GB2221324A

GB2221324A - Optical connector

Info

Publication number: GB2221324A
Application number: GB8916552A
Authority: GB
Inventors: Bruno Bortolin; Norma Ridi
Original assignee: Pirelli Cavi SpA; Cavi Pirelli SpA
Current assignee: Pirelli and C SpA
Priority date: 1988-07-27
Filing date: 1989-07-20
Publication date: 1990-01-31
Anticipated expiration: 2009-07-20
Also published as: GB2221324B; ES2015174A6; IT8821500A0; GB8916552D0; BR8903761A; IT1226315B

Abstract

An expanded beam optical connector comprises a spherical lens 11 and a diverging plano-concave lens 7 which are retained in a frusto-conical portion 2 of a through-cavity of the connector body 1. The through-cavity has a cylindrical portion 3 which supports the end portion of an optical fibre 27. The lens 11 and 7 are in direct mutual contact. The spherical lens 11 seats against the wall of the frusto-conical portion 2 and the diverging lens 7 is accommodated in a cylindrical recess 6 of an annular support member 5 which is elastically deformable radially and is also seated in the frusto-conical portion 2. During assembly of the connector lens 11, on engaging the circular edge 12 of lens 7, causes radial movement of lens 7 until the whole of edge 12 is contacted by lens 11 until the axes of both lenses coincide. <IMAGE>

Description

AN EXPANDED BEAM OPTICAL CONNECTOR This invention relates to an expanded beam optical connector for use in optically connecting an optical fibre to a laser source or to another optical fibre.

Generally, expanded beam connectors comprise lens means for focusing on the end face of an optical fibre a beam of collimated light incident to the lens means of diameter considerably larger than that of the optical fibre end face. Expanded beam connectors wherein the lens means is a single spherical lens are known.

Examples of such expanded beam connectors are disclosed in our UK Patent Specifications Nos.

2190764A and 2211628A.

In such connectors a spherical lens is seated in a fixed position in a frusto-conical portion of a through-cavity in a connector and the optical fibre extends into the through-cavity and has its end face fixed at the focus of the spherical lens.

It is known that the use of a spherical lens in an expanded beam connector has the disadvantage of producing a spherical aberration, i.e. the lens is not able to focus a collimated beam incident thereto at a single point (the geometric focus of the lens), but instead the collimated beam forms on a plane passing through the geometric focus of the lens and perpendicular to the beam a circular image whose diameter increases with an increase in diameter of the collimated beam.

It is also known that the amount of spherical aberration of a spherical lens can be reduced by using the spherical lens in association with a diverging plano-concave lens having a concave face with a radius of curvature smaller that the radius of curvature of the spherical lens facing the spherical lens.

Whilst it is always desirable to reduce the amount of spherical aberration in an expanded beam optical connector, it is particularly important to do so if it is desired to increase the diameter of the collimated beam incident to the spherical lens and/or reduce the diameter of the spherical lens, since both of these changes will produce an increase in spherical aberration.

An example of a situation where it is essential to reduce the amount of spherical aberration is when the connector is used for connecting a laser light source of a predetermined power to an optical fibre.

This is because the diameter of a collimated beam of light emitted by a laser light source increases when the laser power is increased. Hence for the previously explained reason it is necessary to use a diverging plano-concave lens as aforesaid to reduce the amount of spherical aberration of the spherical lens to ensure that in a plane perpendicular to the axis of a beam of collimated light incident to the spherical lens and passing through the geometric focus of the lens system the light area formed because of the spherical aberration has a diameter which is less than the diameter of the core of an optical fibre end face which is positioned at the geometric focus of the lens system.

In expanded beam connectors which have an optical system comprising a spherical lens and diverging lens as aforesaid, it is important that the axis of the diverging lens and the axis of the end portion of the optical fibre in the connector coincide and pass through the centre of the spherical lens and that these axes also coincide with the axis of the beam of collimated light incident to the spherical lens.

This is because any small misalignment between the above-mentioned axes and- any small offset of these axes from the centre of the spherical lens would produce unacceptable reductions in the light power conveyed to the optical fibre.

An object of the present invention is to provide an expanded beam optical connector provided with a spherical lens and diverging lens as aforesaid in which the lenses are located in the connector using only usual mechanical working tolerances of parts of the connector, and without the need for any micrometric adjusting means such that the axis of the diverging lens is coincident with the axis of the connector and passes through the centre of the spherical lens. Mounting of the optical fibre end portion on the optical axis of the connector with its end face at the plane of the geometric focus of the lens system and alignment of the axis of the beam of collimated light with the optical axis of the connector, may be provided by various means.

According to the present invention there is provided an expanded beam optical connector comprising a body provided with a through-cavity having a frustoconical portion, a spherical lens seated in the frusto-conical portion and retained therein by a retention ring engageable with the spherical lens and releasably securable to the body, a support means for a diverging plano-concave lens seated in said frustoconical portion inwardly of the spherical lens such that a plane support surface thereof facing said spherical lens extends radially with respect to the axis of the frusto-conical portion, the support means being elastically deformable radially with respect to the axis of the frusto-conical portion when so seated, a diverging plano-concave lens supported by said support means with a plane face thereof parallel to and facing said plane support surface and with a concave face thereof, which has a smaller radius of curvature than the radius of curvature of the spherical lens, facing the spherical lens, the arrangement being such that on assembly, the spherical lens engages the diverging lens causing the latter to move radially with respect to the axis of the frustoconical portion until the whole of the circular edge of the concave face of the diverging lens contacts the spherical lens and thereby the axis of the diverging lens is coincident with the axis of the frusto-conical portion.

The through-cavity preferably includes a cylindrical portion coaxial with said frusto-conical portion for receiving the end portion of an optical fibre, and in the preferred embodiment of the present invention a ferrule is received in said cylindrical portion of the through-cavity with an outer cylindrical surface in contacting engagement with the internal cylindrical surface of the cylindrical portion, said ferrule having a through-passage coaxial with said outer cylindrical surface for supporting said end portion of an optical fibre. In this way, it is ensured that the axis of the end portion of the optical fibre is aligned with the axis of the diverging plano-concave lens and also passes through the centre of the spherical lens.

The support means preferably comprises a general disc-shaped annular support member with a frustoconical side edge surface of the same conicalness as the frusto-conical portion of the through-cavity.

The plane support surface of the support means is preferably the base of a cylindrical recess provided on the side of the annular support member facing the spherical lens for receiving the diverging lens, the diameter of the recess being greater than the diameter of the diverging lens.

A through-hole preferably extends from the base of the recess to the side of the annular support member facing the cylindrical portion of the throughcavity and receives an end portion of said ferrule.

The support means for the diverging lens may comprise a flat washer seated on the base of said cylindrical recess, one side of the washer being engaged by the plane face of said diverging lens and the other side of the washer being engaged by a flat radial end surface of said ferrule.

In one embodiment of the present invention, the radial elastic deformability of the support means is provided by a radially extending discontinuity in the annular support member.

In another embodiment, the radial elastic deformability of the support means is provided by a spiral discontinuity in the annular support member.

In yet another embodiment, the radial elastic deformability of the support means is provided by a plurality of first radial grooves opening at the side edge of the annular support member and a plurality of second radial grooves opening at the recess and through-hole thereof, the grooves being circumferentially spaced apart with the first grooves alternating with the second grooves.

In order that the present invention may be well understood, the above-mentioned embodiments thereof, which are given by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section of an expanded beam optical connector; Figure 2 is a plan view of a support member of the connector shown in Figure 1; Figure 3 is a plan view of an alternative support member for the connector shown in Figure 1; Figure 4 is a plan view of another alternative support member for the connector shown in Figure 1; Figure 5 schematically illustrates the relative position of the two lenses of the connector shown in Figure 1 during assemble; and Figure 6 schematically shows the relative position of these lenses on completion of assembly.

The expanded beam optical connector shown in Figure 1 comprises a body 1, which is made of metal, and which is provided with a through-cavity, the axis of which is indicated by chain-dotted line 4.

The body of the connector is provided with mechanical means known per se (not illustrated) for connection to a like connector or to a laser device such that the axis of the like connector or the axis of a laser light beam 4l incident to the connector is coincident with the axis 4.

The through-cavity comprises a frusto-conical portion 2 and a cylindrical portion 3, which extends from the smaller base of the frusto-conical portion.

The frusto-conical portion and the cylindrical portion are coaxial with the axis 4 of the connector body.

A spherical lens 11 is seated in the frustoconical portion, as is a support means comprising a general disc-shaped annular support member 5 which is elastically deformable only in a radial direction with respect to the axis 4 of the frusto-conical portion when seated in the frusto-conical portion as illustrated.

A diverging plano-concave lens 7 is supported by the support means with its plane face 8 parallel to and facing a plane support surface of the support means which faces the spherical lens and extends radially with respect to the axis 4 of the frustoconical portion. The plane support surface is the base of a cylindrical recess 6 provided on the side 30 of the annular support member 5 facing the spherical lens, in which recess the diverging lens 7 is received.

A through-hole 9 extends from the base of the recess 6 to the side 8' of the support member 5 facing the cylindrical portion 3 of the through-cavity. The other face 10 of the diverging lens 7 is concave and is directed towards the spherical lens 11.

The circular edge 12 of the concave face 10 of the diverging lens 7 is in direct contact with the spherical lens 11. The diverging lens 7 has a side edge surface 13 of constant depth throughout its circumferential extent. The radius of curvature Rd of the concave face 10 of the diverging lens 7 is smaller than the radius of curvature Rs of the spherical lens 11.

Moreover, the axis of the diverging plano-concave lens 7 which is coincident with the axis 4, as previously described, passes through the centre 14 of the spherical lens 11 when the connector is assembled as illustrated with the spherical lens 11 in contact with the frusto-conical portion 2 of the throughcavity along a circular line 15. Both lenses 7 and 11 in the embodiment are sapphire, but may be made of other materials and furthermore one lens can be made of a material different from that of the other lens.

Both lenses are preferably coated with a transparent and reflection preventing film of a type known per se to the man skilled in the art.

The assembly constituted by the separate parts comprising the annular support member 5, the diverging plano-concave lens 7 and the spherical lens 11, is retained in the frusto-conical portion 2 of the through-cavity of the connector body 1 by a retention ring, or sleeve, 16 which is releasably securable to the body 1 and is preferably made of metal.

In particular, as shown in Figure 1, the sleeve 16 has a cylindrical portion 17 and a frusto-conical portion 18 connected thereto at the greater base of the frusto-conical portion. Moreover, at the smaller base of the frusto-conical portion 18 there is provided a radially inwardly extending projection 19.

The releasable connection of the sleeve to the connector body is realised through screw threading 20 on facing parts of the cylindrical portion 17 of the sleeve and a cylindrical outer surface 17' of the body 1. The frusto-conical portion 18 of the sleeve, by virtue of the internal diameter of the annular projection 19 on the smaller base thereof having a smaller diameter than that of the spherical lens 11 retains the latter seated in the frusto-conical portion of the through-cavity. As shown in Figure 1, an O-ring seal 21 of elastomeric material is interposed between the spherical lens 11 and a radial surface of the projection 19 which faces the lens 11.

As previously noted, the annular support member 5 has a through-hole 9 extending from the base of the recess 6.

A cylindrical end portion 22 of a ferrule 23 is received in the through-hole 9 and a flat washer 24, for example of metal, is seated on the base of the cylindrical recess 6, with one side of the washer being engaged by the plane face 8 of the diverging lens 7 and the other side of the washer being engaged by a flat radial end surface 25 of the ferrule 23.

The thickness of the washer 24 is uniform and constant so that its two faces lie in planes parallel to one another and the thickness of the washer is chosen in such a manner that the face of the washer in contact with the base of the recess 6 lies in the plane containing the geometric focus of the lens system comprising the spherical lens 11 and the diverging plano-concave lens 7.

The ferrule 23 comprises a body, formed for example of a metallic or sintered material, having a cylindrical end portion 22 as aforesaid which projects from a main cylindrical portion 22' to which it is connected by a frusto-conical portion 22'', the diameter of the main portion 22' being greater than that of the end portion 22.

The diameter of the main cylindrical portion 22' is substantially equal to the diameter of the cylindrical portion 3 of the through-cavity and the ferrule portion 22' is at least partially received in the cylindrical portion 3 with its outer cylindrical surface in contacting engagement with the internal cylindrical surface of the cylindrical portion 3. The ferrule is secured in the cylindrical portion 3, for example by a stake pin 23', as illustrated.

The ferrule 23 has a through-passage coaxial with the outer cylindrical surface of its main cylindrical portion 22' in which there is accommodated without any radial clearance, the end portion of an optical fibre 27. The end face 28 of the end portion of the optical fibre 27 is flush with the flat radial face 25 of the ferrule end portion 22.

In this way, the end portion of the optical fibre 27 has its own axis coincident with the axis 4 of the connector.

An essential element of the illustrated connector is the annular support member 5 which is elastically deformable in the radial direction.

One of the characteristics of the annular support member 5, which is shown in plan view in Figure 2 and in cross-section in Figure 1, is that it has a frustoconical side edge surface 29 of the same conicalness as the frusto-conical portion 2 of the through-cavity of the connector body. Specifically, the vertex angles of the longitudinal sections of both the frusto-conical surfaces of the side edge surface 29 of the annular support member 5 and the surface of the frusto-conical portion are the same; moreover both of these frusto-conical surfaces are coaxial with respect to the axis 4 when the annular support member 5 is seated in the frusto-conical portion 2 of the throughcavity.

The side 8' of the support member 5 facing the ferrule is flat and the through-hole 9 extends to that side 8' as stated previously. The opposite side 30 of the support member 5 is frusto-conical and provided centrally with the cylindrical recess 6 for receiving the diverging lens 7, the through-hole 9 extending from a central portion of the base of the recess 6.

Another characteristic of the support member 5 is that the diameter of the cylindrical recess 6 is always larger than the outer diameter of the diverging plano-concave lens 7 received therein and that the base of the recess 6 lies in a plane perpendicular to the axis of the support member 5 and consequentially perpendicular to the axis 4 of the connector body when the support member 5 is seated in the frusto-conical portion 2 of the through-cavity of the body.

The annular support member 5 is provided with a slot 31 in its wall forming a radially extending discontinuity in the annular support member thereby making the support member elastically deformable radially with respect to its axis.

It is to be understood that the provision of a slot 1 forms a particular embodiment of an arrangement for making the annular support member 5 elastically deformable in the radial direction.

The particular embodiment of the connector shown in Figures 1 and 2 is also provided with a series of circumferentially spaced apart radial grooves 32 which open at the side edge 29 of the support member but extend radially inwardly only to an intermediate diameter, here shown as the diameter of the cylindrical recess 6. The provision of these further grooves 32 increase the elastic deformability of the support member 5 in the radial direction thereof.

Alternative embodiments of the connector utilise different means for making the annular support member elastically deformable radially.

Figure 3 shows in plan view an alternative annular support member 33 which differs from the support member 5 previously described with reference to Figures 1 and 2 only in that the radial elastic deformability of the annular member 33 is provided by a spiral slot, or discontinuity 34 in the annular member. As will be appreciated, the spiral slot 34 opens at one end at the recess 6 and through-hole 9 and at the other end at the outer side edge surface of the member.

Figure 4 shows in plan view an annular support member 35 which differs from the support member 5 only in that the radial elastic deformability of the member 35 is provided by a plurality of first radial grooves 36 opening at the outer side edge of the annular member and a plurality of second radial grooves 37 opening at the recess and through-hole thereof, the grooves being circumferentially spaced apart around the annular support member with the first grooves 36 alternating with the second grooves 37.

Assembly of the connector shown in Figures 1 and 2 will now be described. It will be appreciated however that the annular support member 5 of this embodiment may be replaced with the annular support member 33 shown in Figure 3 or the annular support member 35 shown in Figure 4.

Firstly the annular support member 5 is inserted in the frusto-conical portion 2 of the through-cavity of the connector body.

Since the outer side edge surface 29 of the annular support member 5 is frusto-conical with the same conicalness as that of the frusto-conical portion 2 of the through-cavity, the axis of the annular support member automatically coincides with the axis 4 of the through-cavity of the connector body such that the plane support surface formed by the base of the recess 6 extends radially with respect to the axis 4.

The washer 24 is positioned on the base of the cylindrical recess 6 and the diverging plano-concave lens 7 is introduced into the recess 6 so that the plane face 8 thereof is in direct contact with the washer 24.

As the cylindrical recess 6 of the annular support member 5 has a diameter which is larger than that of the diverging plano-concave lens, the latter may take up any position inside the recess and the axis of the diverging lens will almost certainly not coincide with the axis 4 of the connector body when it is initially inserted in the recess 6.

Thereafter, the spherical lens 11 is inserted in the frusto-conical portion 2 of the through-cavity and subsequently the sleeve 16 is connected to the body by the screw-threading 20.

The situation which usually occurs when the spherical lens 11 is introduced into the throughcavity of the connector body is schematically illustrated in Figure 5.

As shown in Figure 5, the axis 4'' of the diverging plano-concave lens 7 lying on the plane referenced 40 in Figure 5 which represents the plane support surface formed by the base of the recess 6 is offset from the axis 4 of the through-cavity of the connector since there is a radial clearance between the diverging lens and cylindrical recess 6. However, the axis of the recess 6 of the annular support member 5 is aligned with the axis 4 of the through-cavity for the reasons discussed above.

In this situation, the spherical lens 11 contacts the diverging plano-concave lens at only one point 38.

At this point 38 the spherical lens transmits a force F on the diverging plano-concave lens as it is pressed against the lens by the pressure exerted on it by the sleeve 16.

This force F is perpendicular to the tangent 39 to the concave surface 10 of the lens 7 at the point 38. The force F comprises two component forces R1 and R2 respectively perpendicular and parallel to the plane 40 on which the lens 7 lies. The component R2 causes the lens 7 to slide on the plane 40 in the direction in which that component acts.

Consequentially, the lens 7 moves relative to the spherical lens 11 and the base of the cylindrical recess 6 of the annular support member 5. This relative movement terminates when the axis 4 '' of the diverging plano-concave lens coincides with the axis 4 of the frusto-conical portion of the through-cavity of the connection as schematically illustrated in Figure 6.

In fact, when the axis of the diverging planoconcave lens coincides with the axis of the frustoconical portion of the through-cavity of the connector body and consequentially the axis of the cylindrical recess 6 of the annular support member 5, the contact between the spherical lens 11 and the concave face of the diverging lens 7 takes place throughout the whole of the circular edge 12 of the concave face of the diverging lens.

In this situation, the spherical lens acts on the edge 12 of the diverging lens 7 with a uniformly distributed force f which acts symmetrically with respect to the axis 4'' of the diverging lens and which has components rl r2 respectively parallel and perpendicular to the axis 4'' with the components r2 not giving rise to any resultant force perpendicular to the axis.

In this way the act of introducing and retaining the spherical lens 11 in the frusto-conical portion 2 of the through-cavity of the connector body causes the diverging lens to move radially with respect to the axis of the frusto-conical portion until the axis of the diverging lens is coincident with the axis of the frusto-conical portion.

Moreover, the elastic deformability of the annular support member 5 in the radial direction and the radial clearance between the diverging lens and the cylindrical recess 6 allows movement of the annular support member 5 longitudinally of the frustoconical portion whilst seated therein and thereby assures contact of the spherical lens 11 with the wall of the frusto-conical portion along the circular line 15 so that the centre of the spherical lens lies on the axis 4 of the through-cavity and the lens 11 is in contact with the circular edge 12 on the concave face of the diverging lens 7.

The ferrule 23 is then introduced into the cylindrical portion 3 of the through-cavity such that the cylindrical end portion 22 of the ferrule is received in the through-hole 9 and the flat radial end surface 25 of the ferrule contacts the washer 24. In this way the end face 28 of the optical fibre 27, which is flush with the flat radial face 25- of the ferrule is automatically positioned in the plane of the geometric focus of the system of lenses 7 and 11 and also the axis of the end portion of the optical fibre is aligned with the axis 4 of the connector body.

This is because independently of the longitudinal position of the annular support member 5 in the frusto-conical portion 2 of the through-cavity of the connector body, when the annular support member 5 is seated in the frusto-conical portion 2 with its side edge 29 in mating contact therewith, the base of the cylindrical recess of the annular support member 5 is always located in a plane perpendicular to the axis 4 of the through-cavity.

From the above description it will be appreciated that the location of the centre of the spherical lens 11 on the axis 4 of the connector body and the alignment of the axes of the diverging lens and the end portion of the optical fibre is obtained in a simple and automatic manner utilising only standard mechanical working tolerances and without the need to provide any micrometric adjusting means.

In fact, no precision is required in the manufacture of the connector components except for the following, all of which are readily obtainable with normal mechanical workshop practice: the provision of the frusto-conical portion 2 of the through-cavity and the side edge 29 of the support member 5 with the same conicalness; coaxial alignment between the frusto-conical 2 and the cylindrical portion 3 of the through-cavity; coaxial alignment of the through-hole 26 of the ferrule 13 with the axis of the cylindrical outer surface of the portion 22' of the ferrule 23; constant thickness throughout its extent of the washer 24 so that its faces are parallel to each other; and the provision of the base of the recess of the annular support member 5 in a plane perpendicular to the axis thereof.

In particular, no provision is required in the diametral and longitudinal dimensions of the annular support member 5 and of course no precision at all is required in the provision of the cylindrical surface of the recess 6.

This is because of the radial elastic deformability of the annular support member. 5 which enables the support member 5 to take up a range of longitudinal positions in the frusto-conical portion 2 of the through-cavity when seated in that portion with its own axis coincident with the axis of the throughcavity to permit the spherical lens to contact the frusto-conical portion 2 and because of the radial clearance between the recess 6 and the diverging lens 7 which prevents continuous contact between the two.

Claims

CLAIMS:

1. An expanded beam optical connector comprising a body provided with a through-cavity having a frustoconical portion, a spherical lens seated in the frusto-conical portion and retained therein by a retention ring engageable with the spherical lens and releasably securable to the body, a support means for a diverging plano-concave lens seated in said frustoconical portion inwardly of the spherical lens such that a plane support surface thereof facing said spherical lens extends radially with respect to the axis of the frusto-conical portion, the support means being elastically deformable radially with respect to the axis of the frusto-conical portion when so seated, a diverging plano-concave lens supported by said support means with a plane face thereof parallel to and facing said plane support surface and with a concave face thereof, which has a smaller radius of curvature than the radius of curvature of the spherical lens, facing the spherical lens, the arrangement being such that on assembly, the spherical lens engages the diverging lens causing the latter to move radially with respect to the axis of the frustoconical portion until the whole of the circular edge of the concave face of the diverging lens contacts the spherical lens and thereby the axis of the diverging lens is coincident with the axis of the frusto-conical portion.

2. An optical connector as claimed in claim 1, wherein the through-cavity includes a cylindrical portion coaxial with the frusto-conical portion for receiving the end portion of an optical fibre.

3. An optical connector as claimed in claim 2, wherein a ferrule is received in said cylindrical portion of the through-cavity with an outer cylindrical surface in contacting engagement with the internal cylindrical surface of the cylindrical portion, said ferrule having a through-passage coaxial with said outer cylindrical surface for supporting said end portion of an optical fibre.

4. An optical connector as claimed in claim 1, 2 or 3, wherein the support means comprises a generally disc-shaped annular support member provided with a frusto-conical side edge surface of the same conicalness as the frusto-conical portion of the through-cavity.

5. An optical connector as claimed in claim 4, wherein said plane support surface is the base of a cylindrical recess provided on the side of the annular support member facing the spherical lens for receiving the diverging lens, the diameter of the recess being greater than the diameter of the diverging lens.

6. An optical connector as claimed in claim 5, when claim 4 is appended to claim 3, wherein a through-hole extends from the base of said recess to the side of the annular support member facing the cylindrical portion of the through-cavity and receives an end portion of said ferrule.

7. An optical connector as claimed in claim 6, wherein said support means for the diverging lens further comprises a flat washer seated on the base of said cylindrical recess, one side of the washer being engaged by the plane face of said diverging lens and the other side of the washer being engaged by a flat radial end surface of said ferrule.

8. An optical connection as claimed in any one of claims 4-7, wherein the radial elastic deformability of the support means is provided by a radially extending discontinuity in the annular support member.

9. An optical connector as claimed in any one of claims 4-7, wherein the radial elastic deformability of the support means is provided by a spiral discontinuity in the annular support member.

10. An optical connector as claimed in claim 6 or 7, wherein the radial elastic deformability of the support means is provided by a plurality of first radial grooves opening at the side edge of the annular support member and a plurality of second radial grooves opening at the recess and through-hole thereof, the grooves being circumferentially spaced apart with the first grooves alternating with the second grooves.

11. An optical connector substantially as bereinbefore described with reference to Figures 1 and 2; 1 and 3; or 1 and 4 of the accompanying drawings.