Device for securing at least one optical fibre to an optical apparatus

Abstract: A device (1) for securing at least one optical fibre (2; 3; 4; 5) to an optical apparatus (6) is proposed, comprising at least one photo-element (20; 21; 22; 23) mounted on a supporting element (24) and at least one optical fibre (2; 3; 4; 5) which can be connected to the photo-element (20; 21; 22; 23); the securing device (1) comprises at least one transparent part, such that a region of the coupling between the fibre and the photo-element is visible. A securing device (1) is also proposed, comprising a slide (7) provided with at least one slot (8), which assumes a first and a second position; in the first position, the slot (8) is coaxial with a hole (25) in the supporting element (24) and freely houses the optical fibre (2; 3; 4; 5), while in the second position the slot (8) is out of alignment with the hole (25) and exerts on the optical fibre (2; 3; 4; 5) a force which keeps it secured in the hole (25).

Description: The present invention relates to a device for securing at least one optical fibre to an optical apparatus. There are known optical apparatus such as, for example, optical sensors operating with a single emission wavelength (colour), comprising a photo-emitter and a photo-detector (photo-elements or, better, opto-electronic elements). The photo-emitter generates a beam of light which is channelled into an optical fibre so that it is transported into a region to be monitored. The light reflected from the monitored region is channelled into another optical fibre and transported to the photo-detector. In known optical sensors, each of the two optical fibres, that used for emission and that used for detection, is held in position, with respect to the photo-emitter and the photo-detector, by its own securing means of the screw, lever or button type. Consequently, each securing means requires its own stage of manufacture, and each fibre requires its own alignment and fixing operation. DE 30 04 379 discloses a housing for an element usable in the fiber optics, comprising a housing portion having an alignment hole, an end of the hole receiving an optical fibre, and a locking device cooperating with the housing portion for bringing a light emitting or detecting element to the other end of the alignment hole for optically coupling it to the optical fibre. The optical fibre is fixed in the hole by means of a transparent epoxy resin, and thereafter the housing is filled with black epoxy resin for further securing the fibre. A cover having an extension may also be provided for further securing the fibre. WO 87 03969, on which the preamble of claim 1 is based, discloses an optical fibre connector comprising a housing having a bore in which an end of the optical fibre is to be positioned and a slot communicating with the bore, and a retaining. member having a slot which edges, when the retaining member is inserted in the housing slot, presses into the jacket of the optical fibre to retain it in the bore. EP 0313956 discloses an optical component, wherein the end of an optical fibre is coupled to a diode carried by a frame. A transparent plastics may be poured over the coupling region between the optical fibre and the diode before the frame is embedded within a non-transparent plastics. WO 96 21875 discloses an optical module for interconnecting two or more optical fibres, comprising a splice/waveguide element and a housing for the splice/waveguide element, the splice/waveguide element being provided with at least one waveguide channel and fiber receiving and alignment grooves at its ends, and the housing being provided with actuating wedges for exerting a clamping force on the splice/waveguide element. The splice/waveguide element can be made of a transparent glass. However, these known sensors and securing devices therefor do not enable the operator to check in a direct way the correct alignment of a fibre with a opto-electronic element. EP 0 328 011 discloses a photo sensor array comprising at least one transparent substrate and a photosensitive portion provided on the substrate, the photosensitive portion comprising a semiconductor layer and two electrodes, and an optical fiber portion being arranged in a transparent substrate on the light-incident side of the photosensitive portion. Because the photosensitive portion and the optical fiber portion are permanently secured through integrated circuit technology and/or adhesive resin, however, the optical fibers can not be disconnected from the photosensitive portion, such as for replacement of a damaged fiber. A first aspect of the present invention therefore consists of a device for securing at least one optical fibre to an optical apparatus, whereby the at least one optical fibre is connected to a respective opto-electronic element of the said optical apparatus, wherein it comprises: (i) a slide provided with at least one slot, the said slide assuming a first and a second predetermined position, the said slot, in the said first position of the said slide, being coaxial with a respective guide hole of said optical apparatus and freely housing the said optical fibre, and the said slot, in the said second position of the said slide, being out of alignment with the said hole and exerting on the said optical fibre a force which keeps the optical fibre secured in the said hole, and (ii) a cover provided with means for attachment to the said optical apparatus and with an enclosure capable of supporting the said slide so that it is free to slide, and in that the said slide and the said cover are made from a transparent material which makes a region of the coupling between the fibre and the opto-electronic element visible from the outside of said securing device. The known securing means are also particularly inadequate for multiple-fibre optical sensors comprising two or three photo-emitters, each capable of emitting a light beam of a predetermined colour and optically connected to a corresponding emission fibre. Typically, for example, three-fibre optical sensors may have red emission for the detection of white-green contrasts, and blue emission for the detection of white-yellow contrasts. Four-fibre sensors offer the function of colour reading and discrimination by means of blue, green and red emission. These optical sensors make different types of emission available to a user and, therefore, have the advantage of being adaptable to different applications. According to a preferred embodiment, the said slide is provided with at least two slots. In particular, there are provided at least two optical fibres. According to another preferred embodiment, said cover is provided with at least one hole for the passage of the said optical fibre, the said enclosure of the said cover being capable of housing elastic means in engagement with the said slide to keep it in the said second position. Preferably, the said slot comprises a semi-circular portion having a radius greater than that of the said optical fibre. In particular, the said semi-circular portion of the said slot has a projecting arm. The said slot is substantially C-shaped. Additionally, the said semi-circular portion has a notch capable of imparting elasticity to the said arm. According to a further preferred embodiment, the said slide is provided with a pin which is used for centring the said elastic means. Preferably, the said transparent material is selected from the group comprising glass, polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile-styrene (SAN), acrylonitrile-butadiene-styrene (ABS), polyphenylene oxide (PPO), polyurethane (PUR), polysulphone (PSU), polyamide (PA), polyvinyl chloride (PVC), and polyphenylene sulphide (PPS). In this way a simple and efficient device for securing one or more optical fibres to an optical apparatus is made. Making the slide and the cover from transparent material provides many advantages. It is possible to see the optical fibres and the holes of the optical apparatus or more specifically of a supporting element thereof through the cover and the slide during the assembly operations. This makes it possible to check the correctness of the coupling of a fibre to a predetermined photo-element or opto-electronic element (photo-emitter or photo-detector) and the positioning of each fibre with respect to its particular opto-electronic element, which is known to be a very delicate operation. It is also possible to check, at the moment of insertion of the optical fibres into the holes of the supporting element of the optical apparatus whether the holes are free or obstructed, and whether a fibre is damaged, by the tearing of a sheath for example. Finally, the opto-electronic elements are visible through a very wide angle. This enables the different photo-emitters to be clearly distinguished by the colours of the light beams emitted and also enables the photo-emitters to be distinguished with certainty from the photo-detectors. Moreover, it is possible to check, even from a distance, whether any of them are damaged. The securing device according to the invention is very practical in terms of assembly, since the slide, by means of each slot, performs the double function of releasing and securing an optical fibre. This is achieved by simple movements of the slide between two predetermined positions. Moreover, a multiplicity of optical fibres can be released and secured simultaneously by operating the slide alone. The degree of force, or compression, exerted by each slot on each optical fibre, is predetermined, to make it possible to fix the fibre without damaging it or adversely affecting its capacity for transmitting light. In a second aspect thereof, the present invention also relates to an optical equipment comprising a securing device as claimed and the said optical apparatus comprising at least one opto-electronic element. Preferably the said at least one opto-electronic element is mounted on a supporting element of the optical apparatus, the said supporting element being made from transparent material. Also preferably, the said transparent material is selected from those mentioned previously. Typically the said supporting element is provided with the said at least one guide hole for the said at least one optical fibre. Characteristics and advantages of the invention will now be explained with reference to an embodiment illustrated by way of non-restrictive example in the attached figures, of which: Fig. 1 is an exploded view of a device for securing optical fibres to an optical apparatus, made according to the invention; Fig. 2 is a front view of a slide of the securing device shown in Fig. 1; Fig. 3 is a rear view of a cover of the securing device shown in Fig. 1; Fig. 4 is a perspective view of the optical apparatus provided with the securing device shown in Fig. 1; Fig. 5 is a front view of a variant of the slide shown in Figs. 1 and 2. Figs. 1 and 4 show a device 1 for securing four optical fibres 2, 3, 4 and 5 to an optical apparatus 6 consisting, in this particular case, of an optical sensor. The device 1 comprises a slide 7 provided with four slots 8 disposed in series. Each slot 8 has a semi-circular portion 9 having a radius greater than that of an optical fibre, and provided with a projecting arm 10. Each slot is substantially C-shaped. The semi-circular portion 9 has a notch 30 (Fig. 2) which has the function of imparting a certain degree of elasticity to the arm 10. The slide is provided with an operating button 13 and an end pin 11 which is used for centring a spring 12. The device 1 also comprises a cover 14 provided with an enclosure 15 consisting of a substantially parallelepipedal recess capable of supporting the slide 7 so that it is free to slide, and of housing the spring 12. The cover 14 is provided with four holes 16 for the passage of the optical fibres 2, 3, 4 and 5. The cover 14 is also provided with projections 18, one above, one below and two in intermediate positions (Fig. 3), which act as end stops for the slide 7. The cover 14 also has four recesses 19 whose function will be explained subsequently. The slide 7 and the cover 14 are made from transparent material selected from the group comprising glass, polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile-styrene (SAN), acrylonitrile-butadiene-styrene (ABS), polyphenylene oxide (PPO), polyurethane (PUR), polysulphone (PSU), polyamide (PA), polyvinyl chloride (PVC), and polyphenylene sulphide (PPS). The optical sensor 6 comprises opto-electronic elements consisting of three photo-emitters 20, 21 and 22 and a photo-detector 23. Each photo-emitter consists, for example, of a light-emitting diode (LED) and emits a light beam of a predetermined colour. For example, the light beams emitted by the three photo-emitters 20, 21 and 22 are blue, green and red respectively, or other colours. The optical sensor 6 also comprises a supporting element 24 for the photo-emitters 20, 21 and 22 and for the photo-detector 23. The supporting element 24 is provided with four guide holes 25 for the optical fibres 2, 3, 4 and 5. Sealing gaskets 26 for the optical fibres, consisting of O-rings capable of providing protection according to lP67, are fitted in the holes 25. The supporting element 24 is provided with four tabs 27 which are snap-fitted into the recesses 19 of the cover 14 at the time of assembly of the securing device 1 and of the optical sensor 6. The sensor 6 is provided with a container 28 (Fig. 4) in which the supporting element 24 and the opto-electronic elements 20, 21, 22 and 23 are mounted. In the sensor 6, the photo-emitters 20, 21 and 22 are optically connected to the optical fibres 2, 3 and 4 respectively, while the photo-detector 23 is optically connected to the optical fibre 5. The optical fibres 2, 3 and 4 transport the light beams towards a region to be monitored, while the optical fibre 5 transports the light reflected (diffused) from the monitored region towards the photo-detector 23. The supporting element 24 may also be made from a material selected from the group indicated above. According to a variant, the optical apparatus 6 may comprise two photo-emitters and two photo-detectors. Fig. 5 shows a slide 17 in which parts identical to those of the slide 7 are indicated by the same numbers. In the slide 17, the semi-circular portions 9 of the slots 8 have no notches. The securing device 1 is assembled by mounting the spring 12 on the pin 11 of the slide 7 and inserting the slide and spring in the recess 15 of the cover 14. The spring 12 pushes the slide 7 upwards against the upper end stop projection 18. In this way, the button 13 of the slide emerges from the enclosure 15 of the cover 14 and can be operated manually (Fig. 4). The sensor 6 is assembled by mounting in the container 28 the supporting element 24 pre-assembled with the photo-emitters 20, 21 and 22, the photo-detector 23 and the sealing gaskets 26 disposed in the holes 25. The securing device 1 is then fixed to the sensor 6 by snap-fitting the cover 14 on the supporting element 24, by means of the tabs 27 which fit into the recesses 19. At this point, the slide 7 is pushed downwards by pressure on the button 13, against the action of the spring 12. In this way, the spring 7 assumes a first end position in which the semi-circular portions 9 of the slots 8 of the slide 7 are disposed coaxially with the holes 16 of the cover 14 and with the holes 25 of the supporting element 24. The optical fibres 2, 3, 4 and 5 can then be inserted through the holes 16, the semi-circular portions 9 of the slots 8 and the holes 25 until they are brought into contact with the photo-emitters 20, 21 and 22 and with the photo-detector 23. Since the cover 14 and the slide 17 are made from transparent material, it is possible to see the optical fibres and to check whether they enter the holes 25 without obstruction and whether they are positioned correctly with respect to the opto-electronic elements. After this, the button 13 of the slide 7 is released, and the slide is pushed upwards by the spring 12, being stopped by the upper projection 18 of the cover 14. In this way, the slide 7 assumes a second end position in which the semi-circular portions 9 of the slots 8 are out of alignment with the holes 16 and 25 and exert a force of a predetermined value on the optical fibres 2, 3, 4 and 5 to secure them in the holes 25.

Claims: Securing device (1) for securing at least one optical fibre (2; 3; 4; 5) to an optical apparatus (6), whereby the at least one optical fibre (2; 3; 4; 5) is connected to a respective opto-electronic element (20; 21; 22; 23) of the said optical apparatus (6), wherein it comprises: (i) a slide (7) provided with at least one slot (8), the said slide (7) assuming a first and a second predetermined position, the said slot (8), in the said first position of the said slide (7), being coaxial with a respective guide hole (25) of said optical apparatus (6) and freely housing the said optical fibre (2; 3; 4; 5), and the said slot (8), in the said second position of the said slide (7), being out of alignment with the said hole (25) and exerting on the said optical fibre (2; 3; 4; 5) a force which keeps the optical fibre (2, 3, 4, 5) secured in the said hole (25), and (ii) a cover (14) provided with means (19) for attachment to the said optical apparatus (6) and with an enclosure (15) capable of supporting the said slide (7) so that it is free to slide, and in that the said slide (7) and the said cover (14) are made from a transparent material which makes a region of the coupling between the fibre and the opto-electronic element visible from the outside of said securing device. Securing device (1) according to claim 1, characterized in that the said slide (7) is provided with at least two slots (8). Securing device (1) according to claim 2, characterized in that said at least one optical fibre (2; 3; 4; 5) comprises at least two optical fibres (2, 3, 4, 5). Securing device (1) according to claim 1, characterized in that the said cover (14) is provided with at least one hole (15) for the passage of the said optical fibre (2; 3; 4; 5), the said enclosure (15) of the said cover (14) being capable of housing elastic means (12) in engagement with the said slide (7) to keep it in the said second position. Securing device (1) according to claim 1, characterized in that the said slot (8) comprises a semi-circular portion (9) having a radius greater than that of the said optical fibre (2; 3; 4; 5). Securing device (1) according to claim 5, characterized in that the said semi-circular portion (9) of the said slot (8) has a projecting arm (10). Securing device (1) according to claims 5 and 6, characterized in that the said slot (8) is substantially C-shaped. Securing device (1) according to claim 6, characterized in that the said semi-circular portion (9) has a notch (30) capable of imparting elasticity to the said arm (10). Securing device (1) according to claim 4, characterized in that the said slide (7) is provided with a pin (11) which is used for centring the said elastic means (12). Securing device (1) according to any one of the preceding claims, characterized in that the said transparent material is selected from the group comprising glass, polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile-styrene (SAN), acrylonitrile-butadiene-styrene (ABS), polyphenylene oxide (PPO), polyurethane (PUR), polysulphone (PSU), polyamide (PA), polyvinyl chloride (PVC), and polyphenylene sulphide (PPS). Optical equipment comprising a securing device according to any of the preceding claims 1 to 10, and the said optical apparatus (6) comprising at least one opto-electronic element (20; 21; 22; 23). Optical equipment according to claim 11, characterized in that the said at least one opto-electronic element (20; 21; 22; 23) is mounted on a supporting element (24), the said supporting element (24) being made from transparent material. Optical equipment according to claim 12, characterized in that the said transparent material is selected from the group comprising glass, polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile-styrene (SAN), acrylonitrile-butadiene-styrene (ABS), polyphenylene oxide (PPO), polyurethane (PUR), polysulphone (PSU), polyamide (PA), polyvinyl chloride (PVC), and polyphenylene sulphide (PPS). Optical equipment according to any of the preceding claims 11 to 13, characterized in that the said supporting element (24) is provided with the said at least one guide hole (25) for the said at least one optical fibre (2; 3; 4; 5).

Inventors: FEI ENZO, LIPPI DANIELE, FEI, ENZO, LIPPI, DANIELE
Applicants: DATASENSOR S P A, DATASENSOR S.P.A.
Application year: 1998
Main classification: G02B6
IPC codes: G02B6