DE1950404U - TWO-BEAM INTERFEROMETER. - Google Patents

Description

RA.292W9-3.6.66

Γ June 3, 196β

Professor Br ₉ -Ingo Ulrich Grigull vmß. => lM «Hans Eottenkolber

Zweistralil ^ Int i

The invention relates to a two-beam interferometer with. Einriohttingen ztas splitting of the light beam emanating from a light source into a measuring beam w & a an equal beam and devices . the measuring beam to. measured object nand the Tergleichsstrahl di => _p rectly to lead to a Beöbachttmgsstelle wherein the partial beams by means anfgespreiat Spreiseinriohtungen and IMD by siae optical divider plate ο "* Samaalsysteme the like at the Beöbaehtwigsstelle zusairaengeführt werdenο

Such iDekannte interferometer with zivei separate light = for working Naeh \ SWEi grnmdlegenden Prinaipiejfto In the one principle runs through the light each of the "two Lieht = · routes NWL ° in a Riehtaago in each of Mehtwege a" won the other various breimpnanktlos © consequence ton

Lenses or mirrors is arranged? w3xd out, however, the liehtlinian extend optically symmetrical and the M®ßstrahl tareh the au observing en subject _P during Naeh the other of the Liehtquelle ύοά coming beam at the Seiler plate w separated & ä of a cable beam by means of a hintex * the ku Tbeoibaehteiiden subject lying mirror again duroh the object reflected tand the comparison =

another mirror is reflected when both parts of the rope are combined in the splitter plate to form the beam to be observed "

All these known two-beam interferometer require almost absolutely precise optical symmetry wan Tergleiehs "and measuring radiant ρ to interference at all to eraiCdgliciien only because due to the need of optical symmetry of both T s eil radiating the removal of successive einaujiastieren" = your equipment components γοη of the Diarchführwag the measurement depends on the necessary master distance ₉ do you see extraordinary difficulties with dea? Installation of this type of device, && @ can only be trained by highly qualified specialists ο To simplify the adjustment, as a rule all of the devices, which are relatively far apart, are mounted on a common heavy base plate _p so that the known devices can be used more accurately = plisiert isa aaechanisMien Aufbaiig, wiihaiidlioh in outer operation

nvaig and difficult * This has led to the ₉ that later = feresizmeßyerfahrenj, despite the knowledge of their advantageous tea & ugungsmögliehlichkeit at a grease »look! tos to =

h.aben found acceptance ₉ Sonder in the Eeg @ i used only in research institutes iverdenc in which entspre · = accordingly wired-staff to adjust waae B <5UE ± ®wmg is available stir "

Bs is the abandoning of the invention smgrnnae lying © _9, such a two-beam _v öasia that no hoehqualifialerten scientifically trained workers is "l2aterferometer = κ" create dae ₉ ia seiaer handling simplified necessary siad tmd sai ^ oime the major modification in Messumgan
arbitrary measuring ranges are feasible. "Through the invention" a device is to be created that also works in the
practical establishments, 2, B = for test procedures in the

The basic idea of the fulfillment goes towards ₉ the ¥ © rgleiighsstrahl in a most dire way with ü% =
Leaves less optical influence on the surface =
lead imagine au gleiehsstrahl _p during the measuring beam imabhäagig ¥ © m fer ° in the time required to scan the object shape up praises and is deflected toward the zn observed object "Both cable rays are only

c 4 _m

loarz Yor merging at the BeoTbaohtttngssteile ami that necessary for the generation of interference

According to the invention, this is achieved _{9 in} that the device uses a laser as the light source _p elae, see got ©

send item in a wide _? the size of the beam adapted to the object _p s © wi <§ eiae sm.

See well-known facility snam collecting this Bünöele of the observatory and a® facility aiming at aiii gen of the comparison beam in the area of the beam collection · = punlctss des gesenaelteii MeSstraliles nand isffimittelibar "^ © r the Seilerplatte staa merging ύοά Meiielis = waä ¥ © rgl @ yqt of the observatory »

With de-M erfiiidiüijgsgessässii device it is possible to put all files in a small common device. If a one: iehtiaag is provided _P raa the measuring beam bms the device hij ^ausrnführeng where egg instructions = · gen provided. are ₉ um. dea measuring beam after influencing diarch the sm measuring object to di® lying in the device ©! aachti> i2i.gsst@lle stariicksmileiakejae

The device svm Znarrücklenken the _MeBstrahles kaöii eiß behind the eyelet to let the GegesstaM li © g © ader hollow

mirror be »This concave mirror sum return the beam canoe on the same side as a device to collect a © s measuring beam ras · the Seilerplatte be formed at the observation point _o It can also be seen a sweiter concave mirror% ^5> © jf rope! *, which as a device stm collecting d @ e MeBstrsh · les T © r Seiler plate on the Beoteelatiusigsstelle In place of the concave mirror can but aueh an iF © a Sanaaellinse and flat mirrors come _s the ^ taken to send G-UBJECT-Nazi Saeaellinse and plane mirror IRDO Likewise, the optical Lead dents themselves be the subject of the ¹ measurement, the facility shme backwards = Iten öes MeSstraliles kSEiisa swei standing next to each other genlsreeht de _p reflsktierenöep flat surface a seia _e The g can τοη the laser serving as a light source: e © hue Aufspre sting "to siir Seiissfplatte i? or · the Observatory

Both;? But © rf iaduagsgesässeH device germ also Las he j, which means mim splitting the light beam and the means aim spreading of the measuring beam wn the lying at the monitoring center Spreiseinrichtung for d © n fergleiehsstrahlo OCE SgffiMelsiiirislat-ang for AESN MeBstrslil UNFI DER Seiler plate & im. SHsaiiEeafilliFea ä & r Seilstrahlea räiaalieli separated ssin »The inventive two-stream, - Int erf © rossetei? © Esaoglicht as © a feelielbige LätM arrangement öes & er-e / ses and measurements ub @ T pralstieeh

Mgs distances _? The fact that this means that considerable work can be done *, oils that can be carried out by normally trained specialists are “necessary”, the wet device can also be manufactured with a significantly lower weight than the known devices ^ in particular, because the heavy round plate can only be dispensed with in the case of feelcasrntea G devices drasch a Inaserj whose characteristics is, the company © hw @ lt Lean times have been known for! ?, s © change is a © besomders ψQT some exemplary training of all öerätesp by the advantages of the light emitted by the laser light beam for DI® dual beam <= Interference measurement can only be used »

The invention is described below with reference to the drawings Embodiments explained in more detail.

The drawings 1 to 11 show schematically the beam guidance in interferometers according to the invention.

One of the possible embodiments of the interferometer according to the invention is shown in FIG. From a laser 1, for example a continuously radiating one Gas laser, an extremely parallel and coherent light beam 2 with a small diameter knife (approx. 5 mm) directed at the divider plate 3. The Hache one

Accordingly, the ρ divider plate only needs to be about 0.4 cm. The splitter plate 3 splits the light beam 2 into the partial beams 4 and 5. The partial beam 4 is made by a short « focal length lens 6 spread open. The focal plane of this Lens 6 coincides with the focal plane of lens 8, the diameter of which limits the model size. The small plane mirror JL is a deflecting mirror, which is preferably in which is introduced near the focal plane of the lens 6. The parallel light beam 4 ″ passes through the model 9 and is collected again by the lens 10. The splitter plate 11 is at or near the focal plane of the Lens 10. The partial beam 5 goes unspread from the splitter plate 3 to the deflection mirror 12, the diameter of which is not

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much larger than the diameter of the unspread laser beam needs to be. The partial beam 5 is finally from an objective 13, for example. a lens so spread open that the focal plane of this lens 13 coincides again with the focal plane of the lens 10. So that the intensities of the two partial beams 4 and 5 in the image plane of the one to be examined Body 9 are about the same size, the focal length of the lens 13 must be matched accordingly. At the The splitter plate 11 becomes the two partial beams 4 and 5 again united so that interference is now possible. I'm lens 14 can be used in addition to the lens 10 to depict the model 9. By simply twisting the divider plate 11 or the mirrors 7 and 12, or the divider plate 3, a lull field or a strip specification can be achieved, depending on whether the focal point of the objective 13 coincides with the focal point of the lens 10 or not. It should be noted that that the focal planes must coincide. All mirrors 7, 12 and the divider plates 3, 11 are either ~ in or near the focal plane or in the laser beam arranged and accordingly their dimensions can be small being. Because of the long coherence length of the laser beam (several kilometers), the partial beams 4 and 5 can be very traverse optical path lengths of different sizes.

The adjustment of the interferometer is described with reference to FIG. 1, for the arrangements given below

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the same considerations apply. Adjustment is extremely easy. It can be accomplished, for example, as follows be «you leave all lenses and objectives 8, 10, 14» 6, 13) initially continued. Due to the extreme parallelism of the laser beam, it is possible to twist this beam and shifting the mirrors 7, 12 and the divider plates 3, 11 to pre-adjust. The beam 2 is through the Divider plate 3 divided and again by the divider plate 11 merged. The two partial beams 4 and 5 are therefore not yet spread open. The two partial beams must don't even lie in one plane. It is sufficient if they are in the same direction after the union on the divider plate 11 have and are brought to cover. This condition can be achieved by rotating the mirror 12 and the divider plate to be met. Now the lenses and objectives are introduced. You just have to make sure that the focal planes of the short focal length objectives 6, 13 coincide with the focal planes of the lenses 8, 10. The in Fig. The specified ee'ctangular shape of the beam path is not necessary, obliquely angled square shapes are also possible.

If the focal plane of the lens 10 does not exactly coincide with the focal plane of the objective 13, concentric ones are obtained Interference fringes. By moving the objective 13, these concentric interference rings can be lost to be brought. There, nn the two focal planes coincide

men. Now you can only by tilting one of the Ceiler plates 11 a zero field or a stripe specification (parallel Stripes at an adjustable angle), depending on whether the focal points of the lens 10 and the objective 13 coincide or not.

Further embodiments are shown with reference to the following ligures, the basic statements which above Hg, 1 cannot be changed.

lig 2 again shows an arrangement with a parallel beam path, which is made by the lens 8 and 10. In contrast to Mg. 1, the long coherence length is here of the laser light very heavily used. The mirror 12 has been exchanged for the divider plate 3 and vice versa. By swapping the mirrors, splitter plates and the laser there are still many similar ones Combinations possible.

lig. 3 shows an arrangement with the concave mirrors 8 ¹ and 10 ¹ , which take the place of the lenses 8 and 10. 'Pig. 3 is an example of an arrangement in which the deflecting mirrors 7 and 12 of the Pig. 1 do not apply. However, this arrangement has astigmatic errors, which is why the arrangement is generally verified

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3? Ig. 4 prefer, in which again small deflecting mirrors 7 and 12 are used. Even with the concave mirror arrangement numerous variants are possible *

I ¹ Ig. 5 shows an arrangement with a convergent beam path. The body 9 to be examined can be in the entering, in and exiting (coincidence arrangement) or in the exiting beam, or the concave mirror 8 ¹ itself can be the body to be examined. Such an arrangement is with the Maeh-Zehnder interferometer not möglieh "Instead of the concave mirror 8, a lens ¹ of course may occur, In

Pig. 6 shows a coincidence arrangement in which the rays are exactly reflected in themselves

7 is constructed similarly to the Michelson interferometer; the body to be examined can be the plane mirror 9 or the lens 8.

ig. 8 is a microscope arrangement, the objective 6 designs an image of the body to be examined 9 which is viewed with the eyepiece H. Even if see the body to be examined 9 in an ever-

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sion liquid is and the partial jet 4 from For this reason, the optical path length differs from that of the partial beam 5, interference occurs, which occurs at a Mach-Zehnder arrangement is not possible.

The principle of the invention can also be used for an interferometric determination of absolute Braeh numbers. For this purpose, for example, is suitable. the arrangement according to fig * 9 «The test body 9 is a chamber which is shown in elevation (wedge-shaped) in FIG. 9A. The partial beam 4 can pass through this chamber 9 twice. * mirrors 7 and 12 »The medium to be examined is introduced into this chamber 9. The partial beam 4 is deflected proportionally to the refractive index of the medium to be examined. The resulting interference fringes are a measure of the absolute refractive index when the system is evacuated The refractive indices of gases could already be determined interferometrically, the interferometric determination of the refractive index of other media against air or vacuum was previously not possible due to the low coherence length of the light sources used. Of course, mirrors, dividing plates and the laser can also be interchanged in this arrangement.

Fig. 9 is also an example of the use of a prism instead of two consecutive mirrors. All

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in general it can be said that one places two one after the other arranged deflecting mirror, which bends the light beam at about 180 °, a totally reflective or mirrored one Can use prism. ! This also applies, for example, to the arrangements according to ^ ig. 2 and 7, "where the mirrors 7 and 12 can be replaced by a prism.

asymmetrical arrangements are listed here, which are possible, but generally cannot be carried out.

The two-beam interferometer according to the invention can be adapted to the requirements of the lall to be examined. The arrangements with a parallel beam path according to FIGS. 1 to 4 are preferably used when the body to be examined has a greater length through which the light beam must traverse. Because of the simple adjustment of the interferometer according to the invention, this length can be considerable (a few meters). These arrangements are therefore always used when the occurring refractive index gradients are very small, for example with small temperature gradients, small concentration gradients, small density gradients, etc. The arrangements according to FIGS. 5, 6, 7 are preferably used for examining lenses and concave mirrors. Especially the arrangement according to S ¹ Ig. 7 is suitable for examining flat surfaces. Likewise can

transparent bodies for refractive index inhomogeneities, "resp. to be checked for uniformity of their thicknesses · To examine density fields, yi / elche when seeing rapidly moving Projectiles occur, the arrangement according to FIG. 6 is preferably used, in which the light beam twice the to examining body passes through. This arrangement is also suitable for examining detonation waves. Pig. 8th shows a microscope arrangement. By shifting the focal planes, E.g. the two objectives 6 and 13 from Pig »8, one obtains concentric hinge, which is a measure of the distance of the two focal planes. This means that the new device is also suitable for length measurement.

Two of the possible arrangements of the simplified two-beam interferometer are in Pig. IO and 11 shown.

Yom laser 1, for example a continuously radiating one Gas laser, the laser beam 22 is emitted and by a short focal length lens "(lens) 26 spread open. In or in the vicinity of the focal plane of this lens 26, a divider plate 23 is arranged, which has only small dimensions needs to have. One partial beam 24 passes twice through the body to be examined. Shortly in Palle The Pig coincidence arrangement is sufficient for models. 10, in which only one concave mirror 28 'is used.

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The arrangement according to FIG. 11 is recommended for all long models. With the aid of the objective (lens) 28, one can obtain one Parallel beam, which must have at least the dimensions of the body to be examined 29 "a mirror 30", in Fig. 11 a plane mirror, but also one for inhomogeneities can be the reflective surface to be examined, preferably reflects the parallel beam in himself.

The body 29 to be examined can also be the concave mirror 28 ', the objective (lens) 28 or the mirror 30' itself being.

The second partial beam 25 is preferably reflected in itself by a concave mirror 27 * with small dimensions. Instead of the concave mirror 27 ', a combination of lens and mirror similar to that in Mg · 11 for the partial beam can also be used 24 shown step. An objective (lens) 34 images the body 29 to be examined.

The adjustment of the described arrangements is completely uncomplicated, since only two parts have to be moved: The concave mirror 28 * or the mirror 30 ° for rough adjustment, the concave mirror 27 'for fine adjustment * with the concave mirror 27 'can also be a zero field or a strip specification can be set. The given strips can be straight

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lines in any direction or concentric binge, both at any distance. The generation -predetermined concentric Rings was with the previously known interferometers, e.g. the Maeh-Zehnder device, not possible.

The position of the splitter plate 23 is only decisive for the intensity distribution of the two partial beams 24 and 25. Me divider plate can e.g. be a partially reflective plane-parallel glass plate or a combination of two on the common hypotenuse surface of partially reflecting prisms. As a laser preferably linearly polarized light emits, in order to avoid unwanted multiple reflections on the splitter plate and mirror, one becomes the level of the optical Let the axes of the entire arrangement and the plane of oscillation of light coincide.

The elements after 3 ig. 10 and 11 let look to two or summarize three assemblies (in the figures by dashed Lines indicated). The first assembly contains the laser 1, the spreading lens 26, the splitter plate 25, the Concave mirror 27 ', and the lens 34. The second assembly contains the objective (lens) 28, the third assembly the mirror 30 ", as shown in Fig. 2" Instead the second and third assembly can only be a single assembly, as shown in üg. 10 is shown with

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the concave mirror 28 'are used. This setup is not mobile and can well match the local conditions and adapted to the body to be examined.

- Protection claims * ~

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Claims (1)

1. Two-beam interferometer with devices for splitting the light beam emanating from a light source into a measuring beam and a reference beam and devices to guide the measuring beam through the object to be measured and the reference beam directly to an observation point, the partial beams being spread out by means of spreading devices a divider plate or the like. and optical collection systems are brought together at the observation point, characterized by a laser (1) as the light source, a device (6, 8, 8 ') known per se for spreading the measuring beam (4) in front of the object to be measured into a wide, the size of the beam to be measured, as well as a known device (10, 10 ', 8, 8 ^j ) for collecting this bundle in front of the observation point and a device (13) for spreading the comparison beam (5) in the area the beam collecting point of the collected measuring beam and immediately in front of the splitter plate (11) for merging the measuring and comparison beam in front of the observation point. 2. Two-beam interferometer according to claim 1, characterized in that that all parts in one common device • 19- are housed and a facility is provided, to guide the measuring beam (4) out of the device, and devices (7, 12, 8 ·, 10 ') are provided to the Measuring beam (4), after being influenced by the object to be measured, to the observation point in the device to steer back. 3 * two-beam interferometer according to claim 2, characterized in that the device for deflecting the measuring beam (4) back is a concave mirror (8 ¹ ) located behind the object to be measured. 4. Two-beam interferometer according to claim 3 »characterized by that a second concave mirror (10 ') the device for collecting the measuring beam in front of the Ceiler plate (11) is (Mg. 3). 5. Two-beam interferometer according to claim 3, characterized in that that the concave mirror (8 ') for returning the measuring beam (4) at the same time as a device for. Collecting the measuring beam (4) in front of the splitter plate (11) is formed (Mg. 5, 6). 6 «two-beam interferometer according to claim 2, characterized in that that the device for redirecting the -20- Measuring beam - (4) is a double prism (7, 12) (Mg. 9). 7 · Two-beam interferometer according to one of Claims 2 to 6, characterized in that the comparison beam (5) from the laser (1) straight to the divider plate (11) is (Pig. 3, 7, 9). 8. Two-beam interferometer according to claim 1, characterized in that the laser (1) _} the device (3) for splitting the light beam (2) and the device (6) for spreading the measuring beam from the spreading device (13) located at the observation point ) for the comparison beam and the splitter plate (11) for merging the partial beams is spatially separated (! ig. 1, 4, 8). 9. Two-beam interferometer according to claim 1, characterized in that that at a short distance from the laser (1) a spreading device (26) for the entire laser beam (22) and in the area of its focal point a splitter plate (25) is arranged in such a way that the measuring beam (24) is straight to the object to be observed (29) and after reflection at right angles to the observation point is deflected, while the comparison beam to a Reflector (27 ') deflected at right angles - and after reflection straight through to the observatory. -21- «21- 10. Two-beam interferometer according to claim 9> characterized in that between the baffle plate (23) and the as Reflection device (30 ") designed in a plane mirror a collecting device (8) for parallel guidance for the measuring beam of the measuring beam (24) is arranged at the measuring point.