Abstract:
Apparatuses and methods for improving the accuracy of an analyte sensor are disclosed. The sensor may include a photodetector and a low angle sensitive (LAS) optical filter. The photodetector may be configured to convert received light into current indicative of the intensity of the received light. The LAS optical filter may be configured to prevent light having a wavelength outside a band pass region from reaching the photodetector and to pass light having a wavelength within the band pass region to the photodetector. The percentage of light passing through the LAS optical filter may decrease as the angle of incidence of the light increases.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of priority to U.S. Provisional Application Ser. No. 62/024,595, filed on Jul. 15, 2014, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates generally to an optical filtering system in a sensor configured to detect an analyte within a medium within a living animal. The present invention also relates to an optical filtering system having low sensitivity to high angle of incidence light. 
         [0004]    2. Discussion of the Background 
         [0005]    A sensor may be implanted within a living animal to measure an analyte in a medium within the living animal. Examples of implantable sensors employing an analyte indicator to measure an analyte are described in U.S. Pat. No. 8,233,953 and U.S. Patent Application Publication Nos. 2013/0211213, 2013/0241745, and 2013/0324819, all of which are incorporated by reference in their entireties. 
         [0006]      FIG. 1  illustrates a cross-sectional view of an example of an existing sensor  100 .  FIG. 2  illustrates a cross-sectional view of the existing sensor  100  in operation.  FIG. 3  is a schematic view of the existing sensor  100 .  FIG. 4  illustrates various sources of light in the optical system of the optical system of the existing sensor  100 . The sensor  100  includes a light source  108  that emits excitation light  129  (e.g., at an excitation wavelength of 378 nm) to an analyte indicator  106  (e.g., a polymer graft) containing indicator molecules  104  (see  FIG. 3 ). The indicator molecules  104  have an optical characteristic that varies based on the concentration of the analyte in the medium. In particular, when excited by the excitation light  129 , indicator molecules  104  that have bound the analyte emit (i.e., fluoresce) light  131  having a wavelength different than the wavelength of the excitation light  129  (e.g., the emission light  131  may have a wavelength range of about 400 nm to 500 nm with a peak emission wavelength around 435 nm) (see  FIG. 4 ). Higher analyte levels correspond to a greater amount of emission light  131  of the indicator molecules  104  in the analyte indicator  106 , and, therefore, a greater amount of photons striking a first photodetector (e.g., photodiode)  110 . 
         [0007]    The sensor  100  includes a first dichroic band pass filter  111  (thin film) that filters light incident on the first photodetector  110 . The first dichroic band pass filter  111  is designed to only pass light having the wavelength of the light emitted by the indicator molecules  104  (e.g., light within the range of about 400 nm to 500 nm) so that, in theory, the first photodetector  110 , which is a signal photodetector, only receives the light emitted by the indicator molecules  104 . 
         [0008]    In sensors having multiple channels (e.g., a signal channel and a reference channel) and/or multiple photodiodes, the sensor may include a dichroic band pass filter for each channel and/or photodetector. For instance, as shown in  FIGS. 1-3 , existing sensor  100  includes a second dichroic band pass filter  113  (thin film) that filters light incident on a second photodetector  112 . The second dichroic band pass filter  113  is designed to only pass light having the wavelength of reference light so that, in theory, the second photodetector  112 , which is a reference photodetector, only receives the reference light. In the existing sensor  100 , the first photodetector  110  and the second photodetector  112  are arranged symmetrically on either side of the light source  108 . 
         [0009]    In the existing sensor  100 , the dichroic band pass filter  111  is coated onto a glass slide  220 , which is then attached to the photodetector  110 , and the dichroic band pass filter  113  is coated onto a glass slide  222 , which is then attached to the photodetector  112 . In existing sensor  100 , light (e.g., reflected excitation light  129  and fluorescent light  131  emitted by the indicator molecules  104  in the analyte indicator  106 ) passes through one or more glass slides  220  and  222 . 
         [0010]    The existing sensor  100  includes a sensor housing  102  (i.e., body, shell, capsule, or encasement), which may be rigid and biocompatible. The sensor housing  102  is formed from a suitable, optically transmissive polymer material (e.g., epoxy), such as, for example, acrylic polymers (e.g., polymethylmethacrylate (PMMA)). The sensor housing  102  may be any shape suitable for implantation into a living animal. The existing sensor  100  includes a substrate  116  and an encoder  118  that encodes the data before it is conveyed to an external transceiver. 
         [0011]    In practice, the dichroic filters  111  and  112  allow the passage of light that was not intended to pass through, which may degrade the accuracy of the sensor. Accordingly, there is a need for sensors having improved accuracy and in which these problems are substantially reduced or eliminated. 
       SUMMARY 
       [0012]    The present invention overcomes the disadvantages of prior systems by providing, among other advantages, a low angle sensitive (LAS) optical filter to reduce the transmission of light having high angles of incidence to the photodetector. That is, the LAS optical filter may have a transmission efficiency that is dependent on angle of incidence such that the transmission efficiency of the LAS optical filter decreases as the angle of incidence increases. In addition, the LAS optical filter may be configured to prevent light having a wavelength outside a band pass region from reaching the photodetector and to pass light having a wavelength within the band pass region to the photodetector. 
         [0013]    One aspect of the invention may provide a sensor for measurement of an analyte in a medium within a living animal. The sensor may include a photodetector and a low angle sensitive (LAS) optical filter. The photodetector may be configured to convert received light into current indicative of the intensity of the received light. The LAS optical filter may be configured to prevent light having a wavelength outside a band pass region from reaching the photodetector and to pass light having a wavelength within the band pass region to the photodetector. The percentage of light passing through the LAS optical filter may decrease as the angle of incidence of the light increases. 
         [0014]    Another aspect of the invention may provide a method of detecting an analyte using a sensor. The sensor may comprise a light source, an analyte indicator, a low angle sensitive (LAS) optical filter having low sensitivity to high angle incidence light, and a photodetector. The method may include irradiating, by the light source, excitation light to the analyte indicator. The method may include emitting, by the analyte indicator, emission light to the LAS optical filter. The method may include receiving, by the LAS optical filter, light including emission light emitted by the analyte indicator. The method may include preventing, by the LAS optical filter, light of the received light having one or more of a wavelength outside a band pass region and a high angle of incidence from reaching the photodetector. The method may include passing, by the LAS optical filter, light of the received light having a wavelength within the band pass region to the photodetector. The percentage of light passed by the LAS optical filter may decrease as the angle of incidence of the light increases. The method may include receiving, by the photodetector, the passed light. 
         [0015]    Another aspect of the invention may provide a method of manufacturing an analyte sensor. The method may include fabricating or mounting a photodetector in or on a substrate and forming a low angle sensitive (LAS) optical filter by depositing layers of metal and oxides on the photodetector. The LAS optical filter may be configured to prevent light having a wavelength outside a band pass region from reaching the photodetector and to pass light having a wavelength within the band pass region to the photodetector. The percentage of light passed through the LAS optical filter may decrease as the angle of incidence of the light increases. 
         [0016]    Further variations encompassed within the sensors, systems and methods are described in the detailed description of the invention below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
           [0018]    The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various, non-limiting embodiments of the present invention. In the drawings, like reference numbers indicate identical or functionally similar elements. 
           [0019]      FIG. 1  is a cross-sectional view of an example of an existing sensor. 
           [0020]      FIG. 2  is a cross-sectional view of the example of an existing sensor in operation. 
           [0021]      FIG. 3  is a schematic view of an existing sensor. 
           [0022]      FIG. 4  illustrates various sources of light in the optical system of the optical system of the existing sensor  100 . 
           [0023]      FIG. 5  is a graph illustrating ideal signal and reference filter passbands, the spectrum of excitation light emitted by the light source, and the spectra of high and low emissions of indicator molecules of the analyte indicator. 
           [0024]      FIG. 6  is a graph illustrating the transmission percentage of a signal channel dichroic band pass filter at different angles of incidence. 
           [0025]      FIG. 7  is a graph illustrating the transmission percentage of a reference channel dichroic band pass filter at different angles of incidence. 
           [0026]      FIGS. 8A-8C  illustrate pre-diced glass slides coated with dichroic filters. 
           [0027]      FIG. 9  is a schematic view of a sensor embodying aspects of the present invention. 
           [0028]      FIG. 10  is a graph illustrating the transmission percentage of a signal channel low angle sensitive filter embodying aspects of the present invention at different angles of incidence. 
           [0029]      FIG. 11  is a graph illustrating the transmission percentage of a reference channel low angle sensitive filter embodying aspects of the present invention at different angles of incidence. 
           [0030]      FIG. 12  is a schematic view of low angle sensitivity (LAS) optical filters on the substrate of a sensor embodying aspects of the present invention and a graph illustrating the transmission percentage of the LAS optical filters at different wavelengths. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0031]      FIG. 9  is a schematic view of a sensor  900  embodying aspects of the present invention. In some non-limiting embodiments, the sensor may be part of an analyte monitoring system. The system may include the sensor and an external transceiver. In some non-limiting embodiments, the sensor may be a fully implantable continuous analyte (e.g., glucose, oxygen, cardiac markers, low-density lipoprotein (LDL), high-density lipoprotein (HDL), or triglycerides) monitoring sensor. The sensor may be implanted in a living animal (e.g., a living human) and may wirelessly communicate with the external transceiver (e.g., via an inductive magnetic link). The sensor may be implanted, for example, in a living animal&#39;s arm, wrist, leg, abdomen, peritoneum, intravenously, or other region of the living animal suitable for sensor implantation. For example, in one non-limiting embodiment, the analyte sensor may be implanted beneath the skin (e.g., in the subcutaneous or peritoneal tissues), and no portion of the sensor protrudes from the skin. Although, in some embodiments, the sensor may be a fully implantable sensor, this is not required, and, in some alternative embodiments, the analyte sensor may be a transcutaneous sensor having a wired connection to an external transceiver. For example, in some alternative embodiments, the analyte sensor may be located in or on a transcutaneous needle (e.g., at the tip thereof). In some embodiments, the analyte sensor may be an optical sensor (e.g., a fluorometer). In some embodiments, the analyte sensor may be a chemical or biochemical sensor. In a non-limiting embodiment, the sensor  900  may be a highly miniaturized dual channel precision fixed wavelength fluorimeter. In some non-limiting embodiments, the analyte sensor may be capable of being continuously implanted for at least 90 days or longer and may be replaced thereafter. 
         [0032]    In some non-limiting embodiments, as illustrated in  FIG. 9 , the sensor  900  may be encased in a sensor housing  102  (i.e., body, shell, capsule, or encasement), which may be rigid and biocompatible. The sensor  900  may include an analyte indicator  106 , such as, for example, a polymer graft coated, diffused, adhered, or embedded on or in at least a portion of the exterior surface of the sensor housing  102 . The analyte indicator  106  (e.g., polymer graft) of the sensor  900  may include indicator molecules  104  (e.g., fluorescent indicator molecules) exhibiting one or more detectable properties (e.g., optical properties) based on the amount or concentration of the analyte in proximity to the analyte indicator element. In some embodiments, the sensor  900  may include a light source  108  that emits excitation light  129  over a range of wavelengths that interact with the indicator molecules  104 . The sensor  900  may also include one or more photodetectors  110 ,  112  (e.g., photodiodes, phototransistors, photoresistors, or other photosensitive elements). The one or more photodetectors (e.g., photodetector  110 ) may be sensitive to emission light  131  (e.g., fluorescent light) emitted by the indicator molecules  104  such that a signal generated by a photodetector (e.g., photodetector  110 ) in response thereto that is indicative of the level of emission light  131  of the indicator molecules and, thus, the amount of analyte of interest (e.g., glucose). In some non-limiting embodiments, one or more of the photodetectors (e.g., photodetector  112 ) may be sensitive to excitation light  129  that is reflected from the analyte indicator  106 . In one non-limiting embodiment, the excitation light  329  may have a wavelength of approximately 378 nm, and the emission light  331  may have a wavelength in the range of 400 to 500 nm with a peak emission around 435 nm, as shown in  FIG. 5 . However, this is not required, and, in some alternative embodiments, the excitation light  329  and/or emission light  131  have different wavelengths. 
         [0033]    In some embodiments, as illustrated in  FIG. 9 , the sensor  900  may include a substrate  116 . In some embodiments, the substrate  116  may be a circuit board (e.g., a printed circuit board (PCB) or flexible PCB) on which circuit components (e.g., analog and/or digital circuit components) may be mounted or otherwise attached. However, in some alternative embodiments, the substrate  116  may be a semiconductor substrate having circuitry fabricated therein. The circuitry may include analog and/or digital circuitry. Also, in some semiconductor substrate embodiments, in addition to the circuitry fabricated in the semiconductor substrate, circuitry may be mounted or otherwise attached to the semiconductor substrate  116 . In other words, in some semiconductor substrate embodiments, a portion or all of the circuitry, which may include discrete circuit elements, an integrated circuit (e.g., an application specific integrated circuit (ASIC)) and/or other electronic components (e.g., a non-volatile memory), may be fabricated in the semiconductor substrate  116  with the remainder of the circuitry is secured to the semiconductor substrate  116 , which may provide communication paths between the various secured components. 
         [0034]    In some embodiments, one or more of the sensor  900 , sensor housing  102 , analyte indicator  106 , indicator molecules  104 , light source  108 , photodetectors  110  and  112 , and substrate  116  may include some or all of the structural and/or functional features described in one or more of U.S. application Ser. No. 13/761,839, filed on Feb. 7, 2013, U.S. application Ser. No. 13/937,871, filed on Jul. 9, 2013, and U.S. application Ser. No. 13/650,016, filed on Oct. 11, 2012, all of which are incorporated by reference in their entireties. 
         [0035]    In some embodiments, light may have to pass through one or more low angle sensitive (LAS) optical filters before reaching the one or more photodetectors. The LAS optical filters may be configured to allow specific wavelengths of light to pass. In some non-limiting embodiments, as shown in  FIG. 9 , the sensor  900  may include a signal channel LAS optical filter  937 , and light may have to pass through the signal channel LAS optical filter  937  before reaching the signal channel photodetector  110 . In some non-limiting embodiments, the sensor  900  may include reference channel LAS optical filter  939 , and light may have to pass through the reference channel LAS optical filter  939  before reaching the reference channel photodetector  112 . 
         [0036]    The signal channel LAS optical filter  937  may be configured to pass a narrow band of wavelengths including the wavelength of the emission light  131  emitted (e.g., fluoresced) by the indicator molecules  104  in the analyte indicator  106 . For instance, in embodiments where the peak emission of the indicator molecules  104  occurs around 435 nm, the signal channel LAS optical filter  937  may be configured to pass light in the range of 400-500 nm and prevent other light from reaching the first photodetector  110  (e.g., by reflecting or absorbing most of the light outside the 400-500 nm range). However, this is not required, and, in other sensors  900 , the emission light  131  may have a different peak emission wavelength and/or the signal channel LAS optical filter  937  may pass light in a different (e.g., narrower, expanded, or shifted) wavelength range. 
         [0037]    The reference channel LAS optical filter  939  may be configured to pass a narrow band of wavelengths including the wavelength of a reference light. In one non-limiting embodiment, the reference light passed by the reference channel LAS optical filter  939  may have the same wavelength as the excitation light  129  (e.g., 378 nm), and the reference channel LAS optical filter  939  may pass light in a narrow band (e.g., 350-400 nm) including the wavelength of the excitation light  129  and prevent other light from reaching the reference photodetector  112 . However, this is not required, and, in other embodiments, the reference light passed by the reference channel LAS optical filter  939  may have a different wavelength than the excitation light  129  (e.g., the wavelength of light emitted by reference indicator molecules that are unaffected or generally unaffected by the presence and/or concentration of the analyte), and/or the reference channel LAS optical filter  939  may pass light in a different (e.g., narrower, expanded, or shifted) wavelength range. 
         [0038]    In some embodiments, the one or more LAS optical filters may utilize both dichroic and absorptive filtering to greatly reduce the angle sensitivity relative to a conventional dichroic filter (e.g., dichroic filters  111  and  113 ) configured to allow the specific wavelengths of light to pass. In some embodiments, an LAS optical filter may have a thickness corresponding to the wavelength range (i.e., spectrum) that the LAS optical filter is configured to pass. In some non-limiting embodiments, the one or more LAS optical filters may be ultrathin (e.g., less than or equal to 800 nm thick) layers of metals and/or metal oxides (e.g., tantalum, silver and/or zinc) deposited onto a glass slide or directly onto a photodetector (e.g., photodetector  110  or  112 ), which may be fabricated in the semiconductor substrate  116 . However, this is not required, and, in alternative embodiments, the one or more LAS optical filters may have different thicknesses. In some non-limiting embodiments, the one or more LAS optical filters may be plasmonic nanostructured filters. 
         [0039]    The conventional dichroic filter technology of dichroic filters  111  and  113  (see  FIGS. 1-3 ) works well at 0-15° angle of incidence, but, at higher angles of incidence, the conventional dichroic filters  111  and  113  begin to shift to lower wavelengths and allow through light that was not intended to pass. As a result, the dichroic band pass filter  111  begins to allow more excitation light  129  to pass through, and the signal channel photodetector  110  begins to capture more excitation light  129 . The dichroic band pass filter  111  also begins to allow infrared light  133  (see  FIG. 4 ), which can pass through the skin and into our optical system, to pass through the filter  111  and be captured by the signal channel photodetector  110 . As illustrated in  FIG. 4 , the dichroic filters  111  and  113  and photodetectors  110  and  112  are subject to high angles of ambient light  133  as well as scattered excitation light  129 . 
         [0040]    As illustrated in  FIG. 5 , at 0° angle of incidence (AOI), conventional dichroic filters  111  and  113  accomplish the ideal filtering scheme. The dark blue line  501  represents the ideal passband for the reference filter  113  placed over the second photodetector  112 , and the purple line  502  represents the ideal passband for the signal filter  111  placed over the first photodetector  110 . The red line  503  represents the excitation light  129 , which peaks at 378 nm, and the high and low emission of the chemistry is shown by the light blue line  504  and orange line  505 , respectfully. As shown in  FIG. 5 , the highest wavelengths of the excitation light  108  may creep into the passband of the signal channel filter  111  at very low levels of throughput. Accordingly, in the ideal situation shown in  FIG. 5 , a negligible amount of excitation light  129  relative to the total amount of the excitation light  129  may pass into the signal channel photodetector  110 . Achieving relatively high signal (i.e., desired light) to noise (i.e., undesired light) ratios provides the purest signal possible, but the conventional dichroic filters  111  and  113  do not perfectly filter light. 
         [0041]      FIG. 6  is a graph illustrating the transmission percentage of the conventional signal channel dichroic band pass filter  111  at different angles of incidence.  FIG. 7  is a graph illustrating the transmission percentage of the conventional reference channel dichroic band pass filter  113  at different angles of incidence.  FIGS. 6 and 7  show the quality of the conventional signal and reference channel dichroic filters  111  and  113  decaying as a function of angle of incidence. When this happens across the light spectrum, the conventional dichroic filters  111  and  113  have a much lower signal to noise ratio, and, therefore, the conventional filters  111  and  113  are not performing as intended. As a result, complex algorithms may be required to obtain useful signal. 
         [0042]      FIG. 10  is a graph illustrating the transmission percentage of one embodiment of the signal channel LAS optical filter  937  at different angles of incidence, in accordance with aspects of the invention.  FIG. 11  is a graph illustrating the transmission percentage of one embodiment of the reference channel LAS optical filter  939  at different angles of incidence, in accordance with aspects of the invention.  FIGS. 10 and 11  show that the downward shift in the passband of the LAS optical filters  937  and  939  as the angle of incidence increases is greatly reduced relative to the downward shift in the passband of the conventional dichroic filters  111  and  113  (see  FIGS. 6 and 7 ). In some embodiments, as shown in  FIGS. 10 and 11 , the downward shift in the passband of the LAS optical filters may be 20 nm or less. In some embodiments, as shown in  FIGS. 10 and 11 , the transmission efficiency of the LAS optical filters is greatly reduced as the angle of incidence increases. 
         [0043]    In some embodiments, the analyte indicator  106  may be positioned relative to the signal channel LAS optical filter  937  and/or the reference channel LAS optical filter  939  such that at least a portion of the emission light reaches the signal channel LAS optical filter  937  and/or the reference channel LAS optical filter  939  as low angle of incidence light. In some non-limiting embodiments, the low angle of incidence light may have, for example, an angle of incidence less than or equal to 25 degrees, an angle of incidence less than or equal to 20 degrees, an angle of incidence less than or equal to 15 degrees, an angle of incidence less than or equal to 10 degrees, or an angle of incidence less than or equal to 5 degrees. In some embodiments, the angle of incidence may be the angle of the optical axis relative to a line perpendicular to a receiving surface of the LAS optical filter. Accordingly, light would have an angle of incidence is 0° if light has an optical axis that is perpendicular to the receiving surface of the LAS optical filter, and light would have an angle of incidence of 90° if the light has an optical axis that is parallel to the receiving surface of the LAS optical filter. 
         [0044]    In addition, the first and second photodetectors  110  and  112  in the small scale optical system of the sensor  100  have light receiving areas of 1 mm 2 , and, as a result, application of the filters may be difficult. As illustrated in  FIG. 8A , the conventional filters  111  and  113  are assembled by dicing glass slides  835  and coating the glass with the filters. The filter-coated glass slides  835  are then attached above the first and second photodetectors  110  and  112 . However, this may be a tedious process with a lot of handling and chances for defects. As illustrated in  FIGS. 8B and 8C , dicing the glass may result in chip outs along the edges of the glass slides  835 , which may allow for areas above the photodiodes to not be filtered. Also, the attachment and alignment of such small pieces of glass is may be expensive, and achievement of consistency may be difficult. 
         [0045]    Accordingly, in some non-limiting embodiments, the one or more LAS optical filters may be deposited directly on the one or more photodetectors (e.g., via magnetron sputter coating), and the directly deposited LAS optical filters may have improved quality and/or attachment relative to filters deposited on glass slides. In some non-limiting embodiments where the one or more photodetectors are fabricated in a semiconductor substrate, the one or more LAS optical filters are deposited directly on the semiconductor substrate. Directly coating the wafer is a lab on a chip assembly process that moves towards complete wafer level processing by having a fully integrated optical system on an integrated circuit. 
         [0046]      FIG. 12  illustrates an embodiment in which the substrate  116  is a semiconductor substrate, the photodetectors  110  and  112  are fabricated on the semiconductor substrate, and the LAS optical filters  937  and  939  are coated on the photodetectors  110  and  112 , respectively. In some embodiments, as shown in  FIG. 12 , the substrate  116  may include a mount  1203  for the light source  108  and additional circuitry  1201 , which may be fabricated in and/or mounted on the substrate  116 .  FIG. 12  also includes a graph illustrating the transmission percentage of the LAS optical filters  937  and  939  at different wavelengths and an angle of incidence of 0°. 
         [0047]    In some embodiments, the signal channel LAS optical filter  937  has a transmission efficiency that is sufficient for detection of modulation in the emission light  131  due to presence and/or concentration of analyte in the medium into which the sensor is inserted (see the high and low emission of the analyte indicator chemistry shown by the light blue line  504  and orange line  505 , respectfully, of  FIG. 5 ). In some embodiments, the LAS optical filters may have low sensitivity to high angle of incidence light. That is, in some embodiments, the LAS optical filters may pass only small percentage of high angle of incidence light. Accordingly, in some embodiments, the sensor  900  having LAS optical filters  937  and  939  may be a highly miniaturized dual channel precision fixed fluorimeter. In some non-limiting embodiments, the sensor  900  may have an excitation wavelength at approximately 380 nm, an emission wavelength range beginning at 390 nm, and the ability to separately isolate and detect the excitation light and emission light (via the photodetectors and LAS optical filters) with a very low signal to noise ratio. In some non-limiting embodiments, the LAS optical filters may be accurate filters with turn on and turn offs of a few nanometers in a narrowband with little to no angle of incidence sensitivity and may allow for a level of detection not achieved by other sensors optical systems. 
         [0048]    In one non-limiting embodiment, the signal channel LAS optical filter  937  and/or reference channel LAS optical filter  939  may have one or more of the following specifications. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
               
               
                 LAS Optical 
                   
                 % Transmission 
                   
                 % Transmission 
               
               
                 Filter 
                 Wavelength 
                 @ 0° AOI 
                 Wavelength 
                 @ 75° AOI 
               
               
                   
               
             
             
               
                 signal channel 
                 300 nm-410 nm 
                 Tave &lt; 2% 
                 300 nm-395 nm 
                 Tave &lt; 1% 
               
               
                 LAS optical 
                 350 nm-410 nm 
                 Tave &lt; 0.5% 
                 350 nm-395 nm 
                 Tave &lt; 0.5% 
               
               
                 filter 937 
                 350 nm-410 nm 
                 Tmax &lt; 2% 
                 350 nm-395 nm 
                 Tmax &lt; 2% 
               
               
                   
                 455 nm-525 nm 
                 Tave &gt; 47% 
                 420 nm-510 nm 
                 Tave &gt; 16% 
               
               
                   
                 600 nm-1100 nm 
                 Tave &lt; 0.1% 
                 600 nm-1100 nm 
                 Tave &lt; 0.1% 
               
               
                   
                 600 nm-1100 nm 
                 Tmax &lt; 1% 
                 600 nm-1100 nm 
                 Tmax &lt; 1% 
               
               
                   
                 Rel 50% T 
                 443.5 nm +/− 5 nm 
                 Rel 50% 
                 410 nm +/− 5 nm 
               
               
                   
                 Rel 50% T 
                 532.0 nm +/− 6 nm 
                 Rel 50 
                 518.5 nm +/− 6 nm 
               
               
                 reference 
                 300 nm-350 nm 
                 Tave &lt; 2% 
                 300 nm-340 nm 
                 Tave &lt; 2% 
               
               
                 channel LAS 
                 376 nm-386 nm 
                 Tave &gt; 33% 
                 350 nm-374 nm 
                 Tave &gt; 4% 
               
               
                 optical filter 939  
                 415 nm-490 nm 
                 Tave &lt; 0.1% 
                 415 nm-490 nm 
                 Tave &lt; 0.1% 
               
               
                   
                 415 nm-1100 nm 
                 Tmax &lt; 4% 
                 415 nm-1100 nm 
                 Tmax &lt; 3% 
               
               
                   
                 415 nm-1100 nm 
                 Tave &lt; 0.5% 
                 415 nm-1100 nm 
                 Tave &lt; 0.5% 
               
               
                   
                 Rel 50% T 
                 372 nm +/− 4 nm 
                 Rel 50% 
                 346 nm +/− 4 nm 
               
               
                   
                 Rel 50% T 
                 394 nm +/− 4.5 nm 
                 Rel 50% 
                 379 nm +/− 4 nm 
               
               
                   
               
             
          
         
       
     
         [0049]    Embodiments of the present invention have been fully described above with reference to the drawing figures. Although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions could be made to the described embodiments within the spirit and scope of the invention.