| 摘要 |
1282272 Measuring distances photo-electrically SIRA INSTITUTE 6 Aug 1969 [6 May 1968] 21379/68 Heading G1A [Also in Division G2] In an apparatus for measuring the thickness of a sheet, a pattern of light, UV or IR radiation is scanned across the surfaces of the sheet and reflected radiation is directed through masks (20, 30) on to photo-dectors (24, 28) to produce respective alternating signals, the phase difference between the signals produced from the two photo-detectors being indicative of the sheet thickness. The pattern is produced by a rotating radial grating 38 positioned adjacent a light source 34, the light from which is divided and directed by a system of mirrors to the two sides of the sheet of material. To measure the thickness of a microcircuit on a substrate, three source/detector combinations may be employed, one monitoring the surface of the circuit while the other two monitor the surface of the substrate Fig.4 (not shown). In a further embodiment Fig. 5 (not shown), a single pattern is formed on both the microcircuit and substrate by a grating, and a further grating (48) is used as a mask. A mirror (50) directs light derived from the microcircuit on to a first photo-cell, while light from the substrate is received directly on a second photo-cell. Alternatively, as shown in Fig. 6, light reflected from the substrate and microcircuit is focussed on to a line of three slits of which only the inner slit receives light reflected from the circuit. Three light guides 73-75 are used to direct the light to multipliers 76-78 whose outputs are combined using two phase-sensitive rectifiers and fed to a meter calibrated directly in thickness units. |
