(19)

(11)

EP 0 391 913 A1

(12)

(43) Date of publication: 17.10.1990 Bulletin 1990/42 (21) Application number: 88908284.0 (22) Date of filing: 19.09.1988

(51) International Patent Classification (IPC):  G03F 7/ 038( . ) (86) International application number: PCT/GB1988/000773 (87) International publication number: WO 1990/003601 (05.04.1990 Gazette 1990/08)

(84) Designated Contracting States: AT BE CH DE FR IT LI LU NL SE (71) Applicant: PLESSEY OVERSEAS LIMITED Ilford Essex IG1 4AQ (GB)	(72) Inventors: JONES, Richard, Glyn Kent CT2 7LD (GB) GRIFFITHS, Llyr, Glyndwr Dyfred (GB) BRAMBLEY, David, Robert Northampton NN4 0DD (GB) (74) Representative: Pritchard, Evan  Intellectual Property Department The Plessey Company plc Vicarage Lane Ilford Essex IG1 4AQ Ilford Essex IG1 4AQ (GB)