SU321678A1 - ELECTROOPTICAL DALNOMER - Google Patents

Description

The invention relates to geodetic instruments, namely, electro-electrical range finders, used to measure lines on the ground.

In the known electro-optical range finders operating at fixed modulation frequencies, the phase of the received signal, containing information about the measured distance, is determined by some phase measuring device: a variable delay line of the optical or electric sial.

The variable optical delay lines included in the light path of the sequence, but with a measured distance, have significant dimensions, are complex in design, and most importantly, cause significant losses of the light signal and a change in its polarization, which often makes it difficult to measure.

Electrical delay lines (phase shifters) also have a number of significant drawbacks. High-frequency phase shifters are not very stable and therefore require frequent calibration or a constant (in the process of measurement) monitoring of the delayed optical line, which has the negative qualities noted above. Phase-shifting low-frequency ones require only monitoring the position of the pool in the measurement process, but in this case frequency conversion requires twice the number of thermostatically controlled quartz oscillators.

In addition, electrical phase measurement cannot in principle be carried out in electro-optical range finders with combined receiving and transmitting paths, where the same element is used for both modulation and demodulation

light signal (for example, Kristall electro-optical range finders).

To increase stability and simplify the design in the proposed range finder, the phase shifter is designed as

a new ray of a birefringent plate, installed after the electro-optical cell, which monitors the rotation of the polarization plane of the output nd, from its iromodulated radiation with an angular velocity,

modulation frequency, e.g.

electro-optical cell based on

the Pockels effect is adjustable by a rotating electro-optical field.

The device can be implemented as in

as a system with a combined receiving and transmitting optical paths, and in the form of a system where these paths are separated.

radiation source; 2 - bipolarisation device; 3 - modulating electro-optical cell, 4 modulating frequency generator; 5-turn quarter-wave plate; 6 - reflector; 7 is a luminous flux indicator that records one of the points at which the first derivative of the curve of variation of the output luminous flux varies.

FIG. 2 shows a range finder scheme with separate receiving and transmittings; paths, where 5 is the radiation source; 9 and 5 - crossed floor roids; 10 and 10 - lodulatory and diluting electrolytic cells; 11 - generator of modulating frequencies; 12 - half-wave rotary plate; 13 - reflector; 14 is a luminous flux indicator recording one of the points at which the sign of the first derivative curve of the output luminous flux changes.

The optical elements, the design, the formation, the sending and the light stream, are not shown in the drawings.

The device works as follows.

The light from the radiation source / passes through one of the channels of the bipolarization device and enters the electro-optical cell 3 as a flat-polarized wave. The electro-optical cell to which a modulating voltage is applied at one of the frequencies / m produced by heparatorol: 4. converts the incident voltage planar radiation of light into a circularly polarized light wave. At the same time, the rotational speed C ohm of rotation of the plane of polarization of the light wave leaving cell 3 is equal to or a multiple of the frequency / m of modulating voltage.

Technically, such an electro-optical cell can be made, for example, either in the form of a four-electrode Kerr liquid cell, controlled by a rotating electric zero, or based on an electro-optical crystal, using the double Transverse-Pockels p effect, also controlled by a rotating field.

The luminous flux discharged from cell 3 and modulated in the plane of polarization passes the plate 5, the measured distance is detached from the reflector 6 and, once again passed the measured distapnia. the quarter-wave plate 5 passes for the second time. Thus, having returned from the distance of the light note, it passes as if through an i-wave plate, again enters the electro-electrical cell 3. But it is known that if the light is polarized in a circle, the plate passes into nol-waves, then rotation of the plane of its polarization D1ep sts on the opposite. Consequently, when the light 3 passes backward, if the modulation phases of the outgoing and incoming light signals are equal, the rotation of the polarization plane of the incoming

the luminous flux, i.e., the plane of polarization of the demodulated luminous flux, again becomes the same as before its modulation. The luminous flux returned from distancip in this case is again taken along the previous one; the channel has a bipolar resonance device and does not fall on the indicator 7.

The phase of the light signal coming from the distance in the proposed system does not depend

only on the length of the measured lshpp, but also on the position of the plate 5. When the plate is rotated in a quarter of a wave around the axis of the system, some additional angle each vector of the light wave after a double

the passage of the quarter-wave plate is further rotated by an angle twice as large. Therefore, the phase of the light signal coming from the distortion will be equal (o, where 9 is the variable angle between the main axis of the plate in a quarter of a wave and the plane in which this axis lay at the initial count, a / o is the first phase angle corresponding to the initial count of the phase-rotating element . In this way,

turning a quarter-wave plate, it is possible at any station to ensure that a constant phase difference occurs between the ambulance and the arriving sigpals, recorded by indicator 7 and, counting

angle 9, to find the desired phase difference introduced during rotation of plastia 5, functionalized with a measured distance.

In the case of performing the proposed device with separate receiver channels (Fig. 2), instead of bipolarizer 2, there are used crossed polids 9 and 9 installed in separate channels. Modulation and demodulation are carried out in separate electro-optical cells 10.

and 10, respectively, and for phase rotation, the phase anisotronic nlastipa is used in half-waves 12, since the light passes it only once. The plate can be installed both in the transmitter and in the receiver of the device.

In the case of working with a non-monochromatic radiation source /, plates 5 or 12 should be designed for the effective wavelength of the device. It is also possible

achromatization of these plates.

The described phase shifter has no elements subject to change over time or mismatch, and therefore is quite stable.

PRED MET & A REFERENCE

An electro-optical range finder containing a radiation source combined or divided with a destructive probe demodulator

electro-optical cells, a modulating generator; its pairs of fixed frequencies, a phase-shifting device, 1CP1; ikator of radiation flux and optical elements for forms; 1prosei parcel, reflection and reception

In order to increase stability and simplify the construction, in it the phase shifting device is designed as a novorotnoy birefringent plate, installed after the electro-optical cell, providing a rotational plane of polarization of the output modulated radiation, with an angular velocity determined by the modulation frequency, for example, an electro-optical cell, ground on the Pockels effect and controlled by a rotating electro-optical field.

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