| 摘要 |
According to this method, a laser beam is conveyed by an optical fibre (16) from a source (14) to a laser head (18) located opposite the surface (11) to be checked. The latter sends a reflected beam which is returned in the optical fibre (16). Beams (Fi, Fr) sampled from the incident laser beam and from the reflected laser beam are converted into electrical signals (Si, Sr) which are sent to a threshold-type differential voltmeter (30). The measurement variations of the voltmeter (30) with respect to a predetermined threshold make it possible to detect geometrical characteristics of the surface to be checked. Application to checking the positioning of a sleeve in a tube and to checking the internal diameter of a tube. <IMAGE>
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