Sira Institute Limited

Ometron Limited

Andrew J Barker

Robert N West

Patricia A West

Rosemary J Hall

Apparatus for measuring the shape of a remote surface (10) comprises a laser (2) whose beam is split into a measuring beam (4) and reference beam (5). The reference beam is passed through a path length modulating mechanism (13, 14) to a datum point (18) while the measuring beam (4) is passed to a point (9) on the remote surface. The reflected beams return along the same paths and are combined at beam splitter (6). The interferometric pattern in the combined beams is analysed to determine the path length of the measuring beam while the transverse coordinates of the point (9) are determined from the position of a beam directing mechanism (12). This process is repeated for a number of points on the surface to measure the shape of the surface (10).

Apparatus for the measurement of surface shape

Test apparatus and method for testing for faults in, for example, transparent sheet material in which two parallel beams of light separated by a distance 'w' are passed through a grating having, for example, light transmitting and absorbing areas separated by a distance 'w', so that as the two beams are scanned across the object and the grating the light output through the grating is generally constant. If, however, there are faults which displace one beam with respect to the other, then the spacing between the beams will change so the light output will vary from the norm. Furthermore, if there is a fault which would cause attenuation of the two beams, then the light output will again vary from the norm.

Optical test apparatus for examining an object

Method and apparatus for detecting holes in sheet material such as tin plate where a beam from a laser is scanned across the sheet by a mirror drum, successive scans being arranged to strike the sheet material from upstream and downstream, and the light passing through a hole in the sheet material is received by a perspex light guide and passed to a photodetector.

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Orpington, United Kingdom

Andrew J Barker