| 摘要 |
To measure the phase shift of a modulation signal on a light beam, a light path change-over switch alternately connects a reference light beam, passing through a known path length, and the reflection light beam of the target object to a photoreceiver in order to eliminate its influences. Since the two light beams are never available at the same time at the receiver end, it is known to compare the phase angle first of a signal derived from the reference light beam and then of a signal derived from the reflection light beam in each case with the phase angle of a reference signal which is continuously generated inside the device and to determine from the two results of the comparisons the phase shift between the signals of interest. This requires three highly accurate crystal-controlled oscillators. To achieve a simpler but very accurate range finder with good resolution, a circuit arrangement is provided as dynamic memory which, when the reference light beam is present, begins to generate a periodic zero-phase signal which is coupled to the reference signal with respect to phase and still generates this zero-phase signal when instead of the reference light beam, the reflection light beam is received so that the phase shift of a signal derived from the reflection light beam with respect to the zero-phase signal can be measured by a digital phase measuring device with high accuracy and high resolution and from this the range of the target object can be determined. <IMAGE>
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