JP2005233767A - Measurement device and measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the shape of the surface to be measured with high accuracy, regardless of accuracy of form of the reference surface, when measuring a shape of a surface to be measured by utilizing light interference. <P>SOLUTION: An optical path B (optical path for a surface to be measured), in which an object to be measured W (a surface to be measured) is placed, is switched between an optical path (optical path for first measurement) in which light split by a first beam splitter 12 bypasses the object to be measured W and runs into a third beam splitter 15 and an optical path (optical path for second measurement), in which the split light runs into the object to be measured W and then into the third beam splitter 15 to measure. The shape of the object to be measured W is obtained, based on the measurement results obtained by interference of the light passing through an optical path A, in which the reference surface is placed and the optical path for first measurement, and the measurement results obtained by interference of the light passing through the optical path A and the optical path for second measurement. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a measuring apparatus and a measuring method for measuring the shape of a surface to be measured using light interference.

Conventionally, as a method for measuring the shape of a glass component or the like with high accuracy, interference light is generated by interference between light applied to a reference surface and light applied to a surface to be measured. A method for measuring the shape of a measured surface as a reference is known. As an apparatus for realizing this measurement method, a Mach-Zehnder interferometer is widely used (for example, see Non-Patent Document 1). A Mach-Zehnder interferometer uses the light interference generated when light emitted from a light source is split and passed through separate optical paths, and the light passing through the separate optical paths is superimposed. Is to measure the shape.
Tetsuo Sueda, “How to use optical components for optronics and points to be noted (supplemented revised edition)”, Optronics Co., Ltd., May 21, 1990, p. 292-294

  By the way, as described above, the interferometer compares the reference surface and the surface to be measured, and measures the shape of the surface to be measured using the reference surface as a reference. For this reason, the measurement accuracy of the interferometer depends on the shape accuracy of the reference surface, and there is a problem in that it is impossible to perform measurement that exceeds the shape accuracy of the reference surface. That is, if the shape accuracy of the reference surface is low, the measurement accuracy is also low. Therefore, a reference surface with high shape accuracy is required to perform high-precision measurement.

  The present invention has been made paying attention to such problems existing in the prior art, and its purpose is to measure the shape of the surface to be measured with high accuracy regardless of the shape accuracy of the reference surface. It is an object of the present invention to provide a measuring apparatus and a measuring method capable of performing the above.

  In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that the light emitted from the light source is dispersed by the spectroscopic means, and the split light is optical path for the reference surface on which the reference surface is arranged and the measurement target. In the measuring apparatus for measuring the shape of the surface to be measured by using the light interference generated when the light is overlapped again after passing through the optical path for the surface to be measured on which the surface is arranged and overlapping the light A first optical path through which the light split by the spectroscopic means reaches the polymerization means without passing through the measured surface; and the light split by the spectroscopic means An optical path switching means for switching to a second optical path that passes through the superimposing means after passing through the optical path for the reference surface and the optical path for the measurement surface when the optical path for the measurement surface is the first optical path. Measurement results obtained by interference of light passing through, and the surface to be measured An arithmetic means for calculating the shape of the measured surface based on a measurement result obtained by interference of light passing through the optical path for the reference surface and the optical path for the measured surface when the optical path is the second optical path; The main point is that

  According to a second aspect of the present invention, in the measurement apparatus according to the first aspect, the optical path switching means is an optical member having a reflecting surface that reflects incident light, and the optical member is the first member. In the optical path, the light split by the spectroscopic means is arranged to be directly reflected by the superposition means, and in the second optical path, the light split by the spectroscopic means passes through the surface to be measured. The gist is that the optical member is arranged so as to be reflected by the superposition means, and the optical member is arranged so as to reflect the light on the same surface in the first optical path and the second optical path.

  According to a third aspect of the present invention, the light emitted from the light source is dispersed by the spectroscopic means, and the dispersed light is used for the reference surface optical path on which the reference surface is arranged and the measurement surface on which the measurement surface is arranged. In the measuring method for measuring the shape of the surface to be measured by using the interference of light generated when the light is superimposed after being overlapped by the superimposing means after passing through the optical path, the light spectrally separated by the spectroscopic means The measurement surface optical path is formed so as to reach the superposition means without passing through the measurement surface, and measurement is performed using interference of light passing through the measurement surface optical path and the reference surface optical path. A first measurement step to be performed; and the light path for the measurement surface is formed so that the light dispersed by the spectroscopic means passes through the measurement surface and then reaches the polymerization means, and the measurement surface optical path and the measurement surface Second measurement is performed by using interference of light passing through the optical path for the reference plane. And a calculation step for calculating the shape of the surface to be measured based on the measurement result obtained in the first measurement step and the measurement result obtained in the second measurement step. To do.

  According to the present invention, the shape of the surface to be measured can be measured with high accuracy regardless of the shape accuracy of the reference surface.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in a measuring apparatus 10 that measures the planar shape (flatness) of an object W using light interference will be described with reference to FIGS. 1 and 2. 1 to 4, the optical path of light used for measurement is indicated by a solid arrow, and the direction of the arrow indicates the direction in which the light travels.

  The measuring apparatus 10 of this embodiment includes a light source 11, a first beam splitter 12 as a spectroscopic unit, a second beam splitter 13 as a reference surface, and a polarizing beam splitter as an optical path switching unit (optical member). 14 and a third beam splitter 15 as a superposition means. The measuring apparatus 10 includes a quarter wavelength plate 16, a light receiving element 17, and a computer 18. In the present embodiment, the light receiving element 17 and the computer 18 constitute an arithmetic means (enclosed by a broken line in each figure). In the following description, the beam splitters 12 to 15 and the quarter wavelength plate 16 are also referred to as optical elements.

  The light source 11 is a light source that emits helium neon laser light (λ = 632.8 nm (randomly polarized light or linearly polarized light)). The first beam splitter 12 is arranged so that light emitted from the light source 11 enters. The first beam splitter 12 has a reflection / transmission surface 12a on which a thin film (dielectric film, metal film, hybrid film, etc.) is deposited so as to function as a half mirror, and converts incident light into reflected light and transmitted light. Spectroscopic (separated). In the present embodiment, the reflected reflected light becomes light passing through the optical path A as the optical path for the reference surface, and the transmitted light that has been split becomes light passing through the optical path B as the optical path for the surface to be measured.

  The second beam splitter 13 is arranged so that the reflected light reflected by the first beam splitter 12 enters. Similar to the first beam splitter 12, the second beam splitter 13 has a reflection / transmission surface 13a, and splits incident light into reflected light and transmitted light. In the present embodiment, the measurement is performed using the reflection / transmission surface 13a of the second beam splitter 13 as a reference surface.

  The polarization beam splitter 14 is arranged so that the transmitted light that has passed through the first beam splitter 12 enters. The polarization beam splitter 14 has a reflection / transmission surface 14a as a reflection surface on which a thin film (dielectric multilayer film or the like) having a polarization separation function is deposited, and converts incident light into s-polarized light (light that vibrates in the horizontal direction). The light is split into reflected light and transmitted light of p-polarized light (light that vibrates in the vertical direction). The quarter-wave plate 16 is disposed between the polarization beam splitter 14 and the object W to be measured so that the transmitted light that has passed through the polarization beam splitter 14 enters.

  The third beam splitter 15 is arranged so that the reflected light reflected by the second beam splitter 13 and the reflected light reflected by the polarization beam splitter 14 are incident thereon. Similar to the first and second beam splitters 12 and 13, the third beam splitter 15 has a reflection / transmission surface 15a. In the third beam splitter 15, the reflected light reflected by the second beam splitter 13 is reflected by the reflecting / transmitting surface 15a, and the reflected light reflected by the polarizing beam splitter 14 is transmitted through the reflecting / transmitting surface 15a. Light is superposed.

  The light receiving element (for example, CCD camera) 17 is disposed so as to receive the light superimposed by the third beam splitter 15. The light receiving element 17 can capture interference fringes according to the optical path difference of the light passing through the optical path A and the optical path B. A computer 18 is connected to the light receiving element 17. The light receiving element 17 converts the received light into an electric signal, and the electric signal is output to the computer 18. The computer 18 inputs an electrical signal and analyzes the interference fringes captured by the light receiving element 17.

  In the measurement apparatus 10 of the present embodiment, the polarization beam splitter 14 is disposed on a rotary table (not shown) so that the incident surface of the light transmitted through the first beam splitter 12 can be changed. Specifically, the polarization beam splitter 14 is arranged on the optical path B in the first measurement state shown in FIG. 1 and the second measurement state shown in FIG. The polarizing beam splitter 14 arranged in the second measurement state (FIG. 2) is arranged so that the polarizing beam splitter 14 arranged in the first measurement state (FIG. 1) rotates clockwise (in the clockwise direction) on the paper surface of FIG. It is in a state rotated 90 degrees. The polarization beam splitter 14 is arranged so that the surfaces that reflect light to the third beam splitter 15 are the same surface in the first measurement state and the second measurement state. The polarizing beam splitter 14 arranged in the second measurement state has rotated the polarizing beam splitter 14 arranged in the first measurement state 90 degrees counterclockwise (counterclockwise) on the paper surface of FIG. It is the same as the state. However, when arranged in this way, the surface that reflects light to the third beam splitter 15 is different.

  Hereinafter, the optical path A and the optical path B formed in the measuring apparatus 10 of the present embodiment will be described in detail. An optical path A and an optical path B indicate optical paths until the light split by the first beam splitter 12 reaches the third beam splitter 15 and is superposed.

  The optical path A is formed by the first beam splitter 12, the second beam splitter 13, and the third beam splitter 15. In the optical path A, the reflected light reflected by the first beam splitter 12 is reflected by the second beam splitter 13 (reference surface), further reflected by the third beam splitter 15, and then received by the light receiving element 17. Light is received.

  The optical path B is formed as two different optical paths according to the arrangement of the polarization beam splitter 14. That is, when the polarization beam splitter 14 is arranged in the first measurement state (FIG. 1), the optical path B is formed by the first beam splitter 12, the polarization beam splitter 14, and the third beam splitter 15. It has become. Hereinafter, the optical path B formed in this way is referred to as a “first measurement optical path Ba”. In the first measurement optical path Ba, the transmitted light that has passed through the first beam splitter 12 is reflected by the polarization beam splitter 14, passes through the third beam splitter 15, and then received by the light receiving element 17. It has become.

  In the first measurement optical path Ba, the transmitted light transmitted through the polarization beam splitter 14 is reflected by the object to be measured W (measurement surface) and enters the polarization beam splitter 14 again. The vibration direction is changed 90 degrees through the quarter-wave plate 16 twice. Therefore, the light reflected by the object to be measured W is reflected in the opposite direction to the third beam splitter 15 and does not pass through the polarization beam splitter 14 (that is, does not become return light to the light source 11). The first measurement optical path Ba is the first optical path because the light split by the first beam splitter 12 reaches the third beam splitter 15 without passing through the surface to be measured.

  On the other hand, when the polarization beam splitter 14 is arranged in the second measurement state (FIG. 2), the optical path B is the first beam splitter 12, the polarization beam splitter 14, the quarter wavelength plate 16, and the object W to be measured. And the third beam splitter 15. Hereinafter, the optical path B thus formed is referred to as a “second measurement optical path Bb”. In the second measurement optical path Bb, the transmitted light that has passed through the first beam splitter 12 passes through the polarization beam splitter 14, passes through the quarter-wave plate 16, and is reflected by the measurement object W (measurement surface). After that, the light is again incident on the polarization beam splitter 14 through the quarter-wave plate 16. The light incident on the polarization beam splitter 14 passes through the quarter wavelength plate 16 twice and the vibration direction is changed by 90 degrees, so that it is reflected by the polarization beam splitter 14 and passes through the third beam splitter 15. After being transmitted, the light receiving element 17 receives the light. In the second measurement optical path Bb, the light split by the first beam splitter 12 reaches the third beam splitter 15 after passing through the surface to be measured, so that it becomes the second optical path.

  In the measurement apparatus 10 of the present embodiment configured as described above, first, measurement 1 using the optical path A and the first measurement optical path Ba (first measurement step), and measurement 2 using the optical path A and the second measurement optical path Bb. (Second measurement step) is performed. Thereafter, the planar shape of the workpiece W (surface to be measured) is calculated from the measurement result of measurement 1 and the measurement result of measurement 2 (calculation step). Either measurement 1 or measurement 2 may be performed first.

  In measurement 1, the polarizing beam splitter 14 is placed in the first measurement state (FIG. 1) to form the first measurement optical path Ba, and the optical path difference between the optical path A and the first measurement optical path Ba (measurement result) ) Can be obtained. In this measurement 1, the shape of the reflection / transmission surface 14a of the polarization beam splitter 14 is measured using the reference surface (the reflection / transmission surface 13a of the second beam splitter 13) as a reference. On the other hand, in the measurement 2, the polarizing beam splitter 14 is arranged in the second measurement state (FIG. 2) to form the second measurement optical path Bb, and the optical path difference between the light passing through the optical path A and the second measurement optical path Bb ( Measurement result). In this measurement 2, the shape of the object to be measured W is measured in addition to the shape of the reflection / transmission surface 14a of the polarization beam splitter 14 with the reference surface (the reflection / transmission surface 13a of the second beam splitter 13) as a reference. It will be.

  Therefore, by calculating the difference between the measurement result of measurement 1 and the measurement result of measurement 2, the planar shape of the workpiece W (measurement surface) can be calculated without being affected by the shape accuracy of the reference surface. It becomes possible. That is, the measurement results of measurement 1 and measurement 2 include shape errors of the reflection / transmission surfaces 12a to 15a of the beam splitters 12 to 15, respectively. Therefore, if the difference between the measurement result of measurement 1 and the measurement result of measurement 2 is obtained, the shape error of each of the reflection / transmission surfaces 12a to 15a included in each measurement result is canceled, and as a result, the object to be measured Only the shape of W (surface to be measured) can be calculated.

Hereinafter, the measurement result of measurement 1 and the measurement result of measurement 2 will be described in more detail.
In the following description, each surface shape of the first beam splitter 12, the second beam splitter 13 (reference surface), the polarization beam splitter 14, the third beam splitter 15, and the surface to be measured (the surface that reflects the light) (Shape) are sequentially indicated as “F12”, “F13”, “F14”, “F15”, and “T”. Each surface shape is represented by a bivalent function. Therefore, when the surface shape is not an ideal perfect plane shape and light is incident on the surface and reflected from an oblique direction, the reflected light is √2 × (with respect to the incident light (plane wave). (Surface shape). “√2” indicates “Route 2”. In addition, when the surface shape is not an ideal perfect plane shape and light is incident perpendicularly to the surface to be reflected, the reflected light is 2 × (surface with respect to the incident light (plane wave). (Shape). The amount of deviation with respect to the plane wave is calculated from the optical path difference between the incident light when it is reflected by the perfect plane and when it is reflected by the actual surface.

From the above, the laser light (plane wave having the same phase) emitted from the light source 11 in the optical path A is affected by the shape of each surface of the first to third beam splitters 12, 13, and √2. X (F12 + F13 + F15) reaches the light receiving element 17 as light shifted from the plane wave. On the other hand, in the first measurement optical path Ba (FIG. 1), the laser light reaches the light receiving element 17 as light shifted from the plane wave by √2 × (F14) due to the influence of the surface shape of the polarization beam splitter 14. Therefore, in the measurement 1, the optical path difference of the light passing through the optical path A and the first measurement optical path Ba is as shown in the equation (1).
√2 × (F14) −√2 × (F12 + F13 + F15) (1)
On the other hand, in the second measurement optical path Bb (FIG. 2), the laser beam is influenced by the surface shape of the polarization beam splitter 14 and the surface shape of the object W to be measured, and is a plane wave by √2 × (F14) + 2 × T. The light reaches the light receiving element 17 as light deviated from the above. Therefore, in the measurement 2, the optical path difference of the light passing through the optical path A and the second measurement optical path Bb is as shown in the equation (2).
√2 × (F14) + 2 × T−√2 × (F12 + F13 + F15) (2)
When the difference between the measurement result of measurement 1 (formula (1)) and the measurement result of measurement 2 (formula (2)) is obtained, only 2 × T is calculated. This means that only the shape of the object to be measured W (surface to be measured) is calculated without being affected by the surface shapes of the beam splitters 12 to 15 (including the surface shape of the reference surface in this embodiment). Is shown.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) The polarization beam splitter 14 is arranged in the first measurement state and the second measurement state, the optical path B is switched to the first measurement optical path Ba and the second measurement optical path Bb, and measurement 1 and measurement 2 are performed. The planar shape of the object to be measured W (surface to be measured) was calculated from the result. In the measurement 1, a measurement result including the shape error of each optical element arranged on the optical path A and the optical path B (first measurement optical path Ba) is obtained. In the measurement 2, the optical path A and the optical path B (first measurement use) In addition to the shape error of each optical element arranged on the optical path Ba), a measurement result including the shape error of the object to be measured W (surface to be measured) is obtained. Therefore, by calculating the difference between the measurement results of measurement 1 and measurement 2, only the shape of the object to be measured W (surface to be measured) can be calculated. Therefore, the shape of the surface to be measured can be measured with high accuracy regardless of the shape accuracy of the reference surface. In addition, since the shape error of each optical element can be removed, the shape of the surface to be measured can be measured with higher accuracy.

  (2) In the first measurement state and the second measurement state, the polarization beam splitter 14 is arranged so as to reflect the incident light on the same surface. Therefore, each measurement result of measurement 1 and measurement 2 can include the same amount as a shape error when light is reflected by the polarization beam splitter 14. Therefore, the shape of the surface to be measured can be measured with higher accuracy.

  (3) A quarter wavelength plate 16 is disposed between the polarizing beam splitter 14 and the object W to be measured. Therefore, in measurement 1 and measurement 2, the light reflected by the object to be measured W (surface to be measured) does not pass through the polarization beam splitter 14 and is directed to the third beam splitter 15 or the direction thereof. Reflected in the opposite direction. Therefore, the return light to the light source 11 can be eliminated. Further, the contrast of the interference fringes captured by the light receiving element 17 can be favorably maintained.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. In the embodiments described below, the same components as those in the embodiments already described are denoted by the same reference numerals, and the redundant description thereof is omitted or simplified.

  In the measuring apparatus 20 of the present embodiment, a fourth beam splitter 21 as an optical path switching unit is disposed on the optical path B. The fourth beam splitter 21 has a reflection / transmission surface 21a similarly to the first to third beam splitters 12, 13, and 15, and similarly to the polarization beam splitter 14 in the first embodiment, a rotary table (not shown). ) Is placed on top. The fourth beam splitter 21 is arranged in the first measurement state shown in FIG. 3 and the second measurement state shown in FIG. The fourth beam splitter 21 is arranged so that the surfaces that reflect light to the third beam splitter 15 are the same surface in the first measurement state and the second measurement state. In the present embodiment, the light emitted from the light source 11 may be randomly polarized light, linearly polarized light, or circularly polarized light.

Hereinafter, the optical path B formed by the measuring device 20 will be described in detail. In addition, since the optical path A is formed similarly to 1st Embodiment, the description is abbreviate | omitted.
The optical path B is formed as two different optical paths (first measurement optical path Ba and second measurement optical path Bb) according to the arrangement of the fourth beam splitter 21. That is, when the fourth beam splitter 21 is arranged in the first measurement state, the optical path B (first measurement optical path Ba) is the first beam splitter 12, the fourth beam splitter 21, and the third beam. It is formed by the splitter 15. In the first measurement optical path Ba, the transmitted light that has passed through the first beam splitter 12 is reflected by the fourth beam splitter 21, passes through the third beam splitter 15, and then is received by the light receiving element 17. It is like that. The first measurement optical path Ba is the first optical path because the light split by the first beam splitter 12 reaches the third beam splitter 15 without passing through the surface to be measured.

  On the other hand, when the fourth beam splitter 21 is arranged in the second measurement state, the optical path B (second measurement optical path Bb) includes the first beam splitter 12, the fourth beam splitter 21, and the object W to be measured. And the third beam splitter 15. In the second measurement optical path Bb, the light transmitted through the first beam splitter 12 passes through the fourth beam splitter 21 and is reflected by the object to be measured W (surface to be measured), and then the fourth beam splitter. 21 is incident. The light incident on the fourth beam splitter 21 is reflected by the fourth beam splitter 21, passes through the third beam splitter 15, and then received by the light receiving element 17. . In the second measurement optical path Bb, the light split by the first beam splitter 12 reaches the third beam splitter 15 after passing through the surface to be measured, so that it becomes the second optical path.

  In the measurement apparatus 20 of the present embodiment configured as described above, the measurement 1 using the optical path A and the first measurement optical path Ba, and the measurement 2 using the optical path A and the second measurement optical path Bb, as in the first embodiment. After the measurement, the planar shape of the workpiece W (surface to be measured) is calculated from the measurement result of measurement 1 and the measurement result of measurement 2. And also in the measuring apparatus 20 of this embodiment, while the measurement result of the measurement 1 can be represented by the above-mentioned formula (1), the measurement result of the measurement 2 can be represented by the above-described formula (2). Therefore, by calculating the difference between the measurement result of measurement 1 and the measurement result of measurement 2, the planar shape of the workpiece W (measurement surface) can be calculated without being affected by the shape accuracy of the reference surface. It becomes possible.

Therefore, according to the present embodiment, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment.
(4) The fourth beam splitter 21 is disposed as an optical path switching means for switching the optical path B to the first measurement optical path Ba and the second measurement optical path Bb. Therefore, the number of parts of the optical element can be reduced, the structure of the measuring device 20 can be simplified, and the manufacturing cost can be reduced.

Each embodiment may be changed as follows.
In each of the above embodiments, the second beam splitter 13 may be changed to a reflecting mirror (mirror). Further, the first to fourth beam splitters 12, 13, 15, and 21 may be changed to half mirrors.

  The measurement devices 10 and 20 of the above embodiments are embodied as devices that measure the planar shape of the object W to be measured. However, when the object to be measured has a curved surface shape, the measurement devices 10 and 20 are specifically exemplified as devices that measure the curved surface shape. May be used. In this case, for example, in the measurement apparatus 20 of the second embodiment, a transmission spherical body and a lens are arranged between the fourth beam splitter 21 and the object W to be measured, and the measurement results of the measurement 1 and the measurement 2 are used. The curved surface shape may be calculated.

  In each of the embodiments, in order to further reduce the influence of the shape error of the optical element on the measurement, the optical element is placed in a liquid having a refractive index close to the refractive index of the optical element to perform measurement. Anyway. 1 and 2 show a state in which the polarizing beam splitter 14, the quarter wavelength plate 16, and the object W to be measured are arranged in a liquid tank 22 (shown by a two-dot chain line) filled with the liquid L. ing. In the measurement using light interference, the wavefront accuracy of light transmitted by multiplying the shape error of the optical element by the difference between the refractive index of the optical element and the refractive index of the surrounding medium is determined. Therefore, if the periphery of the optical element is filled with a medium (liquid L) having a refractive index close to the refractive index of the optical element, a measurement result in which the influence of the shape error of the optical element is further reduced can be obtained. For example, if the optical element has a refractive index of 1.5151 with respect to light having a wavelength of 632.8 nm, a seda having a refractive index of 1.516 with respect to light having a wavelength of 589.3 nm when the temperature is 20 degrees. Use oil. At this time, the influence of the shape error of the optical element is 0.001 (1.516−1.5151 = 0.001). Incidentally, when the optical member is not filled with the liquid L, since the refractive index of air is 1, the influence of the shape error of the optical element is 0.5 times (1.5151-1 = 0.5).

  In each of the above embodiments, a collimator lens is arranged between the light source 11 and the first beam splitter 12 and between the third beam splitter 15 and the light receiving element 17 to constitute the measuring devices 10 and 20. May be.

  -When measuring the to-be-measured object W which permeate | transmits light using the measuring apparatuses 10 and 20 of each said embodiment, you may change as follows. That is, in measurement 1, the measurement object W is measured without being placed on the optical path B, and in measurement 2, the measurement object W is measured with the first beam splitter 12 and the polarization beam splitter 14 (or the fourth beam splitter). 21) and perform measurement. Then, from the measurement result of measurement 1 and the measurement result of measurement 2, the wavefront aberration when light passes through the workpiece W is calculated. In this case, the polarization beam splitter 14 (or the fourth beam splitter 21) is arranged in the state of FIG. 1 (or FIG. 3), and the optical path B is arranged as in the case where the object W to be measured is arranged on the optical path B. It is formed as a different optical path from the case where it is not performed. Accordingly, the means for switching the object to be measured W between the state where it is placed on the optical path B and the state where it is not placed becomes the optical path switching means.

Next, a technical idea that can be grasped from the embodiment and another example will be added below.
(A) The optical member is a polarizing beam splitter, and a quarter-wave plate is disposed between the polarizing beam splitter and the surface to be measured. measuring device.

  (B) The calculation means obtains a difference between an optical path difference of the light passing through the reference surface optical path and the first optical path and a difference of an optical path difference of the light passing through the reference surface optical path and the second optical path. The measuring apparatus according to claim 1, wherein the shape of the surface to be measured is calculated.

Schematic which shows the measuring apparatus of 1st Embodiment. Similarly, schematic. Schematic which shows the measuring apparatus of 2nd Embodiment. Similarly, schematic.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,20 ... Measuring apparatus, 11 ... Light source, 12 ... Beam splitter (spectral means), 14 ... Polarizing beam splitter (optical path switching means), 15 ... Beam splitter (polymerization means), 21 ... Beam splitter (optical path switching means), 17: light receiving element (calculation means), 18: computer (calculation means).

Claims (3)

The light emitted from the light source is dispersed by the spectroscopic means, and the split light is passed through the reference surface optical path on which the reference surface is arranged and the measurement surface optical path on which the measurement surface is arranged, and then the polymerization means In the measuring apparatus that measures the shape of the surface to be measured by using the interference of light generated when the light is superimposed again,
A first optical path through which the light split by the spectroscopic means reaches the polymerization means without passing through the measured surface; and the light split by the spectroscopic means passes through the optical path for the measured surface Optical path switching means for switching to a second optical path after passing through to the polymerization means;
When the optical path for measured surface is the first optical path, a measurement result obtained by interference of light passing through the optical path for reference surface and the optical path for measured surface, and the optical path for measured surface are the first optical path. In the case of two optical paths, an arithmetic means for calculating the shape of the surface to be measured is provided based on the measurement result obtained by interference of the light that has passed through the optical path for the reference surface and the optical path for the surface to be measured. Measuring device characterized by. The optical path switching means is an optical member having a reflecting surface for reflecting incident light,
The optical member is disposed in the first optical path so that the light split by the spectroscopic means is directly reflected by the superposition means, and the light split by the spectroscopic means in the second optical path. Arranged to be reflected by the superposition means after passing through the surface to be measured,
The measuring apparatus according to claim 1, wherein the optical member is arranged so as to reflect the light on the same surface in the first optical path and the second optical path. The light emitted from the light source is dispersed by the spectroscopic means, and the split light is passed through the reference surface optical path on which the reference surface is arranged and the measurement surface optical path on which the measurement surface is arranged, and then the polymerization means In the measurement method for measuring the shape of the surface to be measured by using the interference of the light generated when the light is overlapped again and the light is overlapped,
The light for the surface to be measured is formed so that the light dispersed by the spectroscopic means reaches the superposition means without passing through the surface to be measured, and the light that has passed through the optical path for the surface to be measured and the optical path for the reference surface A first measurement step for measuring using interference of
The light for the surface to be measured is formed so that the light split by the spectroscopic means passes through the surface to be measured and then reaches the superposition means, and the light that has passed through the optical path for the surface to be measured and the optical path for the reference surface A second measurement step for measuring using interference of
A measurement method comprising: an operation step of calculating a shape of the surface to be measured based on a measurement result obtained in the first measurement step and a measurement result obtained in the second measurement step.

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