Method and system for measuring local ultraviolet exposure

Abstract

One variation of a method for measuring ambient ultraviolet light radiation including: calculating a target direct orientation of a light exposure device based on a location, a current date and time, and a direct solar position model; calculating a target diffuse orientation of the light exposure device based on the location, the current date and time, and a diffuse solar position model; in response to detecting alignment between orientation of the light exposure device and the target direct orientation, recording a direct ultraviolet value; in response to detecting alignment between orientation of the light exposure device and the target diffuse orientation, recording a diffuse ultraviolet value; in response to detecting alignment between orientation of the light exposure device and a target global orientation, recording a global ultraviolet value; and calculating an ultraviolet index based on the global ultraviolet value, the direct ultraviolet value, and the diffuse ultraviolet value.

I claim: 
     
         1 . A method comprising:
 tracking an orientation of a mobile device comprising an ultraviolet sensor configured to detect intensity of incident ultraviolet radiation;   in response to the orientation of the mobile device falling within a target global orientation window at a first time, storing a first value read from the ultraviolet sensor at the first time as a first global ultraviolet value; and   calculating a first ultraviolet index proximal a first location of the mobile device at the first time based on the first global ultraviolet value.   
     
     
         2 . The method of  claim 1 , further comprising:
 accessing a set of ultraviolet index curves, each ultraviolet index curve defining a series of ultraviolet indices as a function of time;   selecting a first ultraviolet index curve, from the set of ultraviolet index curves, defining a first predicted index value within a threshold range of the first ultraviolet index, for the first time; and   estimating a first ultraviolet exposure at the mobile device by integrating the first ultraviolet index exposure curve from the first time to a second time succeeding the first time.   
     
     
         3 . The method of  claim 2 , further comprising:
 in response to recording the first global ultraviolet value, transitioning into a low-power mode for a preset duration of time at the mobile device;   in response to conclusion of the preset duration of time:
 entering a high-power mode at the mobile device; 
 tracking the orientation of the mobile device; 
 in response to the orientation of the mobile device falling within the target global orientation window at the second time, storing a second value read from the ultraviolet sensor at the second time as a second global ultraviolet value; and 
 calculating a second ultraviolet index proximal a second location of the mobile device at the second time based on the second global ultraviolet value; and 
   selecting a second ultraviolet index curve, from the set of ultraviolet index curves, defining a second predicted index value within a threshold range of the second ultraviolet index for the second time; and   estimating a second ultraviolet exposure at the mobile device by integrating the second ultraviolet index exposure curve from the second time to a third time succeeding the second time.   
     
     
         4 . The method of  claim 3 , further comprising:
 calculating a total ultraviolet exposure based on a sum of the first ultraviolet exposure and the second ultraviolet exposure;   in response to the total ultraviolet exposure exceeding a threshold ultraviolet exposure, serving a prompt to a user associated with the mobile device to reduce sun exposure.   
     
     
         5 . The method of  claim 4 , wherein serving the prompt to the user comprises rendering a notification, to apply sunscreen, via a display integrated into the mobile device. 
     
     
         6 . The method of  claim 4 , wherein serving the prompt to the user comprises wirelessly transmitting a notification, to seek shade, from the mobile device to an external handheld device associated with the user. 
     
     
         7 . The method of  claim 1 :
 wherein storing the first value read from the ultraviolet sensor at the first time as the first global ultraviolet value comprises, in response to the orientation of the mobile device falling within a first threshold angular range of a vertical orientation at the first time:
 sampling the first value from the ultraviolet sensor at the first time; and 
 storing the first value as the first global ultraviolet value; and 
   further comprising:
 in response to the orientation of the mobile device falling within a second threshold angular range of the vertical orientation at a second time succeeding the first time, the second threshold angular range less than the first threshold angular range, sampling a second value from the ultraviolet sensor at the second time; 
 in response to the second value exceeding the first value, overwriting the second value to the first global ultraviolet value. 
   
     
     
         8 . The method of  claim 1 , further comprising:
 accessing the first location of the mobile device at the first time;   calculating a target direct orientation window in which the ultraviolet sensor falls within a threshold angular range of normal to the Sun at the first time based on the first location;   in response to the orientation of the mobile device falling within the target direct orientation window during a second time, storing a second ultraviolet value read from the ultraviolet sensor at the second time as a first direct ultraviolet value, the first time and the second time occurring within a first time interval;   calculating a direct ultraviolet index based on the direct ultraviolet value; and   in response to variation between the global ultraviolet index and the direct ultraviolet index exceeding a threshold difference and in response to the direct ultraviolet index remaining below the global ultraviolet index, determining that the mobile device is occupying a shaded area during the first time interval.   
     
     
         9 . The method of  claim 8 , further comprising:
 calculating a target diffuse orientation window in which the ultraviolet sensor is biased away from the Sun at the first time based on the first location;   in response to the orientation of the mobile device falling within the target diffuse orientation window during a third time within the first time interval, storing a third ultraviolet value read from the ultraviolet sensor at the third time as a first diffuse ultraviolet value;   calculating a diffuse ultraviolet index based on the diffuse ultraviolet value; and   in response to determining that the mobile device is occupying a shaded area during the first time interval, estimating a first ultraviolet exposure at the mobile device during the first time interval based on the diffuse ultraviolet index.   
     
     
         10 . The method of  claim 8 , wherein storing the second ultraviolet value read from the ultraviolet sensor at the second time as the first direct ultraviolet value comprises:
 during the time interval, recording a sequence of ultraviolet values read from the ultraviolet sensor while the orientation of the mobile device falls within the target direct orientation window;   selecting the second ultraviolet value, from the sequence of ultraviolet values, greater than each other ultraviolet value in the sequence of ultraviolet values; and   storing the second ultraviolet value as the first direct ultraviolet value.   
     
     
         11 . The method of  claim 1 :
 further comprising:
 accessing the first location of the mobile device at the first time; 
 calculating a target direct orientation window in which the ultraviolet sensor falls within a threshold angular range of normal to the Sun at the first time based on the first location; 
 in response to the orientation of the mobile device falling within the target direct orientation window during a second time, storing a second ultraviolet value read from the ultraviolet sensor at the second time, the first time and the second time occurring within a first time interval; 
 estimating an angular offset from a primary axis of the ultraviolet sensor to the Sun when the second ultraviolet value was recorded; and 
 calculating a first direct ultraviolet value proximal the mobile device during the first interval based on the second ultraviolet value, corrected based on the angular offset; and 
   wherein calculating the first ultraviolet index comprises calculating the first ultraviolet index proximal the first location of the mobile device at the first time based on the first global ultraviolet value and the first direct ultraviolet value.   
     
     
         12 . A method for measuring visible ultraviolet light radiation comprising:
 accessing a first location of a mobile device comprising an ultraviolet sensor configured to detect intensity of incident ultraviolet radiation;   tracking an orientation of the mobile device;   during a first sampling interval:
 in response to the orientation of the mobile device falling within a target direct orientation window facing the Sun at a first time, recording a first ultraviolet value read from the ultraviolet sensor at the first time as a direct ultraviolet value; 
 in response to the orientation of the mobile device falling within a target diffuse orientation window biased away from the Sun at a second time, recording a second ultraviolet value read from the ultraviolet sensor at the second time as a diffuse ultraviolet value; 
 in response to the orientation of the mobile device falling within a target global orientation window facing vertically upward at a third time, recording a third ultraviolet value read from the ultraviolet sensor at the third time as a global ultraviolet value; and 
   calculating a first ultraviolet index proximal the mobile device at the first location during the first sampling interval based on a combination of the direct ultraviolet value, the diffuse ultraviolet value, and the global ultraviolet value.   
     
     
         13 . The method of  claim 12 :
 further comprising:
 calculating a diffuse ultraviolet index as a function of the diffuse ultraviolet value; 
 calculating a direct ultraviolet index proportional to the direct ultraviolet value; 
 calculating a global ultraviolet index proportional to the first global ultraviolet value; and 
 in response to variation between the diffuse ultraviolet index, the direct ultraviolet index, and the global ultraviolet index falling below a threshold difference, predicting direct sunlight at the first location; and 
 in response to variation between the diffuse ultraviolet index, the direct ultraviolet index, and the global ultraviolet index exceeding the threshold difference, predicting indirect sunlight at the first location; and 
   wherein calculating the first ultraviolet index comprises:
 in response to predicting direct sunlight at the first location, calculating the first ultraviolet index based on the combination of the direct ultraviolet value, the diffuse ultraviolet value, and the global ultraviolet value; and 
 in response to predicting direct sunlight at the first location, calculating the first ultraviolet index based on the global ultraviolet value. 
   
     
     
         14 . The method of  claim 12 , further comprising:
 calculating a diffuse ultraviolet index as a function of the diffuse ultraviolet value;   calculating a direct ultraviolet index proportional to the direct ultraviolet value; and   in response to variation between the global ultraviolet index and the direct ultraviolet index exceeding a threshold difference and the global ultraviolet index remaining below the direct ultraviolet index:
 determining that the mobile device is occupying a shaded area; and 
 calculating the current ultraviolet index based on the diffuse ultraviolet index and the direct ultraviolet index. 
   
     
     
         15 . The method of  claim 12 :
 further comprising:
 based on the first location and a time and a date of the first sampling interval, calculating a target direct orientation of the mobile device for which a primary axis of the ultraviolet sensor is normal to the Sun during the first sampling period; 
 defining the target direct orientation window around the target direct orientation; and 
 defining the target diffuse orientation window disjoint from the target direct orientation window; and 
   wherein recording the first ultraviolet value as the direct ultraviolet value comprises, in response to the orientation of the mobile device falling within the target direct orientation window at the first time:
 reading the first ultraviolet value from the ultraviolet sensor; and 
 storing the first ultraviolet value as the direct ultraviolet value. 
   
     
     
         16 . The method of  claim 12 :
 further comprising:
 calculating a first vector, within a reference frame, parallel to gravity detected by the mobile device; 
 defining a target global orientation along the first vector: 
 defining the target global orientation window in the form of a first cone coaxial the first vector; 
 identifying a solar zenith of the Sun relative to a first location of the mobile device at a current time and date; 
 defining a second vector, within the reference frame, directed toward a center of the Sun based on the solar zenith; and 
 defining a target direct orientation along the second vector: 
 defining the target direct orientation window in the form of a second cone coaxial the second vector; and 
 defining the target diffuse orientation window, within the reference frame, comprising a three-dimensional zone extending above the horizon, excluding a first sector below a threshold angle above the horizon, and excluding a second sector comprising the solar zenith of the Sun at the current time and date; 
   wherein recording the first ultraviolet value as the direct ultraviolet value comprises, in response to the orientation of the mobile device falling within the target direct orientation window at the first time:
 reading the first ultraviolet value from the ultraviolet sensor; and 
 storing the first ultraviolet value as the direct ultraviolet value; and 
   wherein recording the third ultraviolet value as the global ultraviolet value comprises, in response to the orientation of the mobile device falling within the target global orientation window at the first time:
 reading the third ultraviolet value from the ultraviolet sensor; and 
 storing the third ultraviolet value as the global ultraviolet value. 
   
     
     
         17 . The method of  claim 12 :
 further comprising: during an initial sampling interval preceding the first sampling interval:
 reading an initial visible light value from a visible light sensor integrated into the mobile device; 
 reading an initial ultraviolet value from the ultraviolet sensor; 
 in response to the initial visible light value exceeding a threshold visible light level and in response to the initial ultraviolet value falling below a threshold ultraviolet level:
 predicting indoor occupancy of the mobile device; 
 transitioning into a low-power mode for a preset duration of time at the mobile device; and 
 estimating a null ultraviolet index proximal the mobile device during the initial sampling interval; 
 
   further comprising, in response to conclusion of the preset duration of time:
 entering a high-power mode at the mobile device during the first sampling interval; 
 reading a first visible light value from the visible light sensor; 
 reading a fourth initial ultraviolet value from the ultraviolet sensor; and 
 in response to the fourth ultraviolet value exceeding the threshold ultraviolet level, predicting outdoor occupancy of the mobile device; and 
   wherein tracking the orientation of the mobile device and calculating the first ultraviolet index proximal the mobile device comprises, in response to predicting outdoor occupancy of the mobile device, tracking the orientation of the mobile device and calculating the first non-zero ultraviolet index proximal the mobile device.   
     
     
         18 . The method of  claim 12 , wherein calculating the first ultraviolet index comprises calculating one of UVA irradiance index, UVB irradiance index, and erythemal UV irradiance index proximal the mobile device at the first location during the first sampling interval based on the combination of the direct ultraviolet value, the diffuse ultraviolet value, and the global ultraviolet value.