SU1516910A1 - Refractometer - Google Patents

Abstract

The invention relates to optical instrumentation and can be used to accurately measure the refractive index of solid media. The purpose of the invention is to improve the measurement accuracy. The double-arm interferometer contains a cuvette of the test substance, installed in the subject shoulder of the interferometer and mechanically connected with the block of displacements, as well as the first and second counters of interference fringes at the output of the interferometer, connected to the synchronizer. The cuvette is made in the form of a wedge and is installed with the possibility of translational movement in the plane of one of the edges of the wedge adjacent to its edge, so that the other face of the wedge, adjacent to the edge, is located normally to the optical axis of the interferometer, and this face of the wedge is optically connected the second counter of the interference bands. To further improve the measurement accuracy, two additional beam splitters and a mirror system were introduced into the refractometer, which optically coupled them to each other across the cuvette face opposite to the face, perpendicular to the axis, with one additional beam splitter installed in the interferometer support arm, and the other at the interferometer output, before the second counter of the interference bands. 1 hp f-ly, 2 ill.

Description

The invention relates to the field of optical instrumentation and can be used to measure the refractive index of solid and liquid substances.

The aim of the invention is to improve the measurement accuracy.

Figure 1 is an optical diagram of a refractometer; Fig. 2 is an optical diagram of the refractometer improvement.

The refractometer (Fig. I) contains a coherent radiation source 1, a beam-splitting cube 2, a test cell 3, a mirror 4 and 5, a displacement block 6, counters 7 and 8 of interference fringes and a synchronizer 9.

The refractometer of FIG. 2 contains a source of coherent radiation 1, brightening cubes 2,10 and 11, cuvette 3 of the substance under study, tercalp 4.5, 12-14, block 6 p.remeshnich, seekers 7 and 8 interferential, h could and synchronizer 9,

31516

The dashed line shows the course of the rays falling into the first counter of the interference fringes, and the solid line shows the interference fringes entering the second meter.

In the refractometer (Fig. 1), the interferometer subject shoulder is formed by a light-dividing cube 2, a cuvette 3 of the test substance and a mirror 4, and the supporting arm is formed by a beam-splitting cube 2 and a mirror 5. The displacement unit 6 is connected mechanically with the cuvette 3. Counter 7 interferential the fringes are set at the output of the interferometer, and the meter 8 of the interference fringes is optically coupled to the face of the wedge located normally to the optical axis of the interferometer. Counters 7 and 8 are connected to synchronizer 9.

In the refractometer of FIG. 2, the interferometer objective shoulder is formed by beam splitting cubes 2.10 and 11, cell 3 of the test substance and mirrors 4.12-14, and the reference arm by beam splitting die 2 and mirror scrap 5. The movement unit 6 is mechanically connected 3. A counter of 7 interference fringes is installed at the output of the interferometer, and a counter of 8 interference fringes is optically coupled to a wedge face located normally to the optical axis of the interferometer. Counters 7 and 8 are connected to synchronizer 9.

In addition, a beam splitter 10, which is installed in the reference arm of the interferometer, and a beam splitter 11, which is installed in front of the counter

a combo of 8 interference fringes, a mirror system consisting of mirrors 12–14, optically linking the beam splitters 10 and 11 through the wedge face opposite to the face, perpendicular to the p axis.

The refractometers of FIGS. 1 and 2 include a coherent radiation source 1, which can emit light of one or two wavelengths. Structurally, it can be made in the form of one or two lasers with collimation systems.

Refractometer works as follows.

The source of coherent radiation is switched on and the refractometer is adjusted in such a way that there are 7 interference fringes on the counter

only two beams fall: one beam reflecting from mirror 4, and the other one reflected from the face AB of the cuvette 3 of the sample under study or reflecting from mirror 5. At the same time, it is achieved by adjusting that only two beams hit the counter 8 interference band: one beam , reflected from the face AB of the cuvette 3 of the sample, and the other from the mirror 5. Such adjustment is possible in various ways. You can, for example, diaphragm or shift the mirrors 4 and 5 in such a way that only the radiation reflected from the face of the AV of the wedge and the mirror 4 falls on the counter 7, and reflected from the mirror 5 and reflected from the face of the AV of the wedge to counter 8. If the source of 1 coherent radiation emits radiation of two wavelengths, then it is possible to carry out: - Spectral selection. For the most efficient use of radiation, a light-separating coating can be applied to the edge of the AV cell 3 of the test substance (Fig. 1). This light-splitting coating consists of reflective (shaded) and transmissive parts. When adjusting, it is achieved that the interferometer axis passes through the boundary of the reflecting and transmitting parts. Then, the radiation reflected from mirrors 4 and 5 enters the counter of the 7 interference fringes, and the radiation reflected from the edge of the AV wedge and the mirror 5 hits the counter of 8 interference fringes.

After alignment, block 6 is switched on, which shifts the cuvette 3 of the test substance in the plane of the face of the aircraft. When this occurs, a change in the optical path difference between pairs of rays falling on counters 7 and 8 of the interference bands. Since the radiation falls on the edge of the AB wedge normally, the optical path difference changes as follows:

2 (p-Po) -b; L2. 2 п „-, (1)

and L is the change in the optical path difference between pairs of rays on counters 7 and 8 of the interference fringes;

51516910

n and front are the refractive indices of the test substance and the environment;

h is the change in the geometric length of the light path resulting from the movement of the wedge.

With synchronizer power 9, the counters 7 and 8 of the interionic lanes are simultaneously switched on and, after some t, turn off. Counters register10

The following number of interference bands is detected:

2in; noi h.

Tg

2 n.h

-BUT.

where N I and N

- the number of interference fringes registered by counters 7 and 8;

 A, and A- are the wavelengths of the radiation incident on counters 7 and 8. After registering N, and N, j, they find

, N, Xj N7 to:

-t- 1).

(3)

By the formula (3), the refractive index is calculated.

The difference in the operation of the refractometer in Fig. 2 from the refractometer in Fig. 1 is only in the process of alignment. At the alignment stage, it is achieved that two beams hit the counter of 8 interference fringes: one reflected from mirror 5, and the other reflected from the edge of the AV wedge, beam splitters 2 and 11 mirrors 14 and 13, faces of the sun of the wedge, mirror 12, beamsplitter 10. Dp to avoid interference, it is advisable to use a coherent radiation source 1 with a small (5–20 cm) coherence length and equalize the difference ;; 1 year between the 8 beams falling on the counter. For the rest, the adjustment and operation of the refractometer in FIG. 2 coincides with the adjustment and operation of the refractometer in FIG.

However, in the refractometer of Fig. 2, the measurement error is reduced due to the uncontrolled displacements and reversals of the test substance cuvette relative to the direction of motion. The measurement error in the refractometer in FIG. 1 is 1.5-10, and in the refractometer in FIG. 2

4-10

-7

Thus, the combination of distinctive features allows the analysis of the precision measurement of the refractive index of solid and liquid substances with respect to the current level of technology.

Claims (2)

1. A refractometer containing a two-arm interferometer, a cuvette for the test substance, installed in the subject shoulder of the interferometer and mechanically connected to the displacement unit, as well as an interferometer output counter, characterized in that, in order to increase the measurement accuracy, JQ entered into it the second counter of the interference fringes and the synchronizer connected to the first and second counters, and the cuvette is made in the form of a wedge and installed with the possibility of translational movement in the plane of one of the wedge sides adjacent to its edge, so that the other edge of the wedge, adjacent to the edge, is located normally to the optical axis of the interferometer, and this face of the wedge is optically connected with the second interference fringe counter. 2. The refractometer according to claim 1, about tl and - h and y with the fact that it introduced two additional beam splitters and a mirror system, optically connecting them to each other through the face of the cell opposite to the face, which is located normally to the axis , with one additional beam splitter installed in the reference arm, and the other at the interferometer output before the second interference fringe counter. Phie.1 Phie.g