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(11)

EP 0 248 066 A1

(12)

(43) Date of publication: 09.12.1987 Bulletin 1987/50 (21) Application number: 87900183.0 (22) Date of filing: 04.12.1986

(51) International Patent Classification (IPC):  G02B 6/ 255( . ) G02B 6/ 34( . ) G02B 6/ 28( . ) (86) International application number: PCT/GB1986/000740 (87) International publication number: WO 1987/003701 (18.06.1987 Gazette 1987/13)

(84) Designated Contracting States: DE FR NL (30) Priority: 04.12.1985 GB 19850029861 (71) Applicant: THE GENERAL ELECTRIC COMPANY, p.l.c. London W1A 1EH (GB)	(72) Inventors: GEORGIOU, George, Antony South Gate London N14 (GB) BOUCOUVALAS, Anthony, Christos South Harrow Middlesex HA2 8AW (GB) (74) Representative: MacKenzie, Ian Alastair Robert  The General Electric Company, p.l.c. Central Patent Department Wembley Office Hirst Research Center East Lane Wembley Middlesex HA9 7PP Wembley Middlesex HA9 7PP (GB)