| 摘要 |
An interferometric probe for measuring the distance to the surface of an object has a light source (11) for example a super-luminescent diode, which produces a coherent light beam preferably such as to produce a speckle pattern in light reflected from the object. An interferometer includes a beam splitter which produces a reference beam directed towards a reference diffracting reflector (5) and a measuring beam directed towards the surface (8) of the object to be measured. The diffracting reflector produces a plurality of diffraction orders each of which are combined with portions of the light reflected from the surface (8) to produce interference which is detected by a detector system (9) having a number of individual detectors equal to the number of diffracted orders of the reference beam which are used. Use of the diffracting reflector enables more of the light reflected from the object to be used in the detector and improves signal to noise ratio. A further enhancement of signal to noise ratio can be produced by the addition of a second detector system which uses the reflected part of the combined beam from the beam splitter and is used differentially to improve the signal to noise ratio. |
