An optical sensor for monitoring a tissue surface

Abstract

An optical sensor to be mounted on a tissue surface. The sensor has a groove (32) in the body member having a circular portion (34) extending over an angle of between 30° and 60° and a second groove with a similar shape. A light transmitting optical fiber (23) is arranged in the groove and opens to a measurement chamber (35) in the body member and opening towards a wound in the tissue surface. A light receiving fiber (24) is arranged in a similar fashion. The end surfaces of the fibers are beveled with an angle of between 30° and 60° so that the end surface of the optical fiber extends vertically or horizontally parallel with a corresponding bottom surface of the body member.

Description

[0001] TITLE: DEVICE FOR MONITORING A TISSUE SURFACE

[0002] AREA OF INVENTION

[0003] The present invention relates to a device for monitoring a tissue surface being affected, such as a wound of a human being or other animal. In particular the device is intended for monitoring the tissue surface and a dressing applied to the tissue surface over an extended time duration. In addition, the monitoring device may alert the user or other persons for conditions requiring intervention.

[0004] BACKGROUND

[0005] There are several reasons to monitor a tissue surface or area, such as a wound and a dressing applied on the wound. One aspect may be to determine if the dressing should be exchanged, for example being saturated with wound fluid or exudate or the wound starts bleeding. Another aspect may be to determine if bacteria are present er start to grow in or around the skin area or the wound. A further aspect may be to monitor a damage of the skin, such as skin irritation, skin infection, or skin deceases such as psoriasis. A still further aspect may be to determine if the dressing has been dislocated or removed.

[0006] These aspects may be reached by integrating a plurality of sensors in the dressing applied to the wound for monitoring the dressing over time or arranging a plurality of sensors at a tissue surface. It is desired to avoid using electrical sensors since electrical sensors causes metallic and other types of less sustainable waste and instead optical sensors may be used.

[0007] The patent specification US11033435B2 discloses a multifunctional wound treatment dressing for administering different therapeutic treatments to an open, chronic wound of a human or animal body. The multifunctional wound treatment dressing includes an occlusive wrapping adapted for placing over a wound. The multifunctional wound treatment dressing further includes at least two of the group of electrical, optical or mechanical stimulation means adapted for transmitting electrical, optical or mechanical energy towards the wound to stimulate healing of the wound and / or means for applying a negative (i.e. sub-atmospheric) pressure to the wound. Thus, a variety of different healing stimulation treatments may be performed together or in sequence by wearing the same occlusive wrapping without the need of changing / removing temporarily the wrapping for each change of treatment method. There is also disclosed that the wound treatment dressing further comprises sensors for determining a state or status of the wound, for instance for monitoring a variety of parameters such as pH, temperature, tissue closure, infection, biomarkers of healing, enzymes or moisture level. By measuring or determining such parameters, the stimulation process may be altered during the treatment period to shorten the treatment time or to perform better results.

[0008] The patent specification EP3545827B1 discloses a system including a sensor and a device coupled to the sensor. The sensor is configured to detect in animalia tissue (i) a first electromagnetic radiation extinction dominated by absorption of a first wavelength and (ii) a second electromagnetic radiation extinction dominated by scattering of a second wavelength. The device is configured to aid in diagnosing at least one of infiltration and extravasation in the animalia tissue based on the first and second electromagnetic radiation extinctions detected by the sensor.

[0009] There is a need in the art for an improved sensor based on optical fibers which is simple.

[0010] An object is to provide an optical sensor that can be arranged on a skin surface or be integrated in a dressing for monitoring a skin area over an extended time period.

[0011] Another object is to stabilize the optical fibers so that they measure at the same place of the skin over an extended time period.

[0012] A further object is to arrange the optical fibers so that a light transmitting fiber and a light detecting fiber are arranged so that favorable light conditions are obtained.

[0013] A yet further object is to arrange the fibers so that a distance to the wound is well defined.

[0014] A still further object is to arrange the fibers in parallel with the dressing.

[0015] A still another object is to protect the measuring area from surrounding light.

[0016] A yet another object is to monitor that the dressing is properly applied and maintained in proper position.

[0017] A yet further object is to design the optical sensor so that it is easy to manufacture. SUMMARY OF THE INVENTION

[0018] Accordingly, an object of the present invention is to mitigate, alleviate or eliminate one or more of the above-identified and below mentioned deficiencies and disadvantages singly or in any combination.

[0019] In an aspect, there is provided an optical sensor intended to be applied to a tissue surface to be monitored, comprising: a body member having a bottom surface intended to be arranged substantially parallel with a tissue surface; a first groove arranged in the body member and ending in a first opening in the bottom surface, the first groove having a first inclination angle in the first opening in relation to the bottom surface; a second groove arranged in the body member ending in a second opening in the bottom surface, the second groove having a second inclination angle in the second opening in relation to the bottom surface; a first optical fiber having a predetermined first core diameter and being arranged in the first groove and having a first end arranged in the first opening, the first end being beveled with a first bevel angle so that a beveled end surface of the optical fiber is parallel with the bottom surface, whereby the first optical fiber is configured to illuminate a first area of the tissue surface; a second optical fiber having a predetermined second core diameter and being arranged in the second groove and having a second end arranged in the second opening, the second end being beveled with a second bevel angle so that a beveled end surface of the second optical fiber is parallel with the bottom surface, whereby the second optical fiber is configured to monitor a second area A2] of the tissue surface; characterized by an opaque sleeve arranged perpendicular to the bottom surface and configured to encircle the body member for defining, together with the bottom surface, a measurement chamber opening towards the tissue surface and comprising the first area of the tissue surface and the second area of the tissue surface; whereby the first optical fiber extends in the first groove from the first opening in the body member in a first circular path to a first side opening of the body member in a plane perpendicular to the bottom surface, whereby the first circular path extends over a first angular portion of a circle, which is a quarter of a circle minus the first inclination angle so that the first side opening is substantially parallel with the bottom surface and whereby a first radius of the first circular path is between 4 and 25 times the first core diameter; whereby the second optical fiber extends in the second groove from the second opening in the body member in a second circular path to a second side opening of the body member in a plane perpendicular to the bottom surface, whereby the second circular path extends over a second angular portion of a circle, which is a quarter of a circle minus the second inclination angle so that the second side opening is substantially parallel with the bottom surface and whereby a second radius of the second circular path is between 4 and 25 times the second core diameter, and whereby the first inclination angle and the second inclination angle each are between 30° and 60°, such as 40°, 45° or 50°. The first inclination angle and the second inclination angle may be equal and directed in opposite directions. A distance between a centrum of the first opening and a centrum of the second opening may be between 1 and 10 times the core diameter of the first optical fiber and wherein the core diameter of the second optical fiber is the same as the core diameter of the first optical fiber.

[0020] In an embodiment, the first optical fiber may be configured to illuminate the first area of the tissue surface with an illumination light having an energy exciting florescence in substances of the tissue surface.

[0021] In another embodiment, the first area of the tissue surface is non-overlapping with the second area of the tissue surface. The first inclination angle of the first optical fiber may be 50° and the second inclination angle of the second optical fiber may be 40°.

[0022] In a further embodiment, the sleeve may comprise an inner surface configured to enhance the illumination of the measurement chamber, by reflecting or dispersing illumination light impinging on an inner surface of the sleeve. The sleeve may comprise an insert which reflects and / or disperses illumination light from the first optical fiber. The insert may comprise a curved surface which concentrates optical energy from the first optical fiber towards the monitored second area of the tissue surface.

[0023] In still another embodiment, the first groove and the second groove may be arranged in a mirror-like arrangement at each side of a virtual mirror surface, which is positioned between the first opening in the bottom surface and the second opening in the bottom surface and is perpendicular to the bottom surface and wherein a line interconnecting the first opening and the second opening is perpendicular to the virtual mirror surface. The first optical fiber and the second optical fiber may be arranged in parallel. The first optical fiber and the second optical fiber may be the same fiber.

[0024] In yet another embodiment, the bottom surface may comprise a recess including a recess bottom surface portion perpendicular to a non-recessed bottom surface portion, and wherein the first opening of the first groove opens at the recessed bottom surface portion and wherein the second opening of the second groove opens at the recessed bottom surface portion; wherein the first end of the first optical fiber is beveled with a first bevel angle so that the beveled end surface of the optical fiber is parallel with the recessed bottom surface portion, and wherein the second end of the second optical fiber is beveled with a second bevel angle so that the beveled end surface of the optical fiber is parallel with the recessed bottom surface portion.

[0025] In a still further embodiment, a membrane is arranged between the optical sensor and a tissue surface. The optical sensor may comprise a transparent membrane, which is attached to the sleeve at an area facing away from the bottom surface, whereby the transparent membrane delimits the measurement chamber adjacent the tissue surface. The optical sensor may be attached to a dressing arranged to at least partly cover the tissue surface.

[0026] In a yet further embodiment, the optical sensor may be arranged to measure ambient light received by the light receiving optical fiber for triggering an alarm if the ambient light is above a predetermined level.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further objects, features and advantages of the invention will become apparent from the following detailed description of embodiments of the invention with reference to the drawings, in which:

[0029] Embodiments of the invention are disclosed in the appended drawings, in which:

[0030] Fig. 1 is a schematic view of a first embodiment of the invention.

[0031] Fig. 2 is a schematic view of an alternative arrangement of the first embodiment.

[0032] Fig. 3 is a schematic view of a still alternative arrangement of the first embodiment.

[0033] Fig. 4 is a cross-sectional view of a second embodiment in an enlarged scale.

[0034] Fig. 5 is is a cross-sectional view of a third embodiment. Fig. 6 is is a cross-sectional view of a fourth embodiment.

[0035] Fig. 7 is is a cross-sectional view of a fifth embodiment.

[0036] Fig. 8 is an enlarged cross-sectional view of a sixth embodiment.

[0037] Fig. 9 is a schematic view of a seventh embodiment.

[0038] Fig. 10 is a schematic view of an eighth embodiment.

[0039] Fig. 11 is an enlarged cross-sectional view of a ninth embodiment.

[0040] Fig. 12 is an enlarged cross-sectional view of a tenth embodiment.

[0041] Fig. 13 is an exploded isometric view of an eleventh embodiment.

[0042] Fig. 14 is an isometric view of the embodiment of Fig. 13 in a mounted condition, without showing optical fibers and a sleeve.

[0043] Fig. 15 is a cross-sectional view of the embodiment of Fig. 14.

[0044] Fig. 16 is a plan view of the bottom surface of the embodiment of Fig. 14 with a monitoring area indicated.

[0045] DETAILED DESCRIPTION OF EMBODIMENTS

[0046] Below, several embodiments of the invention are described. These embodiments are described in illustrating purpose in order to disclose the best mode and to enable a skilled person to carry out the invention. However, such embodiments do not limit the scope of the invention, which is only limited by the patent claims. Moreover, certain combinations of features are shown and discussed. However, other combinations of the features described are possible within the scope of the invention.

[0047] Directions when indicated in this specification, such as horizontal or vertical, are indications in relation to the surface of skin or tissue area, the wound or the dressing, which is imagined to be horizontal. Indications such as left and right relates to the respective Figure.

[0048] The expression "tissue surface” is intended to include all types of affected tissue, in particular all types of wounds, including exudates from the tissue and foreign substances such as bacteria and also including areas (peri-wound area) outside a wound or an affected skin area. The expression also includes skin surfaces affected by for example skin irritation, skin infection, or skin deceases such as psoriasis. The optical sensor may be arranged in a dressing applied to the affected tissue surface. However, the optical sensor may be applied to the tissue area separately, without a dressing. The dressing may be only a thin membrane. The dressing may also comprise a more or less thick absorbent material.

[0049] There are several reasons to monitor a tissue surface or area, such as a wound and / or a dressing applied on the wound, for example for determining if the dressing has been dislocated or should be exchanged, such as being saturated with wound fluid or exudate or the wound starts bleeding. The tissue surface should be monitored to determine if bacteria are present or start to grow in or around the skin area or the wound. The tissue surface may be monitored to determine if the tissue or skin has been affected or damaged, such as skin irritation, skin infection, or skin deceases such as psoriasis. The optical sensors may be arranged in the dressing or otherwise be applied to the tissue surface to be monitored. The optical sensors may be maintained at place by an adhesive tape.

[0050] The embodiments described below are constructed with the following precautions in mind.

[0051] The optical sensor should be as easy as possible to manufacture. In particular, optical elements which require alignment may be avoided.

[0052] Optical fibers are considered not to be bent with a small bending radius. The radius is considered to be 100 times or at least 50 times the core diameter of the optical fiber.

[0053] An optical fiber with a core diameter of 500 pm, may be bent with a radius of more than 25 mm (50 times) in order not to unduly lose light. On the other hand, the optical fibers are normally arranged along and parallel with an upper surface of the dressing, i.e. horizontally. In order to emit or collect light from the tissue area, the optical fibers in the sensor need to be bent over an angle of approximately 90°, i.e. to eventually be directed substantially vertically. If a radius of 25 mm should be used, the building height of the optical sensor would be 25 mm and the optical sensor would be 50 mm wide or larger.

[0054] An object of the present invention is to construct an optical sensor with smaller dimensions. For such a purpose, a smaller radius may be used. A smaller radius than the recommended radius of more than 50 times the core diameter, would result in losses, but such losses can be calculated and compensated for. However, if the radius is smaller than about five times of the core diameter, it would be difficult to obtain a sufficient transmission in the optical fibers. Thus, a radius of fifteen times the core diameter, i.e. a radius of 7.5 mm, is used in combination with an optical fiber having a diameter of 0.5 mm in the embodiments described below. The radius may be from 4 to 50 times the core diameter, such as from 4 to 25 times the core diameter of the optical fibers.

[0055] The area which is illuminated by the light transmitting fiber is dependent on the distance from the transmitting fiber end. If the skin area to be illuminated is close to the fiber ending, a small area will be illuminated, which may result in that the light to be collected by the light receiving fiber will be weak, in particular when fluorescence light is to be received. If the wound to be illuminated is far away from the fiber ending, the fiber needs to be bent over an arch of 90°, which makes the optical sensor large.

[0056] Thus, an object of the invention is to arrange an optical sensor that is small by combining two features. The first feature is to bend the optical fiber over less than 90°, for example between 30° and 60°, such as 40°, 45° or 50°. This will reduce the building height and the diameter of the sensor. The second feature is to use a beveled or inclined surface of the end of the optical fiber. Such inclined surface will provide a refraction of the light emitted by the optical illumination fiber which can be used to take care of the remaining “bending” of the light rays to illuminate the measurement area. In addition, the illumination angle will be increased by the inclined surface. Similar reasoning applies to the light receiving optical fiber.

[0057] The embodiments described below are constructed with the above-mentioned limitations in mind.

[0058] An embodiment may comprise an optical sensor intended to be mounted on a dressing applied to a tissue area or a wound to be monitored, comprising: a body member; a first groove in the body member having a circular portion extending over a first angle of between 30° and 60°; a measurement chamber arranged in the body member and opening towards the skin area or the wound; a light transmitting optical fiber arranged in the first groove ending in an end surface of the optical fiber, which end surface is beveled with a second angle of between 30° and 60° in relation to a symmetry axis of the light transmitting optical fiber, whereby the light transmitting fiber ends in the measurement chamber for illuminating the skin are or the wound.

[0059] In addition, the optical sensor may further comprise: a second groove in the body member having a circular portion extending over a third angle of between 30° and 60°; a light receiving optical fiber arranged in the second groove ending in an end surface of the light receiving optical fiber, which end surface is beveled with a fourth angle of between 30° and 60° in relation to a symmetry axis of the light receiving optical fiber, whereby said light receiving optical fiber ends in the measurement chamber for receiving light emitted from the illuminated wound.

[0060] In an embodiment, the first groove and the second groove are arranged in a mirrorlike arrangement wherein the first and the third angles are the same and the second and fourth angles are the same. Each of the first, second, third and fourth angles may be between 30° and 60°.

[0061] In another embodiment, the light transmitting optical fiber and the light receiving optical fiber are arranged in parallel. Alternatively, the light transmitting optical fiber and the light receiving optical fiber are the same fiber.

[0062] In a further embodiment, the light transmitting optical fiber end surface and the light receiving optical fiber end surface are arranged horizontally or alternatively vertically.

[0063] The optical sensor may further comprise an opaque member for preventing surround light to enter the measurement chamber.

[0064] In yet another embodiment, the optical sensor may be arranged to measure ambient light received by the light receiving optical fiber for triggering an alarm if the ambient light is above a predetermined level.

[0065] Fig. 1 shows a dressing in the form of a thin membrane 11, which extends over and covers a wound. The thickness of the membrane may often be around 10 pm or between 5 pm and 500 pm. The membrane is attached to the wound by an adhesive or simply covers the wound without an adhesive. An optical sensor 21 is attached to the membrane 11.

[0066] Fig. 1 shows the optical sensor attached to the upper surface of the membrane via an adhesive 22. An optical light transmitting fiber 23 enters the optical sensor from the left (as seen in the drawing) and a light receiving fiber 24 exits the optical sensor to the right.

[0067] Fig. 2 shows the optical sensor arranged below the membrane 11. The optical sensor is kept in place by the membrane, possibly by the aid of an adhesive. The bottom surface of the optical sensor may be covered by a transparent material 28, for example a membrane as mentioned. Other material may be a sapphire or glass or alternatively a transparent plastics material similar as the optical fiber is made from. The transparent material 28 may be arranged on any of the embodiments mentioned. The transparent material may delimit the measurement chamber towards the tissue surface of wound or dressing. The measurement chamber may comprise a transparent gas, such as air. The transparent material may extend further into the optical sensor almost as far as until in contact with the optical fibers. The transparent material 28 will protect the sensor and create a defined distance to the skin area or the wound.

[0068] Fig. 3 shows the optical sensor attached to the membrane via an adhesive tape 25.

[0069] The optical sensor is arranged to emit light to the skin surface via the light transmitting fiber 23 and receive light via the light receiving fiber 24. The received light from the light transmitting fiber may be reflected, scattered or otherwise influenced upon, such as partly absorbed. In another embodiment, the illumination light may have a sufficient energy (blue light to UV light) to cause fluorescent matter in the tissue area or wound or dressing to emit fluorescent light, which is collected by the light receiving fiber.

[0070] Fig. 4 shows another embodiment of the optical sensor in an enlarged, cross- sectional view, in which the dressing may be thick by comprising an absorbent layer 41 or similar. As an example, the thickness of the absorbent layer may be in the area of 4 mm, or between 2 mm and 10 mm or even thicker. The absorbent layer may be arranged on top of a membrane 42.

[0071] The optical sensor may comprise a body 31 of a cylindrical shape.

[0072] The light transmitting fiber 23 is arranged in a first groove 32 arranged in the body. The groove 32 may start with a straight portion 33, followed by a circular portion 34 with a radius of for example 7.5 mm, as indicated above, and extends over an arc of 50°, resulting in that optical fiber end has an inclination of 40° in relation to the vertical. The fiber end may comprise a small straight portion (not shown).

[0073] The light receiving fiber 24 is arranged in a similar second groove 36 having a straight portion 38 and a circular portion 37 (and possibly a small straight portion) extending over an arc of 50°, resulting in that optical fiber end has an inclination of 40° in relation to the vertical.

[0074] The body 31 is in its bottom surface provided with a cylindrical recess 51 having a substantially vertical wall, which forms a substantially cylindrical recessed bottom surface portion 52 which is perpendicular to a non-recessed bottom surface portion 53 of the body 31. The cylindrical recess 51 may have a circular cross-section or have a rectangular or square cross-section.

[0075] The first light transmitting optical fiber end is arranged in a first opening 54 of the first groove 32 which opens at the vertical recessed bottom surface portion 52. The light receiving optical fiber end is arranged in a second opening 55 of the second groove 36, which opens at the vertical recessed bottom surface portion 52.

[0076] The first end of the first optical fiber is beveled with a first bevel angle so that the beveled end surface of the optical fiber is vertical and is parallel with the recessed bottom surface portion 52. The second end of the second optical fiber is beveled with a second bevel angle so that the beveled end surface of the optical fiber is vertical and parallel with the recessed bottom surface portion 52.

[0077] The groove 32 ends in a measurement chamber 35, the size of which should be as small as possible but sufficiently large to enclose the light emitted from the light transmitting optical fiber and the light to be received by the light receiving optical fiber.

[0078] The body 31 is supported by a cylindrical distance member or sleeve 43 having a height corresponding to the height of the dressing. If the dressing is 4 mm thick, the distance member 43 may be about 3,0 mm and the optical sensor may be 1 mm in the portion extending down into the dressing. The sleeve 43 may have a circular cross-section or may be rectangular, square, oval, octagonal, hexagonal or have another suitable shape.

[0079] The optical sensor may be completely embedded in the dressing so that an upper surface of the optical sensor is substantially flush with an upper surface of the dressing.

[0080] The symmetry axis of the light transmitting fiber 23 may extend with an angle of 40° in relation to the vertical at the end of the light transmitting fiber. The symmetry axis of the light receiving fiber 24 also extends with an angle of 40° in relation to the vertical. The light transmitting fiber is directed opposite in relation to the light receiving optical fiber and in the same vertical plane.

[0081] Other angles may be used, for example between 30° and 60°, such as 40°, 45° or 50°.

[0082] According to the embodiment of Fig. 4, the output surface of the light transmitting fiber is beveled and has a slope or inclination of 50° in relation to the symmetry axis of the light transmitting fiber, i.e. the normal of the end surface has an angle of 50° in relation to the symmetry axis of the optical fiber. This means that the light transmitting fiber is so arranged so that the end surface of the light transmitting fiber is vertical, see Fig. 4. The illumination light emitted through the end surface will be diffracted and forming an illumination area Al and with the light having a cone angle as shown by broken arrows 46 and 47 in Fig. 4.

[0083] As an example, in the embodiment of Fig. 4, the optical fiber may have a refraction index of 1.5 and a numerical aperture of 0.48, resulting in that the cone reaching the end surface from inside of the fiber has a cone angle of about 19° (half the cone) in relation to the symmetry axis of the fiber. The cone will be refracted by the inclined end surface. The left side indicated by broken arrow 46 of the cone after passing the end surface into air surrounding the optical fiber end is vertical and is parallel with the end surface of the optical fiber. The right side 47 of the cone has an angle of about 39° relative to the vertical. The illuminated area Al has a diameter of about 3,2 mm if the dressing height is 4 mm and about 6.6 mm if the dressing height is 8 mm.

[0084] The result is that the optical fiber is required to be bent over only 50° and the refraction due to the inclined vertical end surface takes care of the rest of the necessary “bending” of the light ray until 90° for a part of the light cone outside the optical fiber. Thus, the inclination of the end surface enables a shorter distance between the light transmitting optical fiber and the light receiving optical fiber and enables that the optical fibers are only required to be bent over an arc which is considerably smaller than 90°, such as between 30° and 60°, for example 40°, 45° or 50°.

[0085] In embodiments of the invention, the radius of curvature of the optical fibers is between 4 to 25 times the core diameter of the optical fiber. The optical fiber extends over or is bent over an arc of between 30° and 60°. The normal of the end surface of the optical fiber has an inclination of between 30° and 60° in relation to the optical fiber symmetry axis. The end surface of the optical fiber is in all embodiments parallel with the surrounding surface of the body member.

[0086] There is an advantage if the arc and the inclination are symmetrical so that the end surface is horizontal or vertical.

[0087] The geometry of the illumination is dependent on the numerical aperture of the optical fiber, the refraction index of the optical fiber and the inclination of the end surface of the fiber in relation to the optical axis of the fiber and the vertical or horizontal of the measurement chamber.

[0088] With the above features, is is possible to construct an optical sensor, which is sufficiently small. The outer diameter of the optical sensor can be less than 10 mm.

[0089] In an embodiment and in order to reduce the overall dimensions, the illumination fiber and the reading fiber may be combined into a single optical fiber (not shown), which may reduce the size of the optical sensor by up to 50%.

[0090] In another embodiment, the illumination fiber and the reading fiber may be arranged in parallel, like a single optical fiber but divided in two optical fibers side by side, which is schematically shown in Fig. 5. A further option would be to cross the optical fibers as shown in Fig. 7.

[0091] In addition, the optical sensor does not need to be circular in cross-section, but may be elliptical or rectangular with rounded corners. Another shape would be hexagonal, as shown in Fig. 10, or octagonal.

[0092] Fig. 9 shows a cylindrical and circular optical sensor in which the illumination fiber and the reading fiber are arranged in 180° in relation to each other. By arranging one of the optical fibers as indicated by broken lines in Fig. 9, the size of the optical sensor can be further reduced.

[0093] The arrangement of the fibers as indicated in Fig. 5, 7 and 9 (broken lines) results in that a reflection of the illumination light directly from the illumination fiber to the receiving fiber may be be avoided, which may be an advantage in certain applications.

[0094] The optical sensor according to Fig. 9 may be arranged with several reading fibers, one as shown in solid lines and another one as shown in broken lines. In this case, the reading fiber in solid lines will read reflected light while the reading fiber in broken lines will read without reflection. Both fibers also read fluorescent light and / or scattered light. In another alternative embodiment, the optical sensor may be provided with several illumination fibers. This arrangement may be used in any of the previously mentioned embodiments.

[0095] The size of the optical sensor may be further reduced if the end beveled surface of each optical fibers is provided with a concave or convex surface. Fig. 8 shows a further embodiment adapted to a small distance to the tissue area to be monitored, such as a dressing having a small depth, for example as shown in Fig. 1. A small depth may be that the measurement chamber has a depth of for example 1 mm or smaller, such as 0.5 mm.

[0096] In the embodiment according to Fig. 8, the beveled surface is arranged horizontally. The optical axis of the fiber is arranged at 50° in relation to the horizontal and the end surface of the optical fiber is cut at an angle of 40° in relation to the optical axis. Comparing with the embodiment of Fig. 4, the end surface is rotated 90° around its own shaft or symmetry axis.

[0097] In the embodiment according to Fig. 8, the cone angle of the illumination fiber will be beneficial for an embodiment with a small distance to the wound, as indicated in Fig. 8. The end surface may have another angle, such as that the normal of the end surface has an angle of 40° in relation to the symmetry axis of the optical fiber. In this case, the arc of the optical fiber will be 50°, resulting in that the end surface will be horizontal.

[0098] As shown in Fig. 8, the optical sensor may be constructed in two portions, a body portion 56 comprising the optical fibers and a distance ring or sleeve 57 forming a measurement chamber 58.

[0099] The body portion 56 may have a flat bottom surface as shown in Fig. 8, which enables that the fiber ends can be easily polished after being glued into the fiber grooves.

[0100] The sleeve 57 can be designed to delimit the measurement chamber. A first embodiment of the sleeve 57 is shown in the right portion of Fig. 8. A second embodiment of the sleeve 59 is shown in the left portion of Fig. 8, which more closely follows the cone of the illumination. In addition, a third conical member 60 may be arranged in the center of the measurement chamber as illustrated in Fig. 8 to prevent light from being transmitted directly from the illumination fiber to the receiving fiber.

[0101] The angles may be combined to provide desired characteristics. For example, in the embodiment of Fig. 4, the arc of the optical fiber may be 60° and the angle of the end surface may be 45° which will result in a good illumination of the measurement surface. In this case, the end surface is not vertical but has an angle of 15° in relation to the vertical. Other combinations may be beneficial. Fig. 11 discloses an embodiment of an optical sensor. The optical sensor may be applied to a skin or tissue surface 63 to be monitored. The optical sensor may be retained at the surface 63 by an adhesive tape. Alternatively or additionally, the optical sensor may be attached to a transparent membrane or dressing.

[0102] The optical sensor comprises a body member 61 having a bottom surface 62 intended to be arranged substantially parallel with the tissue surface 63.

[0103] A first groove 64 is arranged in the body member and ends in a first opening 65 in the bottom surface 63 The first groove 64 has a first inclination angle al in the first opening in relation to the vertical.

[0104] A second groove 74 is arranged in the body member and ends in a second opening 75 in the bottom surface 63 The second groove has a second inclination angle a2 in the second opening in relation to the vertical

[0105] A first optical fiber 66 having a predetermined first core diameter dl is arranged in the first groove 64. The first optical fiber has a first end 67 arranged in the first opening 65. The first end is beveled with a first bevel angle so that a beveled end surface of the optical fiber is parallel with the bottom surface 63. The first optical fiber 66 is configured to illuminate a first area Al of the skin surface.

[0106] A second optical fiber 76 having a predetermined second core diameter d2 is arranged in the second groove 74. The second optical fiber has a second end 77 arranged in the second opening 75. The second end is beveled with a second bevel angle so that a beveled end surface of the second optical fiber is parallel with the bottom surface 63. The second optical fiber 76 is configured to monitor a second area A2 of the skin surface.

[0107] An opaque sleeve 81 is arranged perpendicular to the bottom surface 62 and configure to encircle the body member 61. The sleeve 81 defines together with the bottom surface a measurement chamber 82 which opens towards the skin surface 63 and comprises the first area Al of the skin surface and the second area A2 of the skin surface

[0108] The first optical fiber 66 extends in the first groove 64 from the first opening 65 in the body member 61 in a first circular path 68 to a first side opening 69 of the body member 61. The circular path 68 extends in a vertical plane perpendicular to the bottom surface. The first circular path extends over a first angular portion of a circle, which is a quarter of a circle minus the first inclination angle al so that the first side opening 69 is substantially parallel with the bottom surface 62. The first circular path 68 has a first radius R1 which is between 4 and 25 times the first core diameter dl.

[0109] In a similar manner, the second optical fiber 76 extends in the second groove 74 from the second opening 75 in the body member in a second circular path 78 to a second side opening 79 of the body member. The circular path 78 extends in a vertical plane perpendicular to the bottom surface The second circular path extends over a second angular portion of a circle, which is a quarter of a circle minus the second inclination angle a2 so that the second side opening 79 is substantially parallel with the bottom surface 62. The second circular path 78 has a second radius R2 of the second circular path which is between 4 and 25 times the second core diameter d2.

[0110] The first inclination angle and the second inclination angle are each between 30° and 60°, such as 40°, 45° or 50°.

[0111] Fig. 12 shows another embodiment, which is suitable when the illumination takes place with a light having sufficient energy for causing fluorescence in substances at the skin surface, such as substances produced by bacteria. The illumination light may be blue light to UV light. The intensity of the illumination light causing fluorescence is much larger than the intensity of the fluorescent light monitored. Consequently, reflection of the illumination light into the monitoring optical fiber may be avoided.

[0112] In the embodiment of Fig. 12, the inclination angle al of the first optical fiber is large, such as 50°. The illumination cone of the first optical fiber will be substantially as shown in Fig. 12 between first broken arrow 84 and second broken arrow 85. Only a small area Al of the skin surface is illuminated.

[0113] An insert 87 is arranged at the right side of the measurement chamber so that most of the illumination light from the first optical fiber will reach the insert 87. The insert may comprise a curved surface 88, which is provided with a surface material, which reflects and disperses the illumination light as shown by arrows 86.

[0114] The curved surface 88 may be curved to provide a concentration of the reflected illumination light towards the surface A2 monitored by the second optical fiber. The second optical fiber may have a smaller inclination angle a2 of for example 40°.

[0115] A distance D between the first opening of the first groove and the second opening of the second groove may be configured so that the illuminated tissue area Al is small and so that the monitored tissue area A2 is larger. A distance D of approximately three times the core diameter is often good. In the embodiment according to Fig. 12, the distance D may be smaller such as two times the core diameter. More generally, the distance D may be between one and ten times the core diameter in any of the embodiments.

[0116] Often the core diameter of the first optical fiber and the core diameter of the second optical fiber are the equal.

[0117] The dressing may incorporate an attachment member for attaching the optical sensor to the dressing. Figs. 1 to 3 show arrangement using adhesive. Alternatively, there may be a mechanical attachment member integrated in the dressing adjacent a hole made in the dressing intended to encompass the optical sensor. Fig. 4 shows a metal ring 44 arranged in the upper surface of the absorbing layer. The optical sensor may be provided with shoulders 45 arranged to cooperate with the metal ring and keep the optical sensor in place. Alternatively or additionally, the optical sensor may be provided with a strong magnet which interacts with the metal ring.

[0118] Fig. 6 shows an embodiment, in which a cover member 27 is arranged on top of the body member 26. The body member 26 is provided with grooves that open to the upper surface of the body member 26, which makes it easier to mount the optical fibers in the grooves. The cover member 27 keeps the optical fibers in place. The cover member 27 may be glued to the body member 26.

[0119] A core diameter of 500 pm has been mentioned as an example. However, other core diameters may be used such as 250 pm or 125 pm.

[0120] Fig. 13 shows another embodiment in which the body member is arranged as two portions, a first portion 91 and a second portion 92. The second portion 92 comprises a first groove 93 and a second groove 94 extending in circular paths. An optical fiber is intended to be mounted in the groove. The optical fiber comprises a core of an optically transparent material having a refraction index of for example 1.5 and a core diameter of for example 0.500 mm. A cladding is applied at the surface of the core. The cladding has a smaller refraction index of for example 1.3. This arrangement causes total inner reflection inside the optical fiber. Outside the cladding, there is an enclosure or coating for protecting the optical fiber. A side opening 95 comprises an enlargement 96. The optical fiber used in the present optical sensor is stripped from its cover at the end in order to expose the cladding and the optical fiber. An exposed length of about 10 to 15 mm is normally sufficient. The optical fiber without enclosure is arranged in the grooves mentioned above. The cover of the optical fiber may be attached in the enlargement 96.

[0121] The first member 91 also comprises grooves for the optical fiber, see Fig. 15.

[0122] The second member 92 comprises a recess 97 and the first member 91 comprises a shoulder 98, which cooperate to keep the first member and the second member together after assembly. A glue may be arranged in the recess 97.

[0123] Fig. 14 shows the first member and the second member after assembly and without optical fibers. A sleeve may be arranged in the shoulder 99 as shown in broken lines in Fig. 15.

[0124] Fig. 16 shows an area to be monitored by a light receiving optical fiber.

[0125] The outer diameter of the body member may be 16 mm and the inner diameter of the sleeve may be 12 mm. The distance D between the ends of the optical fibers may be 1.44 mm (from centrum to centrum). The height of the assembled body member may be about 2 mm. The height of an attached sleeve may be 2 mm, so that a measurement chamber with a height of 1 mm is formed. The bending radius of the optical fibers may be 7.5 mm. The core diameter of the optical fibers may be the same and 0.500 mm.

[0126] The optical sensor should be protected from ambient light, which may disturb the measurements. The sleeve 43 shown in Fig. 4 may be constructed by an opaque material. Alternatively or additionally, the absorbent layer and / or (part of) the membrane may comprise opaque material. The part of the membrane arranged below the measurement chamber should be transparent. The sleeve 43 may be provided with an inner surface which enhances the illumination of the measurement chamber, for example by reflecting or dispersing the illumination light impinging on the sleeve.

[0127] The optical sensor may be used for determining if the dressing is properly applied to a wound or that the dressing has not been relocalized. Since the measurement chamber is shielded from ambient light, the optical sensor may be connected to an optical detector, which in turn is connected to a computer. The computer may be programmed to measure if the ambient light is below a predetermined threshold, indicating that the dressing is properly arranged.

[0128] In the claims, the term "comprises / comprising" does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit. Additionally, although individual features may be included in different claims or embodiments, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and / or advantageous. In addition, singular references do not exclude a plurality. The terms "a", "an", “first”, “second” etc. do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

[0129] Although the present invention has been described above with reference to specific embodiment and experiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and, other embodiments than those specified above are equally possible within the scope of these appended claims.

Claims

CLAIMS1. An optical sensor intended to be applied to a tissue surface to be monitored, comprising: a body member (61) having a bottom surface (62) intended to be arranged substantially parallel with a tissue surface (63); a first groove (64) arranged in the body member and ending in a first opening (65) in the bottom surface, the first groove having a first inclination angle (al) in the first opening in relation to the bottom surface; a second groove (74) arranged in the body member ending in a second opening (75) in the bottom surface, the second groove having a second inclination angle (a2) in the second opening in relation to the bottom surface; a first optical fiber (66) having a predetermined first core diameter (dl) and being arranged in the first groove (64) and having a first end (67) arranged in the first opening, the first end being beveled with a first bevel angle so that a beveled end surface of the optical fiber is parallel with the bottom surface, whereby the first optical fiber is configured to illuminate a first area (Al) of the tissue surface; a second optical fiber (76) having a predetermined second core diameter (d2) and being arranged in the second groove (74) and having a second end (77) arranged in the second opening (75), the second end being beveled with a second bevel angle so that a beveled end surface of the second optical fiber is parallel with the bottom surface, whereby the second optical fiber is configured to monitor a second area (A2) of the tissue surface; characterized by an opaque sleeve (81) arranged perpendicular to the bottom surface (62) and configured to encircle the body member (61) for defining, together with the bottom surface, a measurement chamber (82) opening towards the tissue surface (63) and comprising the first area (Al) of the tissue surface and the second area (A2) of the tissue surface; whereby the first optical fiber (66) extends in the first groove (64) from the first opening (65) in the body member (61) in a first circular path (68) to a first side opening (69) of the body member in a plane perpendicular to the bottom surface, whereby the first circular path extends over a first angular portion of a circle, which is a quarter of a circleminus the first inclination angle (al) so that the first side opening (69) is substantially parallel with the bottom surface (62) and whereby a first radius (Rl) of the first circular path is between 4 and 25 times the first core diameter (dl); whereby the second optical fiber (76) extends in the second groove (74) from the second opening (75) in the body member in a second circular path (78) to a second side opening (79) of the body member in a plane perpendicular to the bottom surface, whereby the second circular path extends over a second angular portion of a circle, which is a quarter of a circle minus the second inclination angle (a2) so that the second side opening (79) is substantially parallel with the bottom surface (62) and whereby a second radius (R2) of the second circular path is between 4 and 25 times the second core diameter (d2), and whereby the first inclination angle and the second inclination angle each are between 30° and 60°, such as 40°, 45° or 50°.

2. The optical sensor according to claim 1, wherein the first inclination angle and the second inclination angle are equal and directed in opposite directions.

3. The optical sensor according to claim 1 or 2, wherein a distance (D) between a centrum of the first opening (65) and a centrum of the second opening (75) is between 1 and 10 times the core diameter (dl) of the first optical fiber (66) and wherein the core diameter (d2) of the second optical fiber (76) is the same as the core diameter (dl) of the first optical fiber (66).

4. The optical sensor according to claim 2, wherein the first optical fiber is configured to illuminate the first area (Al) of the tissue surface (63) with an illumination light having an energy exciting florescence in substances of the tissue surface.

5. The optical sensor according to claim 4, in which the first area (Al) of the tissue surface is non-overlapping with the second area (A2) of the tissue surface.

6. The optical sensor according to any one of the previous claims, wherein the first inclination angle of the first optical fiber is 50° and the second inclination angle of the second optical fiber is 40°.

7. The optical sensor according to any one of the previous claims, in which the sleeve (81) comprises an inner surface configured to enhance the illumination of the measurement chamber (82), by reflecting or dispersing illumination light impinging on an inner surface (83) of the sleeve (81).

8. The optical sensor according to any one of the previous claims, wherein the sleeve comprises an insert (87) which reflects and / or disperses illumination light from the first optical fiber.

9. The optical sensor according to claim 8, wherein the insert (87) comprises a curved surface (88) which concentrates optical energy from the first optical fiber towards the monitored second area (A2) of the tissue surface.

8. The optical sensor according to any one of the previous claims, wherein the first groove (64) and the second groove (74) are arranged in a mirror-like arrangement at each side of a virtual mirror surface, which is positioned between the first opening (65) in the bottom surface and the second opening (75) in the bottom surface and is perpendicular to the bottom surface and wherein a line interconnecting the first opening and the second opening is perpendicular to the virtual mirror surface.

9. The optical sensor according to any one of the previous claims, wherein the first optical fiber (66) and the second optical fiber (76) are arranged in parallel.

10. The optical sensor according to any one of the previous claims, wherein the first optical fiber (66) and the second optical fiber (76) are the same fiber.

11. The optical sensor according to any one of the previous claims, wherein the bottom surface comprises a recess (51) including a recess bottom surface portion (52) perpendicular to a non-recessed bottom surface portion (53), and wherein the first opening (54) of the first groove opens at the recessed bottom surface portion (52) and wherein the second opening (55) of the second groove opens at the recessed bottom surface portion (52); wherein the first end of the first optical fiber is beveled with a first bevel angle so that the beveled end surface of the optical fiber is parallel with the recessed bottom surface portion (52), and wherein the second end of the second optical fiber is beveled with a second bevel angle so that the beveled end surface of the optical fiber is parallel with the recessed bottom surface portion (52).

12. The optical sensor according to any one of the previous claims, wherein a membrane (42) is arranged between the optical sensor and a tissue surface.

13. The optical sensor according to any one of the previous claims, wherein the optical sensor comprises a transparent membrane (28), which is attached to the sleeve at an area facing away from the bottom surface (62), whereby the transparent membrane delimits the measurement chamber (58) adjacent the tissue surface.

14. The optical sensor according to any one of the previous claims, wherein the optical sensor is attached to a dressing (41) arranged to at least partly cover the tissue surface.

15. The optical sensor according to any one of the previous claims, wherein the optical sensor is arranged to measure ambient light received by the light receiving optical fiber for triggering an alarm if the ambient light is above a predetermined level.

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