DE2012946A1 - Device for determining the distance of an object in relation to a defined position by means of radiation emitted by a transmitter - Google Patents

Description

PHN.

_j _ 3954

Registration from “March 17, 1970

"Device for determining the distance of an object in relation to a defined position by means of radiation emitted by a transmitter! ¹ .

The invention relates to a device for determining the distance of an object with respect to a defined position by means of a radiation emitted by a transmitter, which after the interaction with the object is fed to a receiver.

Such a device is known. In the well-known Device receives radiation in the form of pulses sent out and the point in time of the pulses supplied to the receiver with the point in time of the transmitted pulses compared. From those times and the speed the radiation in the medium in which the radiation is propagates, the distance to be measured can be derived »The disadvantage of the known device is that the Points in time should be measured extremely precisely if the

00984071444

BATH ORIGINAL

Distance should be measured very precisely. An intricate apparatus is indispensable in this case.

The invention aims to overcome this disadvantage. It is characterized in that the frequencies of the Radiation emitted by the transmitter fluctuates around a mean value, which radiation fluctuates around a mean value, which Radiation is fed to an interferometer that has one of the two arms that is mechanically fixed to the object Includes reflector.

It is beneficial to have a polarized one

Apply radiation beam emitting transmitter and in one of the arms of the interferometer take a (n + 1) \ / h plate (n = integer). Two sub-bundles, polarized orthogonally to one another, are then directed at the receiver so that precise measurements are made possible. Thanks to the modulation of the polarization state, precise measurements are possible, since the distance is derived from the polarization state of the radiation emerging from the interferometer and fed to the receiver. This polarization state is not very sensitive to disturbances.

According to an advantageous feature of the invention two bundles of radiation are emitted, the frequency difference of which fluctuates around a mean value. This enables Processing of the electrical signals generated in the receiver to use a simpler electrical circuit.

The invention is explained in more detail with reference to the drawing, for example, which shows a first embodiment in FIG.

BAD ORlGiNAl

009840 / UU ^WNAL

-3- PHN. 395h

management form of a distance meter according to the invention and in Figure 2 illustrates a second embodiment.

According to Fig. 1, this occurs from the radiation source

radiation beam originating from the isotropic partial mirror 3 of an interferometer. The partial bundle reflected on the partial mirror is reflected by a retrodirective element 11, which consists of the lens k and the concave mirror 5 arranged in the focal plane of the lens. The retro-directional element 11 is located at a relatively short distance from the partial mirror 2.,

The partial bundle let through by the partial mirror is reflected on a retrodirective element 12, which from the lens 6 and the concave mirror arranged in their focal plane .7 consists. The retro-directive element 12 is located at a relatively large distance from the partial mirror 3 and is rigidly connected to the object (not shown), its distance from a defined point should be measured. This point on level 2 is the same at an optical distance from the partial mirror 3 the optical distance of the element 11 from the partial mirror.

That reflected on the retro-productive element 11

Bundle wd, approx. from the partial mirror 3 partially transmitted to the radiation-sensitive element 8; the most retro-productive Element 12 is reflected beam from the partial mirror 3 partially to the radiation-sensitive element 8 is reflected.

At the place of the element 8 the radiation, amplitude as a function of time t by:

009840 / UU BAD ORIGINAL

PHN. 395k

A = sin iC t + sin ü & (t- V ) = 2
being represented. Here, w ^ / 2 ^ C denotes the light frequency and L the time during which the partial bundle going to the retroductive element is between level 2 and element 12, i.e.: t = 2z / c, if ζ is the distance between level 2 and the element 12, and c is the speed of the
Propagation of radiation are.

The electrical signal B generated in element 8,

which is proportional to the square of the amplitude is proportional to:

cos toT / 2, i.e. to: 1 + cos lo'l.

If the angular frequency of the radiation emitted by the radiation source 1 is changed, e.g. according to the relationship LO = to (1 + f sin-At), the variable part B _{1 of} the signal B is formed as follows:

cos 2Jf ~ (1 + f sin / Lt),
Xo

where X _n = - ■

The number of Nu11 passages N of this cos function during a period T = Z ^ / fL · is: N = 4 ~ f

If one puts N in the one attached to the element Counter 9, one can calculate the distance ζ given a known value of f.

In one embodiment: A = 0.5 / µm,

Δ to 7

f = - = 0.1 and N = 1.6.10. One calculates ζ = 5 m.

Instead of a sinusoidal change in the angular frequency, a sawtooth change can also be made.

009840/1444

-5- PHN. 395 ^

lead, e.g. according to the relationship:

; ^ = ^ g (i + ■ f ψϊ ~. ■ .- ■ - ■

The variable part B _{1 of} the signal B is then formed as follows:

_cos ζΧψ. (τ ₊ f |).

-\O

During the time t = T of the sawtooth period one obtains: N = - = r-f

passages.

The device according to FIG. 2 is that according to FIG.

very similar. Corresponding individual parts have the same reference numbers in both figures. The radiation source 1 emits linearly polarized radiation, which is split into two sub-bundles 1 by the isotropic partial mirror of the interferometer. A Ji / k plate 21 is attached in the short arm of the interferometer. The angle between the optical axis of the Jt / h plate and the plane of polarization of the incident partial beam is k3 . After reflection, ara the retro-productive element ti; the partial bundle in the fcurzett arm passes through the ^ i / 4 plate 21 again. Overall, this partial bundle has traversed J (^ / Z plate. = Dole Polar! satiouEseVbene des in the kttrzeat arm; partly mirror 3 zttrrückendein; T @ ilbünd! els dLst daheir about ^ & ^ in relation to: on dii.ee des; hiHilatEfendieiiai Temlbündels; gedireht * Έ && Po level; this to uetEödÄti ^ ea element ΐ2 "r / eflefctiefrtem 'ämd & vt don't see« Efas; van · dem! dls © trogen- Teilspmegel % let Teilb & Me?!. B ^ vo? N · diem Tz & t & o, & ± & efc ± ± vi & m Element Tl Is havfc a B®1 arris at Aomsefee-HEe,. D ^ £ e 2 ». Taer" de-Si ant Part |>iieg; el r; e ~ TeilbüMdiels; Bu yg & m amm ! -Etrodrireifeti ^ ren Eleiaenit; f2f -

!. »■ & * IM.ef eilb ^ Sntdlel BL- TüESdi, Bu dhasr / ciilamffeiE eiuie Jl / k

£ U ι 29Α6

Plate 28, the main direction of which forms an angle of 45 ° with the direction of polarization of each of the partial bundles. The J / k plate 28 converts the two linearly polarized partial bundles into a right and left-handed polarized radiation bundle. When combined, these radiation bundles result in a linearly or almost linearly polarized radiation bundle, the azimuth of which depends on the mutual phase of the circularly polarized radiation bundles, or in other words, a shift of 12 is expressed in the form of a rotation of the plane of polarization. This linearly polarized radiation beam hits the isotropic partial mirror 22, which transmits part of the linearly polarized radiation beam and reflects a veined part. The transmitted part passes the polarizer 23, the plane of polarization of which includes an angle O ^ with a selected X-axis, so that the amplitude of the radiation beam striking the radiation-sensitive element 25 is determined by:

cos ( to t - 0-i) + cos I '(u> t - ^) + Q λ ι

can be displayed so that the electrical signal generated in element 25:

1 + cos (tat - 2 / ) is.

The reflected part passes the polarizer Zk _t whose plane of polarization includes an angle ^ with the mentioned X-axis. The amplitude of the radiation beam striking the radiation-sensitive element 27 can be through;

cos (uJ t - f 2

+ cos j {u> t -Ί?) + / ₂ I

and thus the generated in the radiation-sensitive element 27,

00984Q / U44

electrical signal through:

1 + cos (ω t can be represented.

If one chooses 4λ - O and / ₂ = k $ , the signal generated in element 25 can be given by:

1 + cos u>L>
and the signal generated in element 27 by:

1 + sin u » L
indicate. .

Instead of one signal as in the device according to FIG. T, one then has two signals, the variable parts of which have a phase difference of 90 °. If the angular frequency IP is changed in the manner described with reference to the device according to FIG. 1, a number 1 of zero crossings N occurs, which is twice greater than the number that occurs in the device mentioned. These zero crossings are processed in the counter 26.

The position of the plane of polarization of the linearly polarized radiation beam emerging from the A / ij plate 28, which position depends on the mutual phase of the linearly polarized bundles hitting the Λ. / 4 plate 28, can also be determined in the same way as in the older one Patent application (PHN. 290 * 0 is described. Then the series connection of two - ^ / h plates with the same orientation must be attached between the X / k plate and the partial mirror 22, between which an electro-optical crystal is arranged with an orientation direction that differs from ^ 5

009840/1444

with which the Λ / 4 plate has, which crystal is supplied with an appropriate electrical alternating voltage. Relatively slow changes in the position of the plane of polarization of the linearly polarized radiation beam emerging from the X / k plate 28 can then be conveniently measured.

An advantage of the embodiment according to FIG. 2 is, that absorption losses in one of the arms of the interferometer do not affect the azimuth of the polarization ellipse of the exercise the radiation beam concerned.

In the device according to FIG. 2, the radiation source 1 can be replaced by a radiation source which emits circularly polarized radiation. The X./h plate 28 must then be omitted.

You can in the device of Fig. 1 the

Replace radiation source 1 with a radiation source that has radiation bundles of two circular frequencies U> ₁ and lü _? emits which radiation beams have the same polarization state. At the point of element 8, the amplitude of the radiation can be determined by:

A = 2 sin U ^ ₁ (t- ^/ ? / 2) cos to, ΊΪ / 2. + 2
can be specified.

The electrical signal B generated in the "element 8" is the mean value over time of the square of the amplitude of the Radiation proportional.

One calculates:

B = (1 + cosAa ^) (1 + cos <Λ> _ο f) + (i-cos ^ lo ^) (1-cos u> = 2 (1 + m cosui T?),

009840 / UU

Here 2u> _q = W ^ ₊ U> ₂ , äU> = l >> ^ - u> ₂ and m = cos ^ W | C

It should be noted that element 8, while fast, is AWJ in with respect to the cutoff frequency of the element is large.

If you change the angular frequency of the radiation source emitted radiation beam according to the Relationship:

AiAJ = u> _o f sinJTLt,
so will

B / 2 = 1 + cos («■> f Tj- siiUi.t) cos LO " C = 1 + m ₁ cos ί- ° <-.

The modulation depth m ₁ changes periodically.

Not the zero crossings of cos U> f but those of cos

If ■ "■ '■ -.'

(it? f ~ sinJLt) are counted.

You can in the device of Fig. 2 the

Replace radiation source 1 with a radiation source which emits polarized radiation beams with two circular frequencies tu «and ^ ₂ . The planes of polarization of both radiation beams can be the same or can be perpendicular to one another.

If the angle / ^ = 0 and the angle / ^ = are selected, the electrical signal generated in element 25 can be

1 + Gös ^^ i cos a? .. ^ and the signal generated in element 27 through i

<£ O

Again, 2i ^ = (^ +

2 0123 4 6

You have two amplitude-modulated signals whose amplitude-modulated parts have a phase difference of 90 have »The number of zero crossings of the amplitude-modulated Parts that are processed in the counter 26 is twice the number in the apparatus of FIG. 1 with two radiation sources.

You can in the device of Fig. 1 the

Replace radiation source 1 with two radiation sources with mutually perpendicular planes of polarization. If an analyzer is arranged in the radiation path between the isotropic partial mirror 3 and the radiation-sensitive element 8, the plane of polarization of which makes an angle α with that of the radiation source of the radiation with the angular frequency U) , the electrical signal B generated in the element 8 can be generated by:

2 ν Sy ^ 2 / s VO C i

B = 1 + cos WL cos / + cos VO C sin <f

can be specified. If 6 = 0 is: B = 1 + cos 6χΛ. ^u , at σ ~ 90

B = 1 + cos LO u and at f = 45 °: B = 1 + cos - - Uosai

° is: B = 1 cs Again is 2 U) = ά> + ^ ₂ undyja) = U? "

009846/1444

Claims (3)

2012 9Λ6 PATENTAN LANGUAGE: C 1 , J Device for determining the distance of a Object in relation to a defined position by means of a Radiation emitted by a transmitter, which is fed to a receiver after interaction with the object, characterized in that the frequency of the transmitted by the transmitter Radiation fluctuates around a mean value, which radiation is fed to an interferometer, which is in one of the two Arms a reflector that is mechanically fixed to the object contains. 2. Device according to claim 1, characterized in that that the radiation emitted by the transmitter is polarized and in one of the arms of the interferometer an (n + 1) τ · plate (n = whole number) is included. 3. Device according to claim 1 or 2, characterized in that that the transmitter sends out two radiation beams whose frequency difference fluctuates around a mean value. ^. "Device according to claim 2 or 3» characterized in that that the transmitter emits circularly polarized radiation. 009840 / UU