Measurement of angles

Abstract

Angles and angular displacements of ultrasonic beams are measured by using a probe to transmit the beam to a point on a surface, particularly the surface of material being subjected to non-destructive examination, from which the beam is reflected to a receiving probe which may or may not be the same device as the transmitting probe. The length of the path traversed by the beam is varied in accordance with a relationship determined as a function of the angular displacement of the beam from an axis normal to the surface, and the time taken to traverse the path is detected. The variation in the length of the path may be effected by adjusting the separation of the transmitting probe from the surface while the probe is being angularly adjusted to vary the angular displacement of the beam, a fixed mirror being provided to return the beam by way of the point to the probe. Alternatively an angularly adjustable transmitting probe may direct the beam to the point and a separate probe which is both axially and angularly adjustable arranged to receive the relfected beam. In a third alternative, the transmitting probe directs the beam to the point by way of an adjustable mirror, a fixed mirror being arranged to return the beam by way of the point and the adjustable mirror to the probe.

Dependencies are inferred from the claim text.