(19)

(11)

EP 0 419 583 A1

(12)

(43) Date of publication: 03.04.1991 Bulletin 1991/14 (21) Application number: 89910879.0 (22) Date of filing: 21.09.1989

(51) International Patent Classification (IPC):  G01J 1/ 02( . ) G01J 5/ 12( . ) G01J 1/ 44( . ) G01K 7/ 00( . ) (86) International application number: PCT/GB1989/001111 (87) International publication number: WO 1990/003556 (05.04.1990 Gazette 1990/08)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 28.09.1988 GB 19880022693 (71) Applicant: PLESSEY OVERSEAS LIMITED Ilford Essex IG1 4AQ (GB)	(72) Inventors: CARTER, Christopher, Frederick Northampton NN4 0LJ (GB) PORTER, Stephen, George Northampton NN7 4SG (GB) (74) Representative: Allen, Derek  The Plessey Company plc Intellectual Property Department Vicarage Lane Ilford Essex, IG1 4AQ Ilford Essex, IG1 4AQ (GB)