| 摘要 |
<p>A device for measuring the distance to a surface (514) comprising first and second energy detecting means (540, 550) positioned at two different distances (R, R+L) with respect to the surface and energy transmitting means (512) for illuminating said surface with radiation of a first frequency. Phase shift means (570) are connected to one of said detecting means (550) and signal processing means (574, 580, 584) are connected to receive the phase-shifted and the non-shifted signal of the detecting means to produce a resultant output which varies with the ratio therebetween as an indication of the distance to the remote surface.</p> |
