GB2117131A

GB2117131A - Fibre optic light sources

Info

Publication number: GB2117131A
Application number: GB08306213A
Authority: GB
Inventors: Oswald James Houston; Alexander Taylor
Original assignee: Thales Optronics Ltd
Current assignee: Thales Optronics Ltd
Priority date: 1982-03-18
Filing date: 1983-03-07
Publication date: 1983-10-05
Also published as: GB2117131B; GB8306213D0

Abstract

A fibre optic light source (10) comprises a housing (23) (not shown) within which is located a light generator having a lamp and reflector assembly (14) and an integrating rod arrangement (15). A fibre optic light guide (19) is releasably secured to housing (23) to receive light from the arrangement (15) and the other end of the guide (19) terminates in a transillumination probe (20). To eliminate transmission along the guide (19) of infrared radiation emitted by the lamp (11) the reflector (12) has a dichroic filter coating (12A) and a dichroic-coated filter (17) is provided at the output end of the rod arrangement (15). <IMAGE>

Description

SPECIFICATION Fibre optic light sources This invention relates to fibre optic light sources.

Fibre optic light sources have been commercially available for some years intended for multipurpose use primarily in the medical field.

More recently these light sources have been used as transilluminators, as a diagnostic aid, but have not proved totally acceptable because of the hazard of skin burning. Various reports on the dangers concerned have been published in PEDIATRICS for example, Vol. 63, No. 3 p. 422; Vol. 64, No. 4 p. 843 and also p. 958; and Vol. 66, No. 1 p. 1 28.

It is an object of the present invention to provide a fibre optic light source adapted for use as a transilluminator in which the danger of patient skin burning, in use, is minimised.

According to the present invention there is provided a fibre optic light source comprising a housing within which is located a light generator having a lamp and reflector assembly and an integrating rod arrangement, and to which housing there is releasably securable one end of a fibre optic light guide for receiving light from said integrating rod arrangement the other end of said guide terminating in a transillumination probe, wherein the light generator comprises a plurality of dichroic filters arranged such that transmission of infrared radiation from the lamp to the light guide is substantially eliminated.

Preferably the reflector of the lamp and reflector assembly incorporates a first of said plurality of dichroic filters and said integrating rod arrangement incorporates a second of said plurality of dichroic filters.

Preferably also the integrating rod of said arrangement has a diameter substantially greater than the previous standard design diameter required for the lamp and reflector assembly.

Conveniently the diameter oversizing of the integrating rod is of the order of 80%.

Preferably also the diameter of the fibre optic guide equals that of the integrating rod whilst the transillumination probe is substantially greater in diameter than the guide. Conveniently the diameter oversizing of the probe with respect to the guide is of the order of 400%.

Preferably also the transillumination probe is replaceably fitted to the guide and has a substantially planar end face.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 schematically illustrates the principal components of the light source; Fig. 2 illustrates the light generator; and Fig. 3 illustrates the fibre optic guide.

As is shown in Fig. 1 the light source 10 comprises a lamp 11 mounted in an elliptical reflector 12 the operative surface 1 2A of which has a dichroic coating such that infrared radiation emitted by the lamp 11 is transmitted through the coating on surface 1 2A and only light within the visible waveband is reflected from surface 12A. An integrating rod 1 5 is located with its end 15A at the focal plane of the assembly 1 4 formed by the lamp 11 and reflector 12. A dichroic filter 17 is located at the other end 15B of rod 15, the coated surface of filter 17 being adjacent end 1 5B. A fibre optic light guide 1 9 extends from the filter 1 7 and terminates at a transillumination probe 20.

Fig. 2 shows in greater detail the light generator 22 of the source 10 as comprising a housing 23 within which there is mounted the assembly 14 and the rod 1 5 by means of a support structure 24 (only parts of which are illustrated in the interests of clarity). End 15B of rod 15 is a fit in the bore 25 of the tubular holder 26 the body of which is enlarged at one end to form a socket 27 for receiving the light guide 1 9.

This enlargement forms a shoulder on the exterior of holder 26 whereby it is mounted in an aperture formed in wall 28 of the housing 23 and secured in position by a lock nut 31. Located between bore 25 and socket 27 there is a counter bore 32 of intermediate diameter and filter 1 7 is fitted to this counter bore 32 and secured in position by a circlip 33. A radially-extending locking bolt 35 is provided in the enlarged end of holder 26 for securing the end of guide 1 9 when fitted to socket 27.

The guide 19 is illustrated in greater detail in Fig. 3 as comprising a central bundle 40 of optical fibres the end faces 40A, 40B of which are worked so as to be optically flat, the greater part of the length of the bundle 40 being surrounded by flexible armouring 41 which in turn is externally clad with a silicon rubber sheath 42. At its end 1 9A the guide 19 has a connector 43 which is a push-fit in socket 27 (Fig. 2) whilst end 1 9B of guide 19 terminates at a connector 44 for threadedly receiving the transilluminator probe 20. The probe 20, which is shown fitted to the guide 1 9 in Fig. 1, comprises a unitary block of plastics material such as perspex and the end face 20A is substantially planar.

By way of example the lamp 11 may be a 15 volt, 1 50 watt tungsten-halogen lamp, rod 15 may be 8 mm in diameter, bundle 40 also 8 mm in diameter and probe 20 of 18 mm in diameter.

With components of these values a substantially heat-free light emission is achieved at face 20A and probe 20 due to the combined effects of the two dichroic filters 1 2A, 1 7. The characteristics of the coating at 1 2A have already been described and it will be noted that the coating which effectively produces the filtering effect of filter 1 7 requires to be infrared reflecting and/or absorbing whilst being transmissive to light in the visible waveband. This is conveniently achieved by a Barr and Stroud VW2 filter. The lamp 11 is preferably energised at less than its rated voltage in order to enhance the usual life of the lamp and since filter 1 7 is secured by the circlip 33 and has its coated surface facing inwardly of the housing 23 the generator 22 needs little or no maintenance and is relatively tamper-proof. Accordingly the source 10 is adapted to function as a transilluminator which is free of the known disadvantage of skin burning.

Heating of the interior of the housing 23 is prevented by a motorised fan (not shown).

Claims

1. A fibre optic light source comprising a housing within which is located a light generator having a lamp and reflector assembly and an integrating rod arrangement, and to which housing there is releasably securable one end of a fibre optic light guide for receiving light from said integrating rod arrangement, the other end of said guide terminating in a transillumination probe, wherein the light generator comprises a plurality of dichoric filters arranged such that transmission of infrared radiation from the lamp to the light guide is substantially eliminated.

2. A fibre optic light source as claimed in claim 1, wherein the reflector of the lamp and reflector assembly incorporates a first of said plurality of dichroic filters and said integrating rod arrangement incorporates a second of said plurality of dichroic filters.

3. A fibre optic light source as claimed in either preceding claim, wherein the diameter of the fibre optic guide equals that of the integrating rod whilst the transillumination probe is substantially greater in diameter than the guide.

4. A fibre optic light source as claimed in claim 3, wherein the diameter oversizing of the probe with respect to the guide is of the order of 400%.

5. A fibre optic light source as claimed in any preceding claim, wherein the transillumination probe is replaceably fitted to the guide and has a substantially planar end face.

6. A fibre optic light source as claimed in claim 1, and substantially as hereinbefore described with reference to the accompanying drawing.