A sensing unit for physiological measurements

Abstract

The present disclosure provides a sensing unit for measuring physiological parameters that comprises a skin contact surface, one or more light sources configured to emit light through the contact surface onto a subject's skin portion, and at least one light detector configured to detect light returning from the skin portion. A light opaque element is positioned between the light sources and the light detector to block direct illumination. The contact surface is formed by external surfaces of at least two light transmissive elements, a first element overlaying the light source(s) and a second element overlaying the light detector, and by an external edge of an edge portion of the light opaque element. The edge portion is flush with the external surfaces of the light transmissive elements and optically separates them, preventing both direct and indirect light leakage to the detector. This structure enables close proximity between light sources and detector (reducing energy consumption) while maintaining high signal-to-noise ratio by ensuring detected light originates solely from interaction with the subject's tissues.

Description

[0001] A SENSING UNIT FOR PHYSIOLOGICAL MEASUREMENTS

[0002] TECHNOLOGICAL FIELD

[0003] The present disclosure is in the field of sensing units, in particular in the field of physiological sensing units.

[0004] BACKGROUND ART

[0005] References considered to be relevant as background to the presently disclosed subject matter are listed below:

[0006] - US 2016002991

[0007] - US 20140275852

[0008] - WO 2022 / 024113

[0009] Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

[0010] GENERAL DESCRIPTION

[0011] The present disclosure provides a sensing unit for sensing physiological parameters in a skin portion of a subject and a method of manufacturing it. The sensing unit is a type of a plethysmograph (PPG) sensor, namely a sensor that comprises one or more light sources, e.g. a LED, at least one light detector, e.g. a photodiode (PD). The light source and the light detector are housed under and contact surface that in use is in contact with the skip portion. The light source illuminates the skin portion through the contact surface, and the light detector is configured to detect the response of the illumination of the light source on the skin portion, namely the light that is scattered or reflected from tissues, arteries or arterioles of the subj ect back through the contact surface. The detection of the light is indicative of physiological parameters of the subject.

[0012] In the following description all numbers that are mentioned, with or without the "about" modifier, should be understood as meaning a value which is ±5%, ±7.5%, ±10%, ±12.5%, ±15%, ±17.5%, or even ±20% of the specified number.In the sensing unit of the present disclosure, the light source and the light detector are positioned adjacent to one another, e.g. at a distance between edges of the die of the light source and the die of the light detector is less than the distance between such edges and the opposite edges of each. The distance between the dies would be prohibitive without the unique configuration provide by this disclosure (because of relatively large proportion of light emitted by the light source that will reach the lights sensor directly as compared to that that will impinge on and travel back from the skin portion). The distance is, for example, about 150-300 pm. When placing the light source and the light detector in such proximity, in sensing units that do not implement the teaching of the current disclosure, a light emitted from the light source can reach the detector without interacting with the targets in the subject, which results in an increase of the noise of the detected signal. This can results from either direct illumination of the detector by light emitted from the light source, or through scattering or reflection from elements in the sensing unit prior to reaching the subj ect. Therefore, in accordance with the teaching of this disclosure, a light opaque element that extends the contact surface and has an upper face with contours that are continuous with the upper surface of the sensor, is placed between the one or more light source and the at least one light detector to block the undesired, direct illumination. The light opaque element serves as a light barrier not permitting the passage of light therethrough. By embodiments of this disclosure, the contours of the upper face of the light opaque element are continuous with those of said contact surface, both contours define along one axis and those defined along another axis, e.g. normal to the first one.

[0013] The sensing unit of this disclosure comprises a contact surface for contacting a subject's skin portion in a manner that avoids direct light transmission from the one or more light sources to the at least one light detector. The one or more light sources and the at least one light detector are each overlayed with one or more light transmissive (e.g. translucent) elements, the outer face of which defines . Light emitted from the one or more light sources passes through such one or more such elements to a skin portion, and light returning from the skin portion passes through one or more other such elements to the at least one detector.

[0014] In the following description the term "light transmissive" may be used to denote an element or material that transmits light therethrough, including transparent elementsor material or translucent ones. Light transmissive materials or elements may include such that transmit some (typically, most) of the light thereto with or without scattering.

[0015] It was realized in accordance with this disclosure that in order to ensure that no undesired light will reach the light detector, it is not sufficient to block direct illumination, but also indirect illumination through the light transmissive contact surfaces - light that may be reflected or scattered by the light transmissive surface. This may again increase noise.

[0016] All the issues noted above are specifically acute if attempting to bring the light source and the light detector into close proximity, which is an important measure for reducing energy consumption.

[0017] Accordingly, in accordance with this disclosure, the light opaque element has an edge portion that optically separates between light-transmissive element(s) that overlay the one or more light sources and such element(s) overlaying the at least one detector. Moreover, the external edge of the edge portion of the light opaque element is flush with or continuous to the external surfaces of the light-transmissive elements and forms a continuous external skin contact surface therewith. The term "optically separated" should be understood such that light cannot pass between light-transmissive element(s) or that they do not interact optically with each other in a meaningful way. This separation can is achieved through a physical barrier in the form of the light opaque or light blocking element. The light emitted from the light source exits the contact surface through the light transmissive element overlaying the one or more light sources and the light returning from the skin enters the contact surface through the light transmissive element overlaying the at least one detector. By having the structure noted above, the light opaque element efficiently blocks any undesired illumination and, accordingly, practically all the detected light by the light detector arrives from outside the contact surface. The structure of the sensing unit embodying the teaching of this disclosure, accordingly enables (i) low energy light emission from the one or more light sources, resulting from the close proximity of the light sources and light detectors, and (ii) high signal to noise ratio, seeing that stray light does not reach the detector (or reaching it in negligible amount).

[0018] Provided by a first configuration of a first aspect of the present disclosure is a sensing unit for measuring physiological parameters of a subject. The sensing unit comprises a skin contact surface for contacting a skin portion of the subject. The sensing unit comprises one or more light sources configured to emit light through said contactsurface onto a skin portion of the subject when the contact surface is in contact with the skin portion. The sensing unit comprises also at least one light detector that is configured to detect light returning from said skin portion or from tissues below said skin portion through said contact surface. Namely, the light emitted from the one or more light sources interacts with the desired targets in the subject such as tissues, arteries and arterioles, and reflects or scatters back to be detected by the at least one or more light sources and the at least one light detector. The sensing unit further comprises a light opaque or a light blocking element having a portion thereof positioned between the one or more light sources and the at least one light detector and configured to block the light emitted by the one or more light sources, namely to block at least the wavelength range of the these light sources, from directly reaching the at least one light detector.

[0019] The term "directly reaching (or "directly reach", "directly reaches", etc.) means light that reaches the at least one light detector which is not light returning from the skin portion through the contact surface and is, hence, light that directly passes from the one or more light sources to the at least one detector. The term "indirectly reaching" (or "indirectly reaches" means light that reaches the at least one light detector through interaction with elements of the sensing unit, e.g. after being reflected or scattered from such elements.

[0020] The skin contact surface is defined by external surfaces of the at least two light transmissive elements, of which at least one first transmissive element overlays the light source and at least one second transmissive element overlays the light detector, and by an external edge of an edge portion of the light opaque element, the edge portion optically separating the at least one first element from the at least one second element. While the at least one first transmissive element and the at least one second transmissive element are, typically structurally distinct elements, the at least two light transmissive elements may, by some embodiments, be elements that extend from a single body, from common portions of such a body which are positioned in a manner that are not subjected to direct illumination by the light source.

[0021] The contact surface is a continuous surface formed by the external surfaces of the light transmissive elements that allow light to pass therethrough and an external edge of the light opaque element, that is flush with the external surfaces of the light transmissive elements, with the edge portion of the light opaque element optically separating said one or more light transmissive parts. Accordingly, no light from the first light source that ispropagated within a first transmissive element or reflected by such element can reach the second transmissive element and reflected therefrom to the at least one detector.

[0022] The structure of the sensing unit of this disclosure thus ensures that there is no light from the one or more light sources can directly or indirectly reach the at least one detector. Thus, all light reaching the at least one light detector before is light passing through the contact surface from the skin portion after interacting with tissues of the subject; and when the contact surface is not in contact with a skin portion and not illuminated by an external light, the light reading by the at least one detector may be practically close to zero. In other words, such an arrangement provides for a very high signal-to-noise ratio.

[0023] Yet another configuration of the first aspect provides a sensing unit for measuring physiological parameters of a subject. The sensing unit comprises a skin contact surface for contacting a skin portion of the subject. The sensing unit further comprises one or more light sources configured to illuminate first illumination through one or more light transmissive parts of said contact surface. The first illumination is characterized by a first wavelength or first wavelengths range. A light detector of the sensing unit is configured to detect illumination response of said first illumination through said one or more light transmissive parts. The illumination response can be any optical response of the illumination emitted by the one or more light sources, such as reflection, scattering, fluorescence, etc. The sensing unit further comprises a light opaque or light blocking element configured to block light emitted from the one or more light sources, namely the light opaque element is configured to block at least the type of illumination emitted from the one or more light sources. The light opaque element has at least a first part thereof positioned between the first light source and the light detector. The first part separates the sensing unit into a light emitting part that comprises the one or more light sources and a light detecting part that comprises the light detector. The contact surface is entirely formed or at least partially formed by said one or more light transmissive or semi-transmissive parts and an external edge of said first part of the light opaque element. It is to be noted that by this configuration of the first aspect, there may be only a partial optical separation between the one or more light sources and the light detector. Even though a partial optical separation does not yield the optimal result, it is still superior over alternative structures in which there is no part of the light opaque element that forms the contact surface.It is to be noted that any embodiment or combination of embodiments described with respect to an aspect or any configuration of the aspect of this disclosure is applicable also to other aspects. Specifically, it is noted that the below embodiments apply to any of the above-described configurations of the first aspect

[0024] In some embodiments of the sensing unit, at least a first light source of the one or more light sources and one or more of the at least one of the light detectors are adjacent to said first part of the light opaque element, each from a different side. This is particularly so for light sources emitting light at a wavelength below about 600 nm and even below about 550 nm, and their corresponding detectors. The reason is that the photons are doing some sort of a circular movement in the body and the shorter the wavelength the smaller the radius. In the case of IR and red the distance may be larger than lower wavelengths. The term "adjacent" should be understood as less than about 400 pm, about 300 pm or less than 200 pm, typically about 100pm.

[0025] The light opaque element, by some embodiments, may be configured as a straight or folded plate.

[0026] In some embodiments of the sensing unit, the first light source is a first light source element, and the light detector is a first light detector element. A light source element should be understood as an element that includes the light emitting part, e.g. a light-emitting diode (LED) and the carrier that carries it, such as a substrate, package, encapsulation, or enclosure. For example, the light source element may be a light source die. A light detector element should be understood as an element that includes the light detecting part, e.g. a photodiode and the carrier that carries it, such as a substrate, package, encapsulation, or enclosure. For example, the light detector element may be a light detector die.

[0027] In some embodiments of the sensing unit, the light source element and the light detector element have respective portions that are less than about 400, 400, 300, 200, or 150 pm or even about 100 pm, from the first part of the light opaque element, each from a different side.

[0028] In some embodiments of the sensing unit, the external edge and the edge portion of the light opaque element extends between two peripheral portions of the one or more light transmissive parts of said contact surface, to separate between a first light transmissive element overlaying the at least one light source, and a second light transmissive element, overlaying the at least one light detector.In some embodiments of the sensing unit, said external edge of the light opaque element extends between two peripheral portions of the one or more light transmissive parts of said contact surface, thereby defining (i) a first light transmissive part, through which the illumination from the light source propagates towards the skin of the subject, and (ii) a second light transmissive part, through which the illumination response propagates back towards the light detector, and a light opaque element part separating the first light transmissive part and the second light transmissive part. In other words, the first light transmissive part is formed above the first light source or the light emitting part, the second light transmissive part is formed above the light detector or the light detecting part, and the light opaque element part is separating these two parts. This structure ensures that there is no (or at least minimal) leak of undesired illumination from the light source or light emitting part to the light detector or light detecting part, which does not first cross the contact surface.

[0029] In some embodiments, the sensing unit comprises a first light source and a second light source, configured for emitting light at a different wavelength. The first light source is configured to emit light of a first wavelength, or a first wavelength range and the second light source is configured to emit light of a second wavelength or wavelength range. The second wavelength or wavelength range is larger that the first wavelength or wavelength range. The second light source, in such embodiments, is typically positioned further away from the light opaque element than the first light source, at the same side of the first light source with respect to the opaque element. It is to be noted that the light opaque element is configured to block also the light emitted by the second light source and the light transmissive parts of the contact surface or the light transmissive elements of the contact surface are configured to also allow light emitted from the second light source to pass therethrough.

[0030] In some embodiments of the sensing unit, the space between the contact surface and any of the first light source and the light detector is filled with one or more light transmissive materials. This results in a continuous structure of light materials from the contact surface to the light sources and the light detector. This continuous structure may include the contact surface.

[0031] In some embodiments of the sensing unit, the one or more transmissive parts of the contact surface are part of one or more light transmissive elements. The externalsurfaces of said one or more light transmissive elements form the one or more transmissive parts of the contact surface

[0032] In some embodiments of the sensing unit, the one or more light transmissive parts of the contact surface are made of said one or more light transmissive or semi-transmissive materials. Therefore, the contact surface and the volume span between both, the first light source and the light detector, and the contact surface is made of a continuous transmissive material. This is made by injection of the material to one or two molds while the light opaque element is present, therefore parts of the contact surface and the filling of the volume are formed by the one or more light transmissive materials.

[0033] In some embodiments of the sensing unit, the one or more light sources and the light detector are adhered with an adhesive or a curable polymer to said one or more light transmissive or semi-transmissive materials or to said one or more light transmissive elements.

[0034] In some embodiments of the sensing unit, the space between internal faces of the light-transmissive element and any of the one or more light source and of the at least one light detector is filled with one or more light transmissive materials. This results in a continuous light transmissive medium from the contact surface to the one or more light sources and the at least one light detector. This may be achieved by (i) first forming the light transmissive elements, e.g. by the molding method described below, with the light blocking element therebetween; then (ii) a curable liquid polymeric material may be introduced, before combing the block that includes the light-transmissive and the lightopaque element with the electronic elements (that include the light sources and the detectors) in a manner that the entire space between the electronic elements and said internal faces is completely filled with such material; and then (iii) after curing, the continuous light transmissive medium is formed. The curing, as will also be specified below, may typically be a light-curing process, e.g. with UV light, irradiated onto the curable polymer through the light-transmissive elements. Such a curable polymer may also serve as the adhesive that fixes said electronic elements to the block that comprises the light-transmissive elements and the light opaque element; although in some embodiments a separate adhesive or another element may also be used, e.g. at the periphery in a manner that will not impact the overall optical properties of the unit.

[0035] In some embodiments of the sensing unit, said one or more light transmissive materials are light transmissive adhesives filling the space between internal faces of thelight-transmissive element and any of the one or more light source and of the at least one light detector.

[0036] In some embodiments of the sensing unit, the refractive index of the cured polymer is about the same as the refractive index of the light transmissive elements or the light transmissive materials. Therefore, the light does not change significantly its propagation direction when crossing between the mediums of the adhesive and the one or more light transmissive materials. The term “about” with respect to the refractive index should be understood as a deviation of up to ±20%, 10%, 5%, 4%, 3%, 2%, or even up to (i.e. no more than) 1% between the two refractive indexes.

[0037] In some embodiments of the sensing unit, the light source is a light-emitting-diode (LED) and the light detector is a PD.

[0038] In some embodiments of the sensing unit, the one or more light sources comprise short-wavelengths light sources configured to emit light characterized by a wavelength of less than about 600 nanometers. The short-wavelengths light sources are disposed adjacent to the light opaque element.

[0039] In some embodiments of the sensing unit, the short-wavelengths light sources are disposed between 50-200 pm to said light opaque element.

[0040] In some embodiments of the sensing unit, the short-wavelengths light sources are configured to emit light in one of blue, green, or violet spectrums.

[0041] In some embodiments of the sensing unit, the edge portion of the light opaque element has a curvature that conforms or substantially conforms with a curvature of the contact surface. Namely, the contact surface is curved or round to engage with the skin of the subject in a manner that is less disturbing. The edge portion of the light opaque element is also curved to conform with the curvature of the portions of the contact surface that are adjacent thereto.

[0042] The term "substantially conforms" in the context of the curvature of the edge portion of the light opaque element relative to the contact surface curvature should be understood to mean that the edge portion follows or matches the curvature of the contact surface to a degree sufficient to maintain the optical separation function and structural integrity of the sensing unit, while accounting for practical manufacturing tolerances and variations.

[0043] In some embodiments of the sensing unit, said light opaque element is made of or comprises polymeric material.In some embodiments of the sensing unit, said light opaque element is made of or comprises plastic.

[0044] In some embodiments of the sensing unit, said light opaque element comprises a light-absorbing coating configured to absorb light incident thereon.

[0045] In some embodiments of the sensing unit, the one or more light sources each comprise a light-emitting area from which light is emitted, and the light detector comprises a light-detecting area configured to receive light. The physical separation between the light-detecting area and the closest light-emitting area is less than about 1000 pm, thereby reducing energy consumption of the light sources and reducing sensitivity to motion artifacts due to the shortened optical path length.

[0046] Yet another aspect of the present disclosure provides a sensing device that comprises the sensing unit of any of the above-described embodiments or any combination thereof.

[0047] In some embodiments, the sensing device is a wearable system to be worn by the subject, as a wearable device.

[0048] In some embodiments, the sensing device is a medical watch or medical bracelet. Yet another aspect of the present disclosure provides a method for manufacturing a sensing unit. The method may comprise: molding two light transmissive elements, with external and internal surfaces, on two sides of a light opaque element to define a skin contact surface that comprises (a) the external surfaces of the two light transmissive elements, and comprises (b) an external edge of an edge portion of the light opaque element, the two light transmissive elements being optically separated by said edge portion, to obtain a molded product; and combining the molded product with an electronic circuity that comprises (x) one or more light sources configured to emit light onto a skin portion through said contact surface, and (y) at least one light detector configured to detect light returning from said skin portion through said contact surface in response to the emitted light, the combining being such that (i) said one or more light sources being on one side of the light opaque element and said at least one light detector being on the other side, and such that (ii) light to be emitted by the one or more light sources is blocked from reaching the light detector.

[0049] The method may also comprise: (i) providing a mold with a molding surface part, defining an eventual skin contact surface of the sensing unit; (ii) placing the light opaque element in said space in contact with a portion said molding surface, the light opaqueelement having an edge portion with an edge that is congruent with that of said portion of the molding space; (iii) injecting transmissive material into the mold on two sides of the light opaque element, and permitting the material to cure to obtain a molded product that comprises two light transmissive elements separated by said edge portion, having external surfaces defined by said mold surface, and having opposite internal surfaces, and comprises a skin contact surface defined by (a) the external surfaces of the two light transmissive elements, and by (b) the external surface of the light opaque element, the two light transmissive elements being optically separated by said edge portion and; (iv) combining the molded product with an electronic circuity that comprises (x) one or more light sources configured to emit light onto a skin portion through said contact surface, and (y) at least one light detector configured to detect light returning from said skin portion through said contact surface in response to the emitted light, the combining being such that (i) said one or more light sources being on one side of the light opaque element and said at least one light detector being on the other side, and such that (ii) light to be emitted by the one or more light sources is blocked from reaching the light detector.

[0050] In some embodiments of the method, prior to said combining, introducing a liquid polymerizable material into a space delimited by the internal surfaces of the light transmissive elements, the amount of the liquid and the manner of combining being such so that said material fills entire space between said one or more light sources and said at least one light detector and between said internal surfaces, and after said combining, curing the polymerizable material. The term "liquid" in reference to the polymerizable material, means that said material is flowable and may have, for example, a gel-like consistency.

[0051] In some embodiments the curing of the polymerizable material may be by light, e.g. UV light. The curing light may be shone onto the polymerizable material for the purpose of curing through the light transmissive elements.

[0052] In some embodiments the polymerizable material is chosen such that after curing it will have a light refractive index about the same as that of the light-transmissive element.

[0053] In some embodiments, the method further comprises filling a gap between said two light transmissive elements and any one of said at least one light detector and said one or more light sources with a light transmissive material.In some embodiments of the method, said light transmissive material is a light-transmissive adhesive.

[0054] BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0056] Figs. 1A-1D are schematic illustrations of different views of a non-limiting, exemplary embodiment of the sensing unit of the present disclosure, wherein: Fig 1A and Fig. IB are, respective elevational view and top perspective view into the sensing unit with the light transmissive elements removed to show internal elements; Fig. 1C is a perspective view of the molded block with the external contact surface, shown in isolation; and Fig. ID is a longitudinal cross-sectional view of the sensing unit.

[0057] Figs 2A-2B are schematic illustrations of a non-limiting, exemplary embodiment of a sensing device of the present disclosure in the form of a wearable device, wherein:

[0058] Fig. 2A and Fig, 2B are, respective, perspective view and a side view of the wearable device.

[0059] Figs. 3 is a flow chart of a manufacturing process of a sensing unit, according to an embodiment of this disclosure.

[0060] DETAILED DESCRIPTION

[0061] The figures are provided to exemplify embodiments and realization of the present disclosure.

[0062] Reference is made to Figs. 1A-1D, which are schematic illustrations of different views of a non-limiting exemplary embodiment of the sensing unit according to the present disclosure. In the following description reference will be made to relative positions or orientations in accordance with the views seen in the drawing. Thus, for example, a top element means an element that is at a higher level in the figure and a top view is a view from what is perceived to be the top in the figure. As can be understood,an element which is at the top in the drawings, for example the sensing surface, may in use, in wearable device seen in Figs. 2A-2B, be actually the bottom element of the device positioned against a wrist skin portion.

[0063] The sensing unit 100 comprises an electronic circuitry generally designated 101 including a printed circuit board (PCB) or flex PCB 103 fitted within an inner depression 104. First light source 105 and a second light source 106, both configured to emit light, each at a different wavelength, are fitted on PCB 103. The first light source 105 is configured to emit light of a wavelength that is shorter than the wavelength of the illumination emitted by the second light source 106. For example, the first light source 105 may be configured to emit light in the green, blue or velvet spectrum, and the second light source 106 may be configured to emit light in the red or infrared spectrum. The light sources 105,106 are typically light-emitting-diodes (LEDs).

[0064] Further carried on PCB 103 is a light detector 107, such as a photodiode, that is configured to detect illumination of at wavelengths of the first and second light sources 105 and 106. Light sources 105,106 and detector 107 are within respective dies 105A,106A and 107A

[0065] A light opaque element 108 is disposed within the sensing unit that is in the form of a folded plate with a lobed section. The light opaque element 108 may be made of metal, for example, steel such as stainless steel or steel 316L, ands may have a width of about 200 pm, which blocks light from passing therethrough. Element 108 has an edge portion 108A with external edge 108B. All elements of the unit, including those of block 120 forming the contact surface, to be defined below, are fitted within an outer depression 111. Light opaque element 108 in fact divides the unit into two functional parts: a lightemitting part 112 and a light-sensing part 113, which are light-isolated from one another, meaning that light emitted by light sources 105,106 cannot directly reach light detector 107 or through light interactions with elements of the sensing unit 100 without first propagating out of the sensing unit 100. As can also be seen formed in the sensing unit 100 are four circular depressions 115 that are configured to receive cylindrical projections 117 of block 120. Block 120 also have two end projections 118 (only one is seen) that are configured to snugly fit at opposite ends 104A and 104B of inner recess 104, aiding in positioning and attachment of block 120 to unit 100.

[0066] The ability of light opaque element 108 to block light from directly reaching the light detector 107, is specifically meaningful when at least one of the light sources is veryclose to the light detector, as in the illustrated exemplary embodiment. In this specific example, the first light source 105 may be about 400 pm from the light detector 107 and the second light source 106 is about further away. The light sources with relatively short wavelengths, typically less than about 600 nanometers, are placed closest to the light opaque element 108. Therefore, the physical separation, namely the lateral distance between the effective light-emitting area of the closest light sources and the effective light-detecting area of the light detector is less than about 1000 pm. This minimal difference is defined primarily due to manufacturing tolerances, which require a certain minimal gap between the light opaque element and the optical elements that are placed next to it. The purpose of this disclosure is to bring them as close as possible. In the absence of a light barrier as in the present disclosure, such close proximity may cause undesired light directly reaching the sensor, which can lead to a significant increase in the noise, which in turn requires the sensing light sources to emit a light with relatively high intensity, giving rise to significant power consumption. By reducing or even almost totally eliminating the undesired light leakage, in accordance with this disclosure, the light sources can be operated with much less intensity and the power consumption decreases dramatically, and at the same time ensuring a high signal-to-noise ratio.

[0067] In addition, the present disclosure also provides for reduced and almost total elimination of light ability to indirectly reach the sensor. As can be seen in Fig. 1C and Fig. ID block 120, which is typically a molded block, has a top skin contact surface 122 that is defined by (i) the external surfaces 124A and 126A of, respective, first and second light transmissive elements 124 and 126 which overlay the light sources and the light detector, respectively; and by (ii) the external edge 108B of the light opaque element, which is continuous at the same level or flush with adjacent surface portions of surfaces 124A and 124B. Edge portion 108A of element 108 optically separates between first element 124 and the second element 126. This reduces the ability of light to indirectly reach the sensor

[0068] In other words, a top part of the light opaque element 108 forms a part of the contact surface 122. This results in a contact surface 122 that is formed of three parts: (i) a first light transmissive part 124A that is associated with the light sources 105 and 106 such that light emitted from the light sources 105 and 106 propagates through the first part 124A; a second transmissive part 124B that is associated with the light detector 107 such that any light that is detected by the light detector 107 propagates through the secondtransmissive or semi-transmissive part 124B; and a light opaque element part 108B formed by a top part of the light opaque element 108 and separates between the first transmissive part 124A and the second transmissive or semi-transmissive part 124B. The contact surface 122 is curved and the light opaque element part 108B is also curved to form the continuous surface of the contact surface 122.

[0069] Accordingly, any light illuminated from the light sources 105 and 106 can reach the light detector 107 only if it exits through the contact surface 122 and reflects or scatters back from an element in or below the skin portion (not shown) that is in contact with contact surface 122. Thus,

[0070] In this example, each of the first and second transmissive elements 124 and 126 are parts of molded block 120 and have, each, a respective bottom surface 124B and 126B. Elements 124 and 126 may, for example, be made of PMMA 7H. When combined with the other part of the sensing unit, lateral bottom portions of surfaces 124B,126B will come to rest on top of step 128 that is defined between the inner depression 104 and the walls of the outer depression 111. The shape and size of block 120 are sized to fit snugly within the walls of outer recess 111. Block 120, that may be separately formed, for example by molding, as described below, may secured into position by the use of an adhesive or by other techniques.

[0071] Once block 120 is fitted within outer recess 111 there is a gap remaining in the space below the inner, bottom faces 124B,126B and in accordance with an embodiment of this disclosure it is filled with a curable polymeric material, while still in a flowable state, that is permitted to cure, for example by light irradiation, e.g. with UV light, through the overlaying portions of the light transmissive elements 124 and 126. Such polymeric material is preferably one with a refractive index which is about the same as that of the transmissive elements.

[0072] Reference is now made to Figs.2A-2B, which are schematic illustrations of a nonlimiting example of different views of a sensing device in the form of a wearable device according to an embodiment of the present disclosure. In this example, a sensing unit 200, which may be that of Figs. 1A-1D is comprised in a wearable device 250, such as a watch or a bracelet. Fig. 2A shows only the sensing section of the wearable device 250 but it should be understood that this section is coupled with a wrist band (not shown) to be worn over the wrist of the subject. The wearable device 250 comprises two ECG electrodes 252 partially surrounding the sensing unit 200. The ECG electrodes 252 and the sensing unit200 are part of a sensing member 254 that is coupled to a body 256 of the wearable device 250, e.g. the chassis of a watch or wrist band. The coupling of the sensing member 254 to the body 256 is made via a flexible member 258 so as to allow movement of the sensing member 254 at least along an axis Y normal to a plane P defined by the sensing surfaces 260 of the ECG electrodes 252.

[0073] Reference is now made to Fig. 3 showing a block diagram of manufacturing process of a sensing unit of this disclosure. The described process is a molding process 300 although the disclosure is not limited thereto.

[0074] In the first step 302 a mold is provided having a molding surface that defines an eventual skin contact surface of the sensing unit.

[0075] Then at 304 a light opaque element, typically a planar or folded plate, for example a plate defining a lobed plate path of the kind show above in Figs. 1A-1D, is introduced into the mold. The light opaque element has an edge portion with an edge that is congruent with an opposite portion of the molding surface and consequently forms tight contact therewith, and thus divides the mold space into two.

[0076] Then at 306 a material that cures to form light transmissive medium, is injected into the mold on two sides of the light opaque element, and permitted to cure, to obtain a molded product. The molded product has two light transmissive elements that are separated by said edge portion, having external surfaces defined by said mold surface, and having opposite internal surfaces. The external surfaces of the two light transmissive elements, and the edge surface of the light opaque element jointly define the skin contact surface. The two light transmissive elements are optically separated by said edge portion.

[0077] Then at 308 the molded product is combined with an electronic circuity that comprises one or more light sources configured to emit light onto a skin portion through said contact surface, and at least one light detector configured to detect light returning from said skin portion through said contact surface in response to the emitted light. The combining is conducted such that said one or more light sources are each on one side of the light opaque element and said at least one light detector is on the other side; and also such that (ii) light to be emitted by the one or more light sources is blocked from reaching the light detector.

[0078] Optionally, prior to step 308 a liquid polymerizable material is introduced into a space that in the sensing unit is delimited the internal surfaces of the light transmissive elements, the amount of the liquid and the manner of combining being such so that saidmaterial fills entire space between said one or more light sources and said at least one light detector and between said internal surfaces. Then the polymerizable material is permitted to be cured, for example by UV irradiation through the contact surface.

Claims

CLAIMS:

1. A sensing unit for measuring physiological parameters of a subject, comprising:a skin contact surface for contacting a skin portion of the subject;one or more light sources configured to illuminate first illumination through one or more light transmissive parts of said contact surface;at least one light detector configured to detect illumination response of said first illumination through said one or more light transmissive parts;a light opaque element configured to block light emitted from the one or more light sources, wherein the light opaque element has at least a first part thereof positioned between the first light source and the light detector;wherein the contact surface at least partially formed by said one or more light transmissive parts and an external edge of said first part of the light opaque element.

2. The sensing unit of claim 1, comprising one or more light transmissive elements, wherein the external surfaces of said one or more light transmissive elements form said one or more light transmissive parts of said contact surface.

3. The sensing unit of claim 2, comprising two light transmissive elements.

4. The sensing unit of claim 3, wherein said external edge is an external edge of an edge portion, wherein the edge portion and the external edge optically separate two light-transmissive elements.

5. A sensing unit for measuring physiological parameters of a subject, comprising:a skin contact surface for contacting a skin portion of the subject;one or more light sources configured to emit light onto said skin portion through said contact surface;a light detector configured to detect light returning from said skin portion through said contact surface in in response to the emitted light;a light opaque element having a first part thereof positioned between the one or more light sources and the at least one light detector and configured to block light emitted from the at least one light sources from directly reaching the at least one light detector;wherein the skin contact surface is defined byexternal surfaces of at least two light transmissive element, of which at least one first light transmissive element overlays the light source and at least one second transmissive element overlays the light detector, and byan external edge of an edge portion of the light opaque element, the edge portion optically separates the at least one first element from the at least one second element.

6. The sensing unit of any one of claims 1-5, wherein a first light source of said one or more light sources is adjacent to said light opaque element from one side thereof and the light detector is adjacent to the opposite side of said opaque element7. The sensing unit of any one of claims 1-6, wherein the light opaque element is configured as a straight or folded plate.

8. The sensing unit of any one of claims 1-7, wherein the one or more light sources are formed within one or more light sources elements, and the at least one light detector is formed within a light detector element.

9. The sensing unit of claim 8, wherein the light source element and the light detector element have respective portions that are about 100 pm from the light opaque element, each from a different side.

10. The sensing unit of any one of claims 1-9, wherein said external edge extends between two peripheral portions of the contact surface or between two of said one or more light transmissive parts of the contact surface, to thereby separate between a first light transmissive element overlaying the one or more light sources, and a second light transmissive element, overlaying the light detector.

11. The sensing unit of any one of claims 1-10, comprising a first and a second light source, whereinthe second light source emits light of wavelength or wavelength ranges larger than that of the first light source, and whereinthe second light source is positioned further away from the light opaque element than the first light source.

12. The sensing unit of any one of claims 2-11, wherein the one or more light sources and the light detector are fixed to said one or more light transmissive by a polymeric material that is cured by light.

13. The sensing unit of claim 12, wherein the refractive index of the polymeric material is about the same as the refractive index of the light transmissive elements.

14. The sensing unit of any one of claims 1-13, wherein the one or more light sources are one or more light-emitting-diodes (LEDs) and the light detector is a photodiode.

15. The sensing unit of any one of claims 2-5, wherein the space between internal faces of the light-transmissive element and any of the one or more light source and of the at least one light detector is filled with one or more light transmissive materials.

16. The sensing unit of claim 15, wherein said one or more light transmissive materials are light transmissive adhesives filling the space between internal faces of the light-transmissive element and any of the one or more light source and of the at least one light detector.

17. The sensing unit of any one of claims 1-16, wherein the one or more light sources comprise short-wavelengths light sources configured to emit light characterized by a wavelength of less than about 600 nanometers.

18. The sensing unit of claim 17, wherein the short-wavelengths light sources are disposed between 50-200 pm to said light opaque element.

19. The sensing unit of any one of claims 1-18, wherein the edge portion of the light opaque element has a curvature that conforms or substantially conforms with a curvature of the contact surface.

20. The sensing unit of any one of claims 1-19, wherein the one or more light sources each comprise a light-emitting area from which light is emitted, and the light detector comprises a light-detecting area configured to receive light; physical separation between the light-detecting area and the closest light-emitting area is less than about 1000 pm.

21. A sensing device for sensing physiological parameters of a subject, comprising the sensing unit of any one of claims 1-20.

22. The sensing device of claim 21 , being a wearable system to be worn by the subj ect.

23. The sensing device of claim 21 or 22, being a medical watch or medical bracelet.

24. A method for manufacturing a sensing unit, comprising:molding two light transmissive elements, with external and internal surfaces, on two sides of a light opaque element to define a skin contact surface that comprises (a) the external surfaces of the two light transmissive elements, and comprises (b) an external edge of an edge portion of the light opaque element, the two light transmissive elements being optically separated by said edge portion, to obtain a molded product; and combining the molded product with an electronic circuity that comprises (x) one or more light sources configured to emit light onto a skin portion through said contact surface, and (y) at least one light detector configured to detect light returning from said skin portion through said contact surface in response to the emitted light, the combiningbeing such that (i) said one or more light sources being on one side of the light opaque element and said at least one light detector being on the other side, and such that (ii) light to be emitted by the one or more light sources is blocked from reaching the light detector.

25. A method for manufacturing a sensing unit, comprising:providing a mold with a molding surface defining a portion of an eventual skin contact surface of the sensing unit;placing a light opaque element in contact with a portion of said molding surface, the light opaque element having an edge portion with an edge that is congruent or conforms with that of said portion;injecting transmissive material into the mold, and permitting the material to cure to obtain a molded product that comprisestwo light transmissive elements separated by said edge portion, having external surfaces defined by said mold surface, and having opposite internal surfaces, and comprisesa skin contact surface defined by (a) the external surfaces of the two light transmissive elements, and by (b) the external surface of the light opaque element, the two light transmissive elements being optically separated by said edge portion; and combining the molded product with an electronic circuity that comprises (x) one or more light sources configured to emit light onto a skin portion through said contact surface, and (y) at least one light detector configured to detect light returning from said skin portion through said contact surface in response to the emitted light, the combining being such that (i) said one or more light sources being on one side of the light opaque element and said at least one light detector being on the other side, and such that (ii) light to be emitted by the one or more light sources is blocked from reaching the light detector.

26. The method of claim 24 or 25, whereinprior to said combining, introducing a liquid polymerizable material into a space delimited by the internal surfaces of the light transmissive elements, the amount of the liquid and the manner of combining being such so that said material fills entire space between said one or more light sources and said at least one light detector and between said internal surfaces, andafter said combining, curing the polymerizable material.

27. The method of claim 26, wherein said polymerizable material is cured by light, and wherein said material is cured by shing light through light transmissive elements.

28. The method of claim 26 or 27, wherein said material after curing has about the same refractive index as that of the transmissive element.

29. The method of any one of claims 25-28, comprising filling a gap between said two light transmissive elements and any one of said at least one light detector and said one or more light sources with a light transmissive material.

30. The method of claim 29, wherein said light transmissive material is a light-transmissive adhesive.

31. The method of any one of claims 25-30, for the production of the sensing unit of any one of claims 1-20.

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