fig3 a and 3b illustrate the use of an opaque film adjacent another layer or an air gap to absorb shunting light . fig3 a shows the opaque film 34 , before assembly being placed over layers 36 , 36 ′ separated by an air gap 38 . layers 36 , 36 ′ may be mounted on a common substrate ( not shown ). holes 40 and 42 are shown for the emitter and detector . alternately , these can be windows or simply a solid portion of a transparent layer . fig3 b shows the assembled lower layer and opaque film layer 34 . as light attempts to shunt from emitter area 40 to detector area 42 , either passing through the air gap 38 or through layers 36 and 36 ′, it will bounce back and forth between the boundaries of the layer and through the air gap . some of the light that would normally hit the top end of layer 36 or 36 ′ and bounce back into the middle of the layer , will instead pass into and be absorbed by opaque layer 34 , which is tightly coupled to the layers 36 and 36 ′. fig4 illustrates the use of a woven or fiber material 44 on layers 36 and 36 ′, and filling the air gap 38 of fig3 a . fibers in the material will absorb light , thus attenuating light attempting to shunt from emitter area 40 to detector area 42 . an additional cover layer 46 may be placed over the assembly , and which will need to be at least partially transparent for light to escape and be detected . layer 46 can function as another shunting layer . by abutting up against the woven or fiber material 44 , light will be absorbed out of that layer in the same manner as the opaque film 34 of fig3 a and b . alternately , the fiber and woven material can be inserted into layer 46 between the emitter and detector . fig5 shows an alternate embodiment in which a layer 50 is used with an emitter 52 placed on top of it . alternately , layer 50 could have holes 54 and 56 over the emitter and detector , with the emitter 52 being placed through hole 54 onto an underlying layer . a partially opaque layer 58 is placed above emitter 52 in the embodiment shown . layer 58 may extend a portion of the way or all of the way over to where the detector is . the opacity of layer 58 is chosen in conjunction with its thickness to allow transmission of substantially all of the light from emitter 52 through the layer , while substantially reducing the amount of light shunted in a path transverse through the layer from the emitter to the detector . layer 58 preferably attenuates the shunted light so that it is less than 10 %, and more preferably less than 1 % of the total light received by the detector . additionally , of the light detected by the detector and converted into electrical signal , the portion of the electrical signal due to shunted light is preferably less than 10 % and more preferably less than 1 % of the signal value . the layer may be made substantially opaque through coloring . one such color would be a gray created by suspension of carbon black particles in the base material of the layer . this would be substantially opaque to both red and infrared . fig6 shows another embodiment of the invention in which a layer 60 over an emitter 62 and detector 64 has a series of perforations 66 . these perforations block the light path and scatter the light attempting to shunt between the emitter 62 and detector 64 through layer 60 . although light tends to jump air gaps , by providing multiple air gaps in different orientations , the light can be somewhat effectively scattered . alternately , the perforations could be filled with a colored filling material or putty to block the light that might otherwise jump the air gaps , or could have the inside walls of the perforations colored . alternately , embossing ( or other variations in thickness ) could be used rather than perforations . fig7 illustrates a layer 70 having an emitter 72 and detector 74 , covered by another layer 76 . layer 76 may be partially transparent for light to exit from emitter 72 and re - enter to detector 74 . layer 76 has a thinned portion 78 , and layer 70 has a corresponding thinned portion 79 . these portions make the layers thin in that area , thus limiting the amount of light that may be shunted . the layer could be made thin by a number of techniques , such as embossing , welding or heat sealing . the width of the thinned area could be varied , and the shape could be varied as desired . for instance , the thinned area could extend around the sides of the emitter and detector , to prevent shunting of light from the edges of the layers when they are wrapped around a finger . the thinness of the layer contributes to absorption of the light because light which is traveling in a thin layer will more often bounce off the layer boundaries than it would in a thick layer . this provides more chances to escape the layer and be lost or absorbed in an adjoining layer with absorption characteristics . the thickness is preferably less than 0 . 25 mm and more preferably no more than 0 . 025 mm . the length of the thin section is preferably greater than 1 mm and more preferably greater than 3 mm . the thin layer approach could be applied to a re - manufacture or other modification of a sensor which involves adding a layer over the emitter and detector . the entire layer could be made thin , preferably less than 0 . 25 mm , more preferably no more than 0 . 025 mm , in order to limit its shunting effect . fig8 shows a sensor having a layer 80 for an emitter 81 and a detector 82 , having transparent windows 83 and 84 , respectively . a substrate layer 85 supports the emitter and detector , with light being transmitted through transparent window 83 and received through window 84 . in one embodiment , the entire layer 80 is opaque , leaving transparent portions 83 and 84 . alternately , the entire layer 80 may be transparent , or of one color with the windows of another or transparent . in addition , a portion 86 of layer 80 between the emitter and detector may be colored a substantially opaque color to prevent the shunting of light of the wavelengths of interest . in alternate embodiments , portion 86 may be of different shapes , and may partially or totally enclose the windows for the emitter and detector . fig9 shows another embodiment of a sensor according to the present invention mounted on a finger 90 . two portions of a first layer , 91 , 91 ′ have the emitter 92 and detector 93 , respectively , attached to them . a break between layers 91 and 91 ′ is provided in between the emitter and detector , which will be at the tip of finger 90 . normally , this gap would provide an air gap through which light can be shunted between the emitter and detector across the top of the finger . however , by using a backing layer 94 , with an adhesive in the portion between layers 91 and 91 ′, this layer can stick to the tip of finger 90 , removing the air gap and thus substantially preventing shunting between the layers . an alternate embodiment is shown in fig1 , with the finger 100 having a sensor with layers 91 and 91 ′ and emitter 92 and detector 93 as in fig9 . here , however , a separate layer 94 is provided with a foam or other resilient or compressible pad 96 mounted on layer 94 between layers 91 and 91 ′. this material will compress against the tip of the finger , thus also blocking the air gap and preventing the shunting of light if the material is made of a substantially opaque material , such as a color that is substantially opaque to the wavelengths of interest ( e . g ., red and infrared ), or is made of woven material or other material opaque to the light . fig1 is another embodiment of the present invention showing a layer 110 having an emitter 112 and a detector 114 mounted thereon . a covering , transparent layer 116 provides a covering and a window for the transmission and detection of light . shunting of light is prevented by crimping the layers with a metal or other crimp 118 , 120 . the metal or other material is substantially opaque to the shunted light of the wavelengths of interest , and completely penetrates the layer , or substantially penetrates the layer . fig1 shows an alternate embodiment in which a layer 121 has an emitter 122 and a detector 124 ( both shown in phantom ) mounted thereon . over the emitter area is a first transparent layer 126 , with a second transparent layer 128 over the detector 124 . as can be seen , the two layers are overlapping , with the end 129 of layer 128 being on top of layer 126 . thus , instead of an air gap , any shunted light from layer 128 is deflected to be above layer 126 , and vice versa . alternately , since the light will originate from the emitter , it may be more preferable to have the layer overlaying the emitter be on top of the layer overlaying the detector . in the overlapping portion , a radiation blocking layer may be included , such as a colored adhesive . fig1 shows an alternate embodiment of the present invention in which a flexible circuit is printed onto a layer 130 . as shown , emitter 132 and detector 134 are mounted on the flexible layer 130 . a covering layer 133 is provided . layers 130 and 133 may be partially or substantially opaque to prevent the shunting of light . in between the layers , metal traces 136 and 138 can be used to block the shunting of light . instead of making these traces run lengthwise , leaving a clear path between the emitter and detector , they instead follow a tortuous path . this tortuous path not only goes lengthwise , but also goes across the width of the layer 130 , thus providing a barrier to block shunting the light between the emitter and detector . fig1 shows another embodiment of the present invention for modifying a sheath such as sheath 32 of fig2 . fig1 shows a sheath 140 having a first , adhesive layer 142 , and a second layer 144 being transparent and forming a pocket for the insertion of a sensor . layer 144 has opaque colored rings 146 and 148 surrounding windows 147 and 149 , respectively . these windows allow the transmission of light to and from the emitter and detector , while the opaque rings prevent the shunting of light through transparent layer 144 . alternately , more or less of the transparent layer 144 could be colored with an opaque color to prevent the shunting of light . alternately , in the embodiment of fig1 , windows 147 and 149 could be one color , while areas 146 and 148 , which may extend over the rest of the layer 144 , could be of a second color . the second color would be chosen to prevent shunting , while the first color would be chosen to allow the transmission of light while also being of a color which is compatible with the calibration data for an oximeter sensor . if the color over the emitter and detector is not chosen properly , it may interfere with the choice of a proper calibration curve in the oximeter sensor for the particular wavelength of the emitter being used . typically , leds of slightly varying wavelengths are used , with a coding resistor indicating the exact wavelength . the coding resistor is used to choose a particular calibration curve of coefficients in the oximeter sensor . thus , by using a differentially - colored sheath or reinforcing laminate or other layer , with the layer near the emitter and detector chosen to be white , clear or other color which does not interfere with the calibration , shunting can be prevented while allowing the sensor to be used without affecting its standard calibration . preferably , the regions over the emitter and detector have a radius extending at least 2 mm . beyond the borders of the emitter and detector , and preferably at least 5 mm beyond the borders of the emitter and detector . any of the shunt barriers described above could be incorporated into layer 144 of sheath 140 of fig1 . alternately , or in addition , the shunt barriers could be incorporated into a lamination or other layer placed over a sensor in a modifying process . such a modifying process may , for instance , place a non - adhesive layer over an adhesive layer to convert a disposable sensor into a reusable sensor . the shunt barriers described above may also be in an original layer in a sensor , or in a replacement layer added in a remanufacturing process for recycling disposable sensors . as will be understood by those of skill in the art , the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof . accordingly , the foregoing description is intended to be illustrative , but not limiting , of the scope of the invention which is set forth in the following claims .
a pulse oximeter sensor comprising an emitter and a detector disposed on a substrate layer with a thinned portion between the emitter and the detector . a partially transparent covering layer covers the substrate layer and comprises a corresponding thinned portion . the thinned portions attenuate light shunted via the substrate layer and the partially transparent covering layer from the emitter to the detector , and may be configured such that less than 10 % of the light detectable by the detector is shunted light .