JPH0718791B2 - Differential refractometer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a differential refractometer used for, for example, determination of molecular weight.

<Prior Art> A technique for measuring the molecular weight of a sample as a solute by measuring the refractive index of a solution and its concentration dependence has been conventionally known. The measurement of the refractive index of such a sample solution uses, for example, a cell composed of a transparent container that separately stores the sample solution and its solvent, and the sample solution and the solvent are applied when monochromatic light is incident on this cell through a slit. This can be performed by utilizing the fact that the optical path of the incident light is bent according to the difference in the refractive index between and. In this way, the fact that the incident light is deflected according to the refractive index difference between the reference with a known refractive index (solvent of the sample solution in the above example) and the sample with an unknown refractive index (sample solution) is used. The differential refractometer is adapted to measure the refractive index of the sample.

The basic structure of the differential refractometer used conventionally is shown in FIG. Light from the light source 1 is emitted from the slit 2
It is guided to the collimator lens 3 via and is made into parallel light. This collimated light enters the cell 5 as a light beam A whose width is limited by the slit 4. Light flux A from this cell 5
Forms an image of the slit 4 on the detection surface of the photosensor 8 arranged on the focal plane of the imaging lens 6 from the imaging lens 6 through a glass plate 7 for correction which will be described later. Correction glass 7
Is angularly displaced in the direction of arrow R1 by operating the dial 9.

FIG. 22 is a cross-sectional view showing an enlarged structure of the cell 5.
This cell 5 is called a Bryce cell or the like, and the inner space of the cell container 5a made of a transparent cylinder having a rectangular column shape is diagonally partitioned by a partition plate 5b to form a first chamber 51 and a second chamber 52. It was done. For example, when the first chamber 51 is filled with the sample solution whose refractive index is to be measured and the second chamber 52 is filled with the solvent, the light flux A from the slit 4 corresponds to the difference in the refractive index between the sample solution and the solvent. And be deflected.

In measuring the refractive index, the first procedure is the first
Both the chamber 51 and the second chamber 52 are filled with the same solvent, and the image of the slit 4 is detected by the photosensor 8. Then, as a second procedure, for example, the sample solution is put in the first chamber 51 and the solvent is put in the second chamber 52, and the same measurement is performed. This first, second
The image forming position of the slit image changes according to the amount of deflection of the light beam A during the procedure.

The refractive index difference Δn is However, n _S …… Refractive index of sample solution n _R …… Refractive index of solvent e …… Refractive index outside the cell α …… Deflection angle of light flux A θ …… Represented by. In the formula, the sign ± is the refractive index
One of the signs is selected depending on the values of n _S , n _R and the angle θ. On the other hand, assuming that the distance between the cell 5 and the photosensor 8 is l, sin α is calculated by using the change Δx in the imaging position of the slit image. Therefore, the above equation is Will be transformed. In the air, e≈1, so after all, Becomes That is, if the displacement Δx is known, the refractive index difference Δn can be obtained, so that the refractive index of the sample solution can be obtained based on the refractive index of the solvent.

FIG. 23 is a plan view for explaining the action of the correction glass plate 7. The correction glass plate 7 is operated by operating the dial 9.
Is angularly displaced from the reference position 7a (the position shown by the broken line in FIG. 23) by the angle β, the incident angle of the light flux A on the correcting glass plate 7 becomes equal to the angle β. At this time, if the optical path of the light flux A is deviated by Δx ′ due to refraction, the displacement Δx ′ of this optical path is approximately Δx′∝sin β.

Therefore, first, with the correction glass plate 7 in the attitude of the reference position 7a, both chambers 51, 52 of the cell 5 are filled with a solvent to detect the light flux A by the photosensor 8, and then the first chamber 51 of the cell 5 is detected.
When the light beam A that has been deflected when the sample solution is filled is imaged on the photosensor 8 by operating the dial 9, the displacement Δx ′ of the optical path of the light beam A by the correction glass plate 7 is Δx′∝Δx. The displacement Δx ′ is obtained from the value of the dial 9,
Therefore, based on the value of the dial 9, the refractive index difference Δn between the sample solution and the solvent can be obtained from the above equation.

In such a configuration, the work of shifting the image forming position of the slit image by the manual operation of the dial 9 may cause individual differences among operators. Therefore, the reproducibility of data is poor,
As a result, the accuracy of the refractive index measurement is deteriorated.

Another prior art that solves this problem is, for example, Japanese Patent Laid-Open No. 63-1.
It is disclosed in Japanese Patent No. 88744, and its basic configuration is the second
Shown in Figure 4. The light from the light source 11 is collected by the condenser lens 12
The light is focused by, is further focused by the slit 13, and is collimated by the collimator lens 14. The parallel light enters the V block 15 made of a transparent material having a known refractive index. The V block 15 has a V-shaped recess 15a having an apex angle of 90 degrees, and the recess 15a is used as a sample table. This recess 1
A sample 16 having an apex angle of 90 degrees and an unknown refractive index is placed on 5a, and almost half of the parallel light from the collimator lens 14 passes through the sample 16.

The light from the V block 15 passes through the chopper 17 and forms an imaging lens.
The light is condensed by 18 and is incident on the one-dimensional image sensor 19 composed of a one-dimensional CCD (charge coupled device) and the slit.
Form 13 images. The chopper 17 has a fixed piece 17a having an opening corresponding to the light transmitted through the sample 16 and an opening corresponding to the light not transmitted through the sample 16 among the light from the V block 15.
And a movable piece 17 for blocking either one of the openings.
b and.

In measuring the refractive index of the sample 16, first, the light transmitted through the sample 16 is blocked by the chopper 17. The image forming position of the slit image at this time is detected by the one-dimensional image sensor 19,
For example, it is held by a control means (not shown). In this case, since the light passing through the chopper 17 is the light that has passed through only the V block 15 having a uniform refractive index, it is not deflected.

Next, the chopper 17 blocks the light from the block 15 that does not pass through the sample 16. This allows the imaging lens 18 to
Light deflected corresponding to the difference in refractive index between the V block 15 and the sample 16 enters. Therefore, the slit image is imaged at a position different from that in the above case, corresponding to the refractive index difference. This image formation position is detected by the one-dimensional image sensor 19 and taken into the above-mentioned control means. In this control means, the distance between the image forming positions of the slit images formed by the light passing through the sample 16 and the light not passing through the sample 16 is calculated. From this calculation result, sample 16 and V block
The difference in the refractive index from 15 is obtained as in the case of the first prior art shown in FIG. 21 described above.

In the prior art shown in FIG. 24, the measurement of the deflection amount is
One-dimensional image sensor 19 without the need for manual operation
Therefore, the measurement of the refractive index is simplified, and the measurement error due to the individual difference of the measurement operator does not occur, so that the measurement accuracy is improved.

<Problems to be Solved by the Invention> A new problem of the above-mentioned prior art is that the movable piece 17 of the chopper 17 is
Vibration is generated when driving b, and the imaging position of the slit image in the one-dimensional image sensor 19 is displaced due to this vibration, resulting in deterioration of measurement accuracy and a mechanical drive portion. This leads to an increase in the number of parts.

Further, in the first prior art shown in FIG. 21, in addition to the problem that the reproducibility of data is poor due to individual differences among measurement operators as described above, both chambers of the cell 5 are filled with a solvent. In this case, since the detection of the slit image and the detection of the slit image when the first chamber 51 of the cell 5 is filled with the sample solution are performed with a certain time interval, the state of mechanical vibration or air fluctuation There is also a problem that an error factor such as an influence of bending due to a change with time of an optical base and a change with time of an optical base (not shown), and the like, further deteriorates the measurement accuracy.

Therefore, an object of the present invention is to solve the above-mentioned technical problem and to provide a differential refractometer in which the measurement accuracy is remarkably improved.

<Means for Solving the Problem> A differential refractometer according to claim 1 for achieving the above object, a light source and at least two identifications corresponding to the image formation for forming an image by transmitted light. A light transmitting member having an original image having a portion, a lens for condensing the light source light transmitted through the light transmitting member, a lens arranged at a position conjugate with the light transmitting member with respect to the lens, An image sensor that detects an image, and is disposed at any position between the light transmitting member and the image sensor, and allows the light passing through the two identification portions of the original image of the light transmitting member to pass through 2 And a diaphragm member having two openings, and arranged so that light passing through one of the openings of the diaphragm member is obliquely transmitted through an interface between a sample whose refractive index is to be measured and a reference having a reference refractive index. What to do According to the above, the relative refractive index of the sample is measured based on the distance between the portions of the image formation detected on the image sensor corresponding to the two identification points.

The reference may be air (claim 2).

The sample whose refractive index is to be measured and the reference having a reference refractive index may be housed in cells that separately house these substances (claim 3).

The light passing through the other opening is in air, or a portion containing a reference in the cell, a portion containing a sample in the cell, a cell different from the cell, which is filled only with air, or the It may be a cell filled with a medium having a known refractive index, which is different from the cell (claim 4).

The light transmissive member having the original image may be a diaphragm member having openings at at least two locations (Claim 5), or a translucent plate on which a light shield is formed (Claim 6). A light-shielding plate having a light-transmitting portion formed thereon (claim 7),
It may be a transparent plate having graduations (claim 8).

Further, between the light transmitting member and the image sensor,
It is desirable that an aperture having an opening through which the condensed light passes is further provided at a condensing position of the light source light (claim 9).

<Operation> According to such a configuration, the light transmitted through, for example, one of the at least two identification portions of the original image is obliquely transmitted through the interface between the sample and the reference, and the light is transmitted to one portion of the detection surface of the image sensor. The light that is imaged on the other side and passes through another identification point is imaged on another point on the detection surface of the image sensor. These lights are detected at the same time by the image sensor, and the distance between the respective image forming positions of the light transmitted through the respective identification points can be obtained from the output of the image sensor. The distance between the imaging positions corresponds to the amount of deflection received by the light obliquely passing through the interface between the sample and the reference in accordance with the difference in the refractive index between the sample and the reference. Therefore, the refractive index difference between the sample and the reference can be obtained based on the output of the image sensor.

The arrangement according to the invention does not include any mechanically driven components, so that the problem of measurement accuracy deterioration due to vibrations can be overcome. In addition, since the image sensor simultaneously detects the light transmitted through the two identification points of the original image, even if the image forming position of one light is shifted due to vibration or air fluctuation, the image formation of the other light is performed. The position also shows the same change. Therefore, by obtaining the distance between the image forming positions of the light passing through the identification portion, it is possible to cancel the deviation of the image forming position due to the vibration.

Since the light transmitting member and the image sensor are arranged so as to have a conjugate positional relationship with the lens, the original image can be clearly formed on the detection surface of the image sensor. Further, the diaphragm member can surely separate the light that has passed through the two identification portions of the original image, and the light that has passed through both the identification portions can be reliably separated on the detection surface of the image sensor. In this way, the measurement accuracy of the distance between the image forming positions of the light passing through the identification portion is improved.

<Embodiment> An embodiment will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a plan view showing a simplified basic configuration of a differential refractometer according to an embodiment of the present invention, and FIG. 2 is a plan view thereof. Light from the light source 21 is condensed by the condenser lens 23 via the interference filter 22, and passes through the slit 24 having elongated openings 24a and 24b at two places as shown in FIG.
Gives rise to 1, L2. In this embodiment, the slit 24 constitutes a light transmitting member.

Light fluxes L1 and L2 from the slit 24 are transmitted from the imaging lens 25 to a cell 27 via a slit 26a having two openings and an aperture 26 which is a diaphragm member having a pinhole formed on the optical axis of the imaging lens 25. Incident on. The light beams L1 and L2 that have passed through the cell 27 are reflected by the reflecting mirror 28 and then pass through the cell 27 again to form an image of the slit 24 on the one-dimensional image sensor 29. The slit 24 and the one-dimensional image sensor 29 are arranged so as to have an optically conjugate positional relationship with respect to the imaging lens 25, whereby the aperture 24a of the slit 24 is formed on the detection surface of the one-dimensional image sensor 29. The image of 24b is clearly formed. Reference numeral 30 denotes a light-shielding cut plate, which prevents extraneous light from entering the one-dimensional image sensor 29.

FIG. 4 is a cross sectional view of the cell 27. The cell 27 has a first chamber 71 and a second chamber 72 which are formed by diagonally partitioning the inner space of a cell container 27a formed of a transparent cylinder having a rectangular prism shape with a transparent partition plate 27b.
The first chamber 71 is filled with a sample such as a sample solution whose refractive index is to be measured, and the second chamber 71
72 is filled with a reference such as its solvent.

The light flux L2 passes through the partition plate 27b from the second chamber 72, travels through the first chamber 71 toward the reflecting mirror 28, and the light flux L1 passes through only the second chamber 72. The light beams L1 and L2 after being reflected by the reflecting mirror 28 travel in a direction substantially opposite to the direction shown in FIG. Thus, the light flux L2 transmits both the sample solution in the first chamber 71 and the solvent in the second chamber 72, and the light flux L1 transmits only the solvent. The light flux L1 is deflected according to the mutual refractive index difference between the solvents, and the light flux L1 is not deflected due to the refractive index difference. Therefore, the distance between the image formation positions of the images of the openings 24a and 24b of the slit 24 detected by the one-dimensional image sensor 29 corresponds to the difference in refractive index between the sample solution and the solvent. The same is true when the first chamber 71 is filled with the solvent and the second chamber 72 is filled with the sample solution, and the light flux L2 that passes through the partition plate 27b is deflected according to the refractive index difference, and only the second chamber 72 is provided. The light flux L1 that passes through is not deflected due to the difference in refractive index.

The slit 26a provided behind the imaging lens 25 has the light fluxes L1 and L2.
The light beam L2 to ensure that the light flux L2
And the light beam L1 is surely transmitted only through the second chamber 72 of the cell 27. As a result, on the detection surface of the one-dimensional image sensor 29, the light flux L2 that has transmitted both the sample solution and its solvent and the light flux L1 that has transmitted only the solvent are reliably separated and imaged.

FIG. 5 is a perspective view for explaining the measurement principle, and shows how the light beams L1 and L2 are imaged on the detection surface of the one-dimensional image sensor 29. First chamber 71 and second chamber 72 of cell 27
If both of them are filled with the solvent of the sample solution, the light flux L2 is not deflected and is transmitted through the optical path L _REF to the one-dimensional image sensor.
It is incident on 29 detection surfaces. Light flux without this deflection
Misalignment ΔX between the image _forming position S _{REF of} L2 and the image forming position S2 of the light beam L2 that has been deflected when the sample solution is placed in the first chamber 71.
Corresponds to the difference in refractive index between the sample solution and its solvent. What is detected by the one-dimensional image sensor 29 is the distance ΔX1 between the image forming position S1 of the light beam L1 and the image forming position S2 of the light beam L2, but the distance ΔX0 between the image forming positions S1 and S _REF is set in advance. If calculated, the positional deviation ΔX (= ΔX−ΔX0) can be calculated.

In this embodiment, since the optical path is turned back by the reflecting mirror 28 and the light beams L1 and L2 are passed through the cell 27 twice, the light beam L2 is deflected twice. Therefore, the positional deviation ΔX corresponds to a value twice the displacement amount of the slit image in the case of the conventional configuration shown in FIGS. 21 and 24, for example. Therefore, in the differential refractometer of the present embodiment, the refractive index difference Δn is Δ in the above equation.
obtained by replacing x with ΔX / 2, Becomes However, the angle θ is an angle formed by the light flux L2 and the partition plate 27b of the cell 27 (see FIG. 4), and l is the distance from the cell 27 to the detection surface of the one-dimensional image sensor 29.

Further, the distance between elements (not shown) such as a photodiode in the one-dimensional image sensor 29 is 56 × 10 5.
^If it is ^-3 (mm), ΔX = m · 56 × 10 ^-3 (mm) ...... by the number of elements m between the image forming positions of the slit image, so the above equation is Will be transformed.

FIG. 6 is a diagram showing the output signal strength of the one-dimensional image sensor 29. The horizontal axis represents the one-dimensional coordinates on the detection surface of the one-dimensional image sensor 29, and the vertical axis represents the output signal strength. The peak P1 corresponds to the light flux L1, and the peak P2a is the first chamber 71.
It corresponds to the light flux L2 when a solvent is added to the
It corresponds to the luminous flux L2 when the sample solution is put in the chamber 71. The distance ΔX1 shown in FIG. 5 corresponds to the distance between the vertices of the peaks P1 and P2b, the distance ΔX0 corresponds to the distance between the vertices of the peaks P1 and P2a, and the positional deviation ΔX corresponds to the vertices of the peaks P2a and P2b. Corresponds to the distance between. These are shown together in FIG.

Due to the action of the aperture 26, for example, the light flux L1 forming the peak P1 is sufficiently narrowed down, so that the peak P1
Can have a sufficiently sharp shape. This also applies to the peaks P2a and P2b.

In this embodiment, when determining the peak position, the area of the portion surrounded by each peak and the coordinate axis (hereinafter referred to as "peak area") is calculated. Then, the coordinate value that bisects this peak area is determined as the peak position. According to such a peak position determining method, the one-dimensional image sensor
It is possible to determine the peak position more detailed than the inter-element spacing at 29.

As another method for determining the peak position, the average position x _M is calculated based on the following formula with the light amount I _i detected by each element of the one-dimensional image sensor 29 as a weight, and the average position is calculated.
A method in which x _M is the peak position can also be used.

However, x indicates a coordinate position on the detection surface of the one-dimensional image sensor 29.

However, this method has a drawback that data deviated from the average position x _M is emphasized. In the method of setting the coordinate position that bisects the peak area as the peak position as described above, the importance of all lights becomes uniform, and almost all of the received light is treated as valid data. Has the advantage of being higher.

As the technique for determining the peak position, the technique disclosed in, for example, Japanese Patent Laid-Open No. 63-295935 can be used. The disclosed technique is such that when light is received by, for example, five elements in a one-dimensional image sensor,
The center of gravity of the pentagon formed on the graph showing the correlation between the light quantity and the coordinate position is determined as the peak position, and the height of a predetermined base triangle having an area equal to the area of this pentagon is determined as the peak height. Even if the peak position of the intensity of the incident light on the image sensor is in the non-photoelectric conversion region between the elements, the peak position and the peak height can be accurately detected. Also by applying this technique, it is possible to determine the peak position in more detail than the spacing between the elements.

FIG. 7 shows the peak position coordinate x1 of the peak P1 corresponding to the light flux L1.
(See FIG. 6) and the luminous flux when the solvent is put in the first chamber 71.
It is a figure which shows each time change with the peak position coordinate x2a (refer FIG. 6) of the peak P2a corresponding to L2. The image formation positions of the light fluxes L1 and L2 are affected by mechanical vibrations and air fluctuations, and fluctuate with the passage of time as indicated by curves l1 and l2, respectively. However, this change in the imaging position
The distances ΔX0 between the respective imaging positions of the luminous fluxes L1 and L2 show almost no time change as shown by the curve l0, and in the experiment by the present inventors, ± 2/1000
Only the time change in (mm) was measured.

In this way, the distance ΔX0 can be accurately measured by eliminating the influence of mechanical vibration and the like. First chamber of cell 27
The same is true when the sample solution is put in 71, and therefore the distance ΔX1 in FIG. 5 is accurately measured. As a result,
The positional deviation ΔX can be obtained with high accuracy. That is,
In this embodiment, since the light flux L2 that has passed through the sample solution and the light flux L1 that has transmitted only the solvent are detected at the same time,
Effects such as mechanical vibrations and air fluctuations commonly appear as changes in the imaging positions of the light fluxes L1 and L2.Therefore, the distance between the two can be accurately measured by canceling out the above error factors. Will be seen.

For example, if the distance 1 between the cell 27 and the one-dimensional image sensor 29 is 300 (mm) and the angle θ is 45 degrees, the minimum detection sensitivity Δn _min is Becomes As described above, the influence of mechanical vibration or the like is extremely suppressed, so that the detection sensitivity represented by the above equation can be easily obtained.

As described above, in the structure of this embodiment, the mechanical glass such as the correction glass plate 7 in the first prior art shown in FIG. 21 or the chopper 17 in the second prior art shown in FIG. 24 is used. Since it does not include a structure driven by, and each component is stationary during the measurement operation, unwanted vibration does not occur, and the number of parts is reduced, which is advantageous for low cost. Become. Moreover, as described above, the positional deviation ΔX of the image forming position of the light flux L2 is measured with high accuracy without being affected by mechanical vibration, aging of the optical base (not shown), etc. Will be measured with extremely high accuracy.

Further, two light fluxes L1 and L2 are formed from the light from the single light source 21, and the light fluxes L1 and L2 are further narrowed down by the slit 26a so as to be surely divided and incident on the cell 27 respectively. Both the solution and its solvent are transmitted, and the light flux L1 is made to transmit only the solvent, and the slit 24 for forming the light fluxes L1, L2 from the light source light is provided with the one-dimensional image sensor 29 and the optical system with respect to the imaging lens 25. The images of the openings 24a and 24b of the slit 24 are clearly formed on the detection surface of the one-dimensional image sensor 29 by arranging so as to have a conjugate positional relationship. As a result, the one-dimensional image sensor 29
The distance ΔX1 between the image forming positions of the images of the openings 24a and 24b of the slit 24 can be measured with high accuracy.

As a cell for separately storing the sample and the reference, instead of the cell 27 as shown in FIG.
As shown in each of FIGS. 11 to 11, the inner space of the cell container 40 formed of a transparent cylinder having a quadrangular prism shape is partitioned by a transparent partition plate 41 having a V-shaped cross section. For example, one of the chambers 42 has a refractive index measured. A cell may be used in which a sample to be subjected to is placed and a reference having a known refractive index is placed in the other chamber 43. In this case, if the light flux L2 is made to pass through the partition plate 41, this light flux L2 will be deflected by the refractive index difference between the sample and the reference twice by passing through the cell once. The amount of deflection is doubled, so that the accuracy of refractive index measurement can be further improved.

Another example of the cell is the configuration shown in FIG. In this cell, a V block 45 in which a V-shaped recess 45a is formed by a transparent solid material having a known refractive index is formed, and a sample 46 such as a solid or a liquid whose refractive index is to be measured is placed in the recess 45a. It is set or housed. In this case, the V block 45 functions as a reference.

In addition to the cells as described above, when two light fluxes are simultaneously incident, one light flux transmits the sample and the reference, and the other light flux transmits any one of the sample and the reference. Cells may be used. Further, both light fluxes may be configured to pass through the sample and the reference, but in this case, the angles between the two light fluxes and the partition plate partitioning the sample and the reference are made different from each other, It is necessary to prevent the traveling directions of the light beams after deflection from being parallel to each other. Further, the sample and reference need not be a fluid, such as a liquid, but can be solid.

FIG. 13 is a plan view showing a simplified basic configuration of another embodiment of the present invention, and FIG. 14 is a front view thereof. In FIGS. 13 and 14, parts corresponding to the respective parts shown in FIGS. 1 and 2 are designated by the same reference numerals. In this embodiment, a cell 50 having the same structure as the Blythe cell shown in FIG. 22, for example, is used in place of the cell 27 used in the embodiment shown in FIGS. Then, the light flux L2 passes through this cell 50, and the light flux L1
Propagates in the air outside the cell 50. The cell 50 is a partition plate that is arranged so as to be oblique to the light flux L2, and divides its internal space into two chambers, one chamber containing a sample whose refractive index is to be measured and the other chamber having a refractive index. It contains a known reference. This reference may be air.

According to such a configuration, the light flux L2 undergoes the deflection corresponding to the refractive index difference between the sample and the reference,
Since the light flux L1 is not deflected due to the refractive index difference,
The distance between the image forming positions of the light fluxes L1 and L2 detected by the one-dimensional image sensor 29 corresponds to the refractive index difference.
Then, the same action and effect as in the case of the embodiment shown in FIGS. 1 and 2 can be achieved.

As shown in FIG. 15, an empty cell 53 having the same structure as the cell 50 and housed in both chambers may be provided in the optical path of the light flux L1 passing outside the cell 50, and in this case, The image sensor 29 detects the distance between the image forming positions of the light fluxes L1 and L2, and
Since it is possible to cancel the influence on the refractive index, it is possible to further improve the measurement accuracy of the refractive index. Further, instead of the empty cell 53, a solid cell made of a transparent solid material may be used.

Further, as the cell 50, for example, a cell having a partition plate having a V-shaped cross section, similar to the cell shown in FIGS.
It is also possible to use a cell as shown in the figure. In this case, since the light beam L2 passes through the cell and is deflected twice, the measurement accuracy of the refractive index is further improved.

In addition, in each of the above-described embodiments, the slit 24 forms the two separated light beams L1 and L2. However, instead of the slit 24, another light transmitting member may be used.
That is, the light transmitting member is, for example, as shown in FIG.
The transparent plate-like body 33 has at least two light-shielding portions 31, 32 (first
6 Shaded lines are shown in the figure. ) To form a pattern,
The light-shielding portions 31 and 32 may be used as identification points, and as shown in FIG. 17, the light-transmitting member shown in FIG. 16 has a light-shielding portion and a light-transmitting portion that are reversed. Good.

The shape of the light shielding portion is arbitrary, and may be circular or the like as shown in FIG. Further, as shown in FIG. 19, a rectangular light-shielding portion 36 may be formed on the transparent plate-like body 35, and for example, both end portions 36a and 36b of the light-shielding portion 36 may be used as two identification portions. . Further, as shown in FIG. 20, a scale 38 may be formed on the surface of a transparent plate-shaped body 37. By focusing on at least two identification points in this way, the deflection amount of the light transmitted through the sample and the reference can be obtained based on the detection output of the image sensor 29.

In addition, the light blocking plate 30 may be, for example, an aperture 26 and a cell.
27, between the cell 27 and the reflecting mirror 28, or a plurality of light-shielding cut plates may be used.

Furthermore, in each of the above-described embodiments, the optical path is folded back by using the reflecting mirror 28 to make the entire structure compact, and the light beams L1 and L2 are deflected by passing through the cell 27 twice each. The deflection amount of the light beam L2 is increased to improve the measurement accuracy.
Instead of using, the one-dimensional image sensor 29 may be arranged behind the cell 27 to form a linear structure so that the light beams L1 and L2 pass through the cell 27 only once.

Various other design changes can be made without departing from the scope of the present invention.

<Effects of the Invention> As described above, according to the differential refractometer of the present invention, since the mechanically driven component is not included, mechanical vibration is eliminated and the refractive index can be measured with high accuracy. It is possible to reduce the number of parts and contribute to cost reduction. Moreover, since the light transmitted through the two identification points of the original image is detected by the image sensor at the same time,
Even if the image formation position of the light transmitted through one of the identification points shifts due to vibration or air fluctuation, the image formation position of the light transmitted through the other identification point shows the same change. By obtaining the distance between the image forming positions, it is possible to cancel the deviation of the image forming position due to the vibration or the fluctuation of air.

Furthermore, since the light transmitting member and the image sensor are arranged so as to have a conjugate positional relationship with the lens,
Since the image of the light transmission member can be clearly formed on the detection surface of the image sensor, and the diaphragm member surely splits the light transmitted through the two identification portions of the light transmission member. The two lights can be reliably separated on the detection surface of the image sensor. As a result, 2 of the original image
The measurement accuracy of the distance between the image formation positions of the light transmitted through the two identification points becomes good. This can also contribute to improving the accuracy of the refractive index measurement.

[Brief description of drawings]

FIG. 1 is a plan view showing a simplified basic configuration of a differential refractometer according to an embodiment of the present invention, FIG. 2 is a front view thereof, FIG. 3 is a front view of a slit 24, and FIG. A sectional view of the cell 27, FIG. 5 is a perspective view showing the principle of refractive index measurement, FIG. 6 is a view showing the output intensity of the one-dimensional image sensor 29, and FIG. 7 is each of peaks P1 and P2a in FIG. FIGS. 8 to 12 are cross-sectional views each illustrating an applicable cell, and FIG. 13 is a plan view schematically showing the basic structure of another embodiment of the present invention. FIG. 14, FIG. 14 is a front view thereof, FIG. 15 is a plan view showing a basic configuration of still another embodiment of the present invention, and FIGS. 16 to 20 exemplify applicable light transmitting members. A front view, FIG. 21 is a plan view showing a simplified configuration of the first prior art, FIG. 22 is a sectional view of the cell 5, and FIG. Plane for explanatory view, FIG. 24 is a front view schematically showing the structure of a second prior art. 21 ... Light source, 24 ... Slit (light transmitting member), 25 ... Imaging lens, 26 ... Aperture (diaphragm member), 27 ... Cell, 29 ... One-dimensional image sensor, 53 ... Empty cell

Claims (9)

[Claims] 1. A light source (21), a light transmitting member having an original image having at least two identification points corresponding to the image forming for forming an image by transmitted light, and a light transmitting member which transmits the light transmitting member. Lens that collects light from the light source (2
5), with respect to this lens (25), an image sensor (29) arranged at a position conjugate with the light transmitting member to detect the formation of the original image, the light transmitting member and the image sensor (29) And a diaphragm member (26a) having two openings, which are arranged at any position between the two and through which the lights (L1, L2) having passed through the two identification points of the original image of the light transmitting member respectively pass. The light (L2) passing through one opening of the diaphragm member (26a)
By arranging so that the interface between the sample whose refractive index is to be measured and the reference having a reference refractive index is obliquely transmitted, thereby distinguishing between the two images formed on the image sensor (29). A differential refractometer, wherein the relative refractive index of the sample is measured based on the distance between the portions corresponding to the locations. 2. The differential refractometer according to claim 1, wherein the reference is air. 3. The sample whose refractive index is to be measured and the reference having a reference refractive index are respectively contained in cells (27, 50) for separately containing these substances. The differential refractometer according to claim 1. 4. The light (L1) that has passed through the other opening is arranged so as to pass through the medium in the air or any of the following (a) to (d). 3. The differential refractometer described in 3. (A) A portion containing a reference in the cell (27) (b) A portion containing a sample in the cell (27) (c) A cell different from the cell (50) and filled only with air ( 53) (d) A cell (53) filled with a medium having a known refractive index, which is different from the cell (50). 5. The differential refractometer according to claim 1, wherein the light transmitting member having the original image is a diaphragm member (24) having openings (24a, 24b) at least at two positions. 6. The differential refraction according to claim 1, wherein the light transmissive member having the original image is a translucent plate (33, 35) on which a light shield (31, 32, 36) is formed. Rate meter. 7. The differential refractometer according to claim 1, wherein the light transmitting member having the original image is a light shielding plate on which a light transmitting portion is formed. 8. The light transmitting member having the original image is graduated (3
8. The differential refractometer according to claim 1, which is a transparent plate (37) in which 8) is engraved. 9. The light transmitting member and the image sensor (2
9. The differential refractometer according to claim 1, further comprising an aperture (26) which is arranged at a position for condensing the light from the light source and which has an opening through which the condensed light passes. .