing radiation emitted and radiation reflected; 
         FIG. 2  illustrates an exploded view of the sensor; 
         FIG. 3  illustrates the sensor&#39;s field of view. 
         FIG. 4  is diagrammatic representation of communication between sensor components in one example of the sensor; and 
         FIG. 5  is diagrammatic representation of communication between sensor components in an alternative example of the sensor. 
     
    
    
     Further details of the device and its advantages will be apparent from the detailed description included below. 
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1A, 1B and 2 , there is illustrated generally at  10  a sensor for sensing reflective material  12 . In one example, the reflective material is winter precipitation such as, for example, snow, frost, ice or ice pellets. In another example, the reflective material is non-winter precipitation such as reflective liquids, dirt, or particulate material suspended in liquids. Broadly speaking, the sensor  10  includes a housing  14 , a sensor mount  16 , two radiation emitters (radiation sources)  18 ,  20 , and a radiation detector (radiation sensor)  22 . The housing  14  has a transparent window  24  which includes an upper surface  26  and a lower surface  28  which is disposed towards the inside of the housing  14 . The transparent window  24  has an amount of accumulated reflective material  12  located thereon. The sensor mount  16  is located in the housing  14  and angled away from a housing wall  30 . The radiation emitters  18 ,  20  are mounted in the sensor mount  16 . The radiation emitter  18 ,  20  each have a first axis  32 ,  34 . Radiation is emitted from the radiation emitters  18 ,  20  along their respective axes  32 ,  34  towards and through the transparent window  24  until it contacts the reflective material  12 . The radiation detector  22  is mounted in the sensor mount  16  and adjacent and between the radiation emitters  18 ,  20 . The radiation detector  22  is located to receive the radiation that is reflected back from the reflective material  12  located on the transparent window  24  along a second axis  36 . The first axes  32 ,  34  of the radiation emitters  18 ,  20  are both angled towards the second axis  36 . The two radiation emitters  18 ,  20  emit radiation towards a common focal point  38  on the upper surface  26  of the transparent window  24  and at a deviation from normal such that their radiation is not mirror reflected to the radiation detector  22  from the upper or lower transparent window surfaces. The deviation from normal is also not large enough to cause all radiation to be to be reflected back into the housing  14 . The radiation detector  22  is directed to the radiation emitter common focal point  38  on the upper surface of the transparent window. 
     Referring briefly to  FIG. 3 , radiation emitters  18  and  20  and radiation detector  22  have overlapping fields of useful radiation and detection to sense precipitation over area  37 . 
     Still referring to  FIGS. 1A, 1B and 2 , the sensor mount  16  includes two spaced apart cavities  40 ,  42  which are both aligned along their respective first axes  32 ,  34  in which the radiation emitters  18 ,  20  are located. Another cavity  44  is aligned along the second axis  36  in which the radiation detector  22  is located. 
     As best illustrated in  FIG. 1B , the sensor mount  16  is located at a junction  45  between the housing wall  30  and a housing floor  46  so that sensor mount  16  is angled away from the housing wall  30 . 
     Still referring to  FIG. 1B , a radiation baffle wall  48  extends into the housing  14  from the housing wall  30 . The baffle wall  48  may be used to block external radiation sources such as the sun from the radiation detector  22 . A temperature sensor  50  is located on the lower surface  28  of the transparent window  24  out of the radiation detector&#39;s  22  field of view, which will not cause a false reflection to the sensor. The baffle wall  48  can be constructed of any suitable shape to define the boundaries to radiation window  52  through which both the radiation from the radiation emitters  18 ,  20  and the radiation reflected back from the reflective material  12  passes. 
     Each of the radiation emitters is a Light Emitting Diode (LED). The radiation emitters  18 ,  20  are disposed so that radiation emitted through the transparent window  24  is at an angle that does not cause a surface reflection back to the radiation detector  22 . 
     Referring now to  FIG. 1 ,  FIG. 2  and  FIG. 4 , a controller  54 , which is typically a microprocessor or equivalent device, communicates with a variable resister  56  or fixed resister  56 A, the radiation detector  22 , the radiation emitters  18 ,  20  and the temperature sensor  50  to achieve the reflective material sensing function. The controller  54  may be located within the housing  14 , or in another suitable housing. One skilled in the art will understand that other devices and circuitry such as cabling, voltage supply, ground, signal buffering, user communication, controller programming, and the like may also be integrated into the sensing function. 
     Referring now to  FIG. 4 , the radiation sensor  22  operates as an electrical current valve, which permits higher current flow at higher radiation levels. A radiation signal  58  is produced by passing a reference voltage  60  through the variable resister  56  and then the radiation detector. As radiation increases, the current flow through the radiation detector  22  increases, causing an increased voltage drop across the variable resister  56 . To allow for a wide range of radiation, the controller  54  modifies the value of the variable resister  56  to produce a usable signal. For installations where the ambient radiation range is small, an inexpensive fixed resister  56 A may be used, thereby eliminating the need for the controller  54  to modify the resister  56 A value. Alternatively, more than one copy of a fixed but different value resister  56 A and radiation sensor  22  may be used to broaden the sensed radiation range. 
     Referring now to  FIGS. 1, 2 and 5 , the radiation sensor  22  is an integrated circuit  62  which includes a sensor such as a photo diode, photo transistor or light dependent resister and a means to autonomously convert the sensor output to the controller  54  compatible input such as frequency pulses. 
     Still referring to  FIG. 4 or 5 , the controller  54  activates one or both of the radiation emitters  18 ,  20  when required to achieve the sense function. To assist in distinguishing between winter and non-winter precipitation, the controller  54  communicates with the temperature sensor  50  to determine whether winter precipitation is possible. 
     The sensor  10  functions in a wide range of ambient radiations, from direct sunlight to nighttime. It can sense winter precipitation or cold precipitation on, for example, greenhouses, atriums, windows, freezer glass doors, skylights; on planes, helicopters, and motorized transportation including trucks, cars, motor bikes, recreational vehicles, trains, boats and the like; food services, freezers/fridges, spacecraft, buildings, photovoltaic solar (conventional panels and non conventional solar applications), trough reflectors; for landscaping such as grass and garden maintenance, crops; or for weather determination, climate, ecosystem preservation; or for medical applications and storage of tissues and cells, sterilizations; or for food preparation and preservation, and the like. When operated in non-winter conditions, the sensor  10  may also detect dirt on these types of surfaces to support cleaning operations. With a durable transparent cover, it can also sense winter precipitation when installed in sidewalks, driveways, walkways, roads, roofs, infrastructure projects and the like. The sensor  10  can be used in solar applications for building materials such as decking, walls and shingles. 
     While the sensor  10  can be used to sense winter precipitation, it is easily applied to sensing other reflective materials such as, for example, liquids, precipitates, contamination, some gases, suspended solids, and the like, and as such can be applied to manufacturing and distribution processes for food, chemicals, fuels, and the like. 
     Operation 
     Referring now to  FIG. 1  and  FIG. 4 , operation of the sensor  10  will be described. Winter precipitation is sensed by determining the change in the radiation signal  58  when the radiation emitters  18 ,  20  are “off” then “on”. Firstly, the controller  54  determines if winter precipitation is possible by communicating with the temperature sensor  50 . If winter precipitation is possible, then the controller  54  determines a reference ambient radiation signal  58  by first not switching on the radiation emitters  18 ,  20 , then modifying the variable resister  56  until the radiation signal  58  is approximately 90% of the reference voltage  60 . The controller  54  determines the reference ambient radiation by comparing the resultant variable resister  56  resistance with internally stored data. If the fixed resister  56 A is used, the controller  54  determines reference ambient radiation by comparing the radiation signal  58  with internally stored data. 
     Referring now to  FIG. 5 , an alternative operation of the sensor  10  will now be described. Winter precipitation is sensed by determining the change in the radiation signal  58  when the radiation emitters  18 ,  20  are “off” then “on”. Firstly, the controller  54  determines if winter precipitation is possible by communicating with the temperature sensor  50 . If winter precipitation is possible, then the controller  54  determines a reference ambient radiation signal by first not switching on the radiation emitters  18 ,  20  then communicating with the radiation detector  62 . 
     Referring now to  FIGS. 4 and 5 , the controller  54  then turns on one or both of the radiation emitters, depending on the ambient radiation. At high ambient radiation, both radiation emitters  18 ,  20  may be required to obtain an adequate change in the radiation signal  58 . The controller  54  then determines that winter precipitation is present if the radiation signal  58  value has changed from the reference ambient radiation signal value by more than the combined effect of impurities in the transparent window  24  and expected dirt on the transparent window  24 . The controller  54  may also determine the type of winter precipitation based on the combination of the temperature sensor  50  and the radiation signal  58  change. 
     When used in non-winter precipitation mode to sense other materials, the temperature sensor  50  can be eliminated, or used to distinguish between winter precipitation and non-winter reflective material such as accumulating grime. 
     Although the above description relates to a specific preferred embodiment as presently contemplated by the inventor, it will be understood that the WPS in its broad aspect includes mechanical and functional equivalents of the elements described herein.