DE2028573A1 - Light cell with multiple beams - Google Patents

Description

04 P3 D

CAEY -INSIHDMENiBS, Monrovia, California, USA

Light cell with multiple beam paths ^-

Priority: June 11, 1969 United States of America US Serial Number 832 102

Summary:

The invention relates to the use of mirrors and a Light source for exciting a sample, which are arranged with respect to a zone of the sample that the light from the light source Running through a sample in this zone many times increases the intensity of the Raman light emission from the sample considerably to increase.

Introduction:

The present invention relates generally to the field of Spectroscopy, and in particular the increase in the illumination of a sample in spectroscopic systems, the present being Invention particularly applicable to Raman spectrometers is.

The Raman effect was discovered in 1928 by O.V. Raman observed and interpreted while he was investigating Rayleigh scattering, the light source being formed by sunlight that was collected through a telescope and then filtered

100 * 10/1 * 3 *

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to obtain a substantially monochrome tinge. A prism monochromator was used and the Raman lines were visually observed. The fragile "' ^J instruments were cumbersome and had a number of disadvantages. Stable, high-intensity light sources were not readily available. Some instruments allowed a good one Distinguished from Rayleigh scattering of the exciting light. Photographic recordings were made which were usually extremely time consuming: some recordings were required. The preparation of the sample was critical because of the sensitivity of the instruments to scattering of the exciting light. The working procedures were often laborious and complicated.

With new developments in the field of instrument ropes Technology in recent years has reduced the problems encountered with the earlier instruments; it however, certain problems persist, particularly the difficulty of finding a sufficiently intense one Generate Raman radiation.

The Raman effect consists in a molecular scattering of the light. Other types of scatter usually occur at the same time on. The scattering, which is based on the recoil of photons colliding with molecules in a homogeneous medium, is known as Rayleigh scattering, where the energy of the photons is changed to a very small extent by the collisions, so that very small amounts in Rayleigh scattering Changes in wavelength occur. The scattering that occurs on particles in a liquid or in a gas are suspended is known as Tyndall scattering in which no significant change in wavelength occurs. Similarly, it is caused by scratches or other irregularities in or on the cell walls likewise a © scattering without

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Generated wavelength change.

Raman scattering is completely different from Rayleigh and Tyndall scattering. In the Raman process, photons of excited radiation interact with molecules in such a way that a quantized exchange of energy takes place. The energy and thus the frequency of the photons is increased or decreased by such magnitudes that correspond to "certain differences between the energy levels of the molecule. It is assumed, for example, that the frequency of the excitation radiation f ^ and the frequency corresponding to a" certain difference of the Energy levels of the molecule participating in the interaction, f _Q ". When such an interaction occurs, the photon emitted by the molecule has a different energy corresponding to a different frequency f" the frequency f .. of the incident photon changed to a frequency f "of the scattered photon, which can be expressed by the following equation:

f ₂ =

The positive sign is used when the incident photon absorbs energy from the molecule, while the negative sign is used when the incident photon loses energy to the molecule. This expression shows that the spectral properties of the molecule can be observed in terms of the differences (£ q) between the frequencies (f «) of the various Raman lines and the frequency (fj) of the excitation radiation are quantized, these frequency differences have a series of discrete values that characterize the various Raman lines.The Raman lines are not fixed frequencies, but they form frequency shifts based on the nature of the molecule.

■ 10-9810 / 1931

In general, the frequency differences are the Raman lines the same as the frequencies of the lines in the infrared absorption or emission spectrum of the same molecule occur. The Raman spectrum, however, depends on the polarizability rather than the polarization of the molecules, and es is therefore subject to various quantum mechanical selection rules. The effects usually complement each other in the examinations the molecular structure. Also the behavior of the Raman lines, that are excited by polarized light provides valuable additional information about the structure.

TJm to obtain Raman spectra becomes a gaseous, liquid or solid sample irradiated with monochromatic light. The light scattered by the sample is fed to a monochromator, which separates the Raman light from the light resulting from Rayleigh and Tyndall scattering. The Raman light is then fed to a photometer and its intensity is recorded as a function of the wavelength, to make a Raman spectrum. It has been found that the intensity of the light emitted by the Rayleigh and Tyndall scattering of the exciting light arises, in intensity many hundreds of times greater than the Raman light is causing problems in the separation of Raman light and the detection of Raman light at low intensities.

Summary of the Invention;

A primary object of the present invention is to provide an apparatus capable of producing as much Raman light as possible can be collected from a very small sample, with a laser being used for excitation in order to determine the intensity of the Raman light to increase significantly in order to separate it from other radiations and its reliable detection with the help a photodetector to facilitate. This is done according to the

109810/1939

Invention achieved in that a device is provided where the excitation radiation passes through the small many times Trial runs, the arrangement is made so that the Excitation radiation may be temporarily trapped or is held captive so that it can hold the sample or the optical System by which the trapping effect is achieved do not fade can.

In its basic structure, the invention consists in an arrangement which contains two longitudinally separated concave mirrors which define two conjugate image points which lie between the mirrors, the points being a relatively small longitudinal distance in relation to the longitudinal distance of the mirrors along the axis through them Have points, this axis running through the sample space which can accommodate a sample (gas or liquid); the arrangement further includes means for directing a beam of light, such as laser light, so close to at least one of these points that the beam is repeatedly reflected off and between the mirrors so that it repeatedly travels through the sample space. The mirror surfaces can expediently comprise ellipsoids, the image points being at their focal points; on the other hand, the mirror surfaces can also contain spherical sections, which are easier and cheaper to manufacture. If the pixels are relatively close to each other, the reflections continue, with only a slight amplification occurs with each pass; for example , a gain of 1.15 per pass gives up to about 15 passes "before the beam becomes so large that the collection efficiency is significantly reduced. It has recently been found that with a gain of 1.035 on each pass or Passing through and taking into account the reflection losses, the inclination of the input beam and the aberrations, a cell can be designed in which, depending on the bandwidth of the monochromator

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and the optics between the sample and the monochromator ■ - '■■ ·''■'"<> · ' at least 50 to 100 passes can be used.-The ^: ■■■ - ■■ path of a central beam of the beam converges'' ^c typically in the case of successive reflections against a line that is determined by the effective system focal points.

Furthermore, according to the invention, a device is to be provided in order to divert the light transmitted from the sample space to collect, which contains a gap having a reduced image, which is so that the two ends of the Image are in the vicinity of the conjugate image points; in this way these points are brought close to the Ends of the gap mapped so that outwardly emitted light in an effective manner of the light collecting and receiving device is fed.

Furthermore, such an arrangement is sought that the Distance between mirrors is adjustable to accommodate differences in the indices of refraction of different liquids to be able to compensate in the sample space so that the reflected beam repeats through the conjugate points and so that it can repeatedly run through the liquid sample. With such a setting, the effect of Changes in the excitation light wavelength are taken into account.

The invention also aims to provide a sample cell, which is so arranged between the mirrors in relation to the conjugate points that these conjugate points lying outside the cell; such a cell may contain two pairs of windows, one pair having a common center of curvature in one of the conjugate points, and the other pair have a common center of curvature in the has another conjugate point, which is below

18Ü1Ö / 1 %%% '''

should be explained in detail. When using a In such a sample cell it is not necessary to adjust the mirror spacing in order to obtain different refractive indices Compensate for sample fluids.

Furthermore, the aim of the present invention is to to arrange the sample space between the mirrors in relation to the conjugate pixels so that the conjugate pixels lie in the sample room. With such an arrangement, the efficiency is increased by the fact that the whole Light passes through the sample, and around, which is below To be explained, the greatest percentage of radiation should be collected on each particular pass, the Brennoder Pixels lie in the cell windows of the sample or something within the sample,

Additional facilities are expediently provided the positions of the mirrors, the cell for the liquid sample and the monochromator that absorbs the light are mutually exclusive set that errors are switched off.

In the following, the invention will be explained in more detail with reference to preferred embodiments shown in the drawing will. In the drawing show:

Pig. 1 one partly in elevation, partly true to length and partly schematically illustrated embodiment of the present Invention;

Pig. 2 is an illustration showing a sample holder in which the image points are located in the liquid sample;

Fig. 3 is a view of a sample holder in which the pixels lie outside the liquid sample;

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Fig. 4 is a perspective view showing the invention embodying system is shown; and

5-7 modified embodiments of the present invention.

Description of preferred embodiments;

In Fig. 1, a first and a second concave reflector is with 10 and 11, respectively, and these two reflectors are along, a line 14 »which passes through the two conjugate pixels 13 and 13, defined by the respective reflectors 10 and 13, are spaced from one another in the longitudinal direction. The reflectors can advantageously contain ellipsoidal mirrors, in which case the points are located 12 and 13 at the focal points of these ellipsoids.

Alternatively, one or both of the reflectors may contain spherical sections which are lighter and cheaper are to be produced, and in this case the points 12 and 13 form conjugate image points which define the locations of the centers of curvature of the spherical sections Equations are associated with that. should be specified below. ·

The points 12 and 13 have a "relatively small longitudinal distance in relation to the longitudinal distance of the reflectors along the line 14. A _{sample consisting of a fluid such as a liquid or a gas}} can occupy the space 15 between the points 12 and 13 completely "or partially so that the light, which consists in particular of laser light, and which is captured so that it repeatedly passes through the points 12 and 13 and the space 15, can repeatedly pass through the sample, so that from the sample in the lateral direction 16 a Raman light emission is emitted with a relatively high intensity. The dashed lines 17

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2023573

■ ■■ ^t9 ~, I · '. ·

represent schematically a position of a sample container, this position is used to increase the emitted Raman light intensity characterized in that the spatial volume of the Sample within and across the main length of the space 15 between points 12 and 13. It can be either or it can be both Points 12 and 13 inside the sample zone or outside the Sample zone.

Fig. 2 shows an example in which points 12 and 13 in the sample zone 150, in the cell 151 »lie.

According to the invention, means are also provided to radiate a beam of excitation radiation, such as light, so close to one of the conjugate pixels that the beam is repeatedly reflected by and between the reflectors 10 and 11 so that it is repeated through the space 15 runs. As an example, a laser is shown at 18 which radiates a coherent light beam 19 through an optical system 20 (or for example a lens or lenses) which acts to direct the beam 19 onto one of the image points, for example the point 13 , focussed, which is farthest from the optical system 20. The direction of the ray 19 lies with respect to the line or the axis 14- in a pointed Vin kmk £ * £ ^ outside the axis the other image point, for example point 12 in Fig. 1, runs. The ray 22 is reflected on the mirror 10 at 23 so that it passes as ray 24 through the point 13, and it is shown on the mirror 11 at 25 as Beam 26 reflects. This latter beam passes through point 12 and is reflected by mirror 10. As can be seen from the figure, repeated reflections occur, with the light beam transmitting towards the line 14, so that the maximum illumination of zone 15 is obtained because the excitation light is "captured". ¥ it l># relt · just, as was mentioned, with every reflection occurs a ■ \ '■■■■ - f0 * - ■' ■

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light reinforcement; on; However, if the distance of the points 12 and 13 is made as small or small as possible compared to the longitudinal distance of the mirror surfaces 10 and 11, the resulting reinforcement effects are reduced, and it can be achieved that the reflected light 50 to 100 times through the points 12 and 13 and space 15 passes before the successive gains, which cause the beam diameter to exceed the width of the slit image, and the reflection losses at the mirrors reduce the usable remaining light flux to a small fraction of its original size. This number of passages characterizes an extremely effective light harvesting cell compared to known cells.

According to a further feature of the invention, means are provided to collect light (e.g. Raman light) emerging at 16 from the sample space. Such a device can contain, for example, a monochromator 23, to which light is fed through the optical system 24. The monochromator is used to disperse the radiation from the illuminated ^ ⁿ sample, to thereby control the intensity of unwanted background radiation compared to the decrease observed spectral lines to the intensity, wherein Beäug is made to the US-Patentecnrift 2940555 "In this Zusaimoenhaitg it should be pointed out that in Pig. 1, a photodetector 25 which receives the scattered radiation from the monochromator at 26, an amplifier 27, the old of the photo detector is connected to the output, and a recording device 28 are provided, which is connected to the output of Verstärkere. The photodetector generates an electrical signal corresponding to the intensity of at least a part (for example the Raman part) of the light emitted at 16 from the sample. generated.

To achieve the highest degree of effectiveness, the distance between the conjugated image points 12 and 13 can be measured according to the ratio of the length of the honochromator column 29 ee so that mutually opposite ends of the narrowed gap

-, -. 'ν. . BAD ORIGINAL.- ■ it * ". ■■

image formed in zone 15 is nearby and preferably close to points 12 and 13 lie. It should be noted that the optical system 24 slit the long, narrow entrance gap '.29 on the gap between the pixels 12 and 13 and vice versa the gap between the points 12 and 13 on the entrance slit. Of the The exit slit of the mono-ear generator is denoted by 30.

Although different mirror distances can be used, the optimal center distance / \ O of the mirrors, if spheres with equal radii are used, can be obtained from the following equation (which applies to a gas sample):

G = ^ R ² + (Z \ x) ² '-R

where Ii is the radius of curvature of each of the two mirrors,

/ \ X is the distance between the two conjugate pixels,

The distance / \ X between the two conjugate pixels becomes. based on the monochromator and other parameters. of the optical system and on the basis of νοη, .Optimierungsbehlungen selected in order to approximate the length, 4th image of the; Adjust the monochromator entrance slit into the sample space. The choice of the radius of curvature R is a little more complicated: the designer would first select a quantity M, the gain for each pass through the system, with the help of an approximate calculation for the relationship between the efficiency of the overall system and various system parameters, including the quantity M. Once the gain or magnification per pass is chosen, the radius of curvature for each of the two mirrors can be found from the following equation, the only for spherical ones. Systems applies:

• ■■■ '■ -''■' - ' ' - ■ · V-: - * iTi «O'-iij» Ό: - · ■ * -r 12 ::: -.-; r;

X'-ln ^ iI

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η =. 2 μ Ας ₍₂₎

(Μ-1) (M + 1)

If / \ x and R have been calculated in this way, the optimal center-to-center distance \ 0 can be determined directly from equation (I) and the other considerations just outlined.

The distance between points 12 and 13 can remain essentially constant as long as they are in accordance with the description above The fluid sample to be irradiated consists of a gas - where small corrections because of the breaking of the cell window attached v / earth; in the case of a liquid sample, difficulties arise in that with different liquids different refractive indices occur. In this case, the invention provides for such effects to be compensated for before that the longitudinal distance of the mirrors 10 and 11 adjusted will. For example, according to one embodiment of the invention an adjustable device provided with at least one mirror or reflector and with the Sample cell itself is operatively related to the relative distance of the mirrors and the position of the cell between them Adjust mirrors to the refractive index of a sample liquid to compensate in this space, so that the reflected beam despite the passage through a liquid Sample repeatedly passes in the vicinity of the image points which are analogous to the image points 12 and 13.

An arrangement of such an adjusting device is shown in each of Figs. 1 and 5, the adjusting device having a worm gear 35 which is adjustable by a manual control 36 and a toothed rack 37 meshing therewith in order to move the reflector 11 with precision against the reflector 10 or γοη this way to move. A similar

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Arrangement with a button 211, a screw 210, a rack 209, a "movable body 208, and clamps 206, 207" can be used to control the position of a sample cell 201, as shown in FIG. 5. The cell 201 is usually provided with suitable windows 202 and 203 and has a tubular inlet port 204 and a closure device 205 whereby the liquid level in cell 201 can be conveniently maintained at about level 212 above the top of the cell volume. In this system It is, as will be explained below, advantageously not necessary to adjust either the mirror 10 or the angle Jl of the entrance beam 19 with respect to the axis or line 14 in order to adjust the refractive index of a liquid sample in the cell 201 to compensate.

The lower part of FIG. 5 corresponds to FIG. 1 insofar as in both drawings a beam 19, a mirror 10, an axis 14, a point of impact of the return beam 22 and a beam 24, as well as a laser 18 and an optical system 20 Points 215 and 216 of Fig. 5 are the virtual positions of the conjugate image points 12 and 13 of Fig. 1 as seen from the part of the optical space in which the mirror 10 and the optics 20 lie; that is, the points 215 and 216 are each the points towards which a ray 19 seems to run and from which a ray 22 which runs towards the point 23 of the mirror 10 seems to come 1, ala in both drawings there are a reflector 11, a return ray 22, and an impingement point 21 of the ray on the reflector 11. The points 213 and 214 are the virtual locations of the conjugate image points 13 and 12 respectively how they from the part of the optical Of the geoehon in which the reflector 11 is located. During operation, ti-ii? Level Ii in the absence of a sample cell 201 -IHi- ¹ CJh Ue f; ^! ttlgLuig ilen Knop Pe 8 36 ao oi.ngeEitol.lt that the

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BATH ORIGINAL

- 14 points 213 and 214 coincide with points 215 and 216 respectively.

By inserting a cell 201 filled with liquid into the system if that is in the one in Pig. 1 condition shown is caused that the return beam 22 due to the deflection of the beam by the refraction at the various points, such as point 219 in Pig. 5, no longer impinges on the mirror 10 at point 23; when the system has been set so precisely at the beginning that the point 23 is in the vicinity of the edge 226 of the reflector 10, so missed the return beam 22 now completely crosses the mirror 10 by being returned on a path to the left of the Edge 226 lies (as seen from a person looking at the Pig. 5).

In order to maintain the relationships for the conjugate pixels of the entire system, it is desirable ₉ that the return ray

22 hits at exactly the same point 23 where it hits would if cell 201 is absent, as it is in Pig. 1 is shown. It was found that this was the result can be achieved that the paths on which the beam 19 from the laser to the sample, and on which the beams 22 and 24 between the sample and reflector 10 to the point

23 and run from there back to the sample, are roughly the same paths on which the rays travel when there is no sample, as it is in Pig »1 der Pail; and further that the paths on which the rays 19 and 22 travel between the sample and the reflector 11 and back to the sample are roughly the same with respect to the reflector 11 as the paths on which the rays travel in the absence run a sample in cell 201 as described in E ¹ Ig. 1 who is lall.

Dien can be achieved in the illustrated device as follows: When the liquid-filled cell 201 hits the g oLnjieaotzt v / irrl, (lev ftUekkehrstrabl 22

BATH "ORIGINAL

no longer on the reflector 10. Then the button 36 operated to move the reflector 11 upwards until it is observed that the return beam 22 strikes the mirror 10 again at the edge 226. Then the button continued to operate until it is determined that the entire cross-section of the return beam is collected by the mirror 10 will. This clearly defines the position in which the different refractions the beam paths on both mirrors in relation to the mirrors with their original paths collapse before cell 201 was inserted. The optical space in the cell is now in fact more perpendicular Direction lengthened by the refractive effect of the sample in the cell 201, the incident beam 19 now the axis 14 · at point 217 and the return ray 22 now the axis 14- intersects at point 218; these two points in fact represent intersections for subsequent, more central ones running rays, such as ray 24 in FIG. 5, in the same way as points 12 and 13 Form intersections in the absence of a liquid-filled cell 201. The distance between points 217 and 218, the new conjugate image points, is accordingly somewhat larger than the distance between points 12 and 13 in Fig. 1; in fact, this is the length of this critical distance proportional to the refractive index of the liquid in the cell. .

The cell 201 must then be adjusted in the vertical direction so that the actual conjugate pixels 217 and 218 approximate with respect to the nearby ends 221 and 222 of the image of the monochromator entrance slit in the sample space are centered, the image of the entrance slit through the course of the delimiting rays 220 A and 220 B is defined by the monochromator via the optics including the lens 219. Those within the limit that through the boundary rays 220 A and 220 B of the slit image

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is formed, lying scattered radiation becomes, as it is general at 16 in Pig. 5 is indicated, the monochromator and a .Display system forwarded. The setting can be made with the aid of a device as shown at 208, 209, 210 and 211, which is manually operated by the operator of the instrument in order to increase the sensitivity of the instrument for the optical signal to be as large as possible. It has been assumed here that the lens 219 and the im lower beam path arranged optics with respect to the laser 18 and the fixed optics 20 are fixed, and that the Cell by the maximization procedure just described in with respect to these fixed elements is adjusted so that points 217 and 218 are symmetrical about the nominal centerline 220 CL of the entrance slit image are arranged in the sample space.

If the positions of the reflectors 10, 8 Δ and 18 B with respect to the center line 220 CL by the manufacturer are so suitable are chosen that this condition is met for a symmetrical arrangement when the cell with a liquid with a typical or an average refractive index in relation to the range of the expected refractive indices is, then in principle only small adjustments to the position of the cell 201 are required by actuating the button 211, and in practice no settings are necessary at all.

The principle that is applied to the intensely illuminated Volume between conjugate points 217 and 218 to move a vertical adjustment of the cell 201 is indicated in Fig. 6, which is an enlarged view of the lower Middle part of Fig. 5 shows. Form as in Fig. 5 the points 217 and 218 of Fig. 6 the actual conjugate image points through which the incident ray 19 and the first Return ray 22 because of the refractions at points 219 and 223 on window surface 203 and at analogous points the more distant surface of window 202

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the pig. 5 run when the cell 201 and the window 203 are shown in FIG. 6 by the solid lines Position. When cell 201 and window 203 are in corresponding positions 201 'and 203' shown in dashed lines Lines are shown to be shifted so that the ray 19 is refracted in the lower point 219 ', runs the refracted ray along a path 19 '' through a dashed line parallel to the original ray path 19 is indicated in the liquid, so that the jet now the axis 14 in a higher point 217 'crosses. Similarly, the returning ray 22 comes from a higher point 218 'and will arrive a lower point 223 'broken from where the path of this ray with the original path of ray 22 to the Point 23 on the mirror 10 coincides. The designated with 224, intensely illuminated volume between points 217 and 218 is thus the downward movement of the one with a Sample-filled cell 201 and window 203 upwards has been moved to zone 224 '.

5 and 6, it can be seen that when the centerline 220 OL is initially midway between points 215 and 216, which is the case when the system is oriented to effectively collect energy from such samples takes place, the refractive index of which is very close to 1 (i.e. gases), it is not possible to move the cell 201 vertically in order to bring the points 217 and 218 in a symmetrical position with respect to the line 220 OL without the Point 218 to be laid on or under the outer window surface 203. This is not a serious limitation as the system is primarily intended for use with liquids, the indices of which are generally 1.2 and above. However, when di ··· limitation is to be eliminated, the reflectors 10, 18B and 18 L can, as. In Pig 5, can be arranged on a movably guided carriage 231 ,

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BATH ORIGINAL

a rack 232, a worm 233 and an adjustment knob 234, so that points 215 and 216 are upwardly in a symmetrical position with respect to the center line 220 OL can be shifted so that the system can be used for gaseous samples. It should however, it should be noted here that system 208-211 and system 231-234 have certain overlapping functions exercise, since both serve to make the conjugate pixels perpendicular with respect to the center line 220 CL of the collecting optics to move.

Another embodiment, in which this overdetermination is avoided, is shown in FIG. 3. 7 shown! Here the mirrors 10, 18 A and 18 B and the cell 201, as well as the button 36 and the worm 35, are mounted on a slidably guided carriage 235, which in turn is slidable with the aid of a rack 236, a worm 237 and a button 238 to move the entire subsystem in the vertical direction with respect to the center line 220 CL? The mirror-11 is in turn actuated by a button 36 which acts on a rack 37 via a worm 35 _? which is attached to the mirror 11, adjustable with respect to the carriage 235. In this system, first, the mirror 11, with or without liquid in the cell 201, is adjusted so that the return jet 22 hits the precise point 23 on the mirror 10; Secondly, the entire arrangement _9, which consists of the carriage 235 and the components fastened thereon, is then adjusted in the vertical direction by actuating the button 238 in such a way that the center of the conjugate image points is precisely adjusted with respect to the center line 220 CL; is. In this latter setting, the carriage 235 moves parallel to the axis 1 | _p -die'with the ¥ erläag @ Eung of the path of incidence of the beam 19 between, ä®T optics 20 and the reflector 18. B zueamenfftllt ;; on- äi © a © ¥ © Ie ©, the former · Bin®t®llnng <si®g © sp © irfe ₉ Indt »da® overall © system

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ORIGINAL BATHROOM *

«^ Λ ft« ft · «AA«

is moved.

In the above discussion and the following quantitative calculation were the effects of cell windows leading to a Modification of the refractive properties with a liquid filled cell lead, neglected. This is only fully justified if the index of refraction is the cell window coincidentally coincides with the refractive index of the liquid in the cell. In practice the above will be shown However, introducing such additional considerations merely complicates conclusions without affecting any Wise the validity of the conclusions drawn or the usefulness of those described above Systems are enlarged. In the quantitative analysis, of course, the effects of the windows appear; however, since the rich in refractive indices envisaged for the liquid ones Samples to be used in the present device include the refractive index of materials used for Are suitable for use as cell windows, is the sign or direction of the effect caused by the window, which acts as a disturbance to the quantitative calculation, neglecting the ones caused by the windows Effect was carried out, indefinite, so that the calculations that have been carried out under the assumption that the window and the sample have the same refractive indices are sufficiently good.

As will become clear from the following, the optimum center-to-center distance of the mirrors 10 and 11 depends on the refractive index of the sample, consequently, as already described, adjustments are desired in order to compensate for the effects caused by the refraction For the design of the fastening and adjustment device, only the range of the "optimum center ^{distance 11} " needs to be taken into account. In choosing the length of the cell itself, however, the maximum value of the optimum center distance must be taken into account

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can be drawn, and this can be calculated as "? The optimal center distance / \ Q of the mirrors results for a liquid sample, if spherical mirrors with the same radius are used, as follows:

O = I / R ^ + (ΖΛΧ) "- R + * j ^" ¹ '-' (3)

where P is the length of the light path through the sample (for each pass), Z_> X the distance between the two conjugate image points in air, R is the radius of curvature of each mirror, η is the refractive index of the sample liquid.

This equation is then used in exactly the same way as equation (1), but now the path length is used in the liquid and the refractive index are taken into account.

It should be noted that / \ X and P are not the same need to be, because you can relocate the conjugate pixels in the interior of the sample, for example if you have a The sample has a diameter of 10 mm and the distance between the pixels is 8 mm, by the largest percentage Collect radiation with every single passage of light, the image points should lie on the pen windows of the specimen holder or a little inside the specimen.

If one assumes infinitely small image and object points, it is possible to form the band window of a cell in such a way that that the refractive indices of the cell and those contained therein Liquid have little or no effect on the locating properties. In Fig. 3 is a special cell or sample holder 40 is shown for this purpose. The center of curvature of the surface 41 » which forms one of the half-windows of the cell, lies at pixel 42 "

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109810/1939 -

The radii of the surface 41 and the! Surface 43, the windows "form, differ from one another by the cell thickness. The laser light beam 44 passes through the cell without passing through the Faces 41 and 43 is deflected and it is reflected by mirror 45 at 46. The reflected ray 47 runs through the cell windows of areas 48 and 49 without to be distracted, the center of attention of this Window is located in pixel 50. After reflection by the Mirror 51 at point 52, the reflected beam 53 runs without Distraction by the cell windows and by point 42 etc. Thus, the focusing properties are not affected by either Windows (made of glass, for example) still affected by the breaking liquid, and points 42 and 50 can have the same distance for sample liquids with different refractive indices.

Finally, in Fig. 4 is the use of the invention Reflector device, which is designated by 60, in one optical system that forms a complete spectrophotometer.

The laser 61 is attached to a solid frame that is attached to attached to the main instrument. The laser beam is reflected at 65 and then passes through the narrow band filter 62 to reduce the influence of gas emission lines. A A certain proportion of the light that is reflected by the filter can, as is common practice, on a comparison photo tube be judged. The main ray 73 enters the component for the entrance optics and is through the mirror 74 and 75 redirected. The beam then enters the sample of device 60 and Raman radiation enters a lateral beam 67.

The Eaman light coming from the sample cell is with the aid of a lens 77 through the monochromator entrance slit 68 onto a collimator mirror 80 in the first monochromator section

- - 22 -

«« T φ Λ «*

irradiated. The beam is reflected there to the grating 81, gets back to the collimator 80, and then becomes reflected by a mirror 82 through an intermediate slit 85 to the second monochromatoratic section., From the intermediate ™ slit 83, the beam is reflected by a mirror 84 and the second collimator 85 to the second grating 86, goes back to the collimator 85 and then through the exit slit 87. The beam is chopped at 71 and with Focused on a phototube 90 using a lens 93. The phototube signal can be used in the usual way with a Reference signals are compared,

Observations and calculations show that due to the spherical aberration on the mirrors and the windows, the conjugate image points move very slowly outwards and then inwards along the system during successive passes designed arrangement with 15 passages almost "to the south! eastern of a 10 mm high cell to the outside eodaim they move back against their original position and shift in the 34" passage beyond their original positions towards the center of the system ifandern further in the same direction ₉ so that the upper and the lower point in reality are reversed ₉ and the points reached after a total of about 68 passes back to their original distance, but in the opposite sighting _o Simultaneously, the center beam moves the beam bundle _ö rather than monotonically to the axis converge out? roughly in accordance with the migration of the conjugate points away from the axis and onto the axis zvl _o

PaIIe this behavior for the operation of the system should be disadvantageous (which it is notK ϊεοηβ, ϊφ this ¥ kalt @ n da ~

. ■ - 23 -

09810/193 *

be reduced by and essentially completely eliminated by the fact that instead of the spherical mirror ellipsoidal mirrors are used, and that the 'cell windows a suitable one. Emetic juice is bestowed to to keep the aberrations on the planes as small as possible Window areas occur.

However, the migration of the conjugate points and the beam impingement points on the reflectors, while in no way a disadvantage, can be converted into an advantage in various ways. Thus, the enlargement becomes a "reduction" or a reduction in the size of the image with each pass if the conjugate pixels assume reversed positions; this reduces to some extent the rate at which the size of the beam approaches and then exceeds the size of the optical elements on successive passes - this behavior being one of the main effects which limit the number of useful passes . It is also possible to use the migration of the beam to geometrically concentrate the first 20 or 25 passages more closely, whereby an effective illumination can be "traded" as desired against the cell size of the sample and the sample volume required thereby. This forms a further advantage that is implied by the spherical aberrations . '■' ■ .'-. '

line correction of aberrations therefore does not become general deemed necessary, rather the aberrations for certain applications may be desirable.

- 24 -

109810/1939

Claims (1)

04 P3 D Claims (1. Device, "inn light several times through a sample in one Allow the sample space to run, characterized by two concave mirrors (10, 11) separated from one another in the longitudinal direction, which form two conjugate image points (12, 13) lying between the mirrors, these points in relation to the longitudinal spacing of the mirrors along an axis (14) running through these points is relatively small Have a longitudinal distance from each other, whereby this axis runs through the sample space (15), which can accommodate a sample, and by means (18, 20) to generate a light beam at least one of these two points would be in the near future to emit that the light beam repeats through the Mirror and is reflected between the mirrors, so that it runs several times through the sample space »- 2. Apparatus according to claim 1, characterized in that the mirrors by a first and a second concave. Reflector formed v / ground that way with respect to each other are arranged to form first and second focal points of the system, the first focal point closer to the first reflector and the second focal point closer to the second reflector and wherein the device for the irradiation of a light beam is arranged so that this light beam is irradiated into the first focal point and wherein the first reflector is arranged to direct the light beam to the second focus reflected and wherein the second reflector is arranged so that the light beam then on this second reflector and is reflected again by this to the first focal point, so that the light beam several times between runs back and forth over the reflectors. ■ ... ·. ■. - 25 -. _: 109810/1939 3. Apparatus according to claim 2, characterized in that the first and the second focal point of the system in one Distance from each other, which corresponds to a small fraction of the distance between the reflectors. A- * device according to claim 2 or 3, characterized in that a central beam of the light beam converges towards a line which runs through the two focal points of the system during successive reflections. 5. Device according to one of the preceding claims, characterized in that the reflectors or mirrors consist of ellipsoids and that the two conjugate image points or the first and second focal points of the system are formed by the focal points of these ellipsoids . 6. Device according to one of claims 1 to 4, characterized in that the mirrors or reflectors are made of spherical sections. 7. Device according to one of the preceding claims , characterized in that a device (24 ι 25) is provided to collect light that is emitted from the sample space as a result of the multiple irradiation of the sample space by the light beam reflected several times. 8. Apparatus according to claim 7> characterized in that the device (24 »25) for collecting the light emitted from the sample space has a gap (29) which has a has reduced image arranged so that the two sides of this picture each near the conjugated pixels (12, 13) lie. 9. Device according to one of the preceding claims, characterized in that the device (18, 20) for • Sine rays of a light beam »into the device like this arranged lit, since the beam of light under a small one - '■■■' ■. ■■■:. '' -26 - ■ ■ ': Angle (OC) with respect to the axis (14) running through the conjugate image points. 10. Device according to one of the preceding claims, characterized in that the contained in the sample space Sample consists of a gas. 11. Device according to one of claims 1 to 9, characterized in that that the sample contained in the sample space consists of a liquid. 12. The device according to claim 11, characterized in that with at least one mirror an adjusting device (35, 36, 37) is connected to the relative distance of the Mirror (10, 11) adjustable from one another to adjust one based on the refractive index of the sample liquid to be able to carry out the necessary compensation in the sample space (15), so that the reflected light beam several times runs through the shifted conjugate points (217, 218) in the liquid. 13. Device according to one of the preceding claims, characterized in that the sample space (15) is so arranged in relation to the shifted conjugate pixels is that these conjugate pixels lie within the sample space. 14. Device according to one of claims 1 to 11, characterized in that that the sample space (40) is so arranged with respect to the conjugate image points between the mirrors is that the conjugate pixels are outside the sample cell and that the sample cell has two pairs of windows (41, 43, 48, 49), of which a pair window one common means of curvature in © inea of this conjugated Pixels and the other beer window share a common Center of curvature in the other of these conjugated Pixel "has * ^ -; ■ - 27 - «A ft A * A t * A.Ük'm ' 15. Device according to one of claims 9 Ms 13> characterized in that devices (232, 233i 234) are provided with which the angle (OC )> at which the light beam is radiated into the device with respect to the axis, together with the distance between the mirrors can be adjusted. 16. Device according to one of the preceding claims, characterized characterized in that the light source is formed by a laser. 17. Device according to one of claims 2 to 16, characterized in that that the concave reflectors have essentially opaque surfaces, which are at a distance from each other are arranged and facing each other, each of these surfaces having a center of curvature and wherein these Centers of curvature have a distance from one another which is small in relation to the distance between these surfaces. 18. Apparatus according to claim 17 »characterized in that the concave surfaces of the reflectors are essentially spherical. 19. Apparatus according to claim 17 or 18, - characterized in that that the two concave surfaces of the two reflectors approximate have the same radius of curvature and that the distance between these two concave surfaces along a line which is perpendicular to both surfaces, slightly larger than • is the sum of the two radii of curvature. 20. Device according to one of the preceding claims, characterized in that a holder (206, 207, 208, 201) for a sample is provided in the sample space (15) that one Means (23, 24) for collecting light is provided that from the sample as a result of the multiple passage of the reflected light beam through the sample space to the outside " ^: '\' ^: ';""" · ■■ - 28-109810 / 1939 is emitted towards, the emitted light substantially in the transverse direction to the Liehtwege of the multiple reflected light beam is emitted and that one photo electrical device (25, 27 »28) is provided, through which an electrical signal corresponding to the intensity at least part of this emitted light is generated. ο Device according to claim 20, characterized in that the Device for collecting the light emitted from the sample space comprises a monochromator (25) which contains an entry slit (29) and an exit slit (30) that an im on the photoelectric device essential monochromatic light is radiated from the exit slit of the monochromator that means (24) are provided to open the entry slit of the Monoehromators in to map the bead of the centers of curvature of the concave surfaces of the reflectors, and that one on that of the Photoelectric device output signals responding device (28) is provided through which the relative intensity of the light beam is displayed. 22. The apparatus according to claim 21, characterized in that an optical device (24 »219) is provided to to map the entry slit of the monochromator on a line (14) that forms the centers of curvature of the concave Connects the surfaces of the reflectors. 23. Device according to one of the preceding claims, characterized characterized in that means (206, 207 »208) are provided to place a sample on the center of curvature to hold the concave surfaces of the reflectors connecting line (14). 24. Apparatus according to claim 23 »characterized in that - 29 - 109810/1939 Means (209, 210, 211) are provided to the Sample in the longitudinal direction of line (H) in "with respect to at least to move one of the reflectors (10, 11), so that the light emitted from the sample space is generally centered is with the entry slit of the monochromator (23). 25. Device according to one of the preceding claims, characterized in that devices (35, 36, 37) 'are provided are, about the position of a reflector in the longitudinal direction of the axis running through the conjugate pixels opposite to move the other mirror. · 26. Device according to one of the preceding claims, characterized in that devices (236, 237, 238) 'are provided are to the reflectors and the sample as a whole in the longitudinal direction with respect to a generally. = transverse Axis (220 OL) to move, which runs through the entrance slit (29) of the monochromator (23). 3ο Blank page