WO2016000923A1

WO2016000923A1 - An optocoupler and components thereof

Info

Publication number: WO2016000923A1
Application number: PCT/EP2015/062978
Authority: WO
Inventors: Patrick Doyle; John D. Lambkin; Hugh HENNESSY; Michael O'gorman; Thomas Moriarty
Original assignee: Firecomms Limited
Priority date: 2014-07-03
Filing date: 2015-06-10
Publication date: 2016-01-07
Also published as: DE212015000174U1

Abstract

An optocoupler (19) has a first part (20) having a body and a connector (21) for connecting to a board, and a second part (22) having a body and a connector (23) for connecting to a board, and being arranged to mate with the first part. There is a light passage (26), and the parts when mated allow transmission of light between the parts. The first part may include a light passage (26, 29) projecting from the body, and the second part a socket (27) to receive the light passage.

Description

"An Optocoupler and Components Thereof

Introduction This invention is in the field of passing signals between electrical circuits without making electrical connection between them.

Prior Art Discussion When it is desired to pass signals between two electronic circuits which are on the same printed circuit board without making electrical contact between them, it is common to use an optocoupler, as illustrated by the schematic diagram in Fig. 1. In this figure circuit 1 and circuit 2 are not electrically connected, though both circuits are built on the same circuit board. Circuit 1 generates a signal which is connected to an optocoupler, 3, in which it causes a light emitting device, 4, to generate light. A light detecting device 5 within the optocoupler detects this light and passes a signal to the circuit 2. Because the light emitting device and the light detecting device are separated there is no electrical connection between them.

Mechanically, an optocoupler of the prior art is typically constructed by mounting the light emitting device and the light detecting device in a moulded body of electrically non-conducting material, including a transparent material to allow the light from the emitter to reach the light detector, and an overall covering of non-transparent material to prevent ambient light from interfering with the operation of the optocoupler. Metal leads attached to the light emitter and the light detector lead outside the moulded body, so that electrical connections can be made to the circuit board on which the circuits are built. Typically, the optocoupler will be attached to the circuit board by a soldering process after which the board will be cleaned and tested before being assembled into a piece of equipment. US patents numbers 5,064,299 and 5,545,893 and German patent numbers 3,410,176 and 3,526,001 illustrate variations on this type of optocoupler. It will be appreciated that this type of optocoupler is limited to communications between two circuits which are mounted on the same printed circuit board, on which the optocoupler is also mounted, as it is not economical in electronic equipment production to solder part of one component to one printed circuit board and another part of the same component to a different board. Another common approach is to use optical transceivers and an optical cable, as shown in Fig 2. In this figure the circuits are built respectively on boards 10 and 11. Each circuit board carries a transceiver, at least one of which, 12, includes a light emitting element while the other transceiver, 13, includes at least a light receiver. The transceivers may be mounted on the circuit boards by soldering as described above. Later, when the boards have been fixed in their final positions in a piece of equipment, a fibre optic cable assembly, 14, is used to connect them together. This cable assembly consists of two plugs, 15 and 16, which have been mounted on either end of a suitable length of optical cable, 17. It will be appreciated that this type of optical coupling is more expensive to manufacture, because of the need for a number of components and a separate assembly operation to produce the optical cable assembly. Further, it imposes restrictions on the design of the boards and the equipment, in that the two transceivers have to be accessible after the boards have been fixed in position to allow the plugs to be inserted. It will also be appreciated that the cable, being flexible and having necessarily some excess length, may move around when the equipment is in use and cause reliability problems, or may need further operations and components to fix it in place after the plugs have been inserted. A further difficulty, when more than one connection is to be made, is the danger that plugs will be inserted into the wrong sockets by accident, either during assembly or later, if the equipment is partially dismantled and then reassembled for maintenance or other purposes. Another known approach is to provide an optical transmitter on one board, with an optical receiver on another board, with lenses or similar means to direct the light from the transmitter towards the receiver, and lenses or reflectors incorporated in the receiver to direct the light onto the optoelectronic element within the receiver, the light passing through free space between the transmitter and the receiver. Such systems suffer from reliability problems, as dirt or other material may come between the components and obscure the light path, or dirt and dust may build up on the surfaces of the lenses, reflectors or other parts of either transmitter or receiver or both and interfere with the light path between them.

Furthermore it is also possible that external light sources other than the light from the transmitter may inadvertently cause the receiver to respond and generate a false output signal. Such false output signals can have catastrophic consequences particularly in high-current switching applications.

The invention is directed towards providing an improved optocoupler. Summary of the Invention

According to the invention there is provided an optocoupler comprising:

a first part having a body and a connector for connecting to a board, and

a second part having a body and a connector for connecting to a board, and being arranged to mate with the first part,

wherein the parts when mated allow transmission of light between the parts, and wherein the first part includes a light passage projecting from the body, and the second part comprises a socket to receive the light passage of the first part.

In one embodiment, the light passage and the socket are arranged for optical coupling at any of a range of degrees of insertion of the light passage into the socket, in a telescopic arrangement. In one embodiment, the light passage and/or the socket have formations to guide physical insertion of the light passage into the socket with a desired optical alignment.

In one embodiment, the light passage includes a tapered distal edge. In one embodiment, the socket has a tapered or funnel-shaped rim. In one embodiment, the parts have features for engagement of the light passage in the socket at a pre-defined separation of the parts. In one embodiment, said features are arranged to snap-fit together.

In one embodiment, the light passage and/or the socket have a resilient seal to prevent ambient light ingress and/or matter contamination into the light passage and the socket. In one embodiment, the seal is permeable to allow air pressure equalisation on both sides of the seal. In one embodiment, said seal is annular.

In one embodiment, at least one of the parts is arranged to extend through an aperture in a board. In one embodiment, said part is arranged to receive or transmit light from or to an optical element on a side of the board opposed to the light passage or socket. In one embodiment, the element is included in the body of the part. In one embodiment, at least one part has an optical element. In one embodiment, each part has a connector for electrical connection of an optical element to a board for supporting the associated optocoupler part. In one embodiment, the connector includes at least part of a lead frame. In one embodiment, the light passage includes a tube arranged with a reflective inner surface for free space light transmission within the tube. In one embodiment, the light passage includes a lens to focus or direct the light.

In one embodiment, the light passage includes a solid light transmitting rod.

In one embodiment, the light passage comprises a support which contacts the rod at only a small portion of an outer surface of the rod. In one embodiment, the support comprises a plurality of radially inwardly-directed ridges or flats in contact with the rod. In one embodiment, at least one part comprises a seat having a floor and side walls to accommodate a housing of the socket or the light passage. In one embodiment, said part includes an optical element and the seat and the housing are arranged for interference fitting to prevent light ingress. In one embodiment, the seat and the housing are arranged with interface surfaces with at least one corner for blocking of propagation of any light which enters a small gap between the interface surfaces.

In one embodiment, the parts are configured to form a spacer post interconnecting boards.

In another aspect, the invention provides a set of circuit board spacer posts including an optocoupler as defined above in any embodiment.

In another aspect, the invention provides a circuit comprising a plurality of boards, at least two of said boards having a part arranged to couple with a corresponding part of the other board using an optocoupler as defined above in any embodiment.

In another aspect, the invention provides an optical device comprising a seat, a housing and at least one opto-electronic component contained in a space between said seat and said housing, wherein the seat and the housing are arranged with mating surfaces which have an interference fit, and in which the mating surfaces of the seat and the housing have one or more corners or steps to prevent light leakage between the outside of the assembly and the opto-electronic component.

In one embodiment, the seat has a circuit board engaging floor, and the opto-electronic component is mounted with an optical axis which is perpendicular to said floor.

In one embodiment, the opto-electronic component comprises leads, and said leads pass through the seat and project so that they may be attached to a circuit board.

Detailed Description of the Invention

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawing s in which : -

Figs. 1 and 2 are diagrams illustrating optocouplers of the prior, as discussed above;

Fig. 3 is a pair of diagrams showing an optocoupler of the invention, separated in the left diagram and interconnected in the right diagram.

Fig. 4 shows an alternative optocoupler of the invention, when inter-connected;

Fig. 5 is a cross-sectional diagram showing an alternative optocoupler;

Fig. 6 is a cross-sectional diagram showing one part of a coupler incorporating lenses;

Fig. 7 is a cross-sectional diagram showing a still further coupler;

Fig. 8 is a cross-sectional diagram showing a coupler of another embodiment, with a mechanical fixing;

Fig. 9 is a diagram showing an optocoupler assembly with fixing posts for interconnection of boards; Fig. 10(a) is a front view of an alternative optocoupler, Fig. 10(b) is a cross-sectional view showing mechanical alignment of a light passage within a socket of this optocoupler, and Fig. 10(c) is a cross-sectional view of an alternative mechanical alignment arrangement;

Figs. 11 and 12 are a partly cut-away perspective views an alternative optocoupler of the invention, having a seat for minimisation of light ingress into optocoupler;

Fig. 13 is a cross sectional diagram showing a coupler of another embodiment in a horizontal configuration; and

Fig. 14 is a pair of perspective views of an alternative optocoupler of the invention, without a socket to receive a light passage. Description of the Embodiments

An optocoupler is particularly suitable for coupling circuits built on two different boards, but is not limited to this use. This optocoupler is made in at least two parts, such that one part may be fixed on each of the boards to be coupled, and these two parts may be mated directly with one another as the boards are assembled into the equipment of which they form part.

Referring to Fig. 3 an optocoupler of the invention has a first part 20 shown mounted on a circuit board 21 and a second part 22 shown mounted on a second printed circuit board 23. Each part 20 and 22 of the optocoupler has electrical leads, 24 and 25, which provide for electrical connection of an opto-electronic device in that part of the optocoupler to the associated circuit board and thence to other electronic components (not shown) mounted on the same circuit board. The first part 20 has a cylindrical light passage 26 providing an optical path to allow light to pass between an electro-optical device within the part 20 and the tip of the light passage 26. The second part 22 has a hollow tubular protrusion 27 which forms a socket large enough to receive the light passage 26 and which forms an optical path to an electro-optical device in the second part 22. It can be seen that when the first circuit board 21 is mounted into its final position relative to the second circuit board 23, as shown in the right hand diagram, the light passage 26 fits into the socket 27 and light may pass directly between the electro-optical devices in the two parts 20 and 22.

In one embodiment, the parts are configured and the materials chosen to ensure that light from the external environment cannot ingress to reach an optical receiver electro-optical device within one of the parts.

In this embodiment, the light passage 26 has an integral annular seal 29, which serves to seal the joining between the light passage 26 and the socket 27 when they are assembled together, to prevent the ingress of dirt, dust, or light. This sealing element may be elastomeric, to provide a seal against gases and liquids, or may be made of felt or other porous material, to allow gases to pass through, but hinder the entry of dust or other dirt particles.

Alternatively, such an elastomeric or flexible porous element may be fitted internally in the socket, for example, to provide such a sealing action.

Instead of, or in addition to, such an elastomeric sealing element, there may be features such as a moulded ridge on the light guide and a corresponding moulded groove on the inside of the socket, so that when the light guide is forced into the socket the ridge on one engages the groove on the other to provide a positive location feature, so that the assembled optocoupler acts as a "standoff: That is to say that the first circuit board 21 may be, at least partially, held in position mechanically by the assembled optocoupler, avoiding or reducing the need for additional mechanical components to hold the board in place. Such an arrangement therefore provides the dual function of providing both a mechanical pillar and sealing of light or physical contaminant ingress into the light path within the optocoupler.

A method of assembling the optocoupler comprises the operations of:

(a) fixing one part of the optocoupler to one circuit board or similar assembly

(b) fixing the other part of the optocoupler to another circuit board or similar assembly (c) bringing the two circuit boards or assemblies together so that the first optocoupler part engages with the second, forming at least one protected light passage from at least one optical transmitter in one part to at least one optical receiver in the other part, and fixing the circuit boards or assemblies in that position. Instead of mounting the electro-optical devices such that they lie between the boards when they are assembled, one or both parts of the optocoupler may be arranged so that the electro-optical device it contains is on the opposite side of the board from the other part, and the light path passes through the board. This is illustrated in Fig. 4 in which the first part of an optocoupler 30 is mounted on a board 31 as described above but the second part 32 is mounted with the electro- optical component on the bottom of a circuit board 33, with the socket extending through the circuit board 33. The part 30 has a tubular light passage 36 the end of which fits into a socket 37. An advantage of this arrangement is that, for a given distance between the circuit boards, the distance between the electrically conducting elements of the optocoupler is increased, so increasing the "withstand voltage", that is the largest voltage that can be applied between the two electro-optical elements without allowing the passage of an electrical current.

It is envisaged that the optical elements may not be part of the coupler parts, being mounted on the boards and the coupler parts are aligned with them in subsequent assembly operations.

An alternative optocoupler, 40, is shown in Fig 5, in which one part comprises a moulded plastics body 41 housing an opto-electronic device 42 and a transparent rod 43. The rod 43 and the body 41 form a light passage. This part is shown mounted on a circuit board 44. The plastics body 41 has clips 45 which hold the assembly onto the circuit board 44. The opto-electronic device 42 comprises a body moulded of transparent material, a metal lead frame 49 and an active opto-electronic element 46 mounted on the metal frame within the transparent moulded body. The metal lead frame 49 has portions which extend outside the moulded body and provide leads which make electrical connections from this part of the optocoupler to the circuit board 44. The transparent moulded body includes a lens 47 which guides light between the active optoelectronic element 46 and the protruding light passage transparent rod 43.

The second part, 50, comprises a moulded plastics body 51 housing an opto-electronic device 52 and is held in position on a circuit board 54 by means of plastics clips 55 which form part of the body 51. The opto-electronic device 52 comprises an active opto-electronic element 56 mounted on a metal frame 59 within a transparent moulded body which incorporates a moulded lens 57.

It will be appreciated that optocouplers of different overall lengths may be economically produced by using transparent rods of different lengths within the light passage, without necessarily any changes to any of the other components. It can be seen that the housing 41 of the first part 4 is tapered and the socket 51 of the second part 50 is tapered on its inner surface near the tip, and has a further conical taper at the bottom to guide the transparent rod 43 into alignment with a lens 57. Thus the two parts may be assembled to one another without first bringing them into precise alignment.

Further, it can be seen that the transparent rod 43 is held firmly in the portion of the body 41 closest to the opto-electronic device 42. However, there is some free play around it at the other end of the body, as shown at 48, and there is some free play between the outer surface of the (light passage) housing 41 and the inner surface of the socket 51 (tubular portion of part 50). Additionally, there is some space between the tip of the transparent rod 43 and the optoelectronic device 52. These spaces mean that residual misalignment or small relative movements between the circuit boards 44 and 54 can be accommodated.

A further embodiment is shown in Fig 6, which shows only one part, 60, of an optocoupler, mounted on a circuit board 61. This is similar to the optocoupler part 40 in Fig 5, except that the ends of a transparent rod 63 are formed into lenses 62 which improve optical coupling between the rod and the opto-electronic devices.

A further embodiment is shown in Fig 7, in which an optocoupler 70 consists of two parts, 71 and 72, mounted respectively on circuit boards 73 and 74. In this embodiment, a lens 75 is fitted into each part of the optocoupler parts to guide the light from the optical transmitter into a beam that will pass directly to the other lens, which serves to gather the beam and focus it on the optical receiver. With or without the presence of the lenses, light transmission from the transmitter to the receiver may be improved by making the inner surfaces of the passage through which the light passes of a reflective material, or treating the surfaces so as to improve their reflectivity, so that the light is reflected along the passage from the transmitter to the receiver. In some circumstances such reflective surfaces may provide sufficient optical coupling without the use of discrete lenses. A further embodiment is shown in Fig 8, in which an optocoupler consists of two parts, a part 83 having light passage 85 with a circumferential protrusion 80, and a part 84 having a socket 86 with a corresponding groove 81. In this diagram the lower optocoupler part 84 has a split 82 in its socket 86 which allows the tube to bend open to receive the protrusion on the upper optocoupler part. Fig 9 shows an assembly using such an optocoupler, composed of two parts 91 and 92, which have been fixed on circuit boards 93 and 94 respectively. Additional electronic components 95 have also been fitted to these circuit boards. A mechanical stand-off clip 96 has been fixed on one of the circuit boards. The two circuit boards may then be fixed to one another by aligning them and pressing them together, so that the stand-off 96 engages both boards and holds them in position at one end, and the optocoupler parts 91 and 92 hold the boards in position at the other end. The stand-off and the optocoupler are matched in length so that together they form matching pillars separating and supporting the boards 93 and 94.

A further embodiment is shown in Fig 10, in which an optocoupler component 100, mounted on a board 101, includes a transparent light passage rod 102. In the cross-section, the body of the component 103 surrounds the transparent rod 102. The body of the component includes three ridges 105 which serve to hold the transparent rod 102 in the centre of this portion of the body 103, so that it is surrounded by a space 106 filled with air. The surface contact between the tips of the ridges 105 and the surface of the rod 102 is minimal, so that most of the surface of the rod is in contact with air. Air has a lower coefficient of refraction than the material of which the rod is made, so that the combination of the rod and the air surrounding it form a light passage, guiding light from one end of the rod to the other.

Fig. 10(c) shows an alternative embodiment in which a body 108 has a bore with flats 107 in contact with the rod 102, and there is an air gap 109 around the rod 102.

It will be appreciated that it is highly undesirable that the optical receiver should respond to light originating from the environment external to the optocoupler.

A further embodiment is shown in Figs. 11 and 12, in which an optocoupler part 110 has a socket 111 extending from a housing with a rectangular base 117 both of which are fabricated from optically opaque material. The base 117 slides onto a seat 112 around part of which there is an EMI shield 118. An opto-electronic component 115 comprises a body 114 moulded of transparent material, a metal lead frame and an active opto-electronic element mounted on the metal frame. The metal lead frame has portions which extend outside the moulded body and provide leads 116 which make electrical connections from this part of the optocoupler to the circuit board on which it will be mounted. This opto-electronic component 115 is mounted in a recess within the seat 112.

The interface between the seat 112 and the housing base 117 is stepped with multiple corners such as a corner 119, and the seat 112 and the base 117 have an interference fit. Hence the seat 112 in combination with the base 117 of the housing form a light-tight enclosure for the device 115. Figure 12 is another view of the same device, with the housing with its socket removed to reveal the EMI Shield 118 in place on the seat 112. In this view the corners or steps in the surface of the seat, 120, 121 and 122, can clearly be seen and it will be appreciated that, when the base 117 of the housing, with its matching steps or corners, is assembled onto the seat 112 a light proof joint will be formed. This view also shows how the leads 116 from the optoelectronic component pass through the seat 112 in the area 135 to be available for fixing to the printed circuit board. This enclosure would even prevent very high intensity transient light from an electrical arc from penetrating the enclosure. Even if some light were able to penetrate into the very small gap which might exist between two surfaces such light would not penetrate beyond the corners 119, 120, 121, and 122. A problem with many optical systems is that the transmitter, which necessarily involves passing a significant current (typically 20 mA) through the LED or other light generating device, and switching the current on and off at high frequency to transmit data, may generate electromagnetic interference which can cause malfunction of other electronic components nearby. At the same time, the receiver includes an amplifying element to detect the very small electrical signals generated by the photo-detector and amplify them to levels suitable for supplying a signal to the circuit to which it is connected. This amplifying element may be susceptible to electromagnetic interference caused by other nearby electronic components. A known solution to such problems is to surround the optoelectronic components with metal shields, while allowing small openings in such shields for the leads of the electro-optical device to exit and for the optical passage. An advantage of the couplers of the invention is that it is easy to incorporate such a shield, and very effective shielding may be easily achieved by having a ground plane conductor on the printed circuit board under the electro-optical element, and a simple metal shield within the housing, shielding the top and sides of the electro-optical device. When the optocoupler part containing the shield is mounted on the printed circuit board, the shield within it is electrically connected to the ground plane on the printed circuit board, so forming a complete shield around the optoelectronic component.

It is not essential that the optocoupler be arranged to operate vertically as in the embodiments described above. For example, referring to Fig. 13 an optocoupler 140 has a socket 141(a) receiving a light passage 141(b) with a transparent rod 143 for light transmission. The socket 141(a) has a tapered mouth 148 for simple guiding of the light passage 141(b) into the socket. A device 146 has a lens 147 and both are arranged for horizontal light transmission with respect to boards 144. Electrical pins 149 protrude downwardly at right angles to the light guiding axis to extend through the boards 144. The housings have mechanical fixing pins 145 extending through the boards. 144.

An optical device in various other embodiments may not necessarily have a socket or a light passage for entering the socket. It may comprise a seat, a housing and at least one opto-electronic component contained in a space between the seat and the housing. The seat may be arranged to have a floor which rests on a circuit board, The seat and the housing may be arranged with mating surfaces which have an interference fit, they may have one or more corners or steps to prevent light leakage between the outside of the assembly and the opto-electronic component. If the seat has a circuit board engaging floor, the opto-electronic component is preferably mounted with an optical axis which is perpendicular to the floor. The opto-electronic component may have leads which pass through the seat and project so that they may be attached to a circuit board. Fig. 14 shows an optocoupler which is an example of such a device. Fig. 14 shows how an enclosure comprising a housing fitted onto a seat and one or more steps or corners on the mating surfaces, may be used to provide a light seal in alternative optocouplers. An optical connector 150 includes a seat 151 and a housing 152. Two metal EMI shields 153 cover two opto-electronic components 154. The EMI shields 153 incorporate lead pins 155 and the electo-optical components 154 incorporate lead pins 156. The housing includes features for the connection of a plug terminating an optical fibre, in this case the features comprise a cylindrical hole 158 to receive the part of the plug containing the optical fibre and a pair of wings 159 to retain the plug in position. Mating surfaces 160 and 161 of the seat 151 and the housing 152 respectively include a number of steps and corners to prevent the leakage of light through the joint. The above describes various specific embodiments. However optocouplers of the invention may have some or all of the following features:

- The light passage and socket may have any suitable mating features such that when the boards are mounted in an assembly the parts engage one another to provide at least one protected light passage from the at least one transmitter to the at least one receiver, forming an optocoupler. It may for example provide light transmission in free space through the coupler parts, or it may be a solid transparent material with applicable refractive indices.

- The mating surfaces of the two parts may be configured so that they may be assembled at an orientation slightly different from the orientation when they are in operation and / or have tapered or "lead-in" features to guide them into alignment as they are assembled, so as to facilitate an assembly process that includes the steps of engaging the two parts with one another, and then moving one of the boards relative to the other as the boards are fixed in position.

- The engaging features may be configured to allow small amounts of movement between the boards after assembly, so that relative motion between the boards due to vibration, thermal expansion of the assembly and other such causes can be accommodated.

- The optical element (transmitter or receiver) in at least one part is arranged to be mounted on the surface of the circuit board furthest from the other board, with the optical path passing through the plane of the board on which it is mounted.

- Engaging features of the parts may be designed to lock together so as to provide mechanical strength, such that, as well as providing for communication from one board to the other, it may also serve as a mechanical mounting, supporting one board from the other.

- Engaging features of the parts may have one or more flexible sealing elements to prevent the ingress of dirt or other foreign material into the optical path. One or more of the flexible sealing elements may be gas permeable to prevent the ingress of dust etc. into the optical path while still allowing the equalisation of atmospheric pressure between the inside and the outside of the optocoupler.

- The optical path may be provided, at least in part, by means of one or more transparent portions moulded or inserted into one or both parts of the optocoupler. The light passage may have a transparent rod and the socket may be dimensioned so that different lengths of rod may be inserted into otherwise identical housing components to produce optocouplers having different heights when assembled. The light passage may have transparent materials having different indices of optical refraction, with one in the centre and the other around the outside so that the light is internally guided along the rod as is the case in an optical fibre. The light passage may indeed be formed by a conventional optical fibre with a stiff cladding.

- The optical path may be provided, at least in part, by means of one or more lenses configured to guide the light. When part of the light passage is formed by a solid transparent portion it may have a lens formed at one or both ends to improve light coupling. The optoelectronic device in one or both parts may be encapsulated in a transparent material formed to include a lens. Either part of the optocoupler may have a separate lens or lenses formed in a transparent material fixed in the body for alignment with an optical element.

- The lens or lenses may be fixed near at least one of the electro-optical elements so as to guide light and/or to focus light coming from a transmitter onto the sensitive part of a receiver.

- An optical path may be provided, at least in part, by reflective surfaces inside a tubular passage which serve to reflect and guide light.

- A part may have a shield made of conductive material surrounding at least one of the electro-optical elements.

- A part may be designed so that the optoelectronic element is first attached to a circuit board (for example by soldering) and later the rest of the part is fixed to the board to align with the optoelectronic element.

The invention may take the form of one part only, ready to be coupled with another corresponding part provided by a different supplier. The parts may be built into or assembled onto circuit boards by different parties.

The invention is not limited to the embodiments described but may be varied in construction and detail.

Claims

An optocoupler comprising:

a first part (20) having a body (26) and a connector (24) for connecting to a board (21), and

a second part (22) having a body (27) and a connector (25) for connecting to a board, and being arranged to mate with the first part,

wherein the parts when mated allow transmission of light between the parts,

wherein the first part (20) includes a light passage (26) projecting from the body, and the second part comprises a socket (27) to receive the light passage (26) of the first part.

An optocoupler as claimed in claim 1, wherein the light passage and the socket are arranged for optical coupling at any of a range of degrees of insertion of the light passage into the socket, in a telescopic arrangement.

An optocoupler as claimed in either of claims 1 to 2, wherein the light passage and/or the socket have formations to guide physical insertion of the light passage into the socket with a desired optical alignment.

An optocoupler as claimed in claim 3, wherein the light passage includes a tapered distal edge.

An optocoupler as claimed in either of claims 3 or 4, wherein the socket has a tapered or funnel-shaped rim.

An optocoupler as claimed in any preceding claim, wherein the parts have features for engagement of the light passage in the socket at a pre-defined separation of the parts.

An optocoupler as claimed in claim 6, wherein said features (80, 81) are arranged to snap-fit together.

An optocoupler as claimed in any preceding claim, wherein the light passage and/or the socket have a resilient seal (29) to prevent ambient light ingress and/or matter contamination into the light passage and the socket.

An optocoupler as claimed in claim 8, wherein the seal is permeable to allow air pressure equalisation on both sides of the seal.

An optocoupler as claimed in claims 8 or 9, wherein said seal (29) is annular.

An optocoupler as claimed in any preceding claim, wherein at least one of the parts (37) is arranged to extend through an aperture in a board (33).

An optocoupler as claimed in claim 11, wherein said part (32) is arranged to receive or transmit light from or to an optical element on a side of the board opposed to the light passage or socket.

An optocoupler as claimed in claim 12, wherein the element is included in the body of the part.

An optocoupler as claimed in any preceding claim, wherein at least one part has an optical element (46).

An optocoupler as claimed in claim 14, wherein each part has a connector for electrical connection of an optical element to a board for supporting the associated optocoupler part.

An optocoupler as claimed in claim 15, wherein the connector includes at least part of a lead frame.

An optocoupler as claimed in any preceding claim, wherein the light passage includes a tube arranged with a reflective inner surface for free space light transmission within the tube.

An optocoupler as claimed in any preceding claim, wherein the light passage includes lens (75) to focus or direct the light.

19. An optocoupler as claimed in any preceding claim wherein the light passage includes a solid light transmitting rod (63).

An optocoupler as claimed in claim 19, wherein the light passage comprises a support (103, 108) which contacts the rod at only a small portion of an outer surface of the rod.

An optocoupler as claimed in claim 20, wherein the support comprises a plurality of radially inwardly-directed ridges (105) or flats (107) in contact with the rod.

An optocoupler as claimed in any preceding claim, wherein at least one part comprises a seat (112) having a floor and side walls to accommodate a housing of the socket or the light passage.

An optocoupler as claimed in claim 22, wherein said part includes an optical element and the seat and the housing are arranged for interference fitting to prevent light ingress.

An optocoupler as claimed in claim 23, wherein the seat (112) and the housing are arranged with interface surfaces with at least one corner (119) for blocking of propagation of any light which enters a small gap between the interface surfaces.

An optocoupler as claimed in any preceding claim, wherein the parts (91, 92) are configured to form a spacer post interconnecting boards.

A set of circuit board spacer posts (96, 91, 92) including an optocoupler of claim 25.

A circuit comprising a plurality of boards, at least two of said boards (93) having a part arranged to couple with a corresponding part of the other board using an optocoupler of any of claims 1 to 26.

An optical device (150) comprising a seat (151), a housing (152) and at least one optoelectronic component contained in a space between said seat and said housing, wherein the seat and the housing are arranged with mating surfaces which have an interference fit, and in which the mating surfaces of the seat and the housing (160, 161) have one or more corners or steps to prevent light leakage between the outside of the assembly and the opto-electronic component.

29. An optical device as claimed in claim 28 in which the seat has a circuit board engaging floor, and the opto-electronic component is mounted with an optical axis which is perpendicular to said floor. .

30. An optical device as claimed in claims 28 or 29 in which the opto-electronic component comprises leads (155, 156), and said leads pass through the seat and project so that they may be attached to a circuit board.