JP2892075B2 - Measuring method of refractive index distribution and transmitted wavefront and measuring device used for this method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring a refractive index distribution and a transmitted wavefront in a glass block, a transparent ceramic, and the like, and a measuring apparatus used in the method.

[Related Art] In general, measurement of a refractive index distribution in a glass block, a transparent ceramic, or the like is performed by providing two opposing optical planes on a subject to be a measurement target part and including these optical planes in an optical path. Then, the interference fringe is obtained by analyzing an interference fringe obtained when the subject is arranged in one optical path of the two-beam interferometer by the amplitude division.

At this time, the two optical planes may be directly polished by subjecting the subject to optical polishing, or may be optically polished on a facing surface provided on the subject through a liquid (matching oil) layer having a refractive index close to that of the subject. It is formed by a method such as a method of providing each of the transparent plates (oil-on-plate method) (oil-on-plate method).

For a large object, a plurality of measurement units having two opposing optical planes are provided in the same object, and the refractive index distribution of each measurement unit is determined by the above-described method. The method of setting the refractive index distribution in the measurement part having the largest fluctuation range of the distribution to the refractive index distribution in the subject or using a large two-beam interferometer to reduce the refractive index distribution of the entire subject in one time The method of measuring by operation is taken.

What is obtained by such a conventional method accurately indicates distortion of a transmitted wavefront (light wavefront transmitted through the subject) due to the refractive index distribution and the thickness distribution in the subject.

[Problems to be Solved by the Invention] In recent years, large glass lenses and glass plates have been used in laser fusion devices, IC exposure devices, and the like. There is an increasing demand for large precision glass blocks that are within ^-6 . With such an increase in demand, there is an increasing need to accurately measure a refractive index distribution in an optical material and to accurately measure a transmitted wavefront in a large optical member.

However, what is obtained by analyzing the interference fringes obtained when the subject is arranged in one optical path of the two-beam interferometer by the amplitude division is, as described above, exactly, Since this indicates distortion of the transmitted light wavefront), the conventional method of measuring the refractive index distribution has a problem that the refractive index distribution in the portion to be measured in the subject cannot be accurately measured. Further, when the refractive index distribution in the subject changes linearly, there is a problem that this linear change in the refractive index distribution cannot be detected. Furthermore, in order to measure the refractive index distribution (correctly, the distortion of the transmitted wavefront) of the entire large object by the conventional method of measuring the refractive index distribution, a large interferometer must be used. From the viewpoint of accuracy, there is a problem that it is difficult to increase the size of the interferometer in accordance with the increase in the size of the subject, and at the same time, there is a problem in terms of economy.

Therefore, a first object of the present invention is to provide a method of measuring a refractive index distribution and an apparatus for measuring the same, which can accurately measure a refractive index distribution in a subject.

A second object of the present invention is to provide a method for measuring a refractive index distribution which can accurately measure a refractive index distribution over the entire large object without increasing the size of the interferometer even for a large object. And a measuring device therefor.

Further, a third object of the present invention is to provide a method for measuring a transmitted wavefront that can accurately measure a transmitted wavefront of the entire large object without increasing the size of the interferometer even for a large object. It is an object of the present invention to provide a device for measuring the same.

[Means for Solving the Problems] The present invention has been made to achieve the above object, and a method of measuring a refractive index distribution that achieves the first object of the present invention comprises two opposing optical systems. The object obtained by arranging an object provided with an object to be measured having a plane in one optical path of a two-beam interferometer based on amplitude division so that the two optical planes are included in the optical path. A first interference fringe due to an optical path difference between light passing through an optical path on which a specimen is disposed and light passing through an optical path not including the subject, and a cause of the optical path difference causing the first interference fringe The optical path difference between the two optical paths of the two-beam interferometer, which contributes to the second interference fringe due to the optical path difference in the measured part and the optical path difference that causes the first interference fringe And the result of photoelectrically detecting the third interference fringe is converted into binary signal data. The first, second, and third interference fringes are solved based on the binary signal data stored in the storage medium to determine a phase distribution in each interference fringe. The method is characterized in that a refractive index distribution in the object included in the measured part is obtained based on a phase distribution in the fringes (hereinafter, referred to as a first invention).

Hereinafter, the method for measuring the refractive index distribution of the first invention will be described.
This will be described in detail.

The subject to which this method of measuring the refractive index distribution can be applied is a material having a light-transmitting property or a material having a light-transmitting property when two opposing optical planes are provided. There is no particular limitation, and examples thereof include glass, crystallized glass, translucent ceramics sintered body, translucent single crystal, and plastic. Further, a composite composed of these substances may be used.

The two opposing optical planes are parallelism enough to obtain interference fringes using a two-beam interferometer based on amplitude division (depending on the size of the subject and the size of the part to be measured, but generally (Within 30 seconds) means two optical planes (surface accuracy is generally within λ / 4).

The part to be measured having such two opposing optical planes can be provided on the subject by an ordinary method such as an optical polishing method or an oil-on-plate method. If the subject has the two opposing optical planes in advance, the two
The portion sandwiched between the two optical planes can be used as the portion to be measured. In the method for measuring the refractive index distribution of the first invention, like the oil-on-plate method,
When forming an optical plane by providing a transparent plate having an optically polished surface on the subject, as a transparent plate for forming an optical plane, the refractive index distribution of the subject included in the measured portion of the subject. It is assumed that a transparent plate having a refractive index distribution such that the influence on the measurement result can be ignored is used.

Such an object to be measured having two opposing optical planes may be the whole object or a part of the object.

In the method of measuring a refractive index distribution according to the first aspect of the present invention, the subject provided with the above-described measured part is subjected to amplitude division so that two optical planes provided in the measured part are included in an optical path. A first interference fringe due to an optical path difference between light passing through an optical path on which an object is disposed and light passing through an optical path on which no object is disposed, which is obtained by disposing the light in one optical path of a two-beam interferometer. And the second interference fringe due to the optical path difference in the portion to be measured, which contributes to the optical path difference that causes the first interference fringe, and the optical path difference, which causes the first interference fringe to occur. , And the result of photoelectrically detecting the third interference fringe due to the optical path difference between the two optical paths of the two-beam interferometer is stored in the storage medium as binary signal data.

As used herein, as the two-beam interferometer by amplitude division, for example, a Fizeau interferometer, a Twyman-Green interferometer, a Mach-Zehnder interferometer, and the like can be exemplified.
The first interference fringe can be obtained by a conventional method using any one of the two-beam interferometers.
Are affected by the optical path difference due to the refractive index distribution and the thickness distribution in the measured portion, and the optical path difference between the two optical paths themselves of the interferometer.

The above-mentioned second interference fringe is obtained by irradiating parallel light to the measured portion from one optical plane side of the measured portion having two opposing optical planes and irradiating the parallel light with the parallel light. It can be obtained by superimposing the reflected light reflected on the target plane and the light reflected on the other optical plane through the part to be measured and emitted from the optical plane on the side irradiated with the parallel light again. In this specification, the optical system for obtaining the second interference fringes is also included in the two-beam interferometer based on wavefront division. In obtaining the second interference fringes, it is preferable that the incident direction and the incident angle of the parallel light on the measured portion be the same as those in obtaining the first interference fringes. The second interference fringe is affected by an optical path difference due to a refractive index distribution and a thickness distribution in the measured portion.

For the third interference fringe, the same interferometer as the two-beam interferometer used for obtaining the first interference fringe described above is used, and the subject is arranged on each of the two optical paths of the two-beam interferometer. Instead of 2
It can be obtained by superposing respective lights passing through two optical paths. At this time, it is preferable that the incident direction and the incident angle of the parallel light in each of the optical elements constituting the two-beam interferometer are the same as those for obtaining the first interference fringes. This third interference fringe is affected by the optical path difference between the two optical paths themselves in the interferometer.

The order of obtaining these first, second and third interference fringes is as follows.
There is no particular limitation. In addition, when obtaining the first interference fringe, the second and third interference fringes can be obtained simultaneously.

The photoelectric detection of the first, second, and third interference fringes can be performed by a television camera, a CCD camera, a plurality of photodiodes, and the like. The photoelectric detection result is converted into binary signal data by an A / D converter or the like and stored in a storage medium such as a frame memory, a magnetic tape, a floppy disk, or a hard disk.

In the method for measuring the refractive index distribution according to the first invention, the analysis of each interference fringe is performed based on the binary signal data of the photoelectric detection results of the first, second, and third interference fringes stored in the storage medium. To determine the respective phase distributions. The analysis of the first, second, and third interference fringes is performed by a computer using a fast Fourier transform (FFT) method, a fringe scan method, a thinning method, or the like. The data of the phase distribution obtained in this way is converted into a character, a diagram, or a graphic as necessary,
The information may be displayed by display means such as a printer and a display.

Thereafter, based on the obtained phase distribution, a computer calculates a refractive index distribution in the subject included in the measured part.

The calculation of the refractive index distribution in the subject included in the measured part is performed by the first interference fringe, in which the optical path difference due to the refractive index distribution and the thickness distribution in the measured part, and the optical path difference between the two optical paths themselves of the interferometer. That the second interference fringe is affected by the optical path difference due to the refractive index distribution and the thickness distribution in the part to be measured, and that the third interference fringe has two optical paths in the interferometer. Since the phase distributions of the first, second and third interference fringes are determined by the influence of the optical path difference between themselves, the refractive index distribution in the measured portion, the thickness distribution and the interference in the measured portion are obtained. Since three equations are obtained for the three unknowns of the optical path difference between the two optical paths themselves in the meter, it can be performed by solving these three equations.

That is, in the method of measuring a refractive index distribution according to the first aspect of the present invention, the effect of the optical plane of the measured part on the optical polishing method or the measurement result of the refractive index distribution of the specimen included in the measured part can be ignored. Since it is formed by disposing a transparent plate having a refractive index distribution of the degree, the influence on the optical path difference due to the refractive index distribution in the above-described measured part is as follows.
Since the effect on the optical path difference due to the refractive index distribution in the subject included in the measured part is equivalent to the above, by solving the above three equations, only the refractive index distribution in the subject included in the measured part is calculated. Can be determined accurately. In solving the above three equations, the approximate refractive index and thickness of the test object included in the measurement target part are measured in advance by a common method. At this time, only the thickness distribution at the measured portion can be accurately obtained.

In the present specification, the description will be made assuming that the refractive index distribution means a relative refractive index difference in a subject or a measured portion, but it may be obtained in the process of calculating the refractive index distribution in the present specification. Possible, any coefficient in the refractive index distribution,
For example, the refractive index distribution may be obtained by multiplying the value of the thickness of the subject or the value of the thickness of the portion to be measured.

The data of the refractive index distribution obtained in this manner is converted into a character, a diagram or a visual image, and displayed on a display device such as a printer or a display. The distribution can be grasped concretely.

As described above, the method for measuring a refractive index distribution according to the first aspect of the present invention is a method for accurately measuring a refractive index distribution in a subject contained in a measured part, which achieves the first object of the present invention. In order to achieve this object, a refractive index distribution measuring apparatus according to the present invention comprises: a two-beam interferometer based on amplitude division; a photoelectric detector for photoelectrically detecting an interference fringe obtained by the two-beam interferometer; Means for storing the photoelectric detection result of the interference fringe by the means as binary signal data, and two opposite memory means stored in the first storage means.
Obtained by disposing an object provided with a measurement unit having two optical planes in one optical path of a two-beam interferometer by amplitude division such that the two optical planes are included in the optical path. Binary signal data of a photoelectric detection result of a first interference fringe due to an optical path difference between light passing through an optical path on which the subject is disposed and light passing through an optical path on which the subject is not disposed; Binary signal data as a result of photoelectric detection of a second interference fringe due to an optical path difference in the portion to be measured, which contributes to the optical path difference causing the interference fringe, and the optical path difference causing the first interference fringe The first, second and third signals are based on the binary signal data of the photoelectric detection result of the third interference fringe due to the optical path difference between the two optical paths of the two-beam interferometer, which contributes to Phase distribution calculation to obtain binary signal data of phase distribution in interference fringes Means, second storage means for storing binary signal data of the phase distribution in the first, second and third interference fringes obtained by the phase distribution calculation means, respectively, and storage in the second storage means. Said first and second
A refractive index distribution calculating means for obtaining binary signal data of a refractive index distribution in the object included in the measurement target based on binary signal data of a phase distribution in the third interference fringe; Third storage means for storing binary signal data of the refractive index distribution of the subject contained in the measured part obtained by the distribution calculation means, and the second and third storage means;
Each of the binary signal data stored in the storage means is converted into a character,
And a display means for displaying a graphical or visualized image (hereinafter referred to as a second invention).

The first invention and the second invention are for measuring the refractive index distribution of the object included in the measurement section, and are used for measuring the refractive index of the entire large object without increasing the size of the interferometer. When measuring the refractive index distribution, a method for measuring a refractive index distribution (hereinafter, referred to as a third invention) and an apparatus (hereinafter, referred to as a fourth invention) are applied.

That is, the method for measuring the refractive index distribution according to the third invention is based on the method for measuring the refractive index distribution according to the first invention, and includes a plurality of measurement units having two opposing optical planes. Simultaneously or successively, while providing a common area between the adjacent measurement units, provided in the same object, and after determining the refractive index distribution of the object included in the measurement unit for each of the measurement units. By joining the refractive index distribution of each of the subjects based on the refractive index distribution of the subject included in a common region between the measured portions, in a region where the plurality of measured portions are provided. The method is characterized in that a refractive index distribution of the included subject is obtained.

Hereinafter, the method for measuring the refractive index distribution of the third invention will be described.
This will be described in detail.

This method of measuring the refractive index distribution is based on the method of measuring the refractive index distribution of the first invention. In this method, first, a plurality of measured parts having two opposing optical planes are placed next to each other. Simultaneously or sequentially, a common area is provided in the same subject while providing a common area between the corresponding measuring sections.

The part to be measured having two opposing optical planes is the first
It is formed in the same manner as in the method of measuring the refractive index distribution according to the invention of (1).
In the case where an optical plane is formed by providing a transparent plate having an optically polished surface on the subject as in the oil-on-plate method, the optical plane is formed similarly to the method of measuring the refractive index distribution of the first invention. As a transparent plate for forming a target plane, a transparent plate having such a refractive index distribution as to have a negligible effect on the measurement result of the refractive index distribution of the subject included in the measured part is used.

When providing a plurality of measured parts simultaneously or sequentially while providing a common area between adjacent measured parts,
After two optical planes are provided facing the subject, a mark such as a grid that serves as a reference for a plurality of measurement units is written on the two optical planes by oil-based magic or the like. A method of installing a mark such as a grid serving as a reference for a plurality of measured parts in the optical path after being provided facing the subject, and a method of using a two-beam interferometer after providing two optical planes facing the subject. A method of shifting the range of the optical plane included in the optical path for each measurement by moving the subject,
A method in which the position of a transparent plate such as an oil-on plate or the position of an optical polished surface is shifted every measurement can be applied.

In the method for measuring the refractive index distribution according to the third aspect of the present invention, the refractive index distribution of the object included in the measured part is determined by the refractive index distribution according to the first aspect of the invention. Determined by the measurement method

Thereafter, the refractive index distribution of each subject is joined based on the refractive index distribution of the subject included in the common region between the measurement units, and the resultant is included in the region where the plurality of measurement units are provided. Find the refractive index distribution in the subject.

In joining the refractive index distributions of the respective subjects, the difference between the data of the refractive index distributions of the respective subjects included in the common region between the two measurement units having the common region is 2
After adding a certain value to the refractive index distribution data of one subject so that the sum of squares is minimized, the average value of both values is compared with the refractive index distribution data of the subject included in the common region. And the like. By repeating such joining, it is possible to obtain the refractive index distribution of the specimen included in the region where the plurality of measurement units are provided, and therefore, without increasing the size of the interferometer, it is possible to obtain a large specimen. The refractive index distribution in the whole specimen can be obtained.

The data of the refractive index distribution obtained in this manner is converted into a character, a diagram, or a visual image, and is displayed on a display means such as a printer or a display. Similarly to the above, it is possible to specifically grasp the refractive index distribution of the subject included in the region where the plurality of measurement units are provided.

As described above, the method for measuring the refractive index distribution according to the third aspect of the present invention accurately measures the refractive index distribution of the entire large object without increasing the size of the interferometer even for a large object. This is a measuring method for achieving the second object of the present invention. The measuring apparatus for refractive index distribution according to the fourth invention for achieving the object is provided by the measuring apparatus for refractive index distribution according to the second invention. Based on the binary signal data of the refractive index distribution of the subject included in the plurality of measurement units provided in the same subject, stored in the third storage unit that configures the measuring device, From the binary signal data of the refractive index distribution of the object included in the region to be measured included in the region to be measured, the binary signal data of the refractive index distribution of each object included in the object to be measured is connected. In addition, the plurality of portions to be measured are provided. Data synthesizing means for synthesizing binary signal data of the refractive index distribution in the subject included in the region, a fourth storage means for storing binary signal data obtained by the data synthesizing means, 4 is characterized by adding a second display means for displaying the binary signal data stored in the storage means 4 in a characterized form, a graphic form or a visualized image.

As the second display means used in the refractive index distribution measuring device of the fourth invention, the same display means as the display means in the above-described refractive index distribution measuring device of the second invention can be used.

In the first, second, third, and fourth inventions described above, when an optical plane is formed by providing another transparent plate on the subject as in the oil-on-plate method,
As the transparent plate for forming this optical plane, a transparent plate having a refractive index distribution such that the influence on the measurement result of the refractive index distribution in the specimen included in the measured part is negligible was used. However, when the refractive index distribution in the transparent plate for forming the optical plane is unknown, or when it is clear that the effect of the refractive index distribution in this transparent plate can not be ignored, the refractive index distribution described later A measuring method (hereinafter, referred to as a fifth invention) and an apparatus (hereinafter, referred to as a sixth invention) are applied.

That is, the method of measuring the refractive index distribution of the fifth invention is the same as the method of measuring the refractive index distribution of the first and third inventions, except that the measured part having two opposing optical planes A subject having one surface, and at least one of the main surfaces provided on at least one of the two surfaces of the subject via a liquid layer having a refractive index close to the refractive index of the subject is optically polished. A transparent plate, the refractive index distribution in the portion to be measured, and the refractive index distribution in the transparent plate constituting the portion to be measured, the refractive index in the subject included in the portion to be measured It is characterized by obtaining a distribution.

Hereinafter, the method for measuring the refractive index distribution of the fifth invention will be described.
This will be described in detail.

The method for measuring the refractive index distribution is based on the method for measuring the refractive index distribution according to the first and third aspects of the present invention. In this method, first, an object having two opposing surfaces, At least one of the two surfaces is provided via a liquid layer having a refractive index close to the refractive index of the subject, and at least one main surface is formed of a transparent plate that is optically polished. A refractive index distribution in a portion to be measured having an optical plane is obtained.

The refractive index distribution in the measured portion is obtained by calculating the phase distribution in the first, second and third interference fringes in the same manner as in the refractive index distribution measuring method of the first or third aspect of the invention. 3 obtained by calculating the phase distribution of
It can be obtained by solving two equations. Here, in the method of measuring a refractive index distribution according to the fifth invention, since the refractive index distribution in a transparent plate for forming an optical plane must be considered, what is obtained by solving the above three equations is It is not the refractive index distribution of the subject contained in the measuring section, but the refractive index distribution of the measuring section. Before solving the above three equations,
The approximate refractive index and thickness of the test object and the transparent plate constituting the measurement target part are measured by a conventional method.

Next, the refractive index distribution of the transparent plate constituting the measured portion is determined by the method for measuring the refractive index distribution according to the first or third invention. When two transparent plates with both surfaces optically polished are used, the refractive index distribution in each transparent plate is separately obtained, the value of each refractive index distribution is multiplied by the thickness of each plate, and the sum is calculated. The value obtained by dividing the sum of the thicknesses of the plates may be used as the refractive index distribution of the transparent plate constituting the measured portion. When two transparent plates whose at least one main surface is optically polished are used, the two transparent plates are stretched via a matching oil or the like so that the optically polished main surfaces are located outside. In addition, a refractive index distribution is obtained, and this refractive index distribution is used as a refractive index distribution in the transparent plate constituting the part to be measured.

Thereafter, based on the refractive index distribution in the measured portion and the refractive index distribution in the transparent plate forming the measured portion, for example, a value obtained by multiplying the value of the refractive index distribution of the measured portion by the thickness of the measured portion. The optical path difference of the transparent plate (the value of the refractive index distribution of the transparent plate multiplied by the thickness of the transparent plate) is subtracted from (optical path difference), and the value is divided by the thickness of the part to be measured. The refractive index distribution in the subject constituting the measuring section can be obtained.

The data of the refractive index distribution obtained in this manner is converted into a character, a diagram or a visual image, and displayed on a display device such as a printer or a display. The distribution can be grasped concretely.

As described above, the method for measuring the refractive index distribution according to the fifth aspect of the invention uses the transparent plate when the optical plane is formed by providing another transparent plate on the subject as in the oil-on-plate method. If the refractive index distribution is unknown or is a measurement method applied when it is clear that the effect of the refractive index distribution in this transparent plate can not be ignored,
The measuring apparatus for the refractive index distribution according to the sixth aspect of the present invention, which is a measuring apparatus in this case, is different from the measuring apparatus for the refractive index distribution according to the second or fourth aspect described above in that the second storage means constituting the measuring apparatus A test object having two opposed surfaces, and at least one of the two surfaces of the test object provided via a liquid layer having a refractive index close to the refractive index of the test subject. The first and second portions of the first portion to be measured comprising one of the main surfaces and a transparent plate having an optically polished surface.
And binary signal data of the refractive index distribution in the first measured section based on the binary signal data of the phase distribution in the third interference fringe, and stores the binary signal data in the third storage means. A second refractive index distribution calculating means to be stored, binary signal data of a refractive index distribution in the first measured part stored in the third storing means, and the first measured part are constituted. The transparent plates one by one or
From the binary signal data of the refractive index distribution in the second measured portion composed of a composite plate obtained by laminating two transparent plates via a liquid layer having a refractive index close to the refractive index of these transparent plates,
A third refractive index distribution calculating means for obtaining binary signal data of a refractive index distribution in the subject included in the first measured part; and a binary signal obtained by the third refractive index distribution calculating means. A fifth storage unit for storing data;
And a third display means for displaying the binary signal data stored in the storage means in the form of a character, a graphic, or a visual image and displaying it.

As the third display means used in the refractive index distribution measuring device of the sixth invention, the same display means as the display means in the refractive index distribution measuring devices of the second and fourth inventions described above may be used. it can.

Next, the transmitted wavefront of the present invention, which achieves the third object of the present invention to accurately measure the transmitted wavefront of the large object without increasing the size of the interferometer even for a large object, The measurement method of the transmitted wavefront will be described. In this method, a plurality of measurement units having two opposing optical planes are simultaneously or successively provided with a common region between adjacent measurement units. Provided in the sample,
By arranging the object provided with the object to be measured in one optical path of a two-beam interferometer by amplitude division such that the two optical planes are included in the optical path for each of the object to be measured. The first interference fringes resulting from the optical path difference between the light passing through the optical path on which the subject is arranged and the light passing through the optical path without the subject, and the first interference fringe, Storing the result of photoelectrically detecting a second interference fringe caused by an optical path difference between two optical paths of the two-beam interferometer, which contributes to an optical path difference, as binary signal data in a storage medium; The phase distribution in each interference fringe is obtained by analyzing the first and second interference fringes on the basis of the binary signal data stored in the storage unit. After obtaining the wavefront, the transmitted wavefront Connecting the transmitted wavefronts of the plurality of measured parts based on the transmitted wavefront of a common area between the rarely-measured parts, and combining the transmitted wavefronts in the region where the plurality of measured parts are provided. (Hereinafter, referred to as a seventh invention).

Hereinafter, the method for measuring the transmitted wavefront of the seventh invention will be described in detail.

The method for measuring a transmitted wavefront according to the seventh invention is the same as the method for measuring a refractive index distribution according to the third invention described above, except that the optical path difference in the portion to be measured contributes to the optical path difference that causes the first interference fringes. Does not perform photoelectric detection of the second interference fringe,
Except that the binary signal data of the second interference fringe is not used at all, and that what is calculated is not the refractive index distribution of the specimen contained in the measured part but the transmitted wavefront in the measured part. For example, the measurement can be performed basically by the same method as the method for measuring the refractive index distribution of the third invention.

However, when sequentially providing the measured parts having two opposing optical planes while providing a common area between adjacent measured parts, the arrangement position of a transparent plate such as an oil-on plate is determined every time the measurement is performed. The application of the method of providing the part to be measured by shifting is avoided.

By applying the transmitted wavefront measuring method of the seventh aspect, the transmitted wavefront of the entire large object can be obtained without increasing the size of the interferometer.

As described above, the method for measuring the refractive index distribution according to the seventh aspect of the present invention accurately measures the transmitted wavefront of a large object without increasing the size of the interferometer even for a large object. A measuring method for achieving the third object of the present invention is a measuring apparatus for a transmitted wavefront according to the present invention, which achieves this object by using a two-beam interferometer based on amplitude division and an interference fringe obtained by the two-beam interferometer. Photoelectric detection means for detecting, first storage means for storing the photoelectric detection result of the interference fringes by the photoelectric detection means as binary signal data, and two opposing optical elements stored in the first storage means The object provided with a measurement target having a target plane is obtained by disposing the test object in one optical path of a two-beam interferometer by amplitude division so that the two optical planes are included in the optical path. Place the subject Binary signal data of the first interference fringe of the photoelectric detection result by the optical path difference between the light passing through the optical path that has not provided the light and the subject having passed through the optical path, and the first
Based on the binary signal data of the photoelectric detection result of the second interference fringe due to the optical path difference between the two optical paths of the two-beam interferometer, which contributes to the optical path difference that causes the interference fringe Phase distribution calculating means for respectively obtaining binary signal data of the phase distribution in the first and second interference fringes, and binary signal data of the phase distribution in the first and second interference fringes obtained by the phase distribution calculating means Based on the binary signal data of the phase distribution in the first and second interference fringes stored in the second storage unit, based on the binary signal data of the transmitted wavefront in the measured section. Transmitted wavefront calculating means for obtaining binary signal data, third storage means for storing binary signal data of the transmitted wavefront in the measured part obtained by the transmitted wavefront calculating means, and storage in the third storage means The same Based on the binary signal data of the transmitted wavefront in the plurality of measured parts provided in the body, the transmission in the plurality of measured parts is obtained from the binary signal data of the transmitted wavefront in a region common to the measured parts. Data synthesizing means for synthesizing the binary signal data of the wavefront and synthesizing the binary signal data of the transmitted wavefront in the area where the plurality of parts to be measured are provided, and the binary signal obtained by the data synthesizing means Fourth storage means for storing data, and display means for displaying each of the binary signal data stored in the second, third, and fourth storage means in the form of a character, a graphic, or a visual image, and displaying the binary signal data. (Hereinafter referred to as an eighth invention).

Example An example of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 (a) is a schematic diagram showing an example of a refractive index distribution measuring device based on the refractive index distribution measuring method of the first invention, that is, an example of a refractive index distribution measuring device of the second invention. It is.

FIG. 1A shows a refractive index distribution measuring device 1 in which a He-Ne laser (λ = 632.8 nm) 2 as a light source and light emitted from the He-Ne laser 2 are condensed in a slit 3. A lens 4, a lens 5 for converting the diffused light exiting the slit 3 into parallel light, a half mirror 6 arranged in a direction facing the parallel light from the lens 5, and a predetermined distance from the half mirror 6. A beam which is disposed between the lens 5 and the half mirror 6, and which separates the reflected light from the half mirror 6 and the reflected mirror 7 from the parallel light from the lens 5 A splitter 8, two lenses 10 and 11 for condensing light (interference fringes) separated by the beam splitter 8 on a television camera 9 which is a photoelectric detection unit for photoelectrically detecting the light, D
A frame memory 12 serving as a first storage medium for storing a photoelectric detection result of interference fringes by the television camera 9 converted into binary signal data by the converter;
An arithmetic unit 13 for analyzing the interference fringes based on the binary signal data of the photoelectric detection result of the interference fringes stored in the storage unit to obtain a refractive index distribution in the subject included in the measurement unit; The display 14 is a display means for displaying the obtained refractive index distribution, the phase distribution obtained during the calculation, and the like in the form of characters, diagrams, or visual images.

Among them, the He-Ne laser 2, the slit 3, the lenses 4 and 5, the half mirror 6, the reflecting mirror 7, and the beam splitter 8 constitute a Fizeau interferometer,
A subject 15 provided with a measured part having two opposing optical planes is arranged between the half mirror 6 and the reflecting mirror 7. At this time, the direction of the subject 15 is a direction in which the two optical planes are included in the optical path.

Further, as shown in FIG. 1 (b), the arithmetic unit 13 converts the subject 15 into the Fizeau interferometer so that the two optical planes of the subject 15 stored in the frame memory 12 are included in the optical path. The binary signal data of the photoelectric detection result of the first interference fringe obtained by arranging the first interference fringe in one of the optical paths (the optical path between the half mirror 6 and the reflecting mirror 7) generates the first interference fringe. It contributes to the binary signal data of the photoelectric detection result of the second interference fringe due to the optical path difference in the measured part, which contributes to the optical path difference, and to the optical path difference that causes the first interference fringe. The phase distribution of the first, second, and third interference fringes based on the binary signal data of the photoelectric detection result of the third interference fringe caused by the optical path difference between the two optical paths of the Fizeau interferometer. A phase distribution calculating means 20 for respectively obtaining binary signal data; A second storage means for storing binary signal data of the phase distribution in the first, second and third interference fringes obtained by the distribution means, respectively; and a second storage means for storing the binary signal data stored in the second storage means. Based on the binary signal data of the phase distribution in the first, second and third interference fringes,
Refractive index distribution calculating means 22 for obtaining binary signal data of the refractive index distribution in the subject included in the measured part, and in the subject included in the measured part obtained by the refractive index distribution calculating means 22 And third storage means 23 for storing binary signal data of the refractive index distribution.

The phase distribution calculating means 20 in the arithmetic unit 13 analyzes the interference fringes by the FFT method. The data processing in the arithmetic unit 13 is performed as shown in FIG. Input of binary signal data of (step 30),
Calculation of the spectral distribution (power spectrum) of the interference fringes by Fourier transform (Step 31) (Step 32),
This power spectrum is displayed on the display 14 (step 33), the data necessary for the inverse Fourier transform is referenced with the power spectrum displayed on the display 14 as a reference (step 34), and the inverse Fourier transform of the extracted data (step 34) Calculation of phase using the result of step 35) (step 3
6), display of the calculation result of the phase on the display 14 (step 37), connection of the phase using an external input device (step 38), the distribution of the refractive index of the object included in the part to be measured, and the The calculation of the thickness distribution of the measuring section (step 39) and the display of the refractive index distribution of the subject included in the measuring section on the display 14 (step 40) are performed in this order. At this time, steps 31 to 38 are performed by the phase distribution calculating means 20, and step 39 is performed by the refractive index distribution calculating means 22.

Using the refractive index distribution measuring device 1 configured as described above, a cylindrical borosilicate glass block (refractive index: 1.51) having a diameter of 150 mm and a thickness of 100 mm was used as a subject and this glass block was treated in the following manner. Was measured for the refractive index distribution.

First, the parallelism between the upper and lower surfaces of this glass block is set within 5 seconds, and the surface accuracy of the upper and lower surfaces is λ / 6.
(Λ = 632.8 nm) was optically polished, and the measured portion was provided on the entire glass block as two engineering planes whose upper surface and lower surface were opposed to each other.

Next, the half mirror 6 and the reflecting mirror 7 are removed from the two-beam interferometer shown in FIG. 1A, and the above-described second interference fringe due to the optical path difference in the measured section is obtained. 9, the result of the photoelectric detection is stored in the frame memory 12 as binary signal data. Further, in this state, the sample is placed on the refractive index distribution measuring device 1 shown in FIG. 1A so that the two optical planes are included in the optical path.
Between the half mirror 6 and the reflecting mirror 7 constituting
The first is due to the optical path difference between the light passing through the optical path where the subject (measured part) is arranged and the light passing through the optical path where the subject is not arranged.
The interference fringes were obtained, the interference fringes were photoelectrically detected by the television camera 9, and the results of the photoelectric detection were stored in the frame memory 12 as binary signal data. Next, the subject is removed from the optical path to obtain a third interference fringe due to an optical path difference between the two optical paths of the Fizeau interferometer, which has contributed to the optical path difference that causes the first interference fringe. The interference fringes were photoelectrically detected by the television camera 9 and the result of the photoelectric detection was stored in the frame memory 12 as binary signal data.

Thereafter, the arithmetic unit 13 performs data processing in accordance with the steps shown in FIG. 1 (c) to calculate the distribution of the thickness of the measured part and the distribution of the refractive index of the subject included in the measured part, and calculate the result. Displayed on display 14. These results are shown in FIG. 2 and FIG.

FIG. 2 is a diagram showing the distribution of thickness in the measured portion, and the interval between contour lines is 0.2λ.

FIG. 3 is a diagram showing the refractive index distribution of the specimen contained in the measured part, and the interval between contour lines is 2 × 10 ⁻⁶ .

The rectangular frame in FIGS. 2 and 3 is provided for convenience of measurement (the same applies hereinafter), and the curve in the rectangular frame indicates the thickness distribution or the thickness distribution in the measured part. 9 is a contour line showing a refractive index distribution in a subject included in the measurement unit. The contoured area has a contour slightly different from the cross-sectional shape of the measured part due to an extraction error when extracting data at the measured part using an external input device during data analysis. Can be easily corrected (the same applies hereinafter).

Example 2 The refractive index distribution of the glass block provided with the portion to be measured used in Example 1 was measured based on the refractive index distribution measuring method of the third invention.

In this case, the measuring device for the refractive index distribution is the fourth device.
The measurement apparatus of the refractive index distribution based on the invention of the above was used. This refractive index distribution measuring device has the same configuration as the refractive index distribution measuring device 1 shown in FIG. 1A, but uses a computing unit 50 shown in FIG. Was.

That is, as shown in FIG. 4, the calculation unit 50 performs the above-described calculation from the phase distribution calculation unit 20 to the second storage unit 21, the refractive index distribution calculation unit 22, and the third storage unit 23. The same as that of the unit 13, but the binary signal data of the refractive index distribution of the subject stored in the third storage unit 23 and included in each of the plurality of measurement units provided in the same subject. Based on the binary signal data of the refractive index distribution of the object included in the region to be measured included in the area common to the object to be measured, the refractive index distribution of each object included in the object to be measured included in the object to be measured
Data synthesizing means 51 for connecting value signal data to each other and synthesizing binary signal data of a refractive index distribution in the subject included in the region where the plurality of measured parts are provided.
A fourth storage means 52 for storing the binary signal data obtained by the data synthesizing means 51; and a fourth storage means.
Second display means 53 for displaying the binary signal data stored in 52 in the form of a character, a graphic, or a visual image is added. In FIG. 4, portions common to FIG. 1 (b) are denoted by the same reference numerals as in FIG. 1 (b), and description thereof is omitted. As the second display means 53, the same display means as the display 14 in the refractive index distribution measuring device 1 shown in FIG. 1A was used.

First, the measurement of the refractive index distribution in the glass block
As shown in FIG. 5, two measurement units 56 and 57 are provided on a glass block 55 as an object, and the refractive index distribution of the object included in the measurement unit 56 and the refractive index distribution included in the object 57 are included. The refractive index distribution in the subject was obtained in the same manner as in Example 1, and the obtained result was displayed on the second display means 53 (display 14). Note that the measured portions 56 and 57 at this time have a common area 58. These results are shown in FIGS. 6 (a) and 6 (b). FIG. 6 (a) shows the refractive index distribution of the subject contained in the measurement section 56, and FIG. 6 (b) shows the refractive index distribution of the subject contained in the measurement section 57. Is shown. The interval between the contour lines in both figures is 2 × 10 ⁻⁶ .

Thereafter, the data synthesizing unit 51 in the arithmetic unit 50
In the refractive index distribution in the subject included in the measured portion 56 and the refractive index distribution in the subject included in the measured portion 57,
In order to minimize the sum of squares of the difference between the data of the respective refractive index distributions in the subject included in the common area 58, the data of the refractive index distribution in the subject included in one of the measurement units is included. Add the values and average the two values to the common area
By using the data of the refractive index distribution of the subject included in 58, the data of the refractive index distribution of the subject included in the measured portion 56 and the refractive index distribution of the subject included in the measured portion 57 are included. The data and the data were joined together to synthesize a refractive index distribution over the entire glass block 55 as a subject, and the obtained result was displayed on the second display means 53 (display 14). The result is shown in FIG. In addition,
The interval between contour lines in FIG. 7 is also 2 × 10 ₋₆ .

As is clear from the comparison between FIG. 7 and FIG. 3, the numbers and intervals of the contour lines in both drawings are in good agreement, and there is no practical problem even with the method of measuring the refractive index distribution of the third invention. An accurate refractive index distribution is required.

Example 3 By disposing a transparent plate whose main surface is optically polished on two opposing surfaces of a subject via a liquid layer having a refractive index close to the refractive index of the subject, two A flat surface was formed as a portion to be measured, and the refractive index distribution of the sample contained in the portion to be measured was measured based on the refractive index distribution measuring method of the fifth invention.

In this case, the measuring device for the refractive index distribution is the sixth device.
The measurement apparatus of the refractive index distribution based on the invention of the above was used. This refractive index distribution measuring device has the same configuration as the refractive index distribution measuring device 1 shown in FIG. 1 (a), but uses a computing unit 60 shown in FIG. Was.

That is, as shown in FIG. 8, the calculation unit 60 performs the above-described calculation from the phase distribution calculation unit 20 to the second storage unit 21, the refractive index distribution calculation unit 22, and the third storage unit 23. The same as the unit 13 except that the object stored in the second storage unit 21 and having two opposing surfaces and at least one of the two surfaces of the object includes the refractive index of the object. The first, second, and third interference fringes of a first measurement target portion including a transparent plate having at least one main surface optically polished provided through a liquid layer having a close refractive index A second signal data of the refractive index distribution in the first measured portion is obtained based on the binary signal data of the phase distribution in the step (a), and the second signal data is stored in the third storage means. The refractive index distribution calculating unit 61 and the third storage unit 23 Binary signal data of the refractive index distribution in the first measured part, and one of the transparent plates constituting the first measured part, or the two transparent plates are replaced by the refractive indices of these transparent plates. From the binary signal data of the refractive index distribution in the second portion to be measured, which is composed of a composite plate bonded through a liquid layer having a refractive index close to
A third refractive index distribution calculating means 62 for obtaining binary signal data of the refractive index distribution in the subject included in the measured part of FIG.
And 2 obtained by the third refractive index distribution calculating means 62.
Fifth storage means 63 for storing the value signal data;
The binary signal data stored in the storage means 63 is converted into a character,
Third display means 64 for displaying a graphic or visualized image is added. In FIG. 8, FIG. 1 (b)
1 are denoted by the same reference numerals as in FIG. 1 (b), and description thereof is omitted. Third display means 64
Used the same display means as the display 14 in the refractive index distribution measuring apparatus 1 shown in FIG.

Based on the refractive index distribution measuring method of the fifth invention, the measurement of the refractive index distribution using the refractive index distribution measuring device of the sixth invention was performed in the following manner.

First, the two optically polished surfaces of the glass block provided with the portion to be measured, which were used in Example 1 and Example 2, were processed into sand-sand using an abrasive (about # 400). As shown in FIG. 9, a liquid layer 66 having a refractive index close to the refractive index of the subject 65 is provided on the entire surface of the two sand-slip surfaces of the subject 65 as shown in FIG. Through which two borosilicate glass plates whose main surfaces are optically polished (diameter 15
A portion to be measured (first portion to be measured) was provided by disposing 0 mm, a thickness of 20 mm, a parallelism of the main surface of 5 seconds, a surface accuracy of about λ / 10, and a refractive index of 1.51) 67a and 67b.

Next, the refractive index distribution in the measured portion was determined according to Example 1.
Based on the phase distributions of the first, second and third interference fringes obtained in the same manner as described above, the second refractive index distribution calculating means 61 in the calculating section 60 calculates the obtained result, and the obtained result is displayed on the third display means. Displayed on 64 (Display 14). This result is
Shown in the figure. The interval between contour lines in FIG. 10 is 2 ×
It is 10 ^-6 .

Next, as shown in FIG. 11, the two borosilicate glass plates 67a and 67b used for providing the portion to be measured are bonded together via a liquid layer 68 equivalent to the above-described liquid layer 66 to form a composite. A plate (second measured portion) was used, the refractive index distribution in this composite plate was determined in the same manner as in Example 1, and the obtained result was displayed on the third display means 64 (display 14). This result
Figure 12 shows. The interval between contour lines in FIG.
× 10 ^-6 .

Thereafter, the third refractive index distribution calculating means in the arithmetic unit 60
According to 62, the value obtained by multiplying the refractive index distribution in the first measured part by the sum of the thicknesses of the two transparent plates and the subject is used to calculate the refractive index distribution in the second measured part by the two transparent plates. By subtracting the value obtained by multiplying by the thickness of the sample, and dividing the obtained value by the value of the thickness of the subject, the refractive index distribution of the entire glass block 65, which is the subject constituting the first measurement unit, is obtained. The obtained result is displayed on the third display means 64 (display 14). The result is shown in FIG. The interval between contour lines in FIG. 13 is also 2 × 10 ⁻⁶ .

In the third embodiment, two borosilicate glass plates (corresponding to an oil-on-plate) are used, so that the measurement area is smaller than that of the first embodiment in which the measurement area does not use the oil-on-plate due to the configuration of the support base of the measured portion. By about 25%, and the analysis area is the third
This is about 75% of the analysis area shown in the figure. Comparing FIG. 13 with FIG. 3 in consideration of this fact, the numbers and intervals of the contour lines in both drawings are in good agreement, and the method of measuring the refractive index distribution of the fifth invention does not hinder practical use. It is clear that a refractive index distribution with no precision is required.

Example 4 The transmitted wavefront of the glass block provided with the portion to be measured used in Example 1 was measured based on the transmitted wavefront measuring method of the seventh invention.

The transmitted wavefront measuring device based on the eighth invention was used as the transmitted wavefront measuring device at this time. The transmitted wavefront measuring device has the same configuration as the refractive index distribution measuring device 1 shown in FIG. 4, but the arithmetic unit at this time is the refractive index distribution calculation unit 50 shown in FIG. A means for calculating a transmitted wavefront is provided in place of the means 22, and a means for calculating a transmitted wavefront in a plurality of measured parts is provided in place of the data combining means 51.
There is a data synthesizing means for synthesizing the value signal data to obtain binary signal data of one transmitted wavefront. In the following description, the refractive index distribution measuring device 1 shown in FIG.
The same members as described above will be described using the reference numerals given in FIG.

The data processing in the calculation unit is the same as the data processing in the calculation unit 50, except that a step of calculating the refractive index distribution and the thickness distribution in the measured part (steps 39 and 39).
FIG. 1 (c)) is a step of calculating the transmitted wavefront in the measured part, and a step of displaying the refractive index distribution in the measured part on the display 14 (step 40, first step).
FIG. (C) replaces the step of displaying the transmitted wavefront on the display 14 on the portion to be measured.

The measurement of the transmitted wavefront in the glass block after the provision of the part to be measured was performed in the same manner as in Example 2 in the following manner.

First, in the same manner as in the second embodiment, the measurement target portion provided on the glass block 55 as the test subject is connected to the two measurement target portions 56 and 57.
(See FIG. 5), and for each measured part, the light path difference between the light passing through the optical path on which the subject (measured part) is arranged and the light passing through the optical path without the subject is arranged. A first interference fringe is obtained, and this interference fringe is photoelectrically detected by the television camera 9, and
This photoelectric detection result was stored in the frame memory 12 as binary signal data. In addition, for each of the parts to be measured, the subject is removed from the optical path from the state where the first interference fringe is obtained, and the two Fizeau interferometers that contribute to the optical path difference that causes the first interference fringe are generated. A second interference fringe due to an optical path difference between the optical paths themselves is obtained, and this interference fringe is photoelectrically detected by the television camera 9, and
This photoelectric detection result was stored in the frame memory 12 as binary signal data.

Next, data processing was performed in the arithmetic unit to determine the transmitted wavefront in each measured part, and the obtained result was displayed on the display means (display 14). These results are
This is shown in FIG. 14 (a) and FIG. 14 (b). FIG. 14 (a)
FIG. 14 (b) shows a transmitted wavefront in the measured section 56. FIG. 14 (b) shows a transmitted wavefront in the measured section 57. FIG.
The interval between the contour lines in both figures is 0.2λ (λ = 632.8 nm).

Thereafter, the sum of squares of the difference between the data of the transmitted wavefronts in the common area 58 between the transmitted wavefront in the measured section 56 and the transmitted wavefront in the measured section 57 is minimized by the data combining means in the arithmetic section. As described above, by adding a certain value to the data of the transmitted wavefront in one measured part, and by setting the average value of both values as the data of the transmitted wavefront in the common area 58, the data of the transmitted wavefront in the measured part 56 and The transmitted wavefront data in the measured section 57 is joined to combine the transmitted wavefront in the entire glass block 55, which is the subject, and the obtained result is displayed on display means (display).
Displayed in 14). The result is shown in FIG. In addition,
The interval between contour lines in FIG. 15 is also 0.2λ.

In the fourth embodiment, the transmitted wavefronts at the measurement target portion provided by optically polishing the two opposing surfaces of the subject are obtained. A transmitted wavefront in a measurement target portion provided by disposing a transparent plate whose main surface is optically polished via a liquid layer having a refractive index close to the refractive index can be similarly measured.

In the first, second, third, and fourth embodiments described above, the FFT method is used to obtain the phase distribution by analyzing the interference fringes based on the photoelectric detection result of the interference fringes. The analysis is not limited to the FFT method, and can be performed by a fringe scan method, a thinning method, or the like. Any one method may be used alone, or two or more methods may be used in combination.

The fringe scanning method uses a two-beam interferometer based on wavefront splitting that can change the optical path difference between two lights little by little, and obtains a plurality of interference fringes obtained by changing the optical path difference and change data of the optical path difference. Is a measurement method for obtaining the phase distribution of the interference fringes from As a method of changing the optical path difference between the two lights, a method of changing the optical path length of one of the two light paths, a method of changing the wavelength of the light source, and the like can be used. As a measuring device using such a two-beam interferometer, for example, when a Fizeau interferometer is used as a basis, a measuring device shown in FIG. 16 can be exemplified.

In this measuring device 70, a PZT (piezo element) 71 is provided on the back surface of the reflecting mirror 7 constituting the Fizeau interferometer, and the reflecting mirror 7 translates in accordance with the amount of voltage applied to the PZT 71, The movement amount of the reflecting mirror 7 at this time is calculated by the calculation unit 72, and is used as one of the data when obtaining the phase distribution. In the measuring device 70 shown in FIG. 16, members common to the refractive index distribution measuring device 1 shown in FIG. 1 (a) are denoted by the same reference numerals as those in FIG. 1 (a). Description is omitted.

The data processing in the arithmetic unit 72 is performed in accordance with the steps shown in FIG. 16 when the refractive index distribution is obtained based on the refractive index distribution measuring method of the first invention, for example.

That is, application of a high voltage to the PZT (step 80), input of binary signal data of photoelectric detection results of interference fringes obtained at this time (step 81), repetition of steps 80 and 81, movement amount of the PZT and its Of phase distribution from binary signal data of photoelectric detection result of interference fringes at the time (step 8
2) calculation of the refractive index distribution of the specimen contained in the measured part and the distribution of the thickness of the measured part (Step 8)
3), and the display of the refractive index distribution of the subject included in the measured portion on the display 14 (step 84).

The phase distribution of the interference fringes can also be obtained by changing the wavelength of the light source 2 by sending an appropriate signal from the arithmetic unit 72. In this case, the change amount of the wavelength of the light source is
The data of the phase distribution can be obtained from this data and the binary signal data of the photoelectric detection result of the interference fringes.

When the transmitted wavefront is determined, the step of calculating the refractive index distribution of the object included in the measured part and the distribution of the thickness of the measured part (step 83) includes the step of calculating the transmitted wavefront of the measured part; The step of displaying on the display 14 the refractive index distribution of the object included in the measured part on the display 14 (step 84) replaces the step of displaying the transmitted wavefront of the measured part on the display 14, respectively.

When analyzing the interference fringes by the thinning method, the data processing in the arithmetic unit of the measuring device is performed, for example, when the refractive index distribution is obtained based on the refractive index distribution measuring method of the first invention.
This is performed according to the steps shown in FIG.

That is, preprocessing (step 90) of inputting binary signal data as a result of photoelectric detection of interference fringes (step 90), averaging the input binary signal data, binarizing, extracting a ridge line, and the like.
1), thinning based on the data obtained by the preprocessing (step 92), determination of the stripe order using an external input device (step 93), interpolation of the stripe order (step 94), included in the part to be measured The calculation of the refractive index distribution of the object to be measured and the distribution of the thickness of the object to be measured (step 95), and the display of the refractive index distribution of the object included in the object to be measured on the display 14 (step 96) are performed in this order. Done. Note that the phase distribution is obtained at the time of passing through step 94, and the step 95 of calculating the refractive index distribution of the subject included in the measured portion and the distribution of the thickness at the measured portion is performed at the time of passing through step 94. It is based on the data.

When the transmitted wavefront is determined, the step of calculating the refractive index distribution of the object included in the measured portion and the distribution of the thickness of the measured portion (step 95) is replaced with the step of calculating the transmitted wavefront of the measured portion. Display the refractive index distribution of the specimen contained in the part to be measured
The step of displaying on the display 14 (step 96) replaces the step of displaying the transmitted wavefront of the measured portion on the display 14, respectively.

The above-described interference fringe analysis methods may be used in an appropriate combination when measuring the refractive index distribution at one or a plurality of locations or when measuring the transmitted wavefront at one or a plurality of locations.

[Effects of the Invention] As described above, according to the method and the apparatus for measuring the refractive index distribution of the present invention, the refractive index distribution in the subject can be accurately measured, and the method can be applied to a large subject. Without increasing the size of the interferometer, it is possible to accurately measure the refractive index distribution of the large object.

Further, according to the transmitted wavefront measuring method and measuring apparatus of the present invention, the transmitted wavefront of a large object can be accurately measured without increasing the size of the interferometer even for a large object.

[Brief description of the drawings]

FIG. 1 (a) is a schematic diagram showing an example of a refractive index distribution measuring device of the present invention, FIG. 1 (b) is a block diagram showing an example of a calculating section of the refractive index distribution measuring device of the present invention, FIG. 1 (c) is a diagram showing an example of data processing steps in a calculation unit of the refractive index distribution measuring device of the present invention, FIG. 2 is a diagram showing a distribution of thickness in a measured portion, and FIG. FIG. 4 is a block diagram showing another example of a calculation unit of a refractive index distribution measuring device according to the present invention, and FIG. FIG. 6 (a) is a diagram for explaining an example of the case where a measurement unit is provided, and FIG. 6 (a) is a refractive index distribution of a subject included in one of the plurality of measurement units provided on the subject; FIG. 6 (b)
FIG. 7 is a diagram showing a refractive index distribution of a subject included in another one of the plurality of measured portions provided on the subject, and FIG. 7 is a diagram showing a plurality of measured portions provided on the subject. FIG. 8 is a diagram showing a refractive index distribution obtained by synthesizing a refractive index distribution of a subject included in a unit, FIG. 8 is a block diagram showing another example of a calculation unit of the refractive index distribution measuring device of the present invention, and FIG. FIG. 9 is a side view schematically showing an example of a case in which a portion to be measured is provided by arranging a transparent plate on a subject, and FIG. FIG. 11 is a side view schematically illustrating an example of a case where a transparent plate used for providing a measured portion on the subject is a second measured portion, and FIG. FIG. 12 shows a refractive index distribution in a second measured portion made of a transparent plate used for providing the measured portion on the subject. FIG. 13 is a diagram showing a refractive index distribution in a subject included in a measurement part provided by disposing a transparent plate on the subject, and FIG. 14 (a) is a diagram showing a plurality of specimens provided in the subject. FIG. 14 (b) is a diagram showing a transmitted wavefront in one measured part of the measured parts, and FIG. 14 (b) shows a transmitted wavefront in another measured part of a plurality of measured parts provided on the subject. FIG. 15 is a diagram showing a transmitted wavefront obtained by synthesizing transmitted wavefronts of a plurality of measured parts provided on a subject, and FIG. 16 (a) is a diagram showing a refractive index distribution measuring apparatus of the present invention. FIG. 16 (b) is a schematic view showing another example, FIG. 16 (b) is a view showing another example of the data processing steps in the calculation section of the refractive index distribution measuring device of the present invention, and FIG. 17 is a refractive index distribution of the present invention. FIG. 8 is a diagram showing another example of the data processing steps in the calculation unit of the measurement device. 1, 70... Refractive index distribution measuring device, 9... Photoelectric detection means, 12... First storage means, 14... Display means, 20... Phase distribution calculation means, 21. , 22 ... refractive index distribution calculating means, 23 ... third storing means, 51 ... data combining means, 52 ... fourth storing means, 61 ... second refractive index distribution calculating means, 62 ... Fifth storage means.

Continuation of front page (56) References JP-A-56-126742 (JP, A) JP-A-3-218432 (JP, A) JP-A-1-316627 (JP, A) JP-A-1-257229 (JP) , A) JP-A-57-60242 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01J 9/02 G01M 11/02 G01N 21/45

Claims (8)

(57) [Claims] 1. An optical path of a two-beam interferometer based on amplitude division such that an object to be measured provided with a measurement unit having two opposing optical planes is included in an optical path. A first interference fringe resulting from an optical path difference between light passing through the optical path on which the subject is arranged and light passing through the optical path without the subject, A second interference fringe due to an optical path difference in the measured portion that contributes to the optical path difference that causes interference fringes; and the two light fluxes that contribute to the optical path difference that causes the first interference fringe. And the third interference fringe due to the optical path difference between the two optical paths of the interferometer is photoelectrically detected, and the results are respectively stored as binary signal data in a storage medium. The binary signal data stored in the storage medium is stored in the storage medium. The first, second, and third interference fringes are analyzed based on the Obtains a phase distribution in the stripe, and obtains a refractive index distribution in the subject contained in the based on the phase distribution portion to be measured in each of the interference fringes, the measuring method of the refractive index distribution. 2. A device according to claim 1, wherein a plurality of measurement units having two opposing optical planes are provided simultaneously or sequentially in the same subject while providing a common area between adjacent measurement units. After determining the refractive index distribution of the subject included in the measured portion for each of the measured portions, the refractive index distribution of the subject included in a common region between the measured portions is determined based on the refractive index distribution of the subject. The measurement of the refractive index distribution according to claim 1, wherein the refractive index distributions are joined to obtain a refractive index distribution of the subject included in the region where the plurality of measurement portions are provided. Method. 3. An object to be measured having two opposing optical planes, an object having two opposing surfaces, and at least one of the two surfaces of the object being close to a refractive index of the object. A transparent plate provided with a liquid layer having a refractive index, at least one main surface of which is optically polished, and a refractive index distribution in the portion to be measured, and a transparent plate forming the portion to be measured. The method for measuring a refractive index distribution according to claim 1, wherein a refractive index distribution in the subject included in the measurement target part is obtained based on the refractive index distribution. 4. A two-beam interferometer based on amplitude division, photoelectric detecting means for photoelectrically detecting an interference fringe obtained by the two-beam interferometer, and a photoelectric detection result of the interference fringe by the photoelectric detecting means.
A first storage unit for storing as value signal data; and an object provided with a measurement unit having two opposing optical planes, which is stored in the first storage unit. Is included in the optical path, obtained by arranging in one optical path of the two-beam interferometer by amplitude division, the light passing through the optical path in which the subject is arranged and the optical path in which the subject is not arranged Binary signal data as a result of photoelectric detection of the first interference fringe due to an optical path difference from the transmitted light, and an optical path difference in the measured section which contributes to the optical path difference that causes the first interference fringe Binary signal data of a photoelectric detection result of a second interference fringe, and a second signal due to an optical path difference between two optical paths of the two-beam interferometer, which contribute to the optical path difference that causes the first interference fringe. Based on the binary signal data of the photoelectric detection result of the interference fringe of No. 3 and Phase distribution calculating means for respectively obtaining binary signal data of the phase distribution in the first, second and third interference fringes; and phases in the first, second and third interference fringes obtained by the phase distribution calculating means. Second storage means for respectively storing binary signal data of the distribution; and binary signal data of the phase distribution in the first, second and third interference fringes stored in the second storage means. A refractive index distribution calculating means for obtaining binary signal data of a refractive index distribution in the subject included in the measured part; and the subject included in the measured part obtained by the refractive index distribution calculating means. A third storage unit for storing binary signal data of the refractive index distribution in the above, and converting each of the binary signal data stored in the second and third storage units into a character, a graphic, or a visual image. Display means to display and Characterized in that was example, the refractive index distribution of the measuring device. 5. Based on binary signal data of a refractive index distribution of the subject stored in the third storage unit and included in a plurality of measurement units provided in the same subject, respectively. From the binary signal data of the refractive index distribution of the object included in the region to be measured included in the region to be measured, the binary signal data of the refractive index distribution of each object included in the object to be measured is connected. In addition, the refractive index distribution of the subject included in the region where the plurality of portions to be measured are provided is 2
Data synthesizing means for synthesizing the value signal data, fourth memory means for storing the binary signal data obtained by the data synthesizing means, and binary character data stored in the fourth memory means as characters. And a display means for displaying the image in the form of a graph, a diagram, or a visual image. 6. An object having two opposing surfaces stored in the second storage means and at least one of the two surfaces of the object having a refractive index close to the refractive index of the object. The phase distribution of the first, second, and third interference fringes of the first measured portion, which is provided with a transparent plate having at least one main surface optically polished provided through the liquid layer having Second refractive index distribution calculating means for obtaining binary signal data of the refractive index distribution in the first measured part based on the binary signal data, and storing the binary signal data in the third storage means; And binary signal data of the refractive index distribution in the first measured section, which is stored in the third storage means, and one of the transparent plates constituting the first measured section,
Alternatively, binary signal data of a refractive index distribution in a second portion to be measured composed of a composite plate obtained by laminating the two transparent plates via a liquid layer having a refractive index close to the refractive index of these transparent plates; A third refractive index distribution calculating means for obtaining binary signal data of a refractive index distribution in the subject included in the first measured part, and a second refractive index distribution calculating means obtained from the third refractive index distribution calculating means. Fifth storage means for storing the value signal data, and third display means for displaying the binary signal data stored in the fifth storage means in the form of a character, a diagram, or a visual image. The apparatus for measuring a refractive index distribution according to claim 4 or 5. 7. A plurality of measurement units having two opposing optical planes are provided simultaneously or sequentially in the same subject while providing a common region between adjacent measurement units, and In each case, the object provided with the measured part is obtained by disposing the object in one optical path of a two-beam interferometer by amplitude division such that the two optical planes are included in the optical path. A first interference fringe caused by an optical path difference between light passing through an optical path on which the subject is disposed and light passing through an optical path not including the subject; and an optical path difference that causes the first interference fringe. The results of photoelectrically detecting the second interference fringe due to the optical path difference between the two optical paths themselves of the two-beam interferometer are stored in a storage medium as binary signal data, and are stored in the storage medium. The first and second signals are based on the binary signal data. After analyzing the fringes to determine the phase distribution in each interference fringe, determining the transmitted wavefront in the measured section based on the phase distribution in each interference fringe, the transmitted wavefront is included in the transmitted wavefront for each measured section. By connecting the transmitted wavefronts of the plurality of measured parts based on the transmitted wavefront of a common area between the measured parts, combining the transmitted wavefronts in a region where the plurality of measured parts are provided. The method of measuring the transmitted wavefront. 8. A two-beam interferometer based on amplitude division, photoelectric detecting means for photoelectrically detecting an interference fringe obtained by the two-beam interferometer, and a photoelectric detection result of the interference fringe by the photoelectric detecting means.
A first storage unit for storing as value signal data; and an object provided with a measurement unit having two opposing optical planes, which is stored in the first storage unit. Is included in the optical path, obtained by arranging in one optical path of the two-beam interferometer by amplitude division, the light passing through the optical path in which the subject is arranged and the optical path in which the subject is not arranged Binary signal data as a result of photoelectric detection of a first interference fringe due to an optical path difference with transmitted light; and two signals of the two-beam interferometer that contribute to the optical path difference that causes the first interference fringe. Phase distribution calculation for obtaining binary signal data of the phase distribution in the interference fringes of the first and second cities based on the binary signal data of the photoelectric detection result of the second interference fringe due to the optical path difference between the optical paths themselves. Means and the phase distribution calculation means Second storage means for storing binary signal data of the phase distribution in the first and second interference fringes, respectively; and the phase distribution of the first and second interference fringes stored in the second storage means. Transmission wavefront calculation means for obtaining binary signal data of the transmitted wavefront in the measured part based on the binary signal data, and storage of the binary signal data of the transmitted wavefront in the measured part obtained by the transmission wavefront calculation means A third storage unit that performs a communication between the measurement units based on binary signal data of transmitted wavefronts of a plurality of measurement units provided in the same subject and stored in the third storage unit. By connecting the binary signal data of the transmitted wavefront in the plurality of measured parts from the binary signal data of the transmitted wavefront in a common area,
Data synthesizing means for synthesizing binary signal data of a transmitted wavefront in an area where the plurality of measured parts are provided; fourth memory means for storing binary signal data obtained by the data synthesizing means; Each 2 stored in the second, third and fourth storage means
Display means for displaying the value signal data in the form of a character, a diagram, or a visual image, and displaying the value signal data.