Abstract:
A sensor housing and cosine diffuser are provided for the detection and measurement of ultraviolet (UV) irradiance. The cosine diffuser has a tiered structure to efficiently receive and transmit incident light that passes over and/or through the sensor housing structure. The sensor housing structure can be configured to have an irregular, serrated, castellated, and or repeating prong and/or tooth sequence to form a cutoff comb, through which incident light is attenuated. The attenuation of light in turn reduces measurement error caused when too much or too little incident light, relative to the actual intensity and irradiance of ambient incident light, reaches and transmits through a cosine diffuser due to the variation of the zenith angle of incident light over the course of a day.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/864,359, filed on Aug. 9, 2013, the entirety of which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the control of light incident on an irradiance measuring device. More particularly, the present invention relates to the control of light incident on an ultraviolet (UV) irradiance measuring device so as to maintain an accurate cosine response from all zenith angles (Θ), and as the zenith angle of incident light changes. 
       BACKGROUND OF THE INVENTION 
       [0003]    Ultraviolet (UV) radiation is light which has a wavelength (λ) range of 400-100 nm and an energy per photon of 3.10 to 12.4 eV. The UV spectrum is commonly subdivided into three narrower ranges: the Ultraviolet A (UVA) range, characterized as long wave or black light, which has a wavelength range of 400-315 nm and an energy per photon of 3.10 to 3.94 eV; the Ultraviolet B (UVB) range characterized as medium wave, which has a wavelength range of 315-280 nm and an energy per photon of 3.94 to 4.43 eV; and the Ultraviolet C (UVC) range, characterized as shore wave or germicidal, which has a wavelength rage of 280-100 nm and an energy per photon of 4.43 an 12.4 eV. It is beneficial to know the amount of UV radiation due to the effect of UV radiation on living organisms. For example, UVB exposure induces the production of vitamin D in the skin of humans and a lack of exposure to UVB may lead to a lack of vitamin D. Conversely, an excess of UVB exposure can lead to direct DNA damage, sunburn, and skin cancer. Similarly, UVC can cause adverse effects that can variously be mutagenic or carcinogenic. In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin, eyes, and immune system. 
         [0004]    To make a measurement of irradiance, it is required by definition that the response to each ray of radiation be proportional to the cosine of the angle of incidence of that ray. The ideal sensor will give a full response for rays striking the sensor perpendicularly (normal to the surface angle, 0° angle of incidence, 0° zenith angle) and conversely will give zero response for rays coming from the horizon (90° angle of incidence, 90° zenith angle). The ideal sensor will give a fifty percent (50%) response for incident rays with 60° zenith angle. For such sensors, also referred to as pyranometers, it is often useful to take measurements of light, and particularly of ultraviolet light, to determine whether concentrations of UV light are of an intensity which may be harmful. These sensors, however, must be placed in locations where incident radiation effects can introduce error into the desired measurement. In particular, errors may be introduced due to the zenith angle of light changing. Taking the vertical direction normal to the sensor as an zenith angle (Θ) equal to 0°, as the zenith angle increases and cosine Θ approaches zero, the side wall of a photosensor continues to admit light, causing a large positive cosine error relative to the measured intensity. To mitigate against this error, previous applications have used a “cutoff ring” to block light as Θ approaches 90°. The limitation of the cutoff ring is that the blocking of the light tends to be too abrupt, which can lead to irregular and erroneous measurements. 
         [0005]    The previous applications have further tried to mitigate against such errors through use of simple light diffusers which make the intensity of light reaching a photosensor relatively uniform, but such efforts retain inaccuracies. Accordingly, there is a need in the field for an invention that can measure UV irradiance with a minimum of zenith angle cosine error stemming from structural limitations. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    A weather station may include several sensors to monitor, measure, record, and/or transmit desired weather parameters, including but not limited to temperature, humidity, light intensity, and the like. In embodiments of the present invention, the weather station includes a UV light sensor (e.g. a transducer) located within, and protected by, a sensor housing structure. The light that reaches the UV sensor enters through the top of the station and sensor and has to pass through a diffuser. The diffuser operates to normalize the light that is incident on the UV sensor, such that the light incident on the UV sensor is not biased toward one part of the sensor due to the position of the sun and angle of the light incident on the station. In other words, the light intensity of each ray reaching a transducer is proportional to the cosine of the angle of incidence of the related zenith angle. 
         [0007]    The “cosine response” of a light sensor may be defined as the manner in which the measurement of the incident light by a sensor varies as a function of the zenith angle (Θ) of the light. That is to say, radiation incident on a flat horizontal surface at a defined zenith angle will give a measurement result proportional to the cosine of that zenith angle. When the value measured for light rays at Θ=0° is defined as 1 (unity), the ideal sensor will report that the value for all angles of Θ from 0° to ±90° is equal to cosine Θ, i.e. the photosensor will have a vertical directional response which is exactly the same as the cosine response. However, the directional response of a sensor is influenced by the quality, dimensions, and construction of the sensor. 
         [0008]    As used herein a “cosine diffuser” refers to a material that, when struck on a surface by UV radiation from a plurality of light paths, scatters, and thus diffuses, the radiation exiting the material toward the sensing element (e.g. a transducer) has an intensity that is proportional, with minimum error, to the cosine of the zenith angle of that ray when it reached the diffuser. The material forming the cosine diffuser may also be shaped to present multiple surfaces to incident UV radiation and light. 
         [0009]    In many embodiments, a sensor housing is provided which has a molding shaped to have an interior space with which to shield a UV sensor, in which the molding has an upper opening which is configured to have a cosine diffuser situated therein. In some embodiments, the molding can have a ridge in the opening, such when a cosine diffuser is situated in the upper opening of the molding, and where the ridge has a serrated structure such that a first plane of the ridge is relatively higher than an uppermost portion of the cosine diffuser and a second plane of the ridge is relatively lower than an uppermost portion of the cosine diffuser, and a cosine diffuser. In other embodiments, the cosine diffuser has a high-angle tier, through which incident light enters a cosine diffuser at zenith angles of about 90° or less, the zenith angle determined relative to normal from a major surface area of the cosine diffuser, a low-angle tier, through which incident light enters the cosine diffuser at zenith angles of about 75° degrees or less, a base tier, though which incident light enters the cosine diffuse at zenith angles of about 70° or less, a sensor cavity, though which light which has entered the cosine diffuser egresses from the cosine diffuser, and where the cosine diffuser is situated within the upper opening of the sensor housing molding. 
         [0010]    In many embodiments, a sensor housing for an ultraviolet (UV) sensor system is provided, in which a molding is shaped to have an interior space with which to shield a UV sensor, the molding having an upper opening which is configured to have a cosine diffuser situated therein, where the ridge of the upper opening has a serrated structure, such that when a cosine diffuser is situated in the upper opening of the molding, the uppermost plane of the serrated structure is relatively higher than an uppermost portion of the cosine diffuser. 
         [0011]    In many embodiments, a sensor housing for a ultraviolet (UV) sensor can have a sensor cavity which is configured to accommodate a photosensor. In some aspects, the sensor housing molding is shaped to have an interior space with which to shield a UV sensor. In other aspects, the sensor housing molding upper opening is shaped to have a ridge with a serrated structure. In some such aspects, the ridge can be a serrated structure is a cutoff comb, where the cutoff comb can have either or both of a sawtooth structure and a prong and slit structure. In further aspects, the sensor housing molding can be configured such that when the cosine diffuser is situated in the upper opening of the sensor housing molding, a first plane of the ridge is relatively higher than an uppermost portion of the cosine diffuser and a second plane of the ridge is relatively lower than the uppermost portion of the cosine diffuser. 
         [0012]    In many embodiments, a cosine diffuser for an ultraviolet (UV) sensor system is provided, having a high-angle tier, through which incident light enters a cosine diffuser at zenith angles of about 90° or less, the zenith angle determined relative to normal from a major surface area of the cosine diffuser, a low-angle tier, through which incident light enters the cosine diffuser at zenith angles of about 75° degrees or less, a base tier, though which incident light enters the cosine diffuse at zenith angles of about 70° or less, and a sensor cavity, though which light which has entered the cosine diffuser egresses from the cosine diffuser. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Illustrative aspects of the present disclosure are described in detail below with reference to the following drawing figures. 
           [0014]      FIG. 1  is an illustration of a cosine diffuser element situated within a sensor housing for a weather station module, according to many embodiments. 
           [0015]      FIG. 2  is design schematic showing perspectives of a cosine diffuser element, according to many embodiments. 
           [0016]      FIG. 2.1  is a cross-sectional design schematic of a cosine diffuser element, according to many embodiments. 
           [0017]      FIG. 2.2  is a detailed illustration of a cosine diffuser element, according to many embodiments, situated in a housing of a weather station module, according to many embodiments. 
           [0018]      FIG. 3  is a graph comparing the percentage of error in UV light measurement of a cosine diffuser according to the embodiment shown in  FIG. 2.2  as compared to an ideal cosine response. 
           [0019]      FIG. 4  is an illustration of a cosine diffuser element, according to many embodiments, situated in a weather station housing, according to many embodiments. 
           [0020]      FIG. 5  is a detailed illustration of a weather station module sensor housing cutoff comb structure, according to many embodiments. 
           [0021]      FIG. 6  is a graph comparing the percentage of error in UV light measurement of a cosine diffuser situated in a weather station module sensor housing with a cutoff comb structure as shown in  FIG. 5 , as compared to an ideal cosine response. 
           [0022]      FIGS. 7.1 ,  7 . 2 , and  7 . 3  are illustrations of segments of a cutoff comb modification to a cutoff ring, where the comb has a sawtooth structure, according to many embodiments. 
           [0023]      FIG. 8  is a detailed illustration of a weather station module sensor housing cutoff ring structure, according to many embodiments. 
           [0024]      FIG. 9A  is side perspective design schematic of a cutoff comb and weather station module sensor housing  900 , according to many embodiments. 
           [0025]      FIG. 9B  is top perspective design schematic of a cutoff comb and weather station module sensor housing  900 , according to many embodiments. 
           [0026]      FIG. 9C  is bottom perspective design schematic of a cutoff comb and weather station module sensor housing  900 , according to many embodiments. 
           [0027]      FIGS. 9D and 9E  are cross-sectional side perspective design schematics of a cutoff comb and weather station module sensor housing  900 , according to many embodiments. 
           [0028]      FIG. 9F  is a detail section of  FIG. 9E , specifically of the cutoff comb, showing both a side cross-section and top perspective of the cutoff comb, according to many embodiments. 
           [0029]      FIG. 9G  is a detail section of  FIG. 9E , specifically of the prong and slit structure of the cutoff comb, according to many embodiments. 
           [0030]      FIG. 10  is a detailed illustration of a weather station module sensor housing cutoff comb structure, according to many embodiments. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    Throughout this description for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the many embodiments disclosed herein. It will be apparent, however, to one skilled in the art that the many embodiments may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in diagram or schematic form to avoid obscuring the underlying principles of the described embodiments. 
         [0032]    As used in this disclosure, the word “sensor” describes that portion of a weather instrument that directly measures the desired weather parameter, such as UV light intensity. It does not necessarily refer to the rest of the weather instrument, or a non-transitory computer readable medium for processing and conversion of the analog data at the sensor to a digital readout provided to a user. 
         [0033]    In many embodiments, the sensor housing is constructed from UV-resistant acrylonitrile butadiene styrene (“ABS”), which can be specifically be Chi Mei Polylac® PA-757 ABS, and black in color. In many embodiments, the nominal thickness for each molded surface, e.g. the walls of the sensor housing, unless otherwise specified, is 0.060±0.005 inches. In further embodiments, the sensor housing is configured to house a UV sensor as part of a module, which can be part of a larger multi-sensored weather station. 
         [0034]      FIG. 1  is an illustration of a sensor housing containing a tiered cosine diffuser in a weather sensor station module  100  according to an embodiment of the invention. The tiered cosine diffuser  102  is located within an opening of the sensor housing  104 , the tiered cosine diffuser  102  and opening being oriented to the top of the sensor housing  104  in order to be exposed to the sun and receptive to light. The tiered cosine diffuser  102  is positioned within the sensor housing  104  such that it is relatively lower than a cutoff ring  106 , which is a ridge formed by the top surface of the sensor housing  104 . A secondary mounting  108  is present to allow for the mounting of sensors on the weather sensor station module  100  that require direct exposure to environmental conditions, or to hold a bubble level to allow a user to level the weather sensor station  100 . In embodiments of the weather sensor station, at least three mounting points  110  are present for securing the sensor station module  100  to a structure in the environment where weather monitoring is to be performed. Embodiments of the sensor station may also have a UV sensor cable  112  that connects a UV sensor within the sensor station module  100  to a computer-readable media which can store, report, and/or analyze data collected by the UV sensor within the weather sensor station module  100 . In embodiments of the sensor station, the UV sensor is a transducer that is a semiconductor photo diode that only responds to radiation in the region of interest, i.e. in the UV wavelengths. 
         [0035]    A cosine diffuser according to many embodiments is structured to have multiple tiers which controls the amount of light allowed through the translucent cosine diffuser such that the light transmitted follows the cosine response as the zenith angle increases. In some embodiments, the diffuser may be constructed of Teflon or any other appropriate diffusive material.  FIG. 2  is design schematic showing perspectives of a cosine diffuser element  200 , particularly showing a top view  202 , a side elevational view  204 , and a bottom view  206 , where the bottom view  206  indicates with line A-A the location of the cross-sectional view for  FIG. 2.1 . 
         [0036]    An embodiment of the cosine diffuser in  FIG. 2.1  shows a circular and tiered cosine diffuser  200  with a base tier  210 , a low-angle-tier  220 , a high-angle tier  230 , and a transmission cavity  240  (alternatively referred to as a sensor cavity). The tiers are concentric circles positioned in order of decreasing diameter, in increasing distance from the UV sensor positioned below the tiered cosine diffuser  200  in many embodiments. The base tier  210  has a base tier side surface  212  which, measured from the bottom of the cosine diffuser  200 , has a height of 0.038±0.005 inches, which also correlates to the thickness of the base tier  210 . The base tier  210  has a base tier top surface  214  which has a width, from the base of the low-angle tier  220  to the edge of the base tier  210 , of about 0.027 inches. The diameter of the base tier  210  is 0.580±0.002 inches. The corner of the base tier where the base tier side surface  212  meets the base tier top surface can be sloped, this base tier sloped surface  216  oriented at a 45°±5° angle between the substantively vertical base tier side surface  212  and the substantively horizontal base tier top surface  214 , the base tier sloped surface  216  having a length of about 0.007 inches. 
         [0037]    The low-angle tier  220  of the cosine diffuser  200  has a low-angle tier (“LAT”) side surface  222 , a LAT sloped surface  224 , and a LAT top surface  226 . The low-angle tier  220  can have a diameter of about 0.420 to about 0.428 inches, with a preferred diameter of about 0.426 inches. The LAT side surface  222  can have a height, measured from the point of intersection with the base tier  210 , of 0.092±0.005 inches. The low-angle tier  220  has a LAT top surface  226  which has a width, from the base of the high-angle tier  230  to the edge of the low-angle tier  220  (the edge defined as the substantively vertical plane of the LAT side surface  222 ) of about 0.142±0.005 inches. The LAT sloped surface  224  can be oriented at a 45°±5° angle between the substantively vertical LAT side surface  222  and the substantively horizontal LAT top surface  226 , the LAT sloped surface  224  having a length of about 0.025±0.005 inches. 
         [0038]    The high-angle tier  230  of the cosine diffuser  200  has a high-angle tier (“HAT”) sloped surface  234 , and a HAT top surface  236 . The point at which the HAT sloped surface  234  and the LAT top surface  226  intersect is identified as the LAT/HAT interface  232 . The high-angle tier  220  can have a diameter of 0.280±0.005 inches, while the HAT top surface  236 , also having a circular shape, can have a diameter of 0.170±0.005 inches. The high-angle tier can have a height (and corresponding thickness), measured from LAT/HAT interface  232  to the plane of the HAT top surface  236 , of 0.055±0.002 inches. The HAT sloped surface  234  can be oriented at a 45°±5° angle between the substantively horizontal LAT top surface  226  and the substantively horizontal HAT top surface  236 , the HAT sloped surface  234  and having a length of about 0.137±0.005 inches. 
         [0039]    The transmission cavity  240  is a cavity extending from the bottom side of the base tier  210  into the interior of the tiered cosine diffuser  200 , which can also have a circular shape, concentric with the base tier  210 , low-angle tier  220 , and high-angle tier  230 . The transmission cavity  240  is located on the side of the tiered cosine diffuser  200  proximate to a UV sensor, which in many embodiments, is positioned beneath the tiered cosine diffuser within a weather station sensor housing. The transmission cavity  240  can have a diameter of 0.340±0.005 inches and a depth, measured from the bottom of the base tier  210 , of 0.070±0.005 inches. Accordingly, the depth of the transmission cavity  240  can be greater than the height of the base tier  210 , which means that the transmission cavity  240  can extend through the interior volume of the base tier  210  into the interior volume of the low-angle tier  220 . A UV sensor positioned below the tiered cosine diffuser  200  may be within the volume transmission cavity  204  in physical contact with the tiered cosine diffuser  200 , within the volume transmission cavity  204  but not in physical contact with the tiered cosine diffuser  200 , or below the volume transmission cavity  204 . 
         [0040]    In  FIG. 2.2 , defining the direction normal  250  to the primary plane of the tiered cosine diffuser  200  as Θ=0°, as the zenith angle of the incident light increases, the light incident on the tiered cosine diffuser  200  reaches progressively fewer surfaces of the tiered cosine diffuser  200  residing within the sensor housing  202 . When Θ=77.6°, the incident light is blocked by the cutoff ring  204  such that the lowest point on the tiered cosine diffuser  200  exposed to direct light is the point indicated by light path  252 . This means that less light reaches the tiered cosine diffuser  200  (i.e. the surface area below light path  252 ) thus the amount of light reaching a UV sensor positioned below the tiered cosine diffuser in the sensor housing  202  receives less light. When Θ=82.8°, the incident light is blocked by the cutoff ring  204  such that the lowest point on the tiered cosine diffuser  200  exposed to direct light is the point indicated by light path  254 , with proportionally less light reaching a corresponding UV sensor. When Θ=83.8°, the incident light is blocked by the cutoff ring  204  such that the lowest point on the tiered cosine diffuser  200  exposed to direct light is the point indicated by light path  256 , with proportionally less light reaching a corresponding UV sensor. When Θ=88.5°, the incident light is blocked by the cutoff ring  204  such that the lowest point on the tiered cosine diffuser  200  exposed to direct light is the point indicated by light path  258 , with proportionally less light reaching a corresponding UV sensor. When Θ=89.0°, the incident light is blocked by the cutoff ring  204  such that the lowest point on the tiered cosine diffuser  200  exposed to direct light is the point indicated by light path  260 , with proportionally less light reaching a corresponding UV sensor. 
         [0041]    It will be appreciated that embodiments of the disclosed cosine diffuser may also have additional intermediary tiers above, in between, or below, the low-angle tier  220 , high-angle tier  230 , and base tier  210 . Moreover, the transmission cavity  240  may be designed to extend deeper into the interior of the tiered cosine diffuser  200 , or to have a cavity more than one section with different diameters and depths. In further embodiments, a portion of the tiered cosine diffuser  200 , such as the base tier  210 , may be covered by a structure securing the tiered cosine diffuser  200  within in a sensor housing. In such embodiments, the base tier  210  is not exposed to incident light regardless of zenith angle and does not contribute to the transmission of light through the tiered cosine diffuser  200 . 
         [0042]    In various aspects, it can be understood that for a cosine diffuser as disclosed, incident light can enter the high-angle tier of the cosine diffuser at a first range of zenith angles, incident light can enter the a low-angle tier of the cosine diffuser at a second range of zenith angles, and incident light can enter the base tier of the cosine diffuser at third range of zenith angles. In other aspects, the cosine diffuser includes a sensor cavity, which can accommodate a photosensor, and though which light which has entered the cosine diffuser egresses from the cosine diffuser. In further aspects, a cosine diffuser can have transmission characteristic that is independent of the azimuth angle of incident light. 
         [0043]      FIG. 3  is a graph illustrating a comparison of the cosine response between a cosine diffuser according to the embodiment shown in  FIG. 2.2  and an ideal cosine response, as well as the percentage of error in measured UV light measurement. The measurement on the right side y-axis of the graph shows the percentage of error in UV light measurement. The measurement on the left side y-axis of the graph shows a normalized measurement of the intensity (i.e. irradiance) of the light by a UV sensor, the measured light having passed through a cosine diffuse according to an embodiment of the invention. The intensity is shown on a scale from 0.00 to 1.20 normalized to the peak value of the irradiance of the light. As evident from the graph, starting at an zenith angle of about 60° (viewed from either a positive or negative angle side), the amount of light received by the UV sensor is greater than the expected light that should be observed, creating an increasing false-positive error. This false positive error continues to increase to about 4.5% until around about Θ=75°, where at this point, the cutoff ring begins to physically block the incident light from reaching the surfaces of the cosine diffuser. However, in part because the cutoff is abrupt, the amount of light sensed by the UV sensor quickly falls, and the corresponding measurement similarly quickly falls from being a false-positive error value (measuring more light than actually present) to a measuring a erroneously low value, a false-negative error of about negative 7%. The average error, as a percentage of the full range of zenith angles from −90° to 90°, is an error of about negative 0.35%. This error is, as evident, more pronounced and more problematic at the extremes of the angle range. 
         [0044]    In many embodiments, the cutoff ring of the sensor housing is designed and configured to mitigate against erroneous measurements of light by manipulating the amount of light that reaches a cosine diffuser. Such embodiments can use a comb structure where an irregular, serrated, castellated, and or repeating prong and tooth sequence obstructs and thus attenuates incident light from reaching a cosine diffuser resting within the sensor housing. Some embodiments may be distinguished from diffraction gratings, as the irregularity of the obstructions are of a dimensional scale significantly larger than the wavelength of visible or UV light. Thus, while embodiments of cutoff combs may attenuate incident light, they do not necessarily cause light to diffract on a scale close to the wavelength of the incident light. 
         [0045]      FIG. 4  is an illustration of a sensor housing containing a tiered cosine diffuser in a weather sensor station module  400  according to many embodiments. The tiered cosine diffuser  402  is situated within an opening of the sensor housing  404 , the tiered cosine diffuser  402  and opening being oriented to the top of the sensor housing  404  in order to be exposed to the sun and receptive to light. The tiered cosine diffuser  402  is positioned within the sensor housing  404  such that it is relatively lower than a cutoff comb  406 , which is a patterned ridge formed by the top surface of the sensor housing  404 . In embodiments, a secondary sensor  408  can be mounted within a secondary sensor mounting  410 , the secondary sensor  408  being a type of sensor that requires direct exposure to environmental conditions for its related measurements. In embodiments, mounting points  412  are present for securing the weather sensor station module  400  to a structure in the environment where weather monitoring is to be performed. Many embodiments may also have a UV sensor cable  414  that connects a UV sensor within the sensor housing  404  to a computer-readable media which can store, report, and/or analyze data collected by the UV sensor within the weather sensor station module  400 . 
         [0046]    The cutoff comb  406  regulates the amount of light incident on the tiered cosine diffuser  402  as the zenith angle of the incident light increases (again defining the direction normal  250  to the primary plane of the tiered cosine diffuser  402  as Θ=0°). The cutoff comb  406  presents prongs and slits as obstacles to light incident on the tiered cosine diffuser  402 , through which incident light will be attenuated. The interference of the incident light thus alters the amount and intensity of the light as a function of Θ as it passes through the cutoff comb  406  structure and reaching the tiered cosine diffuser  402 . Accordingly, the amount of light that is diffused through the tiered cosine diffuser  402  and reaches a UV sensor below the tiered cosine diffuser  402  and within the sensor housing  404  is dependent on the amount of light that passes through the cutoff comb  406  structure at high zenith angles. 
         [0047]      FIG. 5  illustrates a section of a weather station module  500  according to many embodiments having a sensor housing  502 , a cutoff comb  504  and a tiered cosine diffuser  506  residing in an opening in the top surface of the sensor housing  502 . Generally, as the zenith angle of the incident light increases, the light incident on the tiered cosine diffuser  506  reaches progressively fewer surfaces of the tiered cosine diffuser  506 . In  FIG. 5 , the incident light is shown as striking the weather station module  500  at a zenith angle of Θ=65° (defining the direction normal  501  to the primary plane of the tiered cosine diffuser  506  as Θ=0°). Before the incident light at an increasing zenith angle is occluded and attenuated by the cutoff comb  504 , the amount of light transmitted through the cosine diffuser  506  is 100% of the incident light. Exemplary light paths  508  and  510  represent the range of incident light unobstructed by the cutoff comb  504 , at which 100% (i.e. the full strength) of the incident light is transmitted through the tiered cosine diffuser  506 . When the incident light begins to be blocked in-part by the cutoff comb  504 , the amount of light that passes through the cutoff comb  504 , and thus to the cosine diffuser  506 , is reduced from 100%. At a zenith angle of Θ=65°, incident light below exemplary light path  510  is only 75% of full strength of the incident light. Similarly, the amount of light along the exemplary light path  512  is only 73% of full strength of the incident light and the amount of light above the exemplary light path  514  is only 72% of full strength of the incident light. In embodiments, the cosine diffuser  506  is secured within the sensor housing  502  such that light along and above light path  512  reaches and is transmitted through the cosine diffuser  502 , but light below light path  512  is blocked by a securing structure holding the tiered cosine diffuser  506  within the sensor housing  502 . In such embodiments, no light below exemplary light path  512  reaches the tiered cosine diffuser  506 , and thus the average light transmission that passes through the cutoff comb  504  between exemplary light path  510  and light path  514 , and subsequently transmitted through the cosine diffuser  506 , is 74% of full strength of the incident light. 
         [0048]    In embodiments, the molding of the spaces or slits between the prongs of the cutoff comb  506  is tapered, such that the space between each prong of the cutoff comb  506  narrows toward the bottom of the prongs. The extent of the tapering can affect both the structural strength of the prongs as well as the light attenuation of the cutoff comb  506 , and thus the related cosine response measured. In some embodiments, the individual prongs may be configured to have a T-shaped prong, where a first portion of the prong is constructed along the circumference of a cutoff ring ridge and the second portion of the prong juts out orthogonally to the first portion of the prong. 
         [0049]    In embodiments, a cutoff comb  506  will be constructed to allow incident light to pass through and strike a cosine diffuser  502  with an average and relatively equal intensity in all directions of azimuth. In other words, the alternating prongs and openings of the cutoff comb  506  are distributed such that along any incremental portion of the cutoff comb  506 , there is a ratio of open space (i.e. the slits between the prongs) to closed space (i.e. the space blocked by the prongs) that allows for an evenly distributed amount of light attenuation. In such embodiments, the pitch between the prongs of the cutoff comb  506  can be approximately half the diameter of the cosine diffuser  502 , or less. 
         [0050]      FIG. 6  is a graph illustrating a comparison of the cosine response between a sensor housing according to many embodiments with a cutoff comb as shown in  FIG. 5  and an ideal cosine response as well as the percentage of error in measured UV light measurement. The measurement on the right side y-axis of the graph shows the percentage of error in UV light measurement. The measurement on the left side y-axis of the graph shows a normalized measurement of the intensity (i.e. irradiance) of the light by a UV sensor, the measured light having passed through a cutoff comb according to embodiments of the invention. The intensity is shown on a scale from 0.00 to 1.20 normalized to the peak value of the irradiance of the light. As evident from the graph, starting at an zenith angle of about 60° (viewed from either a positive or negative angle side), the amount of light received by the UV sensor is greater than the expected light that should be observed, creating an increasing false-positive error. This false positive error continues to increase to about 1.7% until around about Θ=75°, where at this point, the cutoff ring begins to physically block the incident light from reaching the surfaces of the cosine diffuser. It is noted that this false-positive error is smaller in magnitude than the error seen in  FIG. 3  which does not include a cutoff comb according to an embodiment of the invention. As the incident light begins to interact and attenuate as it passes through the cutoff comb, the amount of light sensed by the UV sensor falls, and the corresponding measurement similarly falls from being a false-positive error value (measuring more light than actually present) to a measuring a erroneously low value, a false-negative error of less than about negative 1.7%. Again, it is noted that this false-negative error is smaller in magnitude than the error seen in  FIG. 3  which does not include a cutoff comb according to an embodiment of the invention. The average error, as a percentage of the full range of zenith angles from −90° to 90°, is an error of about negative 0.19%. This error is more pronounced at the extremes of the angle range. 
         [0051]      FIGS. 7.1 ,  7 . 2 , and  7 . 3  illustrate embodiments of segments of a cutoff comb where the comb has a sawtooth structure. In  FIG. 7.1 , a first sawtooth structure  700  has, over a repeating span, a first peak  702 , a first vertex  704 , a second peak  706 , and a second vertex  708 . In  FIG. 7.2 , a second sawtooth structure  710  has, over the span of one repeating segment, a first peak  712 , a central vertex  714 , and a second peak  716  (where the second peak  716  may be the first peak  712  of the following segment, and vice versa). In  FIG. 7.3 , a third sawtooth structure  720  has, over the span of one repeating segment, a first peak  722 , a first vertex  724 , a second peak  726 , a second vertex  708 , and a third peak  729  (where the third peak  729  may be the first peak  722  of the following segment, and vice versa). In some embodiments, the sawtooth structure can have twenty teeth equally distributed around the circumference of the cutoff comb, such that each repeating peak and vertex segment constitutes 18° of the circumference. 
         [0052]      FIG. 8  illustrates a section of a weather station module  800  according to many embodiments having a sensor housing  802 , a cutoff comb  804 , and a tiered cosine diffuser  806  residing in an opening in the top surface of the sensor housing  802 . The cutoff comb  804  illustrated in  FIG. 8  represents an embodiment using the sawtooth design as disclosed in relation to  FIG. 7 . In  FIG. 8 , the incident light is shown as striking the weather station module  800  at a zenith angle of Θ=70° (defining the direction normal  801  to the primary plane of the tiered cosine diffuser  806  as Θ=0°). The sawtooth cutoff comb  804  can have prongs or teeth having a height of 0.070 inches, measured from the base of a comb tooth defined by the intersection of the sawtooth comb  804  vertices to the top ridge of the sawtooth comb  804 . Before the incident light at an increasing zenith angle is occluded and attenuated by the sawtooth cutoff comb  804 , the amount of light transmitted through the cosine diffuser  806  is 100% of the incident light. Exemplary light paths  808  and  810  represent the range of incident light unobstructed by the sawtooth cutoff comb  804 , at which 100% (i.e. the full strength) of the incident light is transmitted through the tiered cosine diffuser  806 . When the incident light begins to be blocked in-part by the sawtooth cutoff comb  804 , the amount of light that passes through the sawtooth cutoff comb  804 , and thus to the cosine diffuser  806 , is reduced from 100%. At a zenith angle of Θ=70°, incident light below exemplary light path  810  is only 48% of full strength of the incident light. Similarly, the amount of light along the exemplary light path  812  is only 24% of full strength of the incident light and the amount of light below the exemplary light path  814  is reduced to 0% of the incident light. The average light transmission that passes through the sawtooth cutoff comb  804  between exemplary light path  810  and light path  814 , and subsequently transmitted through the cosine diffuser  806 , is 24% of full strength of the incident light. In embodiments, the angle of the vertex where the individual prongs of the sawtooth cutoff comb  804  meet is about 30°, or about 15° as measured from each side of the slope of the sawtooth structure. 
         [0053]    In embodiments, a sawtooth cutoff comb  804  will be constructed to allow incident light to pass through and strike a cosine diffuser  806  with an average and relatively equal intensity in all directions of azimuth. In other words, the alternating prongs and openings of the sawtooth cutoff comb  804  are distributed such that along any incremental portion of the sawtooth cutoff comb  804 , there is a ratio of open space (i.e. the slits between the prongs) to closed space (i.e. the space blocked by the prongs) that allows for an evenly distributed amount of light attenuation. In such embodiments, the pitch between the prongs of the sawtooth cutoff comb  804  can be approximately half the diameter of the cosine diffuser  806 , or less. 
         [0054]      FIG. 9A  is side perspective design schematic of a cutoff comb and weather station module sensor housing  900  according to an embodiment. In such an embodiment, the sensor housing  902  has a height from the base of the sensor housing to the bottom edge of the cutoff comb  904  of 1.92±0.01 inches. The sensor housing is molded to have an external secondary mounting  906  on one side of the sensor housing  902  flush with the base of the sensor housing  902 , and a first sensor housing mounting point  907  also flush with the sensor housing  902  and directly opposite of the external secondary mounting  906 . The sensor housing  902  additionally has a pair of molded external fin structures  903  located on either side of the sensor housing  902  perpendicular to the axis of symmetry. The external fins  903  can be used to aid in aligning the weather station with the direction of the incident irradiance. 
         [0055]      FIG. 9B  is top perspective design schematic of a cutoff comb and weather station module sensor housing  900  according to an embodiment of the invention. The cutoff comb  904  is molded on the top of the sensor housing  902  and surrounds an upper opening  905  in the top of the sensor hosing  902 . In such an embodiment as shown in  FIG. 9B , the axis of symmetry  901  is represented by the plane A-A. In addition to the first sensor housing mounting  907  positioned opposite of the external secondary mounting  906 , in an embodiment, the second housing mounting  908  and a third housing mounting  909  are positioned on the same side of the sensor housing  902  as the external secondary mounting  906 , equidistant from each other and from the first housing mounting  907 . The distance from the midpoint of the upper opening  905  to the midpoint of the midpoint of the first housing mounting  907  is 0.880±0.005 inches. The distance from the midpoint of the upper opening  905  to the midpoint of the second housing mounting  908  or third housing mounting  909 , along the axis of symmetry  901 , is 0.540±0.005 inches. The distance from the midpoint of the upper opening  905  to the midpoint of the second housing mounting  908  or third housing mounting  909 , perpendicular to the axis of symmetry  901 , is 0.770±0.005 inches. Similarly, the distance from the midpoint of the external secondary mounting  906 , perpendicular to the axis of symmetry  901 , to the midpoint of the second housing mounting  908  or third housing mounting  909  is 0.770±0.005 inches. The distance from the midpoint of the external secondary mounting  906 , along to the axis of symmetry  901 , to the midpoint of the second housing mounting  908  or third housing mounting  909  is 0.52±0.01 inches. Each sensor housing mounting has a hole in its center along the vertical axis of the sensor housing  902  to allow of a mounting structure to pass through, the diameter of the mounting holes  911  each being 0.184±0.005 inches. The external secondary mounting  906  similarly has an external secondary opening  912  vertical axis of the sensor housing  902  having a diameter of 0.30±0.01 inches. The sensor housing  902  can be further molded to have a generally cone-shaped structure, with curved indentations to allow for objects to easily fit into the mounting holes  911  and/or the external secondary opening  912 . 
         [0056]      FIG. 9C  is bottom perspective design schematic of a cutoff comb and weather station module sensor housing  900  according to an embodiment of the invention. In an embodiment, the sensor housing  902  is generally cone-shaped, and has a diameter from its center to the furthest exterior edge of the principal cone structure (i.e. the measurement not including the external secondary mounting or any of the housing mountings) of 1.82±0.01 inches. The molded fins  903  on the sensor housing  902  have a thickness of 0.07±0.01 inches, and the distance between the outermost points of the external fins  903 , i.e. the width of the sensor housing  902  perpendicular to the axis of symmetry  901 , is 1.98±0.01 inches. 
         [0057]      FIG. 9D  is a cross-sectional side perspective design schematic of a cutoff comb and weather station module sensor housing  900  according to an embodiment of the invention, the cross-section being along the along the axis of symmetry  901  represented in  FIG. 9B  as the plane A-A. The interior volume  910  of the sensor housing  902  is the hollow area in which sensors, such as a UV sensor, can reside, the sensor housing  902  acting as a protective shell to such sensors. Internal fin structures  913  are molded from the interior surface of the sensor housing  902 , the internal fins  913  providing structural support to the overall sensor housing  902 . The height from the base of the sensor housing  902  to the top of the cutoff comb  904  is 2.08±0.01 inches. The height from the base of the sensor housing  902  to the top of the external secondary mounting  906  is 0.88±0.01 inches. The height from the base of the sensor housing  902  to the top of each housing mounting  907 ,  908 , and  909  is also 0.88±0.01 inches. The height from the base of each mounting hole  911  in each of the housing mountings to the top of the external secondary mounting  906  is 1.380±0.005 inches. 
         [0058]      FIG. 9D  further details that the external secondary mounting  906  is molded to have an external secondary opening  912 , which is situated at the bottom of a two-stage cavity, having a first stage of the cavity  914  directly proximate to the external secondary opening  912 , and the second stage of the cavity  916  directly proximate to the first sage cavity  914 . In many embodiments, a sensor for a weather station that requires direct exposure to the ambient environment may sit within the two stage cavity,  914  and  916 , connected to additional apparatus through a structure going through the external secondary opening  912 . The distance from the bottom of the external secondary opening  912  to the base of the sensor housing  902  is 0.61±0.01 inches. The distance from the bottom of the first stage cavity  914  to the base of the sensor housing  902  is 0.67±0.01 inches. The first stage cavity  914  can have a diameter of 0.61±0.01 inches and a depth of 0.05±0.01 inches. The second stage cavity  916  can have a diameter greater than the diameter of the first stage cavity  914 , as appropriate to hold an external secondary, where the second stage cavity  916  diameter is 0.70±0.01 inches and the distance from top of the second stage cavity  916  to the base of the sensor housing  902  is 0.88±0.01 inches (i.e. the height from the base of the sensor housing  902  to the top of the external secondary mounting  906 ). The distance from the interior wall surface of the main body of the sensor housing  902  distal to the exterior wall surface of the external secondary mounting  906  is 2.11±0.01 inches. The distance from the midpoint of the main body of the sensor housing  902  (which is in line with the center of the upper opening  905 , as well as the point of intersection between the axis of symmetry  901  and the plane one which the external fins  903  reside) to the exterior wall surface of the external secondary mounting  906  is 1.50±0.01 inches. The distance from the interior wall surface of the main body of the sensor housing  902  proximate to the exterior wall surface of the external secondary mounting  906  is 0.85±0.01 inches. 
         [0059]      FIG. 9E  is a cross-sectional side perspective design schematic of a cutoff comb and weather station module sensor housing  900  according to an embodiment of the invention, the cross-section being along the along the axis of symmetry  901  represented in  FIG. 9B  as the plane A-A. The first housing mounting  907  (as well as the second housing mounting  908  and the third housing mounting  909 , though not shown in  FIG. 9E ) has a mounting hole  911  with an interior diameter of 0.18±0.01 inches. The molded structure forming the mounting hole  911  also has an exterior diameter of 0.31±0.01 inches. The molded structure of the mounting hole  911  forms a column that extends into the interior volume  910  of the sensor housing  902 , where the outer edge of the bottom of that column can be cut at an angle, relative to the horizontal base of the sensor housing  902 , of 30°±5°. The sensor housing  902  and defines an upper opening  905  which has a diameter of 0.74±0.01 inches. The upper opening  905  is located at the bottom of a cavity defined by the cutoff comb  904 , the interior diameter of the cavity defined by the cutoff comb  904  being 1.014±0.005 inches. The portion of the sensor housing  902  forming the floor of the cavity  916  that extends from the base of the cutoff comb  904  to the edge of the upper opening  905  can be beveled to be at an angle equivalent to an zenith angle of 83°, where an zenith angle of 0° is equal to the vertical axis of the sensor housing  902 . The interior wall surface of the cutoff comb  904  can also be molded to be at an angle of 2° from the vertical axis of the sensor housing  902 . The width of the main body of the sensor housing can be 1.28±0.01 inches. 
         [0060]      FIG. 9F  is a detail section of  FIG. 9E , specifically of the cutoff comb  904 , showing both a side cross-section and top perspective of the cutoff comb  904 . The cutoff comb  904  is made of an alternating prong  920  and slit  922  structure, which is molded as a circular ridge along the top of the sensor housing  902 . The pitch, height, and width of the prongs  920 , and the corresponding depth and width of the slits  922 , affect the attenuation effect of light incident that passes through the cutoff comb  904 . The width of a slit  922  in the cutoff comb  904 , and thus the distance between two prongs  920 , is 0.025±0.005 inches. 
         [0061]      FIG. 9G  is a detail section of  FIG. 9E , specifically of the prong and slit structure of the cutoff comb  904 . The slits  922  of the cutoff comb  904  have a valley structure  924  which can be 0.010±0.005 inches in depth, measured from the base plane of the prongs  920  of the cutoff comb  904 . The angle and shape of the valley structure  924  can also affect the attenuation effect of light incident that passes through the cutoff comb  904 . The prongs  920  of the cutoff comb  904  can have a height, measured from the uppermost portion of the valley structure  924 , of 0.070±0.005 inches. 
         [0062]      FIG. 10  is a detailed illustration of a weather station module sensor housing cutoff comb structure  1000  according to an embodiment of the invention. A tiered cosine diffuser  1002  according to such an embodiment resides within a housing structure, where incident light at certain zenith angles is interfered with by the cutoff comb structure  1000  made from prongs  1004  and slits  1006 , connected where the prongs are connected by the base structure  1008  of the cutoff comb  1000 . When the zenith angle of incoming light reaches the top of the cutoff comb structure  1000 , identified as a first cutoff comb plane  1010 , which defined by the top edges of the prongs  1004 , about 75% of the incident light is transmitted past the cutoff comb structure due to attenuation effects. When the zenith angle of incoming light reaches the bottom of the prongs  1004 , identified as a second cutoff comb plane  1012 , which is also defined by the edges of the base structure  1008 , about 72% of the incident light is transmitted past the cutoff comb structure due to attenuation effects. On average, about 73.5% of incident light passes through the cutoff comb structure  1000 . In embodiments, the first cutoff comb plane  1010  is relatively higher than the top surface or uppermost portion of the cosine diffuser  1002 . In other embodiments, the second cutoff comb plane  1012  is relatively lower than the top surface or uppermost portion of the cosine diffuser  1002 . 
         [0063]    In embodiments, the molding of the spaces or slits between the prongs of the cutoff comb structure  1000  is tapered, such that the space of a slit  1006  between each prong  1004  of the cutoff comb structure  1000  narrows toward the bottom of the prongs  1004 . The extent of the tapering can affect both the structural strength of the prongs  1004  as well as the light attenuation of the cutoff comb structure  1000 , thus the related cosine response measured. In some embodiments, at the top of the cutoff comb structure  1000 , the individual prongs  1004  may have a width of about 0.036 inches, and each slit  1006  may have a width of about 0.110 inches. In such embodiments, while at the bottom of the cutoff comb structure  1000 , the individual prongs  1004  may have a width of about 0.041 inches, and each slit  1006  may have a width of about 0.104 inches. In embodiments, the cutoff comb structure  1000  may have a height of about 0.120 inches, as measured from the base of the cutoff comb structure to its top. 
         [0064]    In embodiments, a cutoff comb structure  1000  will be constructed to allow incident light to pass through and strike a tiered cosine diffuser  1002  with an average and relatively equal intensity in all directions. In other words, the alternating prongs  1004  and slits  1006  of the cutoff comb structure  1000  are distributed such that along any incremental portion of the cutoff comb structure  1000 , there is a ratio of open space (i.e. the slits  1006 ) to closed space (i.e. the prongs  1004 ) that allows for an evenly distributed amount of light attenuation. In such embodiments, the pitch between the prongs  1004  of the cutoff comb structure  1000  can be approximately half the diameter of the cosine diffuser  1002 , or less. 
         [0065]    With these aspects in mind, it will be apparent from this description that aspects of the described techniques may be embodied, at least in part, in software, hardware, firmware, or any combination thereof. It should also be understood that aspects can employ various computer-implemented functions involving data stored in a data processing system. That is, the techniques may be carried out in a computer or other data processing system in response executing sequences of instructions stored in memory. In various aspects, hardwired circuitry may be used independently, or in combination with software instructions, to implement these techniques. For instance, the described functionality may be performed by specific hardware components, such as a specialized computer in communication with a photosensor located within a housing receiving sensory stimulus through a cosine diffuser, containing hardwired logic for performing operations, or by any combination of custom hardware components and programmed computer components. The techniques described herein are not limited to any specific combination of hardware circuitry and software. 
         [0066]    The above description is illustrative and is not restrictive, and as it will become apparent to those skilled in the art upon review of the disclosure, that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. For example, any of the aspects described above may be combined into one or several different configurations, each having a subset of aspects. These other embodiments are intended to be included within the spirit and scope of the present invention. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the following and pending claims along with their full scope of equivalents.