(19)

(11)

EP 0 256 074 A1

(12)

(43) Date of publication: 24.02.1988 Bulletin 1988/08 (21) Application number: 87901071.0 (22) Date of filing: 29.01.1987

(51) International Patent Classification (IPC):  G01J 1/ 02( . ) G02B 27/ 42( . ) H01L 31/ 0232( . ) H01L 31/ 108( . ) G01J 1/ 04( . ) H01L 31/ 0216( . ) H01L 31/ 0236( . ) (86) International application number: PCT/GB1987/000060 (87) International publication number: WO 1987/004861 (13.08.1987 Gazette 1987/18)

(84) Designated Contracting States: DE FR GB NL (30) Priority: 01.02.1986 GB 19860002525 (71) Applicant: PA Consulting Services Limited London SW1X 7LE (GB)	(72) Inventor: SAWYERS, Craig Hertfordshire (GB) (74) Representative: Nash, Keith Wilfrid, et al  KEITH W. NASH & Co. Pearl Assurance House 90-92 Regent Street Cambridge CB2 1DP Cambridge CB2 1DP (GB)