(19)

(11)

EP 0 483 277 A1

(12)

(43) Date of publication: 06.05.1992 Bulletin 1992/19 (21) Application number: 90912085.0 (22) Date of filing: 18.07.1990

(51) International Patent Classification (IPC):  G02B 5/ 18( . ) G03F 7/ 20( . ) G03F 7/ 00( . ) G03H 1/ 04( . ) (86) International application number: PCT/US1990/004028 (87) International publication number: WO 1991/001517 (07.02.1991 Gazette 1991/04)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL SE (30) Priority: 18.07.1989 US 19890381597 (71) Applicant: MASSACHUSETTS INSTITUTE OF TECHNOLOGY Cambridge, MA 02139 (US)	(72) Inventors: ANDERSON, Erik Hyde, c/o Mass. Inst. of Technology Cambridge, MA 02139 (US) SMITH, Henry I. Sudbury, MA 01776 (US) SCHATTENBURG, Mark Lee Somerville, MA 02143 (US) (74) Representative: Deans, Michael John Percy, et al  Lloyd Wise, Tregear & CO. Norman House 105-109 Strand London WC2R OAE London WC2R OAE (GB)