JPS6054617B2 - Simultaneous measurement method of refractive index and refractive index dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously measuring refractive index and refractive index dispersion using a refractive index dispersion measuring device that measures the refractive index dispersion of a substance using a prism-shaped sample.

The above-mentioned type of refractive index dispersion measuring device is disclosed in Japanese Patent Application No. 53-08629 filed on July 3, 1978 (Japanese Patent Publication No. 58-1).
743), the refractive index n is determined as a function of the wavelength λ by measuring the minimum polarization angle of light by a prism, and by differentiating it, refraction can be calculated. A method was used to find the variance of the rate.

In other words, in a prism with an apex angle α as shown in Fig. 1dλ,
When light is incident at angle φ, the deflection angle of light by the prism is E, and other symbols are defined as shown in Figure 1. Between these angles, φ1+φ2=E+α...
・・・・・・(1)φ1+φ2=α・・・・・・・・・
・(2) slnφ1 ■nSlnφ1, ,,,,,,,
, (3) sinφ2 ■nsinφ2 ・・・・・・・
...There is the relationship (4).

This when ε becomes the minimum Emln. Solving the equations of
n ■sinC+(Emin+α)] ・・・・・・(
5) sin(+α), and using this formula, n=n(
Find λ).

A device as shown in FIG. 2 is known as a specific device.

In Fig. 2, 1 is a wavelength variable light source, 2 is a rotatable sample stage, and 3 is a rotatable optical position detector that can read the rotation angle. y2φlb, 11-sin2 (two lb)
4 is an optical position detector attached to the table 3, and 5 is a prism-shaped sample.

The operation of this device is to take the light from the wavelength tunable light source 1 to the sample 5, enter it into the optical position detector 4, move the sample stage 2 so that the declination angle becomes the minimum, and then move the sample stage 2 so that the minimum declination angle E,... The refractive index n is determined from equation (5) by reading n using the stand 3.

Evening: The above method measures only the refractive index, and the device has the disadvantage that it requires two high-precision rotary tables that share a rotating axis. In addition, in a conventional refractive index fraction measurement device, the sample stage is rotated so that the light enters the optical position detector fixed at a position close to the minimum deviation angle, and the angle of the sample stage is adjusted to the wavelength of the light source. A method was used to determine the wavelength fraction value by reading the amount of shift corresponding to the difference. This apparatus and method is illustrated in the embodiment of FIG. Third
In the figure, 1 is a wavelength tunable light source, 4 is a light position/detector, and 5 is a wavelength tunable light source.
is a sample prism, and 6 is a sample stage whose rotation angle can be read. The wavelength tunable light source 1 and the optical position detector 4 are fixed at "appropriate positions", and the sample stage 6 is rotated so that the light from the wavelength tunable light source 1 enters the optical position detector 4. (The term "appropriate position" refers to a position determined in advance by calculation or preliminary experiment so that light enters the detector 4 by rotating the sample stage 6.) The wavelength was changed by Δλ. If it is necessary to rotate the sample stage 6 by Δφ1, then the low A
Also l·A... (6) The refractive index dispersion can be determined from dλ dφ1 Δλ.

(6) - in equation dλ needs to be calculated in advance, but in this method, α and E are fixed in equations (1) to (4), so all variables (φ1
, φ2, φ1, φ2) are functions of only n.

Therefore, the above measurements are performed using the formula for refractive index as a function of wavelength λ. The refractive index n and refractive index dispersion N? of the sample prism at ? A method for simultaneously measuring refractive index and refractive index dispersion, characterized by determining the following. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously measuring refractive index and refractive index dispersion using a refractive index dispersion measuring device that measures the refractive index dispersion of a substance using a prism-shaped sample.

The above-mentioned type of refractive index dispersion measuring device is disclosed in Japanese Patent Application No. 53-08629 filed on July 3, 1981 (Japanese Patent Publication No. 5811).
743), the refractive index n is determined as a function of the wavelength λ by measuring the minimum polarization angle of the light by the prism, and the refraction is determined by differentiating it. A method was used to find the variance 41 of the ratio.

In other words, in a prism with an apex angle α as shown in Fig. 1dλ,
If the polarization angle of the light by the prism when the light is incident at an angle φ1 is E, and the other symbols are defined as shown in FIG. 1, then there is a relationship between these angles.

When ε becomes the minimum εMin, solving these and other equations, we get
Using this formula, n=n(λ) is determined.

A device as shown in FIG. 2 is known as a specific device.

In Fig. 2, 1 is a wavelength variable light source, 2 is a rotatable sample stage, 3 is a rotatable stage on which an optical position detector that can read the rotational angle is attached, and 4 is an optical position attached to the stage 3. The detector 5 is a prism-shaped sample. H The operation of this device is to first transfer light from the wavelength tunable light source 1 to the sample 5.
is placed in the optical position detector 4, the sample stage 2 is moved so that the declination angle t becomes the minimum, and the minimum declination angle E. , n are read on the stand 3, and the refractive index n is determined from equation (5). 5. The above method measures only the refractive index, and the device has the disadvantage that it requires two high-precision rotary tables that share a rotation axis. In addition, in a conventional refractive index fraction measurement device, the sample stage is rotated so that the light enters the optical position detector (fixed at a position close to the minimum deviation angle), and the angle of the sample stage is adjusted to the wavelength of the light source. A method was used to determine the wavelength fraction value by reading the amount of shift corresponding to the difference.
This apparatus and method is illustrated in the embodiment of FIG. In FIG. 3, 1 is a variable wavelength light source, 4 is an optical position detector, 5 is a sample prism, and 6 is a sample stage whose rotation angle can be read. The wavelength tunable light source 1 and the optical position detector 4 are fixed at a suitable position, and the sample stage 6 is rotated so that the light from the wavelength tunable light source 1 enters the optical position detector 4. C. The term "appropriate position" refers to a position determined in advance by calculation or preliminary experiment so that light can enter the detector 4 by rotating the sample stage 6. ) When the wavelength is changed by Δ, the sample stage 6 is changed to Δφ1
If it is necessary to rotate the refractive index dispersion N from
? can be found.

41 in equation (6) needs to be calculated in advance, but in this method, α and E are fixed in equations (1) to (4), so all variables (φ
1, φ2, φ1, φ2) is a function only of n.

Therefore, the above measurements are based on the refractive index n as a function of wavelength input.
(λ) is known, and its error is also n(
The disadvantage was that it depended on the error of λ). The present invention
Using a refractive index dispersion measuring device that uses one precision rotary table,
It is an object of the present invention to provide a method for determining refractive index and refractive index dispersion at the same time.

First, FIG. 4 will be used to explain the method of the present invention.
Figure 4 shows the same device as Figure 3, except for 5 (
a) and 5(b) show the sample prism in two positions (described below). (The sample prism is on the sample stage 6.
Since the sample stage 6 is mounted on the sample stage 6, the rotational position of the sample stage 6 is also changed corresponding to 5(a) and 5(b). ) The point where the light from the wavelength tunable light source 1 is perpendicularly incident on the prism surface is defined as zero degree of the rotation angle of the sample stage 6.

The angle of incidence is assumed to be φ1 as shown in FIG. Next, the wavelength of light source 1 is set to λ-, the sample stage is rotated, and the sample stage is stopped several degrees before the incident angle φ10 that gives the minimum deviation angle (accurately, it cannot be measured for reasons explained later). Let the rotation angle of φ1a be φ1a. FIG. 5 shows the above function as a graph with the horizontal axis representing the incident angle φ1 and the vertical axis representing the deflection angle ε.

7 is the φ1-ε curve when the wavelength is λ, 8 is the wavelength is λ
The upper curve of φ1 when +C is shown.

According to this, there is φ1b that gives the same declination angle E at a location several degrees larger than the incident angle φ10 that gives the minimum declination angle, so
Read this angle. Next, the same measurement is performed by changing the wavelength of the light source 1 to λ+ to Δ, and the incident angles corresponding to φ1a and φ1 are set to φ″1a and φ″1b. Since the curve of the graph in Figure 5 is symmetrical near the minimum declination angle,
By finding the average value of φ″1a, φ1a, φ1b, φ″1, the incident angle φ10 that provides the minimum deviation angle can be found. (Since the curve above φ1 in FIG. 5 is flat at the position of φ10, an accurate value cannot be obtained unless such a calculation is performed.) From φ10, the refractive index n can be obtained from the following equation. Regarding the error δn of the refractive index n, when α = 60 degrees, the incident angle φ that gives the refractive index n and the minimum deviation angle is
10 errors are almost equal.

This error is about the same as that obtained using the minimum argument method.

The change Δn in the refractive index due to changing the wavelength λ is given by the following equation.

However, φ″1 represents φ″11 or φ″1b, and φ1
represents φ13 or φ1b.

In this formula, if we ignore the second term and below as errors, we get
The following equation is obtained. (Formula 1a is the measured value φ1a, φ″1a,
The formula for calculating from φ1b, φ″1b, n and set values α, ε, λ is obtained as follows. First, (1)
～If φ1, φ2, and φ2 are eliminated from equation (4), n becomes φ
It is found as a function of 1, α, and ε. If we differentiate it by φ1, we get Therefore, n (desired), that is, φ1 and φ″
-02 in the average value of 1 is given by the following formula.

The measured values of φ1 and φ″1 are the value φ1a at the wavelength λ ]”, the value φ1a at φ″18 and the value φ1 at λ+]
Since there are b and φ″1, the accuracy is improved by taking the average value of n″ obtained from each. Therefore, n″(
Summary b)=n″1+n″. However, it is.

In addition, (by taking the average value for φ1″−φ1 in equation 10, it becomes.

These are obtained by dividing Δn substituted in equation 10 by Δλ.

Incident angles φ1a, φ″1a, φ1 measured using this formula
.
It is sufficient to calculate it from the measurement of the wavelength λ without calculating the average of the measurements of λ and λ+], but in the present invention, the refractive index n and the refractive index dispersion l?
and the angle of incidence φ, . , φ, 5, φ″1a, φ″1b can be obtained simultaneously from the given Δλ, so there is no need to adjust the light source wavelength to λ and newly measure φ1a and φ1b. . Considering the error factors in this measurement, the error may be due to the omission of the third order of Δφ1 (i.e. φ″-φ1) and subsequent parts in equation 1a.
, -φ, ), the error in the change in refractive index is a=60
degree, n=1.46, n″ is −2 to −3
If it is normally measured using Δφ1=3 particles, the error of Δn will be 10 −7 or less.

The error in Δn due to the error in Δφ1 itself is less than 0.1 within 5 degrees from φ1 that gives the minimum deviation angle.

Also, if the reading error of Δφ1 is 10-5 (2 seconds),
The error of Δn is 10 −6 or less. As mentioned above,
According to the present invention, the refractive index and refractive index dispersion of a sample can be measured simultaneously with one rotary table device, and the measurement accuracy can be increased by increasing the number of averaging operations.

[Brief explanation of drawings]

Figure 1 is a diagram to explain the refraction of light by a prism.
Fig. 2 is a block diagram of a conventional refractive index measuring device, Fig. 3 is a block diagram of a conventional refractive index dispersion measuring device, and Fig. 4 shows how to implement the present invention using the measuring device of Fig. 3. The shown configuration diagram and FIG. 5 are graphs of an embodiment for explaining the present invention in detail. 1... Wavelength variable light source, 2... Turntable,
3... Turntable with scale, 4... Optical position detector, 5... Sample prism, 6... Turntable with scale, 7... . . . φ1 upper curve when the light source wavelength is Aλλ−2, 8 . . . φ 1 upper curve when the light source wavelength is λ + Δ blue.

Claims (1)

[Scope of Claims] 1. A sample table having a wavelength tunable light source, a rotation angle readable sample stage equipped with a sample prism having an apex angle α, and an optical position detector, and comprising a wavelength tunable light source, a sample stage capable of reading the rotation angle, and an optical position detector, which converts the light from the wavelength tunable light source into an angle of incidence. The light beam is optically arranged so that it is incident on the sample prism having the apex angle α at φ_1, is refracted by the sample prism, is emitted from the sample prism at an angle of deviation ε relative to the incident light, and is incident on the optical position detector. Using a refractive index dispersion side measurement device, two incident angles φ_1_a and φ_1_b (φ_1_a<φ_1_b) that give one declination angle ε slightly larger than the minimum declination angle are set to wavelength λ=
Measured for light of λ_0-Δλ/2, and similarly wavelength λ=
Two incident angles φ'_1_a and φ'_1_b (φ'_1_
a<φ′_1_b), and the incident angles φ_1_a and φ_1_b, φ′_1_a and φ′_1_b) obtained by the measurement and the previously given α, ε and Δλ
From, φ_1_0=(φ_1_a+φ_1_b+φ'_
1_a+φ′_1_b)/4n=sinφ_1_0/(
sinα/2) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼ dn/dλ={(φ′_1_a−φ_1_a+φ′_1
_b−φ_1_b)/(2・Δλ・sin α)}・(n
'_a+n'_b)/2, the refractive index n and refractive index dispersion dn/d of the sample prism at wavelength λ_0
A method for simultaneously measuring refractive index and refractive index dispersion, characterized by determining λ.