DE1807237A1 - Electromagnetic distance measuring device - Google Patents

Description

Dipl.-Phys. Georg Amon, June 6, 1968

Jena

Electromagnetic distance measuring device

The invention relates to an electromagnetic distance measuring device with a transmitter, which is an electromagnetic Wave emits and a receiver, which the modulated wave after reflection at a distant target arranged reflector receives, in an electrical demodulated Signal converts and this via an amplifier and coupling means for the self-excitation of a frequency dependent on the distance Modulation signal fed to a modulator. The distance measuring device is used both in geodesy and in precision measurement technology applicable.

In the case of such distance measuring devices, the phase positions marked for determining the distance are used a modulation oscillation that is self-excited as a result of the feedback of the received signal to the modulator generated. The existence of this modulation oscillation is a sufficient sign for the fulfillment the excellent phase conditions and their frequency is related to a certain reproducible relationship to the distance to be measured. The total phase shift of the signal is from the distance to be measured and from electronic signal path in the distance measuring device dependent.

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To determine the exact distance, however, the influence of the electronic path can be determined or eliminated. This could be achieved in that each distance measuring device working in this way is calibrated by measuring precisely known distances and the deviations of the actual from the target values of the distance measurement are determined and recorded. However, this requires electronics in the distance measuring device, the behavior of which is exactly reproducible is. However, such electronics are generally not available, especially for precise measurements.

To avoid this inconvenience, the invention takes a different approach. According to the invention by the electronic path caused phase shifts by a switchable. Short-circuit path eliminated, which the signal a to run through the shortened path to be measured, and a phase-rotating device for the demodulated Signal. The phase-rotating device advantageously supplements the phase shifts over the shortened and the entire Signal path to integer multiples of 360 °. A frequency meter is advantageously provided to measure the frequency of the self-excitation modulation whose help phase shifts can be checked and whose frequency display is a measure of the distance to be measured is.

The invention is explained in more detail using an exemplary embodiment shown in the schematic drawing.

0 93 f 77 121

A light bundle with the axis beam 1 emitted by a light source L passes a modulator M ■ · ■■, as well as a transmitting objective O ₃ and hits a distant reflector R-, which is parallel to itself through a receiving objective Og on a detector D reflected. The signal demodulated by the detector D is, after amplification in an amplifier V, fed back to the modulator M as a control signal. The amplifier V has an automatic amplitude control system which always adjusts to an overall gain factor of "one". A phase shifter F is also connected to the detector D and the amplifier V via electrical lines e. The phase shifter F and on the one hand the modulator M and on the other hand a frequency meter Z are also connected via electrical lines e. A reflector R _R , viewed in the direction of light, is arranged directly in front of the transmitting objective Og and behind the receiving objective Og in the beam path of the distance measuring device to form an optical short-circuit path j3 _T k.

.,. _{: i} The setting of the phase shifter P can be done manually or automatically. If the reflector R is in the position shown by the solid lines, the signal runs over the short-circuit path k and a self-extinguishing frequency f ^ is established. In the position of the reflector R _K indicated by the broken lines, the signal runs over the distance to be measured, it builds up

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in self-excitement an oscillation that modulates _{the light with the frequency f ß.} The frequencies f _E and f _K are generally not the same. With the aid of the phase shifter F, however, an additional phase shift is generated for both paths, so that the frequencies n fg and f _K corresponding to these paths are equal to one another. This state is reached when the total phase shifts on both paths are an integral multiple of 360 °. The phase shift component caused only by the distance to be measured is therefore also 360 ° or an integral multiple thereof and the distance s to be measured results from the relationship

where c is the speed of light, f «f« «= f _K and η is an integer.

To determine the identity of the frequencies fj, and f ^ and the frequency meter is used to measure their amount.; *, which, for the sake of simplicity, is in units of length can be calibrated.

The modulation of the light teas also have a directly modulated li'ohtquelle, -. "A B, a SaÄe diode done, '' In this case, would be a separate modulator accounts ,, Certain Modulatorarteii the doppelt® modulation canoe ®nt2t. © h & n _t . Se that in ä & m © l @ fcfronlscla @ a fell the except ö @ ® f! Ia @ ®ascfii © li®r ff an i @ feo Aasteli® u <b &

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Reflector's Rg can be used to guide the Kurzachlußweg «äue, h Use a fiber optic cable «The carrier of the modulation oscillation can be any suitable electromagnetic radiation

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Claims (3)

Claims 1. Electromagnetic distance measuring device with a transmitter that emits a modulated electromagnetic wave and a receiver that receives the modulated wave after reflection at a reflector located in the distant target, converts it into an electrical demodulated signal and this via an amplifier miä coupling means for self-excitation of a relative its frequency dependent on the distance modulation signal to a modulator, characterized by a switchable short-circuit path ,, - which allows the signal to travel a path shortened by the distance to be measured and a phase-rotating device for the demodulated signal. 2. Distance measuring device according to claim 1, characterized in that that the phase rotating device the phase shifts Completed over the shortened and the entire signal path to integer multiples of 360 ° 3. Distance measuring device according to claim 1 or 2, characterized by a frequency meter, - 6 - 2574 ¹ G 33 ^ 0 00 9817/1211 * bad original