Device for coupling radiation into and out of an optical fiber

Abstract

An apparatus for coupling radiation into and out of an optical fiber, comprising: an optical element, a radiation system and a sensor system. The optical element is used to couple radiation into and out of the optical fiber. The radiation system is operable to generate input radiation, and the radiation system is arranged so that the optical element at least partially receives the input radiation. The sensor system is used to receive output radiation from the optical element and is operable to generate a signal indicative of at least one characteristic of the output radiation. The optical element, the radiation system and the sensor system are generally coaxial, and the radiation system and the sensor system are both arranged on the same side of the optical element.

Description

Technical Field

[0001] The present invention relates to an apparatus for coupling radiation into and out of an optical fiber. In particular, it may relate to an apparatus operable to couple radiation into one end of an optical fiber and receive radiation reflected from the other end of the optical fiber so that a characteristic of the reflected radiation (e.g. its color) can be determined.

[0002] Such a device may be used in the field of medical tubes, such as nasogastric and nasoenteric tubes, particularly in confirming correct placement and / or avoiding misplacement of tube sections to prevent fluid leakage. Background Art

[0003] Sick humans or animals are sometimes unable to feed themselves using traditional methods. In such cases, it is desirable to deliver nutrients to the stomach or small intestine via a feeding tube. This is typically accomplished by passing a tube through the patient's nasal cavity, through the gastrointestinal tract, and into the stomach or small intestine. The distal end of such a feeding tube includes one or more liquid output holes, the function of which is to deliver liquid nutrients to a predetermined location, such as the stomach or small intestine. Correct positioning of the liquid output holes within the stomach or small intestine is critical to the safety of the patient. For example, misdirection of a feeding tube that may occur when inserting a feeding tube via the nasal cavity, such that the front end of the feeding tube is directed toward the lungs, is particularly true for patients with suppressed cough or gag reflexes, such as critically ill patients and premature infants. Such misplacement of the liquid output holes during feeding can lead to serious pleuropulmonary complications, such as pneumonia, abscesses, and empyema.

[0004] Furthermore, in some cases, certain liquid nutrients may need to be delivered to specific parts of the digestive system, for example, specifically to the stomach and / or specifically to the small intestine. Likewise, correct placement of the liquid exit orifice is necessary.

[0005] A known system for determining whether a fluid outlet orifice is arranged in the correct position is disclosed in patent document EP 2412311 A2. It describes a feeding tube positioning device having an optical waveguide and a color change indicator (e.g., a pH indicator or a carbon dioxide indicator) at the distal end of the optical waveguide. The optical waveguide is sized to be insertable into the inner cavity of a feeding tube. In use, the optical waveguide transmits input light to a sensor device. A portion of the input light is reflected from the sensor device as output light, the color of the output light indicating the position of the feeding tube. The output light is transmitted by the output optical waveguide to the proximal end of a position confirmation device, where it is viewed by a user to determine the position of the tube in the human or animal body. Summary of the invention

[0006] It may be desirable to provide an alternative apparatus for coupling radiation into and out of an optical fiber which at least partially addresses one or more of the problems of the prior art whether identified herein or elsewhere.Such an apparatus may form part of a feed tube placement measurement system.

[0007] According to a first aspect of the present invention, there is provided a device for coupling radiation into and out of an optical fiber, the device comprising: an optical element for coupling radiation into and out of the optical fiber; a radiation system operable to generate input radiation, the radiation system being arranged so that the optical element at least partially receives the input radiation; a sensor system for receiving output radiation from the optical element and operable to generate a signal indicative of at least one characteristic of the output radiation; wherein the optical element, the radiation system and the sensor system are typically coaxial, and the radiation system and the sensor system are both arranged on the same side of the optical element.

[0008] The device according to the first aspect of the invention provides an arrangement which is operable to couple radiation into or out of an optical fiber. For example, the device may be used in determining properties of a remote location. The radiation system may couple the input radiation into the optical fiber via the optical element. The radiation may propagate along the optical element to the remote location. At least a portion of the radiation may be scattered from the distal end of the optical fiber and propagate back along the optical element to the device, where the sensor system (via the optical element) may at least partially receive and analyze the radiation. For example, in one application, the distal end of the optical fiber may include an indicator material, the color of which indicates the properties of the remote location. For example, the color of the indicator material may indicate the pH value of the remote location. In use, the optical fiber may be inserted into a feeding tube so that a medical professional can determine whether it has been properly placed before using the feeding tube to provide food to a patient.

[0009] It will be appreciated that, in general, radiation may enter and / or exit an optical fiber at a range of angles (at the ends of the optical fiber) that are different from the optical axis of the optical fiber. The extent of the radiation cone is determined by the numerical aperture of the optical fiber. It will be appreciated that rays of radiation that enter or exit an optical fiber at different angles will pass through different portions of the optical element. Light rays that enter or exit an optical fiber at relatively shallow angles pass through the central portion of the optical element, while light rays that enter or exit an optical fiber at relatively large angles pass through the outer portions of the optical element.

[0010] It should be understood that, since the optical element, the radiation system and the sensor system are generally coaxial and both are arranged on the same side of the optical element, one of the radiation system and the sensor system (which may be referred to as the proximal system) is disposed between the optical element and the other of the radiation system and the sensor system (which may be referred to as the distal system). The proximal system is arranged to provide radiation to or receive radiation from the central portion of the optical element. The proximal system will cause the center of the distal system (because it is coaxial with the optical element) to be shielded, so that the distal system cannot provide radiation to or receive radiation from the central portion of the optical element. However, the distal system is arranged to provide radiation to or receive radiation from the outer portion of the optical element. Therefore, the light coupled to or from the optical element by the proximal system is generally from a different portion of the angular distribution of the light coupled to or from the optical element by the distal system. Light rays entering or leaving the optical fiber at relatively small angles are coupled to the proximal system, while light rays entering or leaving the optical fiber at relatively large angles are coupled to the distal system.

[0011] As discussed below, the apparatus according to the first aspect of the invention is advantageous for a number of reasons.

[0012] Firstly, since the optical elements, radiation system and sensor system are typically coaxial, the device provides a compact arrangement for coupling into and out of the optical fiber. This is in contrast to arrangements where the optical axes of the radiation system and sensor system are typically perpendicular to each other and a beam splitter is used to couple both into the optical fiber.

[0013] Secondly, as will now be discussed, the apparatus according to the first aspect of the invention is more advantageous than an arrangement in which the optical axes of the radiation system and the sensor system are parallel but offset, and in which the radiation system and the sensor system are coupled to the optical element via a beam splitter. Likewise, the apparatus according to the first aspect of the invention provides a compact arrangement, particularly in a dimension generally perpendicular to the optical axis of the optical fibre into which the apparatus is arranged to couple and out of.

[0014] Furthermore, for embodiments in which the sensor system is operable to determine the color of the output radiation, the input radiation may include white light, and it may be desirable to minimize the amount of input radiation received by the sensor (in order to maximize color saturation). As described above, with an arrangement in which the radiation system and the sensor system are generally coaxial, and both are arranged on the same side of the optical element, the light coupling the radiation system to the optical element will generally come from a different part of the angular distribution of the light coupling the optical element to the sensor system. Thus, if the end of the optical fiber to which the device is coupled is cut flat and square, all of the input radiation reflected from the end will be transmitted back to the radiation system rather than the sensor system.

[0015] The sensor system may be arranged between the optical element and the radiation system such that the sensor system may be arranged to receive radiation from a central portion of the optical element.

[0016] As discussed below, this arrangement has a number of additional advantages.

[0017] A sensor system arranged such that the output radiation received from the optical element comprises radiation received from a central portion of the optical element is advantageous for a number of reasons. Firstly, the intensity of radiation exiting the optical fibre decreases with increasing angle relative to the optical axis (at the fibre end face). Furthermore, by selecting this central portion of the output radiation, divergence effects are minimised, as the angular spread of the radiation received by the sensor system is minimised. This is particularly advantageous when the sensor system is arranged to determine spectral properties (e.g. hue) of the output radiation, as such dispersion effects may affect such measurements.

[0018] It will be appreciated that some of the radiation produced by the radiation system may be blocked by the sensor system. However, even if the amount of (white) light coupled into the optical fiber is significantly reduced, the increase in output radiation intensity achieved by the sensor system by sampling a central portion of the output radiation of the optical element, and the increase in the entrance aperture allowed by the sensor system (for a given size of the optical element), may still improve the overall efficiency.

[0019] The optical element may include a convex lens.

[0020] It will be appreciated that the optical element may alternatively comprise a mirror.

[0021] The radiation system may include a radiation source operable to generate input radiation and radiation system optics arranged between the radiation source and the optical element.

[0022] The radiation system optics may be arranged to substantially collimate input radiation received by the optical element. For example, the radiation system optics may include a convex lens and the radiation source may be arranged at or near the focal plane of the convex lens. The radiation source may be arranged at or near the optical axis of the device. The radiation system optics may be coaxial with the optical element.

[0023] The sensor system may comprise a sensor and sensor system optics arranged to focus output radiation onto the sensor.

[0024] For example, the sensor system optics may include a convex lens, and the sensor may be arranged at or near the focal plane of the convex lens. The sensor may be arranged at or near the optical axis of the device. The sensor system optics may be coaxial with the optical element.

[0025] The at least one characteristic of the output radiation may include a color of the output radiation.

[0026] The sensor may be a color sensor integrated circuit.

[0027] The sensor may include a two-dimensional array of sensing elements such as photodiodes.

[0028] The device may also include supports for the optical elements, the radiation system and the sensor system.

[0029] The bracket may be formed from any suitable material, for example a metal or plastic material. The bracket may be in the form of a housing or the like, for example a three-part housing. The bracket may assist in the relative positioning and alignment of the device components.

[0030] The bracket may include a fiber optic connection.

[0031] The bracket may include one or more engagement features for one or more of the optical element, the radiation system, and the sensor system.

[0032] It will be appreciated that the engagement features for a radiation system may include engagement features for a radiation source and / or radiation system optics (eg, a lens).

[0033] It will be appreciated that the engagement features for a radiation system may include engagement features for a radiation source and / or radiation system optics (eg, a lens).

[0034] According to a second aspect of the present invention, a measuring device is provided, which comprises: an apparatus according to the first aspect of the present invention; a power supply and a control unit; the control unit is operable to: control the emission of radiation from the radiation system; receive a signal from the sensor system, the signal indicating at least one characteristic of the output radiation received thereby, so as to determine the at least one characteristic of the output radiation from the signal received by the sensor system.

[0035] The power source may include a battery.

[0036] According to a third aspect of the invention, there is provided a system for determining properties of a remote location, the system comprising: a measuring device according to the second aspect of the invention; and an optical fiber having a sensing distal end, the sensing distal end comprising a sensing material operable to change color indicative of the chemical composition of the environment to which it is exposed.

[0037] It will be apparent to those skilled in the art that the various aspects and features of the present invention listed above or below may be combined with various other aspects and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0039] Figure 1 is a side view of an apparatus for coupling radiation into and out of an optical fiber according to an embodiment of the present invention;

[0040] Figure 2 yes Figure 1 A cross-sectional view of the device for coupling radiation into and out of an optical fiber along line AA is shown;

[0041] Figure 3 It is composed Figure 1 and Figure 2 a perspective view of a subassembly of a portion of the illustrated device;

[0042] Figure 4 yes Figure 3 a side view of the subassembly shown;

[0043] Figure 5 yes Figure 3 and Figure 4 The subassembly shown is along line AA (see Figure 4 ) cross-sectional view;

[0044] Figure 6 It is composed Figures 3 to 5 a cross-sectional view of a central housing showing a portion of the subassembly;

[0045] Figure 7 yes Figure 6 an end view of the central housing shown;

[0046] Figure 8 Yes Figures 3 to 5 an exploded perspective view of the measuring device showing the subassembly;

[0047] Fig. 9 yes Figure 8 a perspective view of the measuring device shown;

[0048] Fig.10 is a cross-sectional view of another embodiment of a central housing, which can be replaced Figures 3 to 5 The subcomponents shown in Figure 6 and 7 The central housing shown in ;

[0049] Fig.11 yes Fig.10 An end view of the center housing is shown. DETAILED DESCRIPTION

[0050] Figure 1 and Figure 2An apparatus 2 for coupling radiation into and out of an optical fiber 4 according to an embodiment of the invention is shown. The apparatus 2 comprises a first lens 6 which may be regarded as an optical element for coupling radiation into and out of the optical fiber 4.

[0051] It should be understood that for different embodiments, the size and focal length of the first lens 6 may have a range of different values. In one embodiment, the first lens 6 may be a plano-convex lens with a diameter of 12.7 mm and a focal length of 15 mm.

[0052] The optical fiber 4 may be sized to be inserted into the lumen of a feeding tube. For example, the optical fiber may have a diameter of 0.7 mm.

[0053] The device 2 also includes a second lens 8 and a light source 10, which can be considered as a radiation system. The axis of the second lens 8 can define the axis of the radiation system. The light source 10 is operable to generate light (which can be referred to as input radiation) and can be considered as a radiation source that is operable to generate input radiation. The second lens 8 is arranged between the light source 10 and the first lens 6, and can be considered as a radiation system optical device. The light source 10 is arranged at or near the optical axis 12 of the device 2. It should be understood that the light source 10 can basically act as a point light source and will generate input radiation that propagates within a range of angles away from the light source 10. At least a portion of the input radiation is received by the second lens 8.

[0054] The second lens 8 is arranged to substantially collimate the input radiation, which is partially received by the first lens 6 as will be further described below. To achieve this, the light source 10 is arranged at or near the focal plane of the second lens 8. It should be understood that for different embodiments, the size and focal length of the second lens 8 can have a range of different values. In one embodiment, the second lens 8 can be a plano-convex lens with a diameter of 12.7 mm and a focal length of 15 mm.

[0055] Thus, it may be considered that the radiation system (including the second lens 8 and the light source 10 ) is operable to generate input radiation, the radiation system being arranged such that the input radiation is at least partially received by the first lens 6 .

[0056] For example, the light source 10 may illuminate the sensing distal end with white light having a wavelength in the range of 405 nm to 685 nm. For example, the light source 10 may include a light emitting diode.

[0057] The device 2 also includes a third lens 14, which can be considered as a sensor system, and a sensor 16. The axis of the third lens 14 can define the axis of the sensor system. The third lens 14 is arranged between the sensor 16 and the first lens 6, and can be considered as a sensor system optics. The sensor 16 is arranged at or near the optical axis 12 of the device 2. As will be further described below, the third lens 14 is arranged to focus the output radiation received from the central portion of the first lens 6 onto the sensor 16. To achieve this, the sensor 16 can be arranged at or near the focal plane of the third lens 14.

[0058] It should be understood that for different embodiments, the size and focal length of the third lens 14 can have a range of different values. In one embodiment, the third lens 14 can be a plano-convex lens with a diameter of 6 mm and a focal length of 30 mm. It should be understood that the focal length of the third lens 14 can be larger than the focal length of the first lens 6, for example, 2 times larger than the focal length of the first lens 6. Therefore, the image of the distal end of the optical fiber 4 formed on the sensor 16 can be larger (for example, 2 times) than the distal end of the optical fiber 4. In one embodiment, the optical fiber has a diameter of 0.7 mm, and the image of the distal end of the optical fiber 4 formed on the sensor 16 has a diameter of 1.4 mm. This will overfill the sensor 16.

[0059] The first lens 6 , the second lens 8 and the third lens 14 are coaxial and define an axis 12 of the device 2 .

[0060] The sensor 16 is adapted to receive output radiation from the first lens 6 and is operable to determine at least one characteristic of the output radiation, or to output a signal indicative thereof. The at least one characteristic of the output radiation may comprise a colour of the output radiation.

[0061] The sensor 16 may include a color sensor integrated circuit. The sensor 16 may include a two-dimensional array of sensing elements, such as photodiodes. The sensor 16 may be a red, green, and blue (RGB) detector. The sensor 16 may be operable to determine the intensity of the red, green, and blue components of the output radiation. The sensor 16 may have a generally square active sensing area with dimensions of 0.4 mm×0.4 mm.

[0062] The device 2 also includes a support 18 for the first lens 6, the second lens 8 and the light source 10 (forming a radiation system), the third lens 14 and the sensor 16 (forming a sensor system). The support 18 is in the form of a three-part housing, including: a central body 20, a first end body 22 and a second end body 24. The central body 20 supports the first lens 6, the third lens 14 and the sensor 16. The first end body 22 defines a fiber optic connection, as further described below. The second end body 24 supports the second lens 8 and the light source 10.

[0063] Each of the central body 20, the first end body 22, and the second end body 24 may be formed of any suitable material, such as metal or plastic material. The bracket 18 (including the central body 20, the first end body 22, and the second end body 24) facilitates relative positioning and alignment of device components, as described below.

[0064] Reference now Figures 3 to 7 The central body 20 and the second end body 24 are described in more detail. Figures 1 to 7 In the embodiment of the present invention, a set of consistent right-handed Cartesian coordinate axes is used, wherein the optical axis 12 of the device 2 extends in the z-direction. In the following, unless otherwise specified, it should be understood that the axial direction refers to the direction parallel to the optical axis 12 (i.e. in the z-direction), and the radial direction refers to the direction perpendicular to the optical axis 12 and passing through the optical axis.

[0065] Figures 3 to 5 Shows Figure 1 and Figure 2 2 is a subassembly 25 of the device 2 shown in . The subassembly 25 may be considered as a device for coupling radiation into and out of an optical fiber according to an embodiment of the present invention. Figure 1 and Figure 2 The subassembly 25 of the device 2 shown in FIG. 2 includes all components of the device 2 except the first end body 22 .

[0066] The central body 20 is generally cylindrical and includes, in particular, an inner tube portion 26 and an outer tube portion 28 that are coaxial with each other. The inner tube portion 26 and the outer tube portion 28 are connected by two radially opposed web portions 30, 32, which generally extend radially between the inner tube portion 26 and the outer tube portion 28. The two web portions 30, 32 divide the space between the coaxial inner tube portion 26 and the outer tube portion 28 into two axially extending arcuate holes 34, 36. It should be understood that in Figure 5 In the cross section shown (in the xz plane), the two web portions 30, 32 are visible, while the arcuate holes 34, 36 are not visible. Figure 2 and Figure 6 In the cross-section shown (in the yz plane), the arcuate holes 34, 36 are visible, while the two web portions 30, 32 are not visible.

[0067] like Figure 2 and Figure 4 As shown, the outer tube portion 28 of the center body 20 extends axially beyond the inner tube portion 26 (and the two web portions 30 , 32 ) at a first end 38 of the center body 20 to form a groove 40 .

[0068] The third lens 14 is received in the end of the inner tube portion 26 near the first end 38 of the central body 20. The third lens 14 can be push-fit into the end of the inner tube portion 26. The inner surface of the inner tube portion 26 can be stepped. Specifically, the inner tube portion 26 can include a countersunk hole that forms a shoulder against which the third lens 14 can abut. The shoulder forms a convenient locating feature for the third lens 14 and facilitates accurate placement of the third lens 14. The third lens 14 can be press-fit into the inner tube portion 26. Optionally, in some embodiments, the third lens 14 can be secured in place using a suitable adhesive.

[0069] The first lens 6 is received in an end portion of the outer tube portion 28 proximate the first end 38 of the central body 20. It should be understood that the first lens 6 is received in a recess 40 of the first end 38 of the outer tube portion 28 formed by the greater axial extension of the outer tube portion 28. The first lens 6 can be push-fit into the end of the outer tube portion 28. The inner surface of the outer tube portion 28 can be stepped. Specifically, the outer tube portion 28 can include a countersunk hole that forms a shoulder against which the first lens 6 can abut. The shoulder forms a convenient locating feature for the first lens 6 and facilitates accurate placement of the first lens 6. The first lens 6 can be press-fit into the outer tube portion 28. Optionally, in some embodiments, the first lens 6 can be fixed in place using a suitable adhesive.

[0070] like Figure 3 and Figure 4 As shown, the sensor 16 is disposed on a generally T-shaped sensor printed circuit board (sensor PCB) 42. The sensor PCB 42 is connected to the second end 44 of the central body 20 using screws 46 that engage holes 48 formed in one of the web portions 30. The sensor 16 is received in the end of the inner tube portion 26 near the second end 44 of the central body 20. The inner tube portion 26 may include a countersunk hole that forms a shoulder against which a generally circular bracket for the sensor 16 can abut. The shoulder forms a convenient locating feature for the sensor 16 and helps to accurately place the sensor 16 on the optical axis 12. It should be understood that the sensor PCB 42 is provided with connecting leads 50 or the like to allow signals to be exchanged between the sensor 16 and other components of the device 2.

[0071] On the outer surface of the outer tube portion 28, the center body 20 has a generally annular flange 52 extending around the circumference of the center body 20. As described further below, the flange 52 can provide a locating feature for the center body 20 for mounting the center body 20 within a housing.

[0072] The second end body 24 is generally in the form of a cylindrical cap including a curved cylindrical wall 54 and an end wall 56. The end wall 56 defines a first end of the second end body 24. The inner surface of the curved cylindrical wall 54 is stepped to form two generally annular shoulders, as will now be described.

[0073] The second end 58 of the second end body 24 is open and is provided with a countersunk hole (or a portion of a hole with a larger inner diameter) for receiving a portion of the central body 20 near its second end 44. The countersunk hole forms a shoulder (not shown) against which the second end 44 of the central body 20 can abut. The curved wall 54 has two diametrically opposed, axially extending recesses 60 for receiving a portion of the sensor PCB 42 to allow the second end 44 of the central body 20 to be inserted into the second end 58 of the second end body 24.

[0074] An intermediate hole portion having an inner diameter between the countersunk hole and the main portion is formed between the countersunk hole accommodating a portion of the central body 20 near its second end 44 and the main portion of the curved cylindrical wall 54. The second lens 8 is accommodated in the intermediate hole portion. The intermediate hole portion forms a shoulder portion against which the second lens 8 can abut.

[0075] like Figure 3 and Figure 4 As shown, the light source 10 is disposed on a generally T-shaped radiation source printed circuit board (radiation source PCB) 62. The radiation source PCB 62 is connected to the end wall 56 of the second end body 24 using screws 64, which engage with holes 66 formed in the end wall 56. The generally circular end wall 56 has a central through hole 68. The light source 10 is received in the through hole 68. The through hole 68 may include a countersunk hole that forms a shoulder against which a generally circular bracket for the light source 10 can abut. The shoulder forms a convenient locating feature for the light source 10 and helps to accurately place the light source 10 on the optical axis 12. It will be understood that the radiation source PCB 62 is provided with connecting leads 70 or the like to allow signals to be exchanged between the light source 10 and other components of the device 2.

[0076] like Figure 2 As shown, the first end body 22 is generally a stepped tube including a first cylindrical portion 72 and a second cylindrical portion 74 that are coaxial with each other.

[0077] The first generally cylindrical portion 72 is open and is provided with a countersunk hole (or a portion of a hole with a larger inner diameter) for receiving a portion of the central body 20 near its first end 38. The countersunk hole forms a shoulder against which the first end 38 of the central body 20 can abut and facilitates accurate placement of the central body 20 relative to the first end body 22.

[0078] The second generally cylindrical portion 74 is open and is used to receive a connector 76 provided at the end of the optical fiber 4. The connector 76 is generally cylindrical and is push-fit into the second generally cylindrical portion 74. A generally annular flange 78 is provided on the outer surface of the connector 76, which abuts the end of the second generally cylindrical portion 74.

[0079] Figures 3 to 5 The subassembly 25 shown and described above may form part of a measuring device, as described below with reference to Figure 8 discussed.

[0080] Figure 8 A measuring device 80 according to an embodiment of the present invention is shown. The measuring device 80 comprises Figures 3 to 5 8, and a subassembly 25, a battery 82, and a control unit 84 are shown. The control unit 84 is operable to control the radiation emission of the light source 10 via control signals or the like. The control unit 84 is also operable to receive a signal from the sensor 16 indicating at least one characteristic of the output radiation received thereby. The control unit 84 is also operable to determine the at least one characteristic of the output radiation of the signal received from the sensor 16. The control unit 84 may include any suitable processor or microprocessor, as will be appreciated by the skilled person.

[0081] The control unit 84 is disposed on a main printed circuit board (main PCB) 86. The main PCB 86 supports the subassembly 25 and the battery 82. To this end, the main PCB 86 is provided with: a battery connector 88; a connector 90 for connecting to the connecting leads 50 of the sensor PCB 42; and a connector 92 for connecting to the connecting leads 70 of the radiation source PCB 62. The battery connector 88 is arranged to support the battery 82 (which may be a AA battery) and also provides an electrical connection with the battery to allow the battery 82 to provide power to other components of the measurement device 80. The connector 90 for connecting to the connecting leads 50 of the sensor PCB 42 and the connector 92 for connecting to the connecting leads 70 of the radiation source PCB 62 are arranged to support the subassembly 25. The sensor 16 is operable to send a signal to the control unit 84 through the connecting leads 50 and the connector 90, the signal indicating at least one characteristic of the output radiation received thereby. The control unit 84 is operable to send a control signal to the light source 10 through the connector 92 and the connecting leads 70.

[0082] The measuring device 80 further comprises a first housing member 94 and a second housing member 96. The first housing member 94 and the second housing member 96 are arranged to engage by snap engagement or the like to form a generally cylindrical housing for the subassembly 25, the battery 82 and the control unit 84.

[0083] The second housing member 96 is provided with a plurality of hollow bosses 98 on its inner surface. The main PCB 86 is connected to the second housing member 96 by a plurality of screws 100, which engage with the hollow bosses 98.

[0084] The housing formed by the first housing member 94 and the second housing member 96 defines a bore through which a portion of the central body 20 proximate its first end 38 extends. Each of the first housing member 94 and the second housing member 96 is provided with a portion that forms part of a cylindrical projection of the housing surrounding the bore through which a portion of the central body 20 proximate its first end 38 extends. A groove 102 is formed on the inner surface of the projection for receiving a generally annular flange 52 provided on the outer surface of the outer tube portion 28. This provides a positioning feature for accurately placing the subassembly 25 within the housing and provides support for the subassembly 25.

[0085] The measuring device 80 also includes a user interface 104. It should be understood that the user interface 104 may include a display device for displaying information to the user and an input device for the user to provide input signals. The display device may include one or more light emitting diodes. The input device may include one or more buttons, etc. The user interface 104 has a connector lead 106, which provides communication between the user interface 104 and the control unit 84.

[0086] In use, the measurement device 80 may be used as follows.

[0087] First, the optical fiber 4 is provided with the connector 76 and the first end body 22. The connector 76 is push-fit into the second generally cylindrical portion 74 of the first end body 22. The first generally cylindrical portion 72 of the first end body 22 engages the portion of the central body 20 proximate the first end 38 thereof, which extends from the housings 94,96.

[0088] The optical fiber 4 is sized to be inserted into the lumen of the feeding tube and has a sensing distal end that includes a sensing material operable to change color indicative of the chemical composition of the environment to which it is exposed. The sensing material is operable to change color when the sensing distal end is exposed to an environment having a pH of 5.5 or less. Alternatively, or in addition, the sensing material is operable to change color when the sensing distal end is exposed to an environment having a pH of 4 or less. The sensing material may include one or more of thymol blue, methyl red, bromothymol blue, phenolphthalein, bromocresol green, fluorescein, ether, or a universal indicator. Other suitable indicators will be apparent to those skilled in the art upon reading this disclosure, depending on the particular environment (i.e., physical or chemical environment) that is considered to indicate the desired final position of the feeding tube. Chemical or biological indicators may change color or other optical properties in response to the presence of specific predetermined markers (e.g., pH levels) or biological markers (e.g., human gastric lipase, pepsin, intrinsic factor, mucin, and gastrin).

[0089] The user interface 104 may be used to drive the measuring device 80 by pressing a button or the like. This may send a drive signal to the control unit 84. In turn, the control unit 84 may generate a control signal that is sent to the light source 10 to cause it to emit radiation. For example, the control unit 84 may be operable to enable the light source 10 to emit an input radiation pulse. For example, the input radiation pulse may be in the range of 6 to 10 milliseconds. For example, the input radiation pulse may be 8 milliseconds in duration.

[0090] At least a portion of the input radiation pulse is incident on the second lens 8, which is arranged to generally collimate the input radiation as described above. A portion of the collimated input radiation passes through the two axially extending arcuate apertures 34, 36 and is received by the first lens 6. The first lens 6 is arranged to focus this portion of the input light at or near the end of the optical fiber 4. To achieve this, the optical fiber 4, the connector 76, the first end body 22 and the engagement between the first end body 22 are such that the end of the optical fiber 4 is arranged at or near the focal plane of the first lens 6. This input light propagates along the optical fiber and illuminates its sensing distal end.

[0091] For example, the light source 10 may illuminate the sensing distal end with white light having a wavelength in the range of 405 nm to 685 nm.

[0092] A portion of the input radiation is reflected by the sensing material at the sensing end. The color of the reflected radiation (which may be referred to as output radiation) depends on the color of the sensing material.

[0093] The output radiation is output at the proximal end of the optical fiber 4. It will be appreciated that, since the end of the optical fiber 4 may be arranged at or close to the focal plane of the first lens 6, the first lens may be used to collimate the output radiation.

[0094] The third lens 14 is arranged to focus a portion of the output radiation received from the central portion of the first lens 6 onto the sensor 16. To achieve this, the sensor 16 may be arranged at or close to the focal plane of the third lens 14.

[0095] The sensor 16 is operable to generate one or more signals indicative of one or more characteristics of the output radiation, such as its color or hue. These signals are transmitted to the control unit 84, which is operable to determine one or more characteristics of the output radiation from these signals.

[0096] The first lens 6, the second lens 8 and the third lens 14 are coaxial and define an axis 12 of the device 2. It should be understood that the axis of the second lens 8 may define the axis of the radiation system and the axis of the third lens 14 may define the axis of the sensor system. Thus, the first lens 6, the radiation system (formed by the second lens 8 and the light source 10) and the sensor system (formed by the third lens 14 and the sensor 16) are generally coaxial. The radiation system and the sensor system are both arranged on the same side of the first lens 6.

[0097] The device 2 (and in particular the subassembly 25 ) provides an arrangement operable to couple radiation into or out of the optical fiber 4 .

[0098] It will be appreciated that, in general, radiation may enter and / or exit the optical fiber 4 at a range of different angles to the optical axis of the optical fiber (at the end of the optical fiber). The range of this cone of radiation is defined by the numerical aperture of the optical fiber 4. It will be appreciated that rays of radiation entering or exiting the optical fiber 4 at different angles to the axis will pass through different portions of the first lens 6. Light rays entering or exiting the optical fiber at relatively small angles pass through a central portion of the first lens 6, while light rays entering or exiting the optical fiber at relatively large angles pass through the outer portion of the first lens 6.

[0099] It should be understood that, since the first lens 6, the radiation system and the sensor system are generally coaxial, and the radiation system and the sensor system are both arranged on the same side of the first lens 6, one of the radiation system and the sensor system (which may be referred to as the proximal system) is arranged between the first lens 6 and the other of the radiation system and the sensor system (which may be referred to as the distal system). Specifically, in the above-mentioned embodiment, the sensor system is arranged between the first lens 6 and the radiation system, so that the sensor system is arranged to receive radiation from the central portion of the first lens 6. Therefore, in this embodiment, the sensor system may be referred to as the proximal system, and the radiation system may be referred to as the distal system.

[0100] The sensor system is arranged to receive radiation from a central portion of the first lens 6. The sensor system causes central shadowing of the radiation system such that the radiation system cannot provide radiation to the central portion of the first lens 6. However, the radiation system is arranged to provide radiation to the outside of the first lens 6. Therefore, light coupling the sensor system to or from the first lens 6 typically comes from a different part of the angular distribution than light coupling the radiation system to or from the first lens 6. Light entering or leaving the optical fiber at relatively small angles is coupled to the sensor system, while light entering or leaving the optical fiber at relatively large angles is coupled to the radiation system.

[0101] As discussed below, the apparatus 2 according to the first aspect of the invention is advantageous for a number of reasons.

[0102] Firstly, since the optical element 6, the radiation system and the sensor system are typically coaxial, the device 2 provides a compact arrangement for coupling into and out of the optical fiber. This is in contrast to arrangements where the optical axes of the radiation system and the sensor system are typically perpendicular to each other and a beam splitter is used to couple both into the optical fiber 4, for example.

[0103] Secondly, as now discussed, the apparatus 2 is more advantageous than arrangements in which the optical axes of the radiation system and the sensor system are parallel but offset, and in which the radiation system and the sensor system are coupled to the optical element via a beam splitter. Likewise, the apparatus 2 provides a compact arrangement, particularly in a dimension generally perpendicular to the optical axis of the optical fiber 4 into which the apparatus 2 is arranged to couple in and out.

[0104] Furthermore, for embodiments in which the sensor system is operable to determine the color of the output radiation, the input radiation may include white light, and it may be desirable to minimize the amount of input radiation received by the sensor 16 (in order to maximize color saturation). As described above, with an arrangement in which the radiation system and the sensor system are generally coaxial, and both are arranged on the same side of the optical element, the light coupling the radiation system to the optical element will generally come from a different part of the angular distribution of the light coupling the optical element to the sensor system. Thus, if the end of the optical fiber 4 to which the device 2 is coupled is cut flat and square, all of the input radiation reflected from the end of the optical fiber 4 will be transmitted back to the radiation system rather than the sensor system.

[0105] A sensor system arranged such that the output radiation received by the sensor 16 from the first lens 6 comprises radiation received from a central portion of the first lens 16 is advantageous for a number of reasons. Firstly, the intensity of radiation exiting the optical fibre decreases with increasing angle relative to the optical axis (at the fibre end face). Furthermore, by selecting this central portion of the output radiation, divergence effects are minimised, as the angular spread of the radiation received by the sensor system is minimised. This is particularly advantageous when the sensor system is arranged to determine spectral characteristics (e.g. hue) of the output radiation, as such dispersion effects may affect such measurements.

[0106] It will be appreciated that some of the radiation produced by the radiation system may be blocked by the sensor system. However, even if the amount of (white) light coupled into the optical fiber 4 is significantly reduced, the increase in output radiation intensity achieved by the sensor system by sampling a central portion of the output radiation of the optical element, and the increase in the entrance aperture allowed by the sensor system (for an optical element of a given size), may still improve the overall efficiency.

[0107] Reference now Fig.10 and 11 Description can be replaced Figure 6 and Figure 7 Another embodiment of the central housing 120 of the central housing 20 is shown. Fig.10 is a cross-sectional view of the central housing 120, Fig.11 is an end view of the central housing 120. It should be understood that the central housing 120 may have Figure 6 and Figure 7 Only the differences are described in detail below, and it should be understood that any features that are substantially the same in both embodiments (and differ only in minor details) share a common reference numeral in both embodiments.

[0108] The central body 120 is generally cylindrical. Figure 6 and Figure 7 Like the central housing 20 in the drawings, the central body 120 is hollow and has a central hole 135 therethrough. Figure 6 and Figure 7The two axially extending arcuate holes 34, 36 of the central body 20 are replaced by axially extending circular cross-sectional holes 134, 136, respectively. The circular cross-sectional holes 134, 136 can still be considered to divide the central housing 120 into the inner tube portion 26 and the outer tube portion 28, which are coaxial with each other. The inner tube portion 26 can be considered to be the portion of the central housing located radially inward of the circular cross-sectional holes 134, 136, and the outer tube portion 28 can be considered to be the portion of the central housing located radially outward of the circular cross-sectional holes 134, 136. The first group of circular cross-sectional holes 134 (usually replacing one of the first arcuate holes 34) is separated from the second group of circular cross-sectional holes 136 (usually replacing one of the second arcuate holes 36) by two radially opposed web portions 30, 32, which generally extend radially between the inner tube portion 26 and the outer tube portion 28.

[0109] It will be appreciated that in addition to the two web portions 30 , 32 (occupying space consistent with the shielding provided by the sensor PCB 42 ), an additional connection is formed between the inner and outer tube portions 26 , 28 by providing material between adjacent circular cross-section apertures 134 , 136 .

[0110] With Figure 6 and Figure 7 In a similar manner to the illustrated embodiment, in use, at least a portion of the input radiation output by the radiation system is collimated by the second lens 8 and then propagates through the axially extending apertures 134 , 136 to the first lens 6 .

[0111] From a manufacturing perspective, such an arrangement in which the optical path of the radiation from the radiation system to the first lens 6 includes a plurality of circular cross-section holes may be more convenient. For example, such a circular hole shape may be particularly suitable for manufacturing processes, such as computer numerical control (CNC) machining processes. The circular cross-section holes 134, 136 can be drilled in situ on a CNC lathe and can be made more easily than the conventional CNC lathe. Figure 6 and Figure 7 The arcuate apertures 34, 36 in the illustrated embodiment are easier to form. Furthermore, any reduction in the amount of radiation reaching the first lens 6 is likely to be negligible.

[0112] and Figure 6 and Figure 7 As with the illustrated embodiment, in use, the sensor 16 is received in the end of the inner tube portion 26 proximate the second end 44 of the central body 120. Figure 6 and Figure 7As with the illustrated embodiment, the inner tube portion 26 includes a countersunk bore that forms a shoulder 145 against which a generally circular bracket for the sensor 16 can abut. The shoulder 145 forms a convenient locating feature for the sensor 16 and helps to accurately place the sensor 16 on the optical axis 12. In addition, in this embodiment, a radially extending slot 147 or recess is formed on the second end 44 of the central body 120, and a countersunk bore that forms the annular shoulder 145 is formed in the slot 147. The slot 147 generally extends through the second end 44 of the central body 120 and is sized to accommodate the sensor PCB 42. Likewise, the slot 147 can form a mounting and / or alignment feature for the sensor PCB 42, aiding in the assembly of the device 2. It can also constrain the sensor PCB 42 to reduce its movement. Likewise, a hole 48 is formed in one of the web portions 30 to facilitate connecting the sensor PCB 42 to the second end 44 of the central body 120 using a screw 46.

[0113] In addition, at the second end 44 of the central body 120, the outer surface of the outer tube portion 28 has some features that may assist in positioning and assembling the second end body 24. In particular, at the second end 44, the outer tube portion 28 of the central body 120 is stepped to provide a smaller diameter portion 151 that can be at least partially received within the second end body 24 in use. In addition, the main (larger diameter) portion of the outer tube portion 28 is provided with two diametrically opposed flattened portions 149. These flattened portions 149 can engage with complementary features on the interior of the second end body 24 to provide alignment and / or assembly features. Additionally or alternatively, the step formed between the smaller diameter portion 151 and the main (larger diameter) portion of the outer tube portion 28 can engage with complementary features on the interior of the second end body 24 to provide alignment and / or assembly features.

[0114] Additionally, at the first end 38 of the center body 120, the outer surface of the outer tube portion 28 has features that can assist in positioning and assembling the first end body 22. In particular, at the first end 38, the outer tube portion 28 of the center body 120 is stepped to provide a smaller diameter portion 153 that can be at least partially received within the first end body 22 during use. A step 155 formed between the smaller diameter portion 153 and the main (larger diameter) portion of the outer tube portion 28 can engage with a complementary feature within the first end body 22 to provide an alignment and / or assembly feature.

[0115] Although specific embodiments of the present invention have been described above, it should be understood that the present invention may be implemented in different circumstances than those described above. The above description is intended to be illustrative rather than limiting. Therefore, it will be apparent to those skilled in the art that the present invention may be modified without departing from the scope of the claims.

Claims

1. A device for coupling radiation into and out of an optical fiber, the device comprising: optical components for coupling radiation into and out of optical fibers; a radiation system operable to generate input radiation, the radiation system being arranged such that the optical element at least partially receives the input radiation; and a sensor system for receiving output radiation from the optical element and operable to generate a signal indicative of at least one characteristic of the output radiation; wherein the optical element, the radiation system and the sensor system are coaxial, and the radiation system and the sensor system are both arranged on the same side of the optical element; The device further comprises: a central body, a first end body and a second end body; the optical element and the sensor system are arranged in the central body, the first end body defines an optical fiber connection part, and the radiation system is arranged in the second end body.

2. The device according to claim 1, characterized in that The sensor system is arranged between the optical element and the radiation system such that the sensor system is arranged to receive radiation from a central portion of the optical element.

3. The device according to claim 1, characterized in that The optical element includes a convex lens.

4. The device according to claim 1, characterized in that The radiation system comprises a radiation source operable to generate the input radiation and radiation system optics arranged between the radiation source and the optical element.

5. The device according to claim 1, characterized in that The sensor system comprises a sensor and sensor system optics arranged to focus the output radiation onto the sensor.

6. The device according to claim 5, characterized in that The sensor is a color sensor integrated circuit.

7. The device according to claim 5 or 6, characterized in that The sensor comprises a two-dimensional array of sensing elements.

8. The device according to claim 7, characterized in that The sensor includes a photodiode.

9. The device according to claim 1, characterized in that The device further comprises a support for the optical element, the radiation system and the sensor system.

10. The device according to claim 9, characterized in that The bracket also includes an optical fiber connecting portion.

11. The device according to claim 9 or 10, characterized in that The support includes one or more engagement features for one or more of the optical element, the radiation system, and the sensor system.

12. A measuring device comprising: An apparatus as claimed in any preceding claim; power supply; and A control unit operable to: controlling radiation emission from the radiation system; A signal is received from the sensor system, the signal being indicative of at least one characteristic of the output radiation received thereby, to determine the at least one characteristic of the output radiation from the signal received from the sensor system.

13. A system for determining a property of a remote location, the system comprising: The measuring device according to claim 12; and An optical fiber having a sensing distal end including a sensing material operable to change color indicative of the chemical composition of the environment to which it is exposed.

Images