| 摘要 |
<p>Method and apparatus for measuring variations in the distance between a point of reference and the surface of an object, in which method light emitted from a substantially monochromatic light source is reflected from the surface of the body and in an interferometer is combined with a reference beam with a known path and from the same light source and by means of light sensitive means is converted into an electric signal, which is converted into an output signal in digitized signal processing means comprising means for a continuous processing of the first derivative of the curve of the electric signal, which output signal is an expression for the said variation in distance. In order in a simple way to determine the sign or polarity of variation of the distance without recuding the wide field of measuring obtained by the method the length of the path of the reference beam is substantially momentarily changed with a value corresponding to 1/4 wavelength of the emitted light, the digitzed signal processing means being adapted to establish whether a change in sign takes place with respect to a mean value for said signal, the same or the opposite sign being applied to the registered variation of the distance if the electrical signal is positive or negative after the momentary change, providing the momentary change is an increase of the length of the path and the opposite application of the sign, if the change is a decrease of the length of the path of the reference beam. </p> |
