JPH1048130A - Refractive index measuring method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a refractive index without being affected by a change in the quantity of light of a light source. SOLUTION: In a refractive index measuring method by a total reflection method, a refractive index is calculated on the basis of a ratio of the total quantity of the reflected light from the predetermined region within the total reflection region 3a of a substance to be inspected obtained from a specific light source 1 and the total quantity of the reflected light from the region containing the critical angle point 3c of the substance to be inspected obtained from the same light source as the above mentioned light source. By this constitution, standard quantity of light can be simply formed without branching separate reference light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring a refractive index by a total reflection method and an apparatus therefor, and more particularly, to a method of measuring a refractive index by a total reflection method, which can measure a refractive index without being affected by a change in light amount of a light source. And its device.

[0002]

2. Description of the Related Art Conventionally, as a method of measuring the refractive index by the total reflection method, for example, using a refractive index measuring apparatus shown in FIG. Then, there is a method in which the light reflected by the one surface 102 is received by the light receiver 104, and the refractive index is calculated using a computer based on the amount of light received by the light receiver 104 or a distribution curve thereof.

[0003] In the transmission region where the incident angle i is smaller than the critical angle, most of the reflected light incident on the one surface 102 of the prism 101, that is, the surface of the test substance from the light source 103 is refracted and refracted. In the total reflection region where the light is transmitted through the test substance and the incident angle i is larger than the critical angle, all the incident light is reflected. Therefore, the light amount distribution of the reflected light reflected by the one surface 102 is, for example, as shown in FIG. , Strength 2 at the critical angle point
Become a step.

[0004] As the light receiver 104, one having a large number of light receiving elements such as a CCD, for example, can be used. Also, as shown by a broken line in FIG. A configuration is also adopted in which a light receiver 104a having a single light receiving element is arranged at this image forming point, and the refractive index is calculated based on the amount of light received by the light receiver 104.

In the conventional method and apparatus for measuring the refractive index by the total reflection method, the amount of light of the light source 103 changes during a long period of use or the influence of the ambient temperature after the power is turned on. There is a problem that occurs.

Therefore, in this conventional method of measuring the refractive index by the total reflection method, a part of the reflected light emitted from the light source 103 is received by another light receiving element 106 as reference light, and the received light amount La of this light receiving element 106 is The light receiver 104 is calculated by the ratio (La / L ₀ ) to the reference light receiving amount L ₀ corresponding to the predetermined reference light amount.
The light receiving amount Lb is divided to calculate a corrected light receiving amount L (= Lb · La / L ₀ ) corresponding to a predetermined reference light amount, and the refractive index is calculated based on the corrected light receiving amount L.

The another light receiving element 106 may be simply arranged near the light source, or may receive reflected light branched via a spectroscope including a mirror and a prism.

[0008]

However, according to the conventional method and the apparatus for measuring the refractive index, the light source 103 is used.
Of the intensity distribution of the light source may not appear linearly in all directions (in the direction toward the sample or in the direction of the reference light) but may appear differently depending on the direction. In this case, before and after the intensity change of the light source, The use of reference lights of different intensities results in measurement errors.

When a reference optical path branched from the measuring optical path is provided, a spectroscope is required.
There is a problem that the device becomes large. In addition, there is a problem that the number of parts is large and the configuration is disliked, and there is a disadvantage that the assembling workability is increased.

The present invention has been made in view of the above circumstances, and can accurately measure the refractive index of a test substance without being affected by a change in the amount of light of a light source, and achieve miniaturization and downsizing. And the number of parts is small,
It is an object of the present invention to provide a refractive index measuring method which has a simple structure and can further improve the assembling workability, and a total reflection type refractive index measuring device which can execute this method.

[0011]

The present invention employs the following means to achieve the above object. That is,
In the refractive index measurement method by the total reflection method, the total amount of reflected light from a predetermined area in the total reflection area of the test substance obtained from a specific light source, and the test substance obtained from the same light source as the specific light source The refractive index is determined based on the ratio to the total amount of light reflected from the region including the critical angle point.

More specifically, as shown in FIG. 1, a light receiving element 7a for receiving a total amount of reflected light of a test substance obtained from a specific light source 1 from a predetermined area in a total reflection area, A light receiving element 7b for receiving the total amount of reflected light from a region including the critical angle point of the test substance obtained from the same light source 1 as the light source;
An arithmetic unit 10 for calculating the refractive index based on the ratio of the amounts of light received by the two light receiving elements 7a and 7b is provided.

In the above, the focal point of the convex lens 4 on the incident side is set near the exit-side prism surface, and the light-receiving element 7a for receiving the total amount of reflected light from a predetermined area in the total reflection area on the exit-side prism surface. And a light receiving element 7b for receiving the total amount of reflected light from a region including the critical angle point. With this configuration, the lens on the emission side can be omitted.

Further, if a single module formed from the same wafer is used as the light receiving element 7a and the light receiving element 7b, the change in the electrical characteristics of the two light receiving elements 7a and 7b becomes the same. It can be further reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. The refractive index measuring apparatus according to one embodiment of the present invention shown in the configuration diagram of FIG. 1 includes a light source 1 and a prism 2, and irradiates the sample surface 3 of the prism 2 with dispersed light from the light source 1 at a predetermined angle. I am trying to do it.

That is, the convex lens 4 is disposed between the light source 1 and the prism 2, and the light emitted from the light source 1
In this way, light diffused from the pseudo light source point 5 enters the sample surface 3.

The test substance comes into contact with the sample surface 3 and the light source 1
Critical angle ic at which the incident angle of light is determined by the analyte
In the larger total reflection area 3a, the incident light is totally reflected,
In the transmission region 3b smaller than the critical angle ic, most of the incident light is refracted and transmitted through the test substance. The boundary between the total reflection area 3a and the transmission area 3b is a critical angle point 3c.

The reflected light in a certain area in the total reflection area 3a is converged and received by the first light receiving element 7a of the light receiver 7 through another convex lens 6, and the critical angle point 3c and its The reflected light from the region 3d including the critical angle point extending to the total reflection region 3a and the transmission region 3b on both sides passes through the same convex lens 6 and converges on the second light receiving element 7b of the light receiver 7 and is received.

In the present invention, the amount of received light La from a predetermined area of the total reflection area 3a of the test substance and the amount of received light Lb from an area including the critical angle point are obtained in this manner. Then, the ratio (Lb / L) of the light reception amount La from a predetermined region of the total reflection region 3a to the light reception amount Lb from the region 3d including the critical angle point.
Since a certain relationship as shown in FIG. 3, for example, is established between a) and the refractive index n, the arithmetic means 10 determines the amount of received light La from a predetermined region of the total reflection area 3a and the critical angle point. By calculating the ratio (Lb / La) of the amount of received light Lb from the included region 3d and obtaining the refractive index n based on the ratio (Lb / La), the refractive index n can be accurately determined regardless of the change in the light amount of the light source 1. You can ask.

Further, in this case, since the direction of the incident light from the light source corresponding to the predetermined area in the total reflection area and the area including the critical angle point does not largely shift, the intensity change of the light source 1 is changed in both areas (total reflection). Area including the area and the critical angle point), and therefore, the light receiving amounts of the two light receiving elements 7a and 7b also appear linearly with the change in the intensity of the light source 1, thereby enabling more accurate measurement. Become.

Further, since the area 3d including the critical angle point includes the total reflection area 3a, the optical path of the reflected light is changed by the convex lens 6.
, The light receiving elements 7a and 7b can be adjacent to each other at a very small distance, so that the size and size of the device can be reduced, and the assembling workability can be improved. Further, since there is no need to split the light from the light source 1 with a spectroscope or the like, the above-mentioned miniaturization and compactness can be further promoted.

In particular, in this embodiment, when a single module in which two adjacent light receiving elements 7a and 7b are formed from the same wafer is used, the number of parts is further reduced,
The structure is simpler, the assembling workability can be further improved, and the electrical characteristics of both light receiving elements 7a and 7b are hardly varied, so that the measurement accuracy can be further improved.

In a refractive index measuring apparatus according to another embodiment of the present invention shown in FIG. 2, a light receiver 7 is attached to an emission surface 8 of a prism 2, and light emitted from a light source 1 is reflected by a convex lens 4. The light is incident on the sample surface 3 of the prism 2 while being focused, is reflected on the sample surface 3, that is, the surface of the test substance, and is then focused near the light receiver 7.

However, in the example shown in FIG. 2, since the light from the lens 4 is not once converged, the total reflection area 3a and the transmission area 3a are not reflected.
b, and the region 3d including the critical angle point is reversed left and right from the example shown in FIG.

With the above configuration, the second convex lens 6 on the emission surface 8 side can be omitted, the number of parts can be further reduced, the configuration can be further simplified, and the entire apparatus can be further reduced in size and size. In addition, it is possible to further reduce the size and further enhance the assembling workability.

The other constructions, operations and effects of this embodiment are the same as those of the above-described embodiment, and therefore, description thereof will be omitted to avoid duplication.

[0027]

As described above, according to the present invention, the total amount of light reflected from a predetermined area in the total reflection area of a test substance is determined.
The refractive index is determined based on the ratio to the total amount of reflected light from the area including the critical angle point.Moreover, in this case, the direction of the total reflection area and the area including the critical angle point are substantially the same. Changes linearly in both directions, and the refractive index of the test substance can be accurately measured without being affected by the change in the intensity of the light source.

Also, the element for receiving the reference light or the spectral structure provided between the conventional light source and the prism is omitted,
The number of parts can be reduced and the configuration can be simplified. Further, by providing both light receiving elements adjacent to each other, it is possible to make the entire device small and compact. Further, by using two light receiving elements incorporated in a single module as the two adjacent light receiving elements, it is possible to further reduce the size and size of the device and to improve the assembling workability. The effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a light amount ratio and a refractive index in a region including a critical angle point and a predetermined region in a total reflection region according to the present invention.

FIG. 4 is a configuration diagram of a conventional example.

FIG. 5 is an intensity distribution diagram of reflected light from the surface of a test substance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 3a Total reflection area 3b Transmission area 3c Critical angle point 7a, 7b, light receiving element

Claims (4)

[Claims] In a method of measuring a refractive index by a total reflection method, a total amount of reflected light of a test substance obtained from a specific light source from a predetermined area in a total reflection area and obtained from the same light source as the specific light source. A method for measuring a refractive index based on a ratio of a total amount of reflected light from a region including a critical angle point of a test substance to be measured. 2. A light-receiving element for receiving a total amount of reflected light of a test substance obtained from a specific light source from a predetermined region in a total reflection area, wherein the specific light source is provided. A light-receiving element for receiving the total amount of reflected light from a region including the critical angle point of the test substance obtained from the same light source; and calculating means for calculating a refractive index based on a ratio between the outputs of the two light-receiving elements. A refractive index measuring device, comprising: 3. A light-receiving element for receiving a total amount of reflected light from a predetermined area in the total reflection area on the exit-side prism surface, wherein a focal point of the entrance-side convex lens is set near the exit-side prism surface; The refractive index measuring device according to claim 2, wherein a light receiving element that receives a total amount of reflected light from a region including the corner point is attached. 4. A light receiving element for receiving the total amount of reflected light from a predetermined area in the total reflection area and a light receiving element for receiving the total amount of reflected light from an area including the critical angle point are formed from the same wafer. The refractive index measuring device according to claim 2 or 3, which is a single module.