JP2013024720A - Refractive index measurement method, refractive index measurement instrument, and refractive index measurement program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure a refractive index of an optical element without requiring measurement of a thickness of the optical element.SOLUTION: A refractive index measurement instrument 20 is an optical system for interfering test light and reference light each other, is capable of placing a test optical element in an optical path of the test light, and is used together with an interference optical system including optical path length changing means 3 for changing an optical path length of one of the test light and the reference light. The instrument 20 obtains difference of interference setting values between an interference setting value of the optical path length changing means 3 when the test light transmitted through the test optical element placed in the optical path interferes with the reference light and an interference setting value when the test light and the reference light interfere with each other without the test optical element in the optical path, with respect to each of mutually different first and second wavelengths included in wavelength bands of the test light and the reference light. The instrument 20 calculates a refractive index of the test optical element using difference in the first wavelength, the difference in the second wavelength, and dispersion of the test optical element.

Description

  The present invention relates to a technique for measuring the refractive index of an optical element such as a lens by utilizing interference of light.

  Low coherence interferometry is often used to measure the refractive index of optical elements. As one of the low coherence interferometry, the refractive index of the optical element is measured by detecting the interference between the reflected light on the front and back surfaces of the optical element (sample) and the reference light and the interference between the reflected light on the reference surface and the reference light. A method has been proposed. Further, Non-Patent Document 1 discloses a method for measuring the refractive index of an optical element using a dispersion curve of the optical element measured using a low coherence interferometry and the thickness of the optical element measured separately. Yes.

High-precision indexmeasurement in anisotropic crystals using white-light spectral interferometry; author H. Delbarre published Applied Physics B

  The above-described method of detecting the interference between the reflected light and the reference light on the surface of the optical element and measuring the refractive index of the optical element is easily affected by the surface shape of the optical element, and the measurement accuracy is low. This is because the wavefront of the reflected light on the surface of the optical element has a very large aberration.

  Although the method disclosed in Non-Patent Document 1 does not measure the interference between the reflected light on the surface of the optical element and the reference light, it is necessary to measure the thickness of the optical element in advance. However, it is very difficult to measure the thickness of an optical element having a lens shape or the like with necessary accuracy.

  The present invention provides a refractive index measurement method, a refractive index measurement device, and a refractive index measurement program that can measure the refractive index of an optical element with high measurement accuracy while making it unnecessary to measure the thickness of the optical element.

  A refractive index measuring apparatus according to an aspect of the present invention is an optical system that causes test light and reference light to interfere with each other, and allows the test optical element to be installed in the optical path of the test light. And an interference optical system including an optical path length changing means for changing one optical path length of the reference light, and measures the refractive index of the optical element to be tested. When the optical path length changing means obtains an optical path length at which the test light and the reference light interfere with each other, when the value indicating the setting of the optical path length changing means is used as the interference set value, the test light and the reference Interference setting value when the test light transmitted through the test optical element installed in the optical path interferes with the reference light in each of the first wavelength and the second wavelength different from each other included in the light wavelength band And the difference between the interference setting value when the test light and the reference light interfere with each other with the test optical element removed from the optical path. The apparatus calculates the refractive index of the test optical element using the difference at the first wavelength, the difference at the second wavelength, and the dispersion of the test optical element.

  The refractive index measuring apparatus according to one aspect of the present invention is an optical system that causes the test light and the reference light to interfere with each other, and a liquid that can immerse the test optical element in the optical path of the test light. It is used together with an interference optical system that includes an optical path length changing unit that changes the optical path length of one of the test light and the reference light, and measures the refractive index of the test optical element. When the optical path length changing means obtains an optical path length at which the test light and the reference light interfere with each other, when the value indicating the setting of the optical path length changing means is used as the interference set value, the test light and the reference An interference set value when the test light transmitted through the test optical element immersed in the liquid and the reference light interfere with each other in the first wavelength and the second wavelength different from each other included in the wavelength band of the light; The difference between the test light transmitted through the liquid not immersed in the test optical element and the interference set value when the reference light interferes is obtained, and the test optical element is obtained at each of the first and second wavelengths. The interference setting value when the test light transmitted through the liquid in which the liquid is not immersed interferes with the reference light, and the test light and the reference light interfere with each other with the test optical element and the liquid removed from the optical path The refractive index of the liquid is obtained using the interference setting value. The apparatus uses the difference at the first wavelength, the difference at the second wavelength, the refractive index of the liquid at each of the first and second wavelengths, and the dispersion of the test optical element. The refractive index is calculated.

  A refractive index measurement method (refractive index measurement program) as another aspect of the present invention is an optical system that causes test light and reference light to interfere with each other, and the test optical element is in the optical path of the test light. The refractive index of the optical element to be measured is measured using an interference optical system that includes an optical path length changing unit that changes the optical path length of one of the test light and the reference light. When the measurement method (measurement program) sets the value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is set as the interference setting value by the optical path length changing means, The test light and the reference light that have passed through the test optical element installed in the optical path interfere with each other in the first wavelength and the second wavelength that are different from each other in the wavelength bands of the test light and the reference light. Determining a difference between the interference setting value when the test light and the reference light interfere with the test optical element removed from the optical path, and the difference in the first wavelength, Calculating the refractive index of the test optical element using the difference at the second wavelength and the dispersion of the test optical element.

  Furthermore, a refractive index measurement method (refractive index measurement program) as another aspect of the present invention is an optical system that causes test light and reference light to interfere with each other, and the test optical element is in the optical path of the test light. The refractive index of the optical element to be measured is measured using an interference optical system including an optical path length changing unit that changes the optical path length of one of the test light and the reference light. . When the measurement method (measurement program) sets the value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is set as the interference setting value by the optical path length changing means, When the test light transmitted through the test optical element immersed in the liquid and the reference light interfere with each other in the first wavelength and the second wavelength included in the wavelength bands of the test light and the reference light, respectively. Determining a difference between the interference set value of the first and second interference wavelengths when the test light transmitted through the liquid in which the test optical element is not immersed and the reference light interfere with each other, and In each case, the test light with the test light transmitted through the liquid in which the test optical element is not immersed interferes with the reference light, and the test light with the test optical element and the liquid removed from the optical path. And the interference setting value when the reference beam interferes And a step of determining a refractive index of the liquid. Then, the refractive index of the test optical element is calculated using the difference at the first wavelength, the difference at the second wavelength, the refractive index of the liquid at each of the first and second wavelengths, and the dispersion of the test optical element. And a calculating step.

  According to the present invention, the detection light and the reference light transmitted through the optical element can be transmitted without requiring the detection of the reflected light by the optical element that decreases the measurement accuracy and the high-precision measurement of the thickness of the optical element. The refractive index of the optical element can be accurately measured using low coherence interference.

The figure which shows the structure of the refractive index measurement system containing the refractive index measuring apparatus which is Example 1 of this invention. 3 is a flowchart for explaining a refractive index measurement method in Embodiment 1. The figure which shows the structure of the refractive index measurement system containing the refractive index measuring apparatus which is Example 2 of this invention. 9 is a flowchart for explaining a refractive index measurement method in Embodiment 2. The figure which shows the target board in an Example. The figure explaining the effect of an Example.

Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration of a refractive index measuring system including a refractive index measuring apparatus that is Embodiment 1 of the present invention.

  Reference numeral 1 denotes a white light source (hereinafter simply referred to as a light source), which outputs light having a wide wavelength band in order to shorten the coherence length. As the light source 1, for example, a super continuum (SC) light source that outputs light from ultraviolet to infrared or two super luminescent diodes (SLD) that output different wavelengths are used.

  A focus adjuster 18 has a function of performing focusing so that light from the light source 1 is focused on a test lens as a test optical element. The focus adjuster 18 is adjusted in advance so as to be focused on the lens to be examined, and always maintains a constant state during measurement.

  A demultiplexer 2 divides light from the light source 1 (focus adjuster 18) into two, and propagates one light to the reference light path and the other light to the test light path. As the duplexer 2, for example, a beam splitter having no wavelength dependency and having a wedge so that back surface reflected light is not mixed in an interference signal is used.

  An optical path length adjuster (optical path length changing means) 3 is provided in the reference optical path. The optical path length adjuster 3 has a driving stage having two reflecting surfaces, and the optical path length of the reference light reflected by the two reflecting surfaces can be adjusted (changed) by moving the driving stage. The optical path length adjuster 3 can output a set value as a value indicating the setting of the optical path length adjuster 3, that is, the position of the two reflecting surfaces that move with the drive stage (that is, the position of the drive stage). The set value is a value that changes as the drive stage moves, that is, the optical path length of the reference light changes.

  In the following description, the set value of the optical path length adjuster 3 is referred to as a stage value, and the set value when the optical path length of the reference light where the test light and the reference light interfere is obtained as the interference stage value (interference setting). Value).

  In the present embodiment, the optical path length adjuster 3 is disposed in the reference optical path, but may be disposed in the test optical path. That is, the optical path length adjuster 3 may be provided on one of the reference optical path and the test optical path.

  A test stage 15 on which the test lens 6 can be installed is provided in the test light path. The test stage 15 has a structure in which the test lens 6 can be installed and removed and the parallel eccentricity and inclination of the installed test lens 6 can be adjusted.

  The eccentricity of the test lens 6 is adjusted using the eccentricity adjustment target plate 14 as an index. For example, white paper is used for the target plate 14. As shown in FIG. 5, bright spots of test light and reference light are formed on the target plate 14. The eccentricity of the test lens 6 is adjusted so that the bright spot of the test light is spatially superimposed on the bright spot of the reference light.

  The test lens 6 is an optical element whose dispersion is known and through which the test light can pass. The center of the test lens 6 means a line connecting the center of curvature of one lens surface of the test lens 6 and the center of curvature of the other lens surface. Further, the central portion of the lens 6 to be examined means a region including the center and the vicinity thereof.

  Reference numeral 7 denotes a multiplexer that spatially superimposes the light propagating through the test optical path and the reference optical path. As the multiplexer 7, for example, a beam splitter having no wavelength dependency and having a wedge so that back surface reflected light is not mixed into an interference signal is used.

  The wavelength divider 8 spatially divides light having a wide wavelength band into two lights having different wavelengths. For example, a dichroic mirror is used as the wavelength divider 8.

Reference numerals 9 and 10 denote wavelength selectors, which are included in each of the two lights divided by the wavelength divider 8 (that is, included in the test light and the reference light), and only light components in different specific wavelength bands. Is transmitted (that is, band-pass filtering is performed). The width of the specific wavelength band is desirably set to about 40 nm or less. In FIG. 1, the center wavelength of light transmitted through the wavelength selector 9 is denoted as λ ₁ (first wavelength), and the center wavelength of light transmitted through the wavelength selector 10 is denoted as λ ₂ (second wavelength).

  Reference numerals 11 and 12 denote light intensity detectors that detect the intensity of light transmitted through the wavelength selectors 9 and 10, respectively. As the light intensity detectors 11 and 12, for example, photodiodes are used. The light source 1 to the light intensity detectors 11 and 12 described above constitute an interferometer including an interference optical system.

  Reference numeral 20 denotes a refractive index measuring device, which is constituted by a personal computer that operates according to a refractive index measuring program as a computer program. The refractive index measuring device 20 receives the stage value from the optical path length adjuster 3 and the outputs from the light intensity detectors 11 and 12. The refractive index measuring device 20 adjusts (controls) the position of the drive stage of the optical path length adjuster 3 so that the test light and the reference light interfere with each other while monitoring the outputs of the light intensity detectors 11 and 12.

  A refractive index measurement device (hereinafter simply referred to as a measurement device) 20 executes a refractive index measurement program (refractive index measurement method) shown in the flowchart of FIG. 3 to perform a refractive index (group refractive index) at the center of the test lens 6. Measure. Here, it is assumed that the test lens 6 is installed on the test stage 15 and arranged in the test optical path, and the parallel eccentricity and inclination are also adjusted.

In step 1, the measurement apparatus 20 obtains a signal (hereinafter referred to as an interference signal) indicating the interference between the reference light having the wavelengths λ ₁ and λ ₂ and the test light as outputs of the light intensity detectors 11 and 12. Then, the position of the drive stage of the optical path length adjuster 3 is adjusted. Then, to obtain the interference stage values S1, S2 of the optical path length adjuster 3 when the respective interference signals of wavelengths lambda ₁ and wavelength lambda ₂ is obtained.

Next, the test lens 6 is removed from the test stage 15 (test optical path), and the test light does not pass through the test lens 6. In this state, in step 2, the measuring apparatus 20 adjusts the position of the drive stage of the optical path length adjuster 3 so that the interference signals having the wavelengths λ ₁ and λ ₂ can be obtained from the light intensity detectors 11 and 12. Then, to obtain the interference stage values S3, S4 of the optical path length adjuster 3 when the respective interference signals of wavelengths lambda ₁ and wavelength lambda ₂ is obtained.

The reference light and the test light having the wavelengths λ ₁ and λ ₂ interfere with each other when the optical path lengths of the reference light and the test light match at the respective wavelengths. In an ideal interference optical system, when the dispersion of air is approximated to 0, the interference stage values S3 and S4 have the same value, and only S3 needs to be acquired. However, actually, the interference stage values S3 and S4 are different from each other due to a system error such as a difference in thickness of the beam splitter. Therefore, it is better to acquire both interference stage values S3 and S4.

  Further, the interference stage values S3 and S4 are different from the interference stage values S1 and S2 because the optical path length of the test optical path changes depending on the presence or absence of the test lens 6.

  It is desirable to perform the processing of steps 1 to 4 quickly in order to reduce the influence due to the environmental change of the measurement system. For this purpose, it is better to obtain the interference stage values S1 and S2 before the interference stage values S3 and S4 in order to save time for adjusting the installation posture of the lens 6 to be examined.

Next, in step 3, the measurement apparatus 20 determines, for each of the wavelengths λ ₁ and λ ₂ , the difference in interference stage values α, when the test lens 6 is placed in the test optical path and when it is not placed. β is calculated as follows.
α = S1-S3
β = S2-S4
The differences α and β are such that D is the center thickness of the test lens 6, _ng (λ) is the group refractive index of the test lens at the wavelength λ, the air group refractive index is _{ng_air,} and its dispersion is 0. and when,

It can be expressed as. The group refractive index _{ng_air} of air can be calculated using Edlen's equation by measuring the temperature, pressure and humidity in the measuring device.

  In step 4, the measuring apparatus 20 calculates the center thickness D of the test lens 6 from the differences α and β determined in step 3 and the known dispersion of the test lens 6. The dispersion of the test lens 6

Becomes known by measuring in advance.

  The thickness D is obtained by the following formula.

In step 5, the measuring device 20 calculates the group refractive index of the center of the lens 6 to be measured at the wavelengths λ ₁ and λ ₂ from the difference α and the difference β and the center thickness D of the lens 6 to be tested. The group refractive index calculated here is averaged in the direction in which the light beam passes through the center of the lens 6 to be examined.

Moreover, the measuring apparatus 20 performs conversion from a group refractive index to a phase refractive index using the following formula as necessary. N _g is a literature value of the group refractive index, and N _p is a literature value of the phase refractive index. _ng is an actual measurement value of the group refractive index obtained by the above equation (a), and _NP is an actual measurement value of the phase refractive index to be obtained. N _g and N _p is, for example, a manufacturer and catalogs of producing a glass material which is the material of the lens 6.

The effect of the present embodiment will be described with reference to FIG. The inclination of the incident light with respect to the normal of the lens surface of the lens 6 to be examined is θ, the inclination of the transmitted light with respect to the incident light is θ _t, and the inclination of the reflected light with respect to the incident light is θ _r . Furthermore, the refractive index of the test lens 6 is n, and the refractive index of the medium around the test lens 6 is n ′. In this case, from Snell's law, between the θ and θ _t the following relationship holds.
n'sinθ = nsin (θ-θ _t )
Since it can be assumed that θ is sufficiently small, the slope θt is

It can be expressed as. In addition, since the inclination θ _{r of the} reflected light is twice θ,

This relationship holds. Here, since the refractive index of the lens 6 to be examined is 1 <n <2, the inclination of the light beam passing through the lens 6 is smaller than that of the reflected light beam. Therefore, the measurement accuracy of the refractive index is improved by measuring only the transmitted light having a small ray inclination and a small wavefront aberration.

According to the results of experiments (simulations) by the inventor, by using the measurement method of this example, the optimum wavelengths λ ₁ and λ ₂ (for example, λ ₁ = 400 nm, λ ₂ = 800 nm) can be selected. The refractive index of the test lens 6 can be measured with an accuracy of 2 × 10 ⁻⁴ .

  FIG. 2 shows a configuration of a refractive index measuring system including a refractive index measuring apparatus that is Embodiment 2 of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description is omitted.

  In this embodiment, a liquid tank 16 filled with a liquid 17 capable of immersing the test lens 6 is disposed in the test optical path of the interference optical system. The portion of the wall surface of the liquid tank 16 through which the test light passes is formed as a window glass. The window glass is formed using a glass material having high parallelism on the front and back surfaces, and the incident-side window glass and the emission-side window glass in the liquid tank 16 are arranged in parallel to each other. An interval (liquid interval) L between the entrance side window glass and the exit side window glass is measured in advance.

  The liquid 17 has a higher refractive index than air, does not completely absorb the test light, and does not change the refractive index during measurement of the refractive index of the test lens 6. In the present embodiment, a liquid 17 having a refractive index closer to the lens 6 to be examined than air is used. When the test lens 6 is immersed in such a liquid 17, the refraction of the test light on the lens surface can be reduced.

  According to the equation (b) described in the first embodiment, as n ′ is closer to n, the inclination t of the transmitted light becomes smaller, and the measurement accuracy of the refractive index at the center of the lens 6 to be measured is improved.

  Reference numeral 30 denotes a refractive index measuring device, which is constituted by a personal computer that operates according to a refractive index measuring program as a computer program. The refractive index measuring device 30 receives the stage value from the optical path length adjuster 3 and the outputs from the light intensity detectors 11 and 12. The refractive index measurement device 30 adjusts (controls) the position of the drive stage of the optical path length adjuster 3 so that the test light and the reference light interfere with each other while monitoring the outputs of the light intensity detectors 11 and 12.

  The refractive index measuring apparatus (hereinafter simply referred to as a measuring apparatus) 30 of this embodiment executes a refractive index measuring program (refractive index measuring method) shown in the flowchart of FIG. Group refractive index). Here, it is assumed that the test lens 6 is placed on the test stage 15 and immersed in the liquid 17 filled in the liquid tank 16 together with the test stage 15 and arranged in the test optical path. It is also assumed that the parallel eccentricity and inclination are adjusted.

In step 11, the measuring apparatus 30 uses the optical path length adjuster 3 so that an interference signal indicating interference between the reference light having the wavelengths λ ₁ and λ ₂ and the test light can be obtained as the outputs of the light intensity detectors 11 and 12. Adjust the position of the drive stage. Then, to obtain the interference stage values S1, S2 of the optical path length adjuster 3 when the respective interference signals of wavelengths lambda ₁ and wavelength lambda ₂ is obtained.

Next, the test lens 6 is removed from the test stage 15 (test light path), so that the test light does not pass through the test lens 6 and passes through the liquid 17 in the liquid tank 16. In this state, in step 12, the measuring apparatus 30 adjusts the position of the drive stage of the optical path length adjuster 3 so that the interference signals having the wavelengths λ ₁ and λ ₂ can be obtained from the light intensity detectors 11 and 12. Then, to obtain the interference stage values S3, S4 of the optical path length adjuster 3 when the respective interference signals of wavelengths lambda ₁ and wavelength lambda ₂ is obtained.

Further, the liquid 17 is also removed from the test light path (liquid tank 16), and the test light does not pass through the test lens 6 and the liquid 16. In this state, in step 13, the measuring device 30 adjusts the position of the drive stage of the optical path length adjuster 3 so that the interference signals having the wavelengths λ ₁ and λ ₂ can be obtained from the light intensity detectors 11 and 12. Then, to obtain the interference stage value S5, S6 of the optical path length adjuster 3 when the respective interference signals of wavelengths lambda ₁ and wavelength lambda ₂ is obtained.

Subsequently, in step 14, the measuring apparatus 30 determines the refractive index (group refraction) of the liquid 17 at the wavelengths λ ₁ and λ ₂ from the interference stage values S 3, S 4, S 5, S 6 and the liquid bath interval L obtained in the previous step. Rate). Specifically, first, differences γ and ε between the interference stage values S3, S4, S5 and S6 are calculated as follows.
γ = S3-S5
ε = S4-S6
Then, the group refractive index _{ng_oil} (λ) of the liquid 17 at the wavelength λ is calculated by the following equation.

Next, in step 15, the measurement apparatus 30 determines, for each of the wavelengths λ ₁ and λ ₂ , the difference between the interference stage values α and β when the test lens 6 is placed in the test optical path and when it is not placed. Is calculated.
α = S1-S3
β = S2-S4
The differences α and β are such that D is the center thickness of the test lens 6, _ng (λ) is the group refractive index of the test lens at the wavelength λ, and _{ng_oil} (λ) is the group refractive index of the liquid 17 at the wavelength λ. And when

It can be expressed as.

  Next, in step 16, the measuring apparatus 30 obtains the center thickness D of the test lens 6 from the differences α and β obtained in step 15 and the known dispersion of the test lens 6. The dispersion ν of the test lens 6 is known as described in the embodiment.

  And thickness D is calculated | required with the following formula | equation.

Subsequently, in step 17, the measuring apparatus 30 determines the object to be measured at the wavelengths λ ₁ and λ ₂ from the differences α and β, the center thickness D of the lens 6 to be measured, and the group refractive index _{ng_oil} (λ) of the liquid 17. The group refractive index at the center of the analyzing lens 6 is calculated. The group refractive index calculated here is averaged in the direction in which the light beam passes through the center of the lens 6 to be examined.

Moreover, the measuring apparatus 30 performs conversion from a group refractive index to a phase refractive index using the following formula as necessary. N _g is a literature value of the group refractive index, and N _p is a literature value of the phase refractive index. _ng is an actual measurement value of the group refractive index obtained by the above equation (c), and _NP is an actual measurement value of the phase refractive index to be obtained. N _g and N _p is, for example, a manufacturer and catalogs of producing a glass material which is the material of the lens 6.

  In each of the above-described embodiments, it is not necessary to detect reflected light from the lens 6 to be measured and reduce the thickness of the lens 6 to be measured with high accuracy. Therefore, according to each embodiment, the refractive index of the test lens 6 can be accurately measured by using the low coherence interference between the test light transmitted through the test lens 6 and the reference light.

  In the first and second embodiments, a beam splitter may be used as the wavelength divider 8. In the first and second embodiments, the Mach-Zehnder type is used as the interferometer (interference optical system). However, other interferometers such as a ring interferometer may be used.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  It is possible to provide a refractive index measurement technique for accurately measuring the refractive index of an optical element by using light interference.

3 Optical path length adjuster 6 Test lens 17 Liquid 20, 30 Refractive index measuring device

Claims (6)

An optical system for causing the test light and the reference light to interfere with each other, and a test optical element can be installed in the optical path of the test light, and the optical path length of one of the test light and the reference light is set A refractive index measuring device that is used together with an interference optical system including an optical path length changing means for changing, and measures a refractive index of the optical element to be tested.
When a value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is obtained by the optical path length changing means as an interference setting value,
The test light transmitted through the test optical element installed in the optical path in each of the first wavelength and the second wavelength different from each other in the wavelength bands of the test light and the reference light, and the A difference between the interference setting value when the reference light interferes and the interference setting value when the test light and the reference light interfere with the test optical element removed from the optical path. Seeking
A refractive index measuring apparatus that calculates a refractive index of the optical element to be measured using the difference at the first wavelength, the difference at the second wavelength, and dispersion of the optical element to be measured. An optical system for causing the test light and the reference light to interfere with each other, wherein a liquid capable of immersing the test optical element is disposed in an optical path of the test light, and the test light and the reference light A refractive index measuring device that is used together with an interference optical system including an optical path length changing means for changing one optical path length and measures the refractive index of the optical element to be tested,
When a value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is obtained by the optical path length changing means as an interference setting value,
The test light transmitted through the test optical element immersed in the liquid and the reference at different first wavelengths and second wavelengths included in the wavelength bands of the test light and the reference light, respectively A difference between the interference setting value when the light interferes with the interference setting value when the test light transmitted through the liquid in which the test optical element is not immersed interferes with the reference light. Seeking
In each of the first and second wavelengths, the interference set value when the test light transmitted through the liquid in which the test optical element is not immersed interferes with the reference light, and the test Obtaining the refractive index of the liquid using the interference set value when the test light and the reference light interfere with each other in a state where the optical element and the liquid are removed from the optical path,
The test optical element using the difference at the first wavelength, the difference at the second wavelength, the refractive index of the liquid at each of the first and second wavelengths, and the dispersion of the test optical element The refractive index measuring apparatus characterized by calculating the refractive index of. An optical system for causing the test light and the reference light to interfere with each other, and a test optical element can be installed in the optical path of the test light, and the optical path length of one of the test light and the reference light is set A refractive index measurement method for measuring a refractive index of the optical element to be measured using an interference optical system including an optical path length changing unit to change,
When a value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is obtained by the optical path length changing means as an interference setting value,
The test light transmitted through the test optical element installed in the optical path in each of the first wavelength and the second wavelength different from each other in the wavelength bands of the test light and the reference light, and the A difference between the interference setting value when the reference light interferes and the interference setting value when the test light and the reference light interfere with the test optical element removed from the optical path. Seeking steps,
Calculating a refractive index of the test optical element using the difference in the first wavelength, the difference in the second wavelength, and dispersion of the test optical element. Measuring method. An optical system for causing the test light and the reference light to interfere with each other, wherein a liquid capable of immersing the test optical element is disposed in an optical path of the test light, and the test light and the reference light A refractive index measurement method for measuring a refractive index of the optical element to be measured using an interference optical system including an optical path length changing unit for changing one optical path length,
When a value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is obtained by the optical path length changing means as an interference setting value,
The test light transmitted through the test optical element immersed in the liquid and the reference at different first wavelengths and second wavelengths included in the wavelength bands of the test light and the reference light, respectively A difference between the interference setting value when the light interferes with the interference setting value when the test light transmitted through the liquid in which the test optical element is not immersed interferes with the reference light. Seeking steps,
In each of the first and second wavelengths, the interference set value when the test light transmitted through the liquid in which the test optical element is not immersed interferes with the reference light, and the test Obtaining a refractive index of the liquid using the interference setting value when the test light and the reference light interfere with each other in a state where the optical element and the liquid are removed from the optical path;
The test optical element using the difference at the first wavelength, the difference at the second wavelength, the refractive index of the liquid at each of the first and second wavelengths, and the dispersion of the test optical element Calculating a refractive index of the refractive index. On the computer,
An optical system for causing the test light and the reference light to interfere with each other, and a test optical element can be installed in the optical path of the test light, and the optical path length of one of the test light and the reference light is set A refractive index measurement program for executing a measurement of the refractive index of the optical element to be measured using an interference optical system including an optical path length changing unit to be changed,
When a value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is obtained by the optical path length changing means as an interference setting value,
The test light transmitted through the test optical element installed in the optical path in each of the first wavelength and the second wavelength different from each other in the wavelength bands of the test light and the reference light, and the A difference between the interference setting value when the reference light interferes and the interference setting value when the test light and the reference light interfere with the test optical element removed from the optical path. Seeking steps,
Calculating a refractive index of the test optical element using the difference in the first wavelength, the difference in the second wavelength, and dispersion of the test optical element. Measurement program. On the computer,
An optical system for causing the test light and the reference light to interfere with each other, wherein a liquid capable of immersing the test optical element is disposed in an optical path of the test light, and the test light and the reference light A refractive index measurement program for performing a measurement of the refractive index of the optical element to be measured using an interference optical system including an optical path length changing means for changing one optical path length,
When a value indicating the setting of the optical path length changing means when the optical path length at which the test light and the reference light interfere with each other is obtained by the optical path length changing means as an interference setting value,
The test light transmitted through the test optical element immersed in the liquid and the reference at different first wavelengths and second wavelengths included in the wavelength bands of the test light and the reference light, respectively A difference between the interference setting value when the light interferes with the interference setting value when the test light transmitted through the liquid in which the test optical element is not immersed interferes with the reference light. Seeking steps,
In each of the first and second wavelengths, the interference set value when the test light transmitted through the liquid in which the test optical element is not immersed interferes with the reference light, and the test Obtaining a refractive index of the liquid using the interference setting value when the test light and the reference light interfere with each other in a state where the optical element and the liquid are removed from the optical path;
The test optical element using the difference at the first wavelength, the difference at the second wavelength, the refractive index of the liquid at each of the first and second wavelengths, and the dispersion of the test optical element And a step of calculating the refractive index of the refractive index measurement program.