JP2009079933A - Interferometer device for measuring large-sized sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interferometer device for measuring a large-sized sample acquiring in a short period of time a plurality of interference fringe images corresponding to portions in a domain to be measured necessary for aperture synthesis, respectively, and measuring highly accurately thickness irregularities over the whole area of the domain to be measured of a specimen, concerning the large-sized sheet-shaped specimen. <P>SOLUTION: The first interferometer heads 1A-1G for irradiating measuring light from one surface 9a side of the specimen 9, and acquiring the first interference fringe image carrying transmission wavefront information of each first domain on the specimen 9, and the second interferometer heads 2A-2F for irradiating measuring light from the other surface side 9b of the specimen 9, and acquiring the second interference fringe image carrying transmission wavefront information of each second domain on the specimen 9, are arranged so that the first domain and the second domain which are mutually adjacent are overlapped partially, and that the domain to be measured is included wholly by respective first domains and second domains. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an interferometer device for measuring thickness unevenness of a sheet-like subject, and more particularly to a large sample measuring interferometer device suitable for measuring thickness unevenness of a large subject having a wide measurement region.

  Conventionally, a pair of interferometers are arranged so as to face each other with a sheet-shaped subject opaque to the measurement light beam, and the shape difference between one surface of the subject and the reference surface of the interferometer, and the subject The applicant of the present invention has proposed a method for measuring the shape difference between the other surface and the reference surface of the other interferometer, and calculating the thickness unevenness of the subject based on the measured shape difference ( See Patent Document 1 below).

  In addition, a reflective reference surface is arranged on the back side of the subject in the form of a sheet that is transparent to the measurement light beam, and light that has been transmitted through the subject and then reflected by the reflective reference surface and transmitted through the subject again is transmitted. There is also known a technique for obtaining transmitted wavefront information of a subject by causing interference with reference light reflected from a reference surface of a reference plate and obtaining thickness unevenness or refractive index distribution of the subject based on the transmitted wavefront information.

  In addition, by using an interferometer device having a path match path unit that divides a low coherent light beam into two, demultiplexes one light beam with respect to the other light beam, and then combines and outputs them, The reflected wavefront information from one side of the subject that is transparent and thick, the reflected wavefront information from the other side, and the transmitted wavefront information are acquired, and the shape of the one side of the subject is obtained based on the obtained wavefront information. The applicant of the present application has proposed a method for obtaining a refractive index distribution corresponding to the shape of the other surface, thickness unevenness, and a predetermined thickness of the subject (see Patent Document 2 below).

  On the other hand, an aperture synthesis method is known as a technique used when the measurement area of the subject is larger than a single measurable range of the interferometer. In this method, the surface to be measured is divided into a plurality of small areas where adjacent portions partially overlap, the measurement is performed for each small area, and after processing each measurement result, each measurement result is connected. Thus, various aperture synthesis methods have been proposed depending on the shape of the test surface and the data processing method (see Patent Documents 3 to 5 below).

JP 2000-275022 A JP 2005-274236 A JP 2002-162214 A JP-A-8-219737 JP-A-10-332350

  In recent years, there has been an increasing demand for measuring thickness unevenness of a large sheet-like object transparent to measurement light. Since such a large subject often has a region to be measured larger than a single measurable range of the interferometer, it is necessary to apply the aperture synthesis method described above.

  When the aperture synthesis method is applied, it is common to move the interferometer relative to the subject and capture an interference fringe image each time the interferometer is moved. In addition, the number of times the interference fringes are imaged increases, and the time required for measurement increases.

  In addition, it is difficult to maintain such a large subject while maintaining a constant posture with respect to the measurement system, and posture changes such as partial deformation or total deflection occur. easy. When deformation or the like occurs, it becomes difficult to perform aperture synthesis processing, and it is difficult to obtain a highly accurate measurement result. Therefore, a plurality of interference fringe images corresponding to each part in the measurement target region can be obtained as much as possible. It is important to take an image within a short time.

  In particular, in order to perform measurement with the subject moving with respect to the measurement system, such as in-process measurement, it is necessary to acquire interference fringe images over the entire measurement region at the same time. It becomes extremely difficult.

  The present invention has been made in view of such circumstances, and in a large sheet-like subject, a plurality of interference fringe images corresponding to each portion in the measurement region necessary for aperture synthesis are acquired in a short time. An object of the present invention is to provide a large sample measuring interferometer device that can measure thickness unevenness over the entire measurement region of a subject with high accuracy.

In order to solve the above problem, an interferometer apparatus for measuring a large sample according to the present invention is provided with a first interferometer head disposed on one surface side of a sheet-like subject and the other surface side of the subject. A second interferometer head; a first reflection plane disposed between the subject and the first interferometer head; and a portion disposed between the subject and the second interferometer head. An interferometer device comprising: a second reflection plane; and an analysis means for analyzing the interference fringe image,
The first interferometer head irradiates measurement light to a first region including a part of the measurement region of the subject from the one surface side, transmits the subject, and transmits the second reflection plane. The transmitted wavefront information of the first region is carried by the optical interference between the return light that is reflected by the reflected light, returns through the subject, and returns to the first interferometer head, and the reference light from the first interferometer head. Configured to obtain a first interference fringe image,
The second interferometer head irradiates measurement light to a second region including another part of the measurement region of the subject from the other surface side, passes through the subject, and transmits the first region. The transmitted wavefront of the second region is reflected by the optical interference between the return light that is reflected by the reflection plane and returns to the second interferometer head through the subject and the reference light of the second interferometer head. Configured to obtain a second interference fringe image carrying information;
The first interferometer head and the second interferometer head are arranged such that the first region and the second region adjacent to each other partially overlap each other and each of the first region and the second region. A predetermined number of each is arranged so as to include the measurement area,
The analysis means analyzes the transmitted wavefront information of the first area and the second area based on the first interference fringe image and the second interference fringe image, respectively, and the analysis of the first area and the second area The present invention is characterized in that an aperture synthesis process is performed on each analysis result relating to each transmitted wavefront information so as to obtain thickness unevenness of the subject in the measurement region.

In the present invention, the measurement light output from the first interferometer head and the measurement light output from the second interferometer head are composed of linearly polarized light whose polarization directions are orthogonal to each other.
The first interferometer head includes first light detecting means for passing linearly polarized light output from the first interferometer head and blocking linearly polarized light output from the second interferometer head. ,
The second interferometer head includes second light detecting means for passing linearly polarized light output from the second interferometer head and blocking linearly polarized light output from the first interferometer head. It can be said that.

In addition, the measurement light output from the first interferometer head and the measurement light output from the second interferometer head are configured to have different wavelengths.
The first interferometer head includes first wavelength selection means for allowing measurement light output from the first interferometer head to pass therethrough and blocking measurement light output from the second interferometer head. ,
The second interferometer head includes second wavelength selection means for allowing measurement light output from the second interferometer head to pass therethrough and blocking measurement light output from the first interferometer head. It can also be said.

Further, the measurement light output from the first interferometer head is within the exposure period of the first interference fringe image in the first interferometer head and the second interference fringe in the second interferometer. Configured to output only the first light emission period set outside the exposure period of the image,
The measurement light output from the second interferometer head is within the exposure period of the second interference fringe image in the second interferometer head and the first interference fringe image in the first interferometer. Only the second light emission period set outside the exposure period may be output.

  Each measurement light output from the first interferometer head and the second interferometer head can be output as pulsed light.

Further, each measurement light output from the first interferometer head and the second interferometer head includes a low coherence light having a coherence distance shorter than twice the optical distance of the thickness of the subject. And
The first interferometer head and the second interferometer head branch the low coherence light output from a light source into two light beams, and bypass one of the two light beams for a predetermined optical path length with respect to the other. A path match path that re-combines into one light beam after adjusting the first optical path length in the first area and the second area by adjusting the predetermined optical path length in the path match path section. Configured to obtain each reflected wavefront information from the side,
The analysis means analyzes each reflected wavefront information from the one surface side and the other surface side, and performs an aperture synthesis process on each analysis result, whereby the one surface of the subject in the measurement region It may be configured to obtain the respective shapes on the side and the other surface side.

Each measurement light output from the first interferometer head and the second interferometer head is a laser beam from a wavelength-modulated light source capable of wavelength scanning that oscillates a single longitudinal mode laser beam. ,
The first interferometer head and the second interferometer head modulate the laser light into a plurality of wavelengths with a sufficiently short period with respect to one light accumulation period of an element that receives the interference light. It is configured to obtain each reflected wavefront information from the one surface side and the other surface side in the first region and the second region,
The analysis means analyzes each reflected wavefront information from the one surface side and the other surface side, and performs an aperture synthesis process on each analysis result, whereby the one surface of the subject in the measurement region It can also be comprised so that each shape of a side and the said other surface side may be calculated | required.

  In that case, the analysis unit is configured to obtain a refractive index distribution corresponding to a predetermined thickness of the subject in the measurement region based on the shape on the one surface side, the shape on the other surface side, and the thickness unevenness. can do.

  The analysis means may be configured to analyze the interference fringe image using a Fourier transform method that performs phase analysis based on the fringe image on which the spatial carrier frequency is superimposed.

  According to the interferometer apparatus for measuring a large sample of the present invention, the following effects can be obtained by providing the above configuration.

  That is, unlike the conventional method, the interferometer head is moved relative to the measurement area of the subject, and instead of capturing an interference fringe image each time it is moved, the measurement is performed on one side and the other side of the subject. Since the first and second interferometer heads are arranged so as to include the region, a plurality of interference fringe images corresponding to each part of the region to be measured can be captured in a very short time.

  Therefore, it is difficult to keep the measurement system while maintaining a constant posture, and even a large subject subject to a change in posture, such as partial deformation or total deflection, is subject to the measurement. It becomes possible to measure the thickness unevenness over the entire measurement region with high accuracy.

  In particular, according to the aspect in which each measurement light output from the first and second interferometer heads is a pulsed light, a plurality of interference fringe images corresponding to each part of the measurement target region can be obtained substantially simultaneously and instantaneously. Since imaging can be performed, it is suitable for in-process measurement of the subject moving relative to the first and second interferometer heads.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a large sample measuring interferometer device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a relationship between a measurement region of a subject and a measurable region of each interferometer head. is there.

  A large sample measuring interferometer apparatus (hereinafter sometimes simply referred to as “interferometer apparatus”) shown in FIG. 1 is a flexible film-shaped large subject 9 that moves in a direction perpendicular to the paper surface. Are measured in-process, and a plurality of (seven in this embodiment) first interferometer heads 1A to 1G arranged downward on one surface 9a side (upper side in the figure) of the subject 9 A plurality (six in the present embodiment) of second interferometer heads 2A to 2F and first interferometer heads 1A to 1G arranged upward on the other surface 9b side (downward in the figure) of the subject 9. First reference plate 3 disposed between the subject 9 and the subject 9, the second reference plate 4 disposed between the second interferometer heads 2A to 2F and the subject 9, and each interferometer. Various performances for fringe analysis etc. based on interference fringe images obtained by the heads 1A-1G, 2A-2F An analysis device 5 for an image display device 6 for displaying an analysis result or the like, comprising a input device 7 for performing various inputs to the analyzer 5.

The first interferometer heads 1 </ b> A to 1 </ b> G include a part of a measurement area S (area within a rectangle indicated by a one-dot chain line in FIG. 2) of the subject 9 from the one surface 9 a side of the subject 9. One region P _{1 to} P ₇ (each region in a circle indicated by a solid line in FIG. 2) is irradiated with measurement light, and optical interference between the return light from the first region P _{1 to} P ₇ and the reference light Thus, an interference fringe image (first interference fringe image) carrying transmission wavefront information of the first regions P _{1 to} P ₇ is obtained.

On the other hand, the second interferometer heads 2A to 2F are second regions Q _{1 to} Q ₆ including other part of the measurement region S from the other surface 9b side of the subject 9 (shown by broken lines in FIG. 2). Each region in a circle shown) is irradiated with measurement light, and the transmitted wavefronts of the second regions Q _{1 to} Q ₆ are caused by optical interference between the return light from the second regions Q _{1 to} Q ₆ and the reference light. Each is configured to obtain an interference fringe image (second interference fringe image) carrying information.

As shown in FIG. 2, the first interferometer heads 1 </ b> A to 1 </ b> G and the second interferometer heads 2 </ b> A to 2 </ b> F have a first region and a second region (for example, a first region P ₁ and a second region) Q ₁ and the first region P ₄ and the second region Q ₄ ) partially overlap each other, and the measurement region S can be included by each of the first regions 1A to 1G and the second regions 2A to 2F. As shown in FIG. 1, the necessary number is arranged.

  Here, the configuration of the first interferometer heads 1A to 1G and the second interferometer heads 2A to 2F will be described in more detail. Each of the first interferometer heads 1A to 1G has the same configuration, and each of the second interferometer heads 2A to 2F has the same configuration. Based on the first interferometer head 1A and the second interferometer head 2A as an example. FIG. 3 is a schematic configuration diagram of the first interferometer head and the second interferometer head.

  As shown in FIG. 3, the first interferometer head 1A includes a light source 11, a diverging lens 12 for expanding a beam diameter, a beam splitter 13, a collimator lens 14, and a first analyzer 15 as a first analyzing means, The imaging camera 16 includes an imaging lens 16 and an imaging element 18 such as a CCD or a CMOS. The light beam output from the light source 11 is linearly polarized light having a predetermined vibration surface, and the first analyzer 15 transmits the linearly polarized light output from the light source 11 and is orthogonal to the vibration surface of the linearly polarized light. The linearly polarized light having the vibrating surface (linearly polarized light output from the light source 21 described later) is blocked. The light source 11 is a light source having a mechanism such as a pulse laser light source or a beam chopper, and a light beam output from the light source 11 is pulsed light having a short light emission period.

  On the other hand, the second interferometer head 2A includes a light source 21, a diverging lens 22 for expanding a beam diameter, a beam splitter 23, a collimator lens 24, a second analyzer 25 as a second analyzing means, an imaging lens 26, And an imaging camera subject 27 having an imaging element 28 such as a CCD or CMOS. The light beam output from the light source 21 is linearly polarized light having a vibration surface orthogonal to the vibration surface of the linearly polarized light output from the light source 11, and the second analyzer 25 is a straight line output from the light source 21. The polarized light is transmitted, and the linearly polarized light having the vibration plane orthogonal to the plane of vibration of the linearly polarized light (linearly polarized light output from the light source 11) is blocked. The light source 21 is a light source having a mechanism such as a pulse laser light source or a beam chopper, and a light beam output from the light source 21 is pulsed light having a short light emission period.

  In the first interferometer head 1A, the light beam composed of linearly polarized light output from the light source 11 passes through the diverging lens 12 and enters the beam splitter 13, and the light beam splitting surface 13a of the beam splitter 13 moves downward in the figure. The reflected light is further collimated by the collimator lens 14 and output to the subject 9 as measurement light.

A part of the output measurement light is reflected by the reference surface 3a of the first reference plate 3 to become reference light, and the remaining measurement light passes through the first reference plate 3 and passes through the first reference plate 3 of the subject 9. One region P ₁ (see FIG. 2) is irradiated. The irradiated measurement light is transmitted through the subject 9, and then a part thereof is reflected on the reference surface 4a of the second reference plate 4 (functioning as a second reflection plane). The return light passes through the reference plate 3 and enters the first interferometer head 1A. The interference light between the return light and the reference light passes through the collimator lens 14, the beam splitter 13, the first analyzer 15, and the imaging lens 16 and is imaged on the image sensor 18. A first interference fringe image carrying transmitted wavefront information relating to one region P ₁ is captured by the imaging camera 17.

  On the other hand, in the second interferometer head 2A, the light beam composed of linearly polarized light output from the light source 21 passes through the diverging lens 22 and enters the beam splitter 23, and in the light beam branching surface 23a of the beam splitter 23 in the drawing. The light is reflected upward, further converted into parallel light by the collimator lens 24, and output to the subject 9 as measurement light.

A part of the output measurement light is reflected by the reference surface 4a of the second reference plate 4 to become reference light, and the remaining measurement light passes through the second reference plate 4 and passes through the second reference plate 4 of the subject 9. Two areas Q ₁ (see FIG. 2) are irradiated. The irradiated measurement light passes through the subject 9, and a part thereof is reflected on the reference surface 3a (functioning as the first reflection plane) of the first reference plate 3, and further, the subject 9 and the second The return light is transmitted through the reference plate 4 and incident on the second interferometer head 2A. Interference light between the return light and the reference light from the reference surface 4a passes through the collimator lens 24, the beam splitter 23, the second analyzer 25, and the imaging lens 26 and is imaged on the image pickup device 28. A second interference fringe image carrying transmitted wavefront information regarding the second region Q ₁ of the specimen 9 is captured by the imaging camera 27.

Note that the first interference fringe image and the second interference fringe image are captured substantially simultaneously at the same timing. Since the first region P ₁ and the second region Q ₁ partly overlap each other, the part of the measurement light from the first interferometer head 1A enters the second interferometer head 2A, the second Part of the measurement light from the interferometer head 2A is incident on the first interferometer head 1A, but each measurement light is blocked by the second analyzer 25 and the first analyzer 15, respectively. The imaging of the first interference fringe image and the second interference fringe image is not affected. A part of the measurement light is reflected on the one surface 9a and the other surface 9b of the subject 9, but the first and second reference plates 3 and 4 are placed on the subject 9 as shown in FIGS. Accordingly, the reflected light from the subject 9 is prevented from returning to the first and second interferometer heads 1A and 2A.

  Further, although the first reference plate 3 and the second reference plate 4 described above are each formed in a parallel plate shape, each back surface is arranged so that reflected light from each back surface does not enter each interferometer head. It is preferable to apply a wedge or to apply an antireflection coating.

The above description relates to the first interferometer head 1A and the second interferometer head 2A, but the same applies to the other first interferometer heads 1B to 1G and the other second interferometer heads 2B to 2F. It is. That is, the first interferometer heads 1A to 1G use the first interferometer heads 2A to 2F to convert the first interference fringe images carrying the transmitted wavefront information of the first regions P _{1 to} P ₇ into the second region. The respective second interference fringe images carrying the transmitted wavefront information of Q _{1 to} Q ₆ are captured substantially simultaneously.

Each captured first interference fringe image and second interference fringe image are input to the analysis device 5 shown in FIG. 1, and based on the first and second interference fringe images, the first regions P _{1 to} P ₇ are input. and each of the transmitted wavefront information of the second region Q ₁ to Q ₆ are analyzed respectively. Then, by performing aperture synthesis processing on each analysis result regarding each transmitted wavefront information, the thickness unevenness of the subject 9 over the entire measurement region S is obtained.

  Note that various methods described in Patent Documents 3 to 5 and the like described above can be applied to specific processing of aperture synthesis. In the present embodiment, the refractive index of the subject 9 is assumed to be constant (no refractive index distribution) in each part of the subject 9, and the thickness unevenness of the subject 9 is obtained from the transmitted wavefront information. On the other hand, when the thickness of the subject 9 can be regarded as constant (no thickness unevenness) in each part of the subject 9, the refractive index distribution of the subject 9 can be obtained from each of the transmitted wavefront information.

  The analysis process of each transmitted wavefront information is Fourier transform described in “Sub-Fringe Interferometry Basics” on pages 55 to 65 of “Optics” Vol. 13 No. 1 (February 1984). The law can be applied. This Fourier transform method is to perform a Fourier transform on the fringe image on which the spatial carrier frequency is superimposed, remove the spatial carrier frequency in the frequency domain, and then perform an inverse Fourier transform to perform phase analysis. For example, by providing a relative inclination between the first reference plate 3 and the second reference plate 4, the spatial carrier frequency can be superimposed on each of the first interference fringe image and the second interference fringe image. It becomes possible. By applying the Fourier transform method, it is possible to perform sub-fringing measurement on the moving subject 9 and to obtain the thickness unevenness of the subject 9 with higher accuracy.

  As mentioned above, although one Embodiment of the interferometer apparatus for large sample measurement which concerns on this invention was described, this invention is not limited to this Embodiment, A various aspect can be changed.

  For example, the measurement light output from the first interferometer head and the measurement light output from the second interferometer head are configured to have different wavelengths, and the first interferometer head has the first interferometer head. The first interferometer head includes first wavelength selection means for allowing the measurement light output from the second interferometer head to pass therethrough and blocking the measurement light output from the second interferometer head. Measurement light output from the interferometer head may be provided, and second wavelength selection means for blocking measurement light output from the first interferometer head may be provided.

  Specifically, in the embodiment shown in FIG. 3, the wavelength of the output light from the light source 11 and the wavelength of the output light from the light source 21 are made different from each other. Further, in place of the first analyzer 15, a first wavelength selection filter is installed so that the wavelength range of the output light from the light source 11 is transmitted and the wavelength range of the output light from the light source 21 is cut off. Instead of the photon 25, a second wavelength selection filter is provided that transmits the wavelength range of the output light from the light source 21 and blocks the wavelength range of the output light from the light source 11.

  The above embodiment is suitable when the subject moves. However, when the subject does not move, the measurement light output from the first interferometer head is used for the exposure period of the first interference fringe image. And the measurement light output from the second interferometer head is configured to output only the first light emission period set outside the exposure period of the second interference fringe image. It may be configured to output only the second light emission period set within the exposure period and outside the exposure period of the first interference fringe image. In this case, it is not necessary to make each output light from the light sources 11 and 21 linearly polarized or have different wavelengths, and the first and second analyzers 15 and 25 and the first and second wavelength selections. There is no need to install a filter. For this reason, the configuration of the first and second measurement heads can be simplified.

  Each measurement light output from the first interferometer head and the second interferometer head is a low coherence light having a coherence distance shorter than twice the optical distance of the thickness of the subject, In the interferometer head and the second interferometer head, the low coherent light output from the light source is branched into two light beams, and one of the two light beams is detoured by a predetermined optical path length with respect to the other light beam. May be provided with a path match route section for recombining. Then, in the path match path section, by adjusting the predetermined optical path length, each reflected wavefront information from the one side and the other side of the subject is obtained, and each reflected wavefront information is analyzed by the analyzing means, By performing aperture synthesis processing on the analysis result, the shapes of the one surface side and the other surface side of the subject in the measurement region are obtained.

  Specifically, in the embodiment shown in FIG. 3, between the light source 11 and the diffusion lens 12 of the first interferometer head 1A and between the light source 21 and the diffusion lens 22 of the second interferometer head 2A, A path match path portion is provided for each. Further, the first and second reference plates 3 and 4 are arranged so as to be substantially parallel to the subject 9.

When measuring the shape of the one surface 9a of the subject 9, the first interferometer head 1A uses the reference of the first reference plate 3 out of the measurement light output from the first interferometer head 1A. Only optical interference occurs between the reference light reflected by the surface 3 a and the return light that is transmitted by the first reference plate 3 and then reflected by the one surface 9 a of the subject 9 and then transmitted through the first reference plate 3. As described above, the optical path length is adjusted in the path match path portion. Then, to image the interference fringe image carrying reflected wavefront information from the one surface 9a side of the first region P ₁ (third interference fringe image). In the second interferometer head 2A, the reference light reflected by the reference surface 4a of the second reference plate 4 out of the measurement light output from the second interferometer head 2A, and the second interferometer head 2A Then, the optical path length is adjusted in the path matching path so that only the optical interference with the return light reflected by the one surface 9a of the subject 9 after passing through the reference plate 4 and transmitted through the second reference plate 4 occurs. Then, to image the interference fringe image carrying reflected wavefront information from the one surface 9a side of the second region Q ₁ (5 interference fringe image).

On the other hand, when measuring the shape of the other surface 9b of the subject 9, the first interferometer head 1A uses the first reference plate 3 out of the measurement light output from the first interferometer head 1A. Only the optical interference between the reference light reflected by the reference surface 3a and the return light that is transmitted through the first reference plate 3 and then reflected by the other surface 9b of the subject 9 and further transmitted through the first reference plate 3 So that the optical path length is adjusted in the path match path section. Then, to image the interference fringe image carrying reflected wavefront information from the other surface 9b side (fourth interference fringe image) of the first region P _1. In the second interferometer head 2A, the reference light reflected by the reference surface 4a of the second reference plate 4 out of the measurement light output from the second interferometer head 2A, and the second interferometer head 2A The optical path length is adjusted in the path matching path so that only the optical interference with the return light that is transmitted through the reference plate 4 and then reflected by the other surface 9b of the subject 9 and transmitted through the second reference plate 4 occurs. . Then, to image the interference fringe image and the reflected wavefront information carrying (Sixth interference fringe image) from the other surface 9b side of the second region Q _1.

Furthermore, the analysis means analyzes each reflected wavefront information from the third interference fringe image and the first region P ₁ and the second one surface 9a side of the region Q ₁ on the basis of the fifth interference fringe image. Then, by performing the processing of the aperture synthesis for each of the analysis results to determine the one surface 9a side of the shape of the first region P ₁ and the second region Q subject 9 across _one. Furthermore, analyzes the reflected wavefront information from the other surface 9b side in the first region P ₁ and the second region Q ₁ on the basis of the fourth interference fringe image and the sixth interference fringe image, opening to each of the analysis results by performing the processing of synthesis and to obtain the other surface 9b side of the shape of the first region P ₁ and the second region Q subject 9 across _one.

  In addition, as a specific aspect of the path match path part, those described in Japanese Patent Application Laid-Open Nos. 9-21606 and 2005-274236 can be applied.

  As another aspect, each measurement light output from the first interferometer head and the second interferometer head is converted from a laser from a wavelength-modulated light source capable of wavelength scanning to oscillate a single longitudinal mode laser beam. It can also be light. Then, in the first interferometer head and the second interferometer head, the laser light is modulated into a plurality of wavelengths at a sufficiently short period with respect to one light accumulation period of the element that receives the interference light. In addition to obtaining each reflected wavefront information from one side and the other side of the subject in the region and the second region, the analysis unit analyzes each reflected wavefront information from the one side and the other side of the subject, You may make it obtain | require each shape of the one surface side of the to-be-examined object in a to-be-measured area | region, and an other surface side by performing an aperture synthesis process with respect to an analysis result.

  In this embodiment, the laser light from the wavelength-modulated light source is wavelength-scanned and adjusted so that only the return light from the predetermined surface interferes with the reference light, similar to the above-described one having the path match path section. Specifically, in the embodiment shown in FIG. 3, the light source 11 of the first interferometer head 1A and the light source 21 of the second interferometer head 2A may be the above-described wavelength modulation light source. In addition, as a wavelength modulation light source capable of wavelength scanning that oscillates a single longitudinal mode laser beam, and a specific mode of wavelength scanning, those described in Japanese Patent No. 3621693 can be applied. .

  Further, in the aspect provided with the above-described path match path portion and the aspect provided with the wavelength modulation light source, the obtained shape of the one surface side and the other surface side of the subject, and the transmitted wavefront of the subject Based on the thickness unevenness obtained from the information, a refractive index distribution corresponding to a predetermined thickness of the subject in the measurement region can be obtained. In addition, as a specific method for obtaining a refractive index distribution corresponding to a predetermined thickness of the subject, one described in the above Japanese Patent Application Laid-Open No. 2005-274236 can be applied.

  Also, the number of first interferometer heads and the second interferometer heads (at least one is necessary) and the arrangement method should be changed as appropriate according to the size and shape of the set measurement area. Can do. For example, the first interferometer head and the second interferometer head can be arranged in a vertical and horizontal array.

  In the above-described embodiment, a flexible film is exemplified as the subject 9, but the present invention is also applicable to a plate-like subject having no flexibility such as a liquid crystal panel. Applicable.

1 is a schematic configuration diagram of a large sample measuring interferometer device according to an embodiment of the present invention. The figure which shows the relationship between the measurement area | region of a test object and the measurable area | region of each interferometer head Schematic configuration diagram of the first interferometer head and the second interferometer head

Explanation of symbols

1A to 1G First interferometer head 2A to 2F Second interferometer head 3 First reference plate 3a Reference surface (of the first reference plate) 4 Second reference plate 4a (of the second reference plate) Reference surface 5 Analyzing device 6 Image display device 7 Input device 9 Subject 11, 21 Light source 12, 22 Diverging lens 13, 23 Beam splitter 13a, 23a Beam splitting surface 14, 24 Collimator lens 15 First analyzer 16, 26 Imaging lens 17, 27 the imaging camera 18, 28 image sensor 19 tilt adjustment stage 25 and the second analyzer S measurement area P ₁ to P ₇ first region Q ₁ to Q ₆ second region

Claims (9)

A first interferometer head disposed on one side of the sheet-like subject; a second interferometer head disposed on the other side of the subject; and the subject and the first interferometer head A second reflection plane disposed between the subject and the second interferometer head, and an analysis means for analyzing the interference fringe image. An interferometer device comprising:
The first interferometer head irradiates measurement light to a first region including a part of the measurement region of the subject from the one surface side, transmits the subject, and transmits the second reflection plane. The transmitted wavefront information of the first region is carried by the optical interference between the return light that is reflected by the reflected light, returns through the subject, and returns to the first interferometer head, and the reference light from the first interferometer head. Configured to obtain a first interference fringe image,
The second interferometer head irradiates measurement light to a second region including another part of the measurement region of the subject from the other surface side, passes through the subject, and transmits the first region. The transmitted wavefront of the second region is reflected by the optical interference between the return light that is reflected by the reflection plane and returns to the second interferometer head through the subject and the reference light of the second interferometer head. Configured to obtain a second interference fringe image carrying information;
The first interferometer head and the second interferometer head are arranged such that the first region and the second region adjacent to each other partially overlap each other and each of the first region and the second region. A predetermined number of each is arranged so as to include the measurement area,
The analysis means analyzes the transmitted wavefront information of the first area and the second area based on the first interference fringe image and the second interference fringe image, respectively, and the analysis of the first area and the second area For large sample measurement, characterized in that it is configured to obtain thickness unevenness of the subject in the measurement region by performing aperture synthesis processing on each analysis result regarding each transmitted wavefront information Interferometer device. The measurement light output from the first interferometer head and the measurement light output from the second interferometer head are composed of linearly polarized light whose polarization directions are orthogonal to each other.
The first interferometer head includes first light detecting means for passing linearly polarized light output from the first interferometer head and blocking linearly polarized light output from the second interferometer head. ,
The second interferometer head includes second light detecting means for passing linearly polarized light output from the second interferometer head and blocking linearly polarized light output from the first interferometer head. The interferometer apparatus for measuring a large sample according to claim 1, wherein The measurement light output from the first interferometer head and the measurement light output from the second interferometer head are configured to have different wavelengths.
The first interferometer head includes first wavelength selection means for allowing measurement light output from the first interferometer head to pass therethrough and blocking measurement light output from the second interferometer head. ,
The second interferometer head includes second wavelength selection means for allowing measurement light output from the second interferometer head to pass therethrough and blocking measurement light output from the first interferometer head. The interferometer apparatus for measuring a large sample according to claim 1, wherein The measurement light output from the first interferometer head is within the exposure period of the first interference fringe image in the first interferometer head and the second interference fringe image in the second interferometer. Configured to output only the first light emission period set outside the exposure period,
The measurement light output from the second interferometer head is within the exposure period of the second interference fringe image in the second interferometer head and the first interference fringe image in the first interferometer. 2. The interferometer apparatus for measuring a large sample according to claim 1, wherein the interferometer apparatus is configured to output only the second light emission period set outside the exposure period.   5. Each measurement light output from the first interferometer head and the second interferometer head is output as pulsed light, respectively. 6. The interferometer apparatus for large sample measurement described. Each measurement light output from the first interferometer head and the second interferometer head is a low coherence light having a coherence distance shorter than twice the optical distance of the thickness of the subject,
The first interferometer head and the second interferometer head branch the low coherence light output from a light source into two light beams, and bypass one of the two light beams for a predetermined optical path length with respect to the other. A path match path that re-combines into one light beam after adjusting the first optical path length in the first area and the second area by adjusting the predetermined optical path length in the path match path section. Configured to obtain each reflected wavefront information from the side,
The analysis means analyzes each reflected wavefront information from the one surface side and the other surface side, and performs an aperture synthesis process on each analysis result, whereby the one surface of the subject in the measurement region The interferometer apparatus for measuring a large sample according to any one of claims 1 to 4, wherein the interferometer apparatus is configured to obtain respective shapes on the side and the other surface side. Each measurement light output from the first interferometer head and the second interferometer head is a laser beam from a wavelength-modulated light source capable of wavelength scanning to oscillate a single longitudinal mode laser beam,
The first interferometer head and the second interferometer head modulate the laser light into a plurality of wavelengths with a sufficiently short period with respect to one light accumulation period of an element that receives the interference light. It is configured to obtain each reflected wavefront information from the one surface side and the other surface side in the first region and the second region,
The analysis means analyzes each reflected wavefront information from the one surface side and the other surface side, and performs an aperture synthesis process on each analysis result, whereby the one surface of the subject in the measurement region The interferometer apparatus for measuring a large sample according to any one of claims 1 to 4, wherein the interferometer apparatus is configured to obtain respective shapes on the side and the other surface side.   The analysis unit is configured to obtain a refractive index distribution corresponding to a predetermined thickness of the subject in the measurement region based on the shape on the one surface side, the shape on the other surface side, and the thickness unevenness. The interferometer apparatus for measuring a large sample according to claim 6 or 7. The analysis means is configured to analyze an interference fringe image using a Fourier transform method that performs phase analysis based on a fringe image on which a spatial carrier frequency is superimposed. The interferometer device for large sample measurement according to any one of -8.

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