GB2346733A

GB2346733A - Making a light-outputting device

Info

Publication number: GB2346733A
Application number: GB9827538A
Authority: GB
Inventors: William John Baillie-Hamilton
Original assignee: Fibre Optic Lamp Co Ltd
Current assignee: Fibre Optic Lamp Co Ltd
Priority date: 1998-12-15
Filing date: 1998-12-15
Publication date: 2000-08-16
Also published as: GB9827538D0; WO2000036338A1

Abstract

A method of fabricating a light outputting device made up of a containment for housing an element for emitting light; an axially extending light conducting element having an axial length substantially greater than its width transverse the axis; the light conducting element being aligned axially with the element for emitting light by means of the containment or an extension thereof; the light conducting element having a light input region such as an end face whereby light generated by the element for emitting light is caused to pass axially into the light conducting element by way of its associated light input region, the method being characterised by the steps of: providing the light conducting element in the form of a longitudinal member 12 with a first longitudinal axis A and a given cross section, such as a circular cross section having a given diameter and an end face forming a light input region; providing a hollow member 15 with a second longitudinal axis one end having a similar outside configuration to that of the light conducting element and having an annular end comparable in cross section to the light input region of the conducting element; causing the one end of the hollow member to be contiguously juxtaposed with the end face of the light conducting element with the first and second longitudinal axis to be in line with one another forming a butt joint by fusing or otherwise gas tightly joining the juxtaposed ends of the hollow member and the light conducting element; so as to provide in combination the hollow member and the light conducting element as an elongate member of substantially constant cross section; locating the element for emitting light 20 within the hollow member in predetermined alignment with the end face of the light conducting element; deforming a part of the hollow member so as to form together with the light input region of the light conducting element the containment for the element for emitting light; sealing the deformed part of the hollow member to cause the containment to form a gas tight enclosure for the element emitting light.

Description

2346733 LIGHT EMITTING DEVICE This invention relates to a light emitting

device. In particular it is concerned with a light emitting device where light emitted from a source thereof is efficiently gathered for transmission along a light conducting element. Such devices have a wide range of applications and some impose design limitations arising from at least one of the following: small size, generated heat, containment, manufacturing problems, vandalism, lamp replacement, linkage to light using or transmitting devices.

In our co-pending International Application PCT/GB97/01121 there is described amongst other aspects of the invention:

A light outputting device comprising: a containment for housing an element for emitting light; at least one axially extending light conducting element having an axial length substantially greater than its width transverse the axis; the light conducting element being aligned axially with the element for emitting light by means of the containment or an extension thereof; the, or each, light conducting element having a light input region such as an end face whereby light generated by the element for emitting light is caused to pass axially into the, or each, light conducting element by way of its associated light input region. The containment or an extension thereof serves to locate the element for emitting light closer to the light input region of the, or each, light conducting element than to the major part of the containment remote from the light input region or regions. Typically the light outputting device incorporates a reflector located relative to the element for emitting light and the, or at least one, light conducting element so as to reflect light from the element for emitting light axially into the, or at least one, light conducting element by way of its associated light input region.

The international Application goes on to disclose a method of fabricating such a device is characterised by the steps of:

providing the light conducting element in the form of a longitudinal member with end faces and an outer surface apart from the end faces; locating around the light conducting element a sleeve member of greeter length than the light conducting element with its first end of the light conducting element at or near one end of the sleeve so as to leave a length of sleeve projecting beyond 2 the opposite end of the light conducting element to the first end; the opposite end of the light conducting element to the first end forming, at least in part, the light input region; causing the sleeve member to be contiguously juxtaposed with the outer surface of the light conducting element; locating the element for emitting light in the length of sleeve projecting beyond the opposite end; deforming the length of sleeve so as to form together with the light input region of the light conducting element the containment for the element for emitting light; and Sealing the deformed length of the tube to cause the containment to form a gas tight enclosure for the element for emitting light.

According to a first aspect of the present invention there is provided a method of fabricating a light outputting device made up of a containment for housing an element for emitting light; an axially extending light conducting element having an axial length substantially greater than its width transverse the axis; the light conducting element being aligned axially with the element for emitting light by means of the containment or an extension thereof; the light conducting element having a light input region such as an end face whereby light generated by the element for emitting light is caused to pass axially into the light conducting element by way of its associated light input region, the method being characterised by the steps of:

I providing the light conducting element in the form of a longitudinal member with a first longitudinal axis and a given cross section, such as a circular cross section having a given diameter and an end face forming a light input region; 2 providing a hollow member with a second longitudinal axis one end having a similar outside configuration to that of the light conducting element and having an an annular end comparable in cross section to the light input region of the conducting element; 3 causing the one end of the hollow member to be contiguously juxtaposed with the end face of the light conducting element with the first and second longitudinal axis to be in line with one another 4 forming a butt joint by fusing or otherwise gas tightly joining the juxtaposed ends of the hollow member and the light conducting element; so as to provide in combination the hollow member and the light conducting element as an elongate member of substantially constant cross section; 3 locating the element for emitting light within the hollow member in predetermined alignment with the end face of the light conducting element; 6 deforming a part of the hollow member so as to form together with the light input region of the light conducting element the containment for the element for emitting light; 7 sealing the deformed part of the hollow member to cause the containment to form a gas tight enclosure for the element emitting light.

According to a first preferred version of the first aspect of the present invention wherein the step of locating the element for emitting light within the hollow member includes locating a mirror for reflecting light generated by the element to provide for the mirror to be enclosed with the element prior to the deforming an sealing steps.

LS According to a second aspect of the present invention there is provided a light outputting device manufactures by the method of the first aspect or of the first preferred version thereof.

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings of light emitting devices of which:

Figure 1 is a side view and Figure 2 a plan view of a first embodiment of a light emitting device; Figure 3 is a plan view showing in more detail a component referred to in connection with Figures 1 and 2; Figure 4, 5 and 6 shows further embodiments of a light emitting device incorporating a mirror reflector of which Figure 4 shows a plane mirror; Figure 5 shows a parabolic mirror; and Figure 6 shows a cylindrical mirror.

4 FIGURES 1, 2 AND 3 Light emitting device 11 includes a solid light conducting member 12 (about 25 mm long) of quartz with a circular cross section of outside diameter D (of about 10mm) and having a longitudinal axis A. The member 12 has an end face 13 of which the central region forms a light input region R.

The device 11 further includes a hollow tube 15 which prior to a deformation step during fabrication of the device 11 is a tube about 25 mm long) of circular cross section with longitudinal axis of symmetry A2 as shown over undeformed length C (Figure 1). This circular section has an outside diameter D" identical to that of the member 12. During fabrication of the device the undeformed tube is presented to end face 13 of the member 12 so that axis A, A2 are in line and the ends of the two components are fused as a butt joint on section E.

Once the butt joining is completed a tungsten element 20 in the form shown in Figure 3 with coiled section 21 and conductors 22, 23 is introduced into the hollow tube 15 and located with coiled filament 21 at a predetermined distance from the end face 13. Ends 22A, 23A of, respectively, conductors 22, 23 are attached to molybdenum foil strips, respectively 22B, 23B, which are in turn connected to, respectively, contact pins 22C, 23C by means of which the filament is energised.

Once these various components are located within, or in the case of pins 22C, 23C partially projecting from, hollow tube 15 then the unit is subjected to heating and deformation to provide the form of the device 11 as shown in Figure 1 and 2. As a result the filament 21 is enclosed within a gas tight containment 25 at a closely toleranced location relative to the end face 13 of light conducting member 12.

The device 11 can be used in a range of applications which will determine whether the containment 25 is evacuated or contains an inert gas or gases.

FIGURES 4, 5 AND 6 I As shown in Figures I and 2 the device 11 contains a tungsten coil filament 21 alone in containment 25. However applications in which the device 11 is used can benefit from the use of a reflector or mirror which is installed at the time of fabricating the device at the step of locating the light emitting device in the as yet undeformed tube.

Figure 4 shows in outline a light emitting device 41 similar in form and function to that of device 11 in Figures 1 and 2 saving for the provision of a plane mirror 42 transverse longitudinal axis A2 and facing end face 43 of light conducting member 44. The mirror 42 is shown sideways on spaced from filament 45 but viewed from the front the mirror 42 is of circular shape. The mirror 42 is of tungsten with a surface of high reflectivity. The plane mirror 42 forms a virtual image of the filament 45 as far behind the mirror on axis A2 as the filament 45 is in front of the mirror. The combined effects of low mirror reflectivity and the distance of the virtual image from end face 43 of the light conducting member 44 will result in only a small fraction of the light from the rear side of the filament 45 reaching back end 47 of containment 48.

Figure 5A (plan view), 5B (side view) show in outline a light emitting device 51 similar to device 11 of Figures 1 and 2 saving for the provision of a parabolic mirror 52 transverse longitudinal axis A2 and facing towards end face 53 of light conducting member 54. The mirror 52 is appropriately spaced from end face 53.

The use of a parabolic mirror 52 provides significant optical advantages and in particular the normal incidence of the reflected light onto the end face 53 of the light conducting member 44. This could give a theoretical 50% improvement in transmitted light. Filament 55 (corresponding in form and function to filament 21 of Figuresl to 3 described above) is located at the optical focus of the parabolic mirror 52.

Figure 6A (plan view), 6B (side view) show in outline a light emitting device 61 similar to device 11 of Figures land 2 saving for the provision of a cylindrical trough mirror 62 transverse longitudinal axis A2 and facing towards end face 63 of light conducting member 64. The mirror 62 is appropriately spaced from end face 63. The use of a cylindrical mirror 62 acts to redirect light on to filament 65 when 6 the filament 65 is placed at the centre of curvature of the mirror 62. However it is envisaged that the filament 65 could usefully be off set from the centre of curvature so that in effect a real image of the filament generated by the mirror 62 is located symmetrically with filament 65 on opposite sides of the axis A2 and at the same distance from face 63.

The light emitting device of the present invention can incorporate most available means of light generation and in particular gas discharge and bright arc where a sold is vapourised within the enclosure to give a bright arc with subsequent vapour condensation when the power supply is removed.

The present invention also envisages the use of coatings for the devices to govern optical behaviour and also for the use of doped silicon substrates to promote colour or other requirements.

I 7

Claims

I A method of fabricating a light outputting device made up of a containment for housing an element for emitting light; an axially extending light conducting element having an axial length substantially greater than its width transverse the axis; the light conducting element being aligned axially with the element for emitting light by means of the containment or an extension thereof; the light conducting element having a light input region such as an end face whereby light generated by the element for emitting light is caused to pass axially into the light conducting element by way of its associated light input region, the method being characterised by the steps of:

I providing the light conducting element in the form of a longitudinal member with a first longitudinal axis and a given cross section, such as a circular cross section having a given diameter and an end face forming a light input region; 2 providing a hollow member with a second longitudinal axis one end having a similar outside configuration to that of the light conducting element and having an annular end comparable in cross section to the light input region of the conducting element; 3 causing the one end of the hollow member to be contiguously juxtaposed with the end face of the light conducting element with the first and second longitudinal axis to be in line with one another 4 forming a butt joint by fusing or otherwise gas tightly joining the juxtaposed ends of the hollow member and the light conducting element; so as to provide in combination the hollow member and the light conducting element as an elongate member of substantially constant cross section; 5 locating the element for emitting light within the hollow member in predetermined alignment with the end face of the light conducting element; 6 deforming a part of the hollow member so as to form together with the light input region of the light conducting element the containment for the element for emitting light; 7 sealing the deformed part of the hollow member to cause the containment to form a gas tight enclosure for the element emitting light.

8 2 A method as claimed in Claim 1 wherein the step of locating the element for emitting light within the hollow member includes locating a mirror for reflecting light generated by the element to provide for the mirror to be enclosed with the element prior to the deforming an sealing steps. 3 A light outputting device manufactured by the method of any preceding claim. 4 A method of fabricating a light outputting device as hereinbefore described with reference to the accompanying drawings. 5 A light outputting device as hereinbefore described with reference to the accompanying drawings.