JPH07167630A - Equipment and method for measuring interference - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement even when there is a defocus in the measurement of the aberration of an article to be detected. CONSTITUTION:An interference measuring equipment 1a has a Fizeau type interferometer 2a, an image sensing section 11, an image processor 12, an arithmetic means 13, a monitor device 14 and a memory 15 exclusive for data. The interferometer 2a has a light source 3, an objective 4, a collimator lens 5, a half mirror 6, a prototype lens 7, a driving means 711, a moving means 9 and an observation lens 10. The arithmetic means 13 develops a value obtained by interference fringe analysis to an approximate polynomial displaying a wavefront aberration, acquires values corresponding to each term, and corrects quaternary or more of axially symmetric aberrations from a secondary aberration component generated by a de-focus in the measurement of the aberration of the surface to be detected 81 of the an article to be detected 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference measuring device and an interference measuring method.

[0002]

2. Description of the Related Art There are many known measuring methods and measuring devices for measuring surface shapes of various optical systems such as optical elements using an interferometer. For example, it is limited by the accuracy of the reference lens or reference surface installed in the interferometer.

As a method of removing the aberration of the interferometer itself, a spherical surface measuring method proposed by Browning et al.
An interferometer device and the like described in Japanese Patent No. 129707 are known.

In the measuring method proposed by Browning et al., An object to be measured (object to be measured) is moved to perform measurement under three conditions, and an inherent aberration of the interferometer is removed by arithmetic processing.

Further, in the interferometer device disclosed in the above-mentioned Japanese Patent Laid-Open No. 62-129707, the standard surface is rotated to perform measurement at several points, and this is subtracted from the measured value as correction data to cause interference. The internal aberration of the meter is removed.

However, in both the measuring method proposed by Browning et al. And the interferometer device disclosed in Japanese Patent Laid-Open No. 62-129707,
It is difficult to correct the aberration newly generated due to the setting state of the test object.

For this reason, when the object to be inspected is installed in the interferometer, the object to be inspected is set at a predetermined position and at a predetermined angle so that aberration due to setting error of the object does not occur. Must be placed exactly.

[0008] Therefore, there is a problem in that the alignment when the object to be inspected is installed in the interferometer needs to be carried out carefully, so that the workability is poor and a highly accurate alignment device is required.

Moreover, even if the placement of the object to be inspected is carefully set using a high-precision alignment apparatus, it is difficult to completely eliminate the setting error (for example, defocus) of the object to be inspected. . As described above, the presence of the defocus causes high-order aberrations having axial symmetry such as spherical aberration, which lowers the measurement accuracy.

Further, when the NA ₀ (numerical aperture) value of the condensing lens of the interferometer is large, that is, when a bright lens is used, there is a problem that the measurement accuracy is greatly reduced due to defocus. is there.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an interference measuring device and an interference measuring method which can obtain high measurement accuracy regardless of the setting error between the interferometer and the object to be measured.

[0012]

These objects are achieved by the present invention described in (1) to (23) below.

(1) The light from the light source is divided into two, one is used as the reference light from the reference surface and the other is used as the test light from the test object, and the reference light and the test light are superposed. An interference measurement device that obtains an interference fringe in combination and detects a phase difference between the reference light and the test light based on the interference fringe, wherein the interference fringe is an approximation that specifies the phase difference. The first means for developing into a polynomial and the interference measurement of the test object based on the numerical aperture of an effective light beam that is incident on the test area of the test object or exits from the test area of the test object. Second means for calculating error information appearing in a specific term of the approximate polynomial due to a set position error with respect to the apparatus; and the first information based on the error information and the numerical aperture obtained by the second means. The coefficient of the term that specifies the phase difference in the approximate polynomial obtained by And a third means for correcting the interference.

(2) The interference measuring apparatus according to the above (1), wherein the interference measuring apparatus has a condensing optical member.

(3) The interference measuring apparatus according to (2), wherein the condensing optical member satisfies a sine condition.

(4) The interference measuring apparatus according to (2) or (3), wherein the approximate polynomial in the first means is the equation (1) shown in the following equation 9.

[0017]

[Equation 9]

(5) The second means calculates the coefficient W ₂₀ of the quadratic term of the approximate polynomial. (4)
An interferometer according to item 1.

(6) The third means shows a correction value for correcting the coefficient of the term that specifies the phase difference and the coefficient W _{20 of the} quadratic term of the approximate polynomial and the following expression (10). )
The interference measuring apparatus according to (5), which is calculated based on the equation.

[0020]

[Equation 10]

(7) The interference measuring apparatus according to the above (6), wherein the third means corrects the coefficient W ₄₀ of the fourth-order term of the approximate polynomial by the equation (6) shown in the following Expression 11. .

[0022]

[Equation 11]

(8) The third means is for correcting the coefficient W ₆₀ of the 6th order term of the approximate polynomial by the equation (7) shown in the following expression 12 or (6) or (7). Interferometer.

[0024]

[Equation 12]

(9) The light from the light source is divided into two, one is used as the reference light from the reference surface, and the other is used as the test light from the test object, and the reference light and the test light are overlapped. An interference measurement method of obtaining an interference fringe in combination and detecting a phase difference between the reference light and the test light based on the interference fringe, wherein the interference fringe is obtained by a first means. It is expanded to an approximate polynomial for specifying the phase difference, and by the second means, based on the numerical aperture of the effective light flux that is incident on the test area of the test object or exits from the test area of the test object, The error information appearing in the specific term of the approximate polynomial due to the set position error of the object to be measured with respect to the interferometer is calculated, and the error information and the aperture obtained by the second means are calculated by the third means. The approximate polynomial obtained by the first means based on the number An interferometry method characterized by correcting a coefficient of a term that specifies a phase difference.

(10) The interference measuring method according to the above (9), wherein the reference light or the test light passes through a condensing optical member.

(11) The interference measuring method according to (10), wherein the condensing optical member satisfies a sine condition.

(12) The approximate polynomial in the first means is the equation (1) shown in the following equation 13 and the above (10)
Alternatively, the interference measurement method according to (11).

[0029]

[Equation 13]

(13) The interference measuring method according to (12), wherein the second means calculates the coefficient W ₂₀ of the quadratic term of the approximate polynomial.

(14) The correction value for correcting the coefficient of the term that specifies the phase difference by the third means is shown by the coefficient W _{20 of the} quadratic term of the approximate polynomial and the following Expression 14 (3 ) The interference measurement method according to (13) above, which is calculated based on

[0032]

[Equation 14]

(15) The interference measuring method according to (14), wherein the third means corrects the coefficient W ₄₀ of the fourth-order term of the approximate polynomial based on the equation (6) shown in the following Expression 15.

[0034]

[Equation 15]

(16) The above-mentioned (14) or (1) in which the coefficient W ₆₀ of the sixth-order term of the approximate polynomial is corrected based on the equation (7) shown in the following equation 16 by the third means.
The interference measurement method described in 5).

[0036]

[Equation 16]

(17) The light from the light source is divided into two, one of which is reflected by the reference surface to be a reference light, and the other of which is made into a convergent light or a divergent light by an optical member and made incident on the surface to be inspected. As the test light reflected on the inspection surface, while obtaining the interference fringes by superimposing the reference light and the test light, the phase difference between the reference light and the test light based on the interference fringes. An interference measuring device for detecting the interference fringes, wherein the interference fringes are expanded into an approximate polynomial for specifying the phase difference, and a numerical aperture of an effective light beam incident on a test region of the test surface is determined. Second means for calculating error information appearing in a specific term of the approximate polynomial due to a position error of the surface to be measured with respect to the interference measuring device; and the error information obtained by the second means. And the first based on the numerical aperture
And a third means for correcting the coefficient of the term for specifying the phase difference in the approximate polynomial obtained by the means.

(18) The interference measuring apparatus according to the above (17), wherein the optical member is a standard lens having the reference surface.

(19) The interference measuring apparatus according to (17), wherein the optical member is a lens having a positive power.

(20) The interference measuring apparatus according to the above (17), wherein the optical member is a lens having negative power.

(21) The interference measuring apparatus according to any one of (17) to (20), wherein the numerical aperture NA ₀ is obtained by the following equation. NA ₀ = h _max / f = sin θ _max (where, h _max is the maximum incident height from the optical axis when an effective light beam irradiating the test region is incident on the optical member, and f is the optical The focal length of the member, θ _max, is the angle between the outermost ray of the effective luminous flux and the optical axis after passing through the optical member.)

(22) The light from the light source is divided into two, one of which is used as a reference light, and the other of which is transmitted as an inspection light by passing through an object having a function of converging or diverging a light beam. An interference measuring device for detecting the phase difference between the reference light and the test light based on the interference fringe, while obtaining an interference fringe by superimposing the test light and the test light on each other. , A first expansion into an approximate polynomial specifying the phase difference
Means and the numerical aperture of the effective light flux focused or diverged by the test object, the error appearing in the specific term of the approximate polynomial due to the set position error of the test object with respect to the interferometer. Second means for calculating information, and correction of a coefficient of a term specifying a phase difference in the approximation polynomial obtained by the first means, based on the error information and the numerical aperture obtained by the second means. And a third means for performing the interference measurement apparatus.

(23) The interference measuring apparatus according to (22), wherein the numerical aperture NA ₀ is obtained by the following equation. NA ₀ = h _max / f = sin θ _max (where, h _max is the maximum incident height from the optical axis when an effective light beam focused or diverged by the object is incident on the object, f is , Focal length of the test object, θ _max
Is the angle between the outermost ray of the effective luminous flux and the optical axis after passing through the test object. )

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The interference measuring apparatus and the interference measuring method of the present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. FIG. 1 is a diagram schematically showing a first embodiment of the interference measuring apparatus of the present invention. As shown in FIG.
a is a Fizeau interferometer (hereinafter referred to as an interferometer) 2a
An image pickup unit 11 which is an interference fringe detection unit, an image processing device 12 including an A / D converter and an image memory, a calculation unit 13, a monitor unit 14, and a data dedicated memory (hereinafter, memory) which is a storage unit. 15).

The interferometer 2a in the interferometer 1a is
The light source 3, the objective lens 4, the collimator lens 5, the half mirror 6, the prototype lens 7 also serving as a condensing optical member and a reference member, and the prototype lens 7 are moved with respect to the optical axis 73 with high precision, and the phase shift is performed. The driving means 711 such as PZT for performing the method and the object 8 also serving as the reflecting member are the prototype lens 7
It has a moving means 9 for positioning in the optical axis 73 direction and a direction perpendicular to the optical axis 73, and an observation lens 10. In the interference measuring apparatus 1a having such a configuration, as shown in FIG. 1, an xyz coordinate system in which the optical axis 73 of the prototype lens 7 is the z axis is assumed.

Here, the final surface of the prototype lens 7, that is, the surface of the prototype lens 7 facing the object 8 constitutes a reference surface 71. The reference surface 71 is formed into a concave curved surface having a predetermined center of curvature, and is configured to reflect a part of incident light and allow a part of the incident light to pass through. The center of curvature of the reference surface 71 coincides with the condensing point 75 of the light transmitted through the prototype lens 7.

In general, an aplanatic lens that substantially satisfies the sine condition and has substantially no spherical aberration is used as the prototype lens. When the sine condition is satisfied, f · sin θ = h holds.

In this case, as shown in FIG. 1, h represents an arbitrary height of incident light on the standard lens 7 (hereinafter referred to as incident height), and f represents a focal length of the standard lens 7. . In addition, as shown in FIG. 1, θ is an angle (hereinafter, referred to as an angle between the light beam 16 incident from the reference surface 71 of the light ray incident on the standard lens 7 at the incident height h and the optical axis 73 of the standard lens 7). , Collection angle).

The surface of the object 8 facing the prototype lens 7,
That is, the test surface 81 is formed into a concave curved surface having a predetermined center of curvature 85, and is configured to be able to reflect at least a part of the emitted light.

The moving means 9 includes a base for fixing the object 8 to be inspected and a base for aligning the surface 81 to be inspected with the base in the optical axis 73 direction (z direction) of the prototype lens 7 and the optical axis. 7
It is configured by means (neither shown) for moving in a direction perpendicular to 3 (x direction, y direction).

The image pickup section 11 in the interference measuring apparatus 1a is
For example, the solid-state image sensor (CCD) 17 and the CCD 17
And a drive circuit (not shown) for driving the. The observation lens 10 is for forming an image of the surface 81 to be inspected on the observation surface at an appropriate magnification.

Computing means 13 in the interference measuring device 1a
Is for analyzing interference fringes, which will be described later, based on digital data (digital signal) obtained by the image processing device 12, and for performing predetermined arithmetic processing in aberration correction and the like, and is configured by, for example, a microcomputer. ing.

In this case, the calculating means 13 is a first means for expanding the interference fringes into an approximate polynomial for specifying the phase difference (optical path difference) between the reference light and the test light, as will be described later. ,
Numerical aperture of an effective light beam that enters or is emitted from the inspection region of the inspection object 8 (in the present embodiment, the aperture of the effective light beam that is incident on the inspection region of the inspection surface 81). The second means for calculating the error information appearing in the specific term of the approximate polynomial due to the position error of the object to be measured 8 with respect to the interference measuring device 1a, and the second means. Third means for correcting the coefficient of the term that specifies the phase difference in the approximate polynomial obtained by the first means based on the error information and the numerical aperture. Here, the “effective light flux” refers to a light flux that covers the entire area of the test object (test surface) under test and can interfere with the reference light.

When the test object has a predetermined test surface as in this embodiment, the phase difference between the reference light and the test light corresponds to the shape of the test surface. When the test object is a lens, the phase difference between the reference light and the test light corresponds to the wavefront aberration of the lens.

Next, the interference measuring method of the present invention will be described. The interference measuring method of the present invention uses the above-described interference measuring device 1a shown in FIG. 1 to measure the surface 81 to be inspected of the object to be inspected 8 and perform fringe analysis on the obtained interference fringes to determine wavefront aberration. Along with developing into an approximate polynomial (approximate polynomial of aberration), a second-order aberration caused by a setting error of the inspection object 8 in the direction of the optical axis 73 (deviation from an appropriate position when the installation position of the inspection object 8 is not appropriate) Component (second order term), that is, the Difukas term, is used to correct the even-order aberration terms (axisymmetric aberrations) of the fourth order and above developed by the approximate polynomial, and the corrected aberration term (corrected aberration term) And the case where both the uncorrected aberration terms are used), the shape of the surface 81 to be inspected is obtained.

First, the outline of the interference measuring method of the present invention will be described. The reference light reflected by the reference surface 71 of the prototype lens 7 and the test light reflected by the test surface 81 of the test object 8 are caused to interfere with each other to obtain an interference fringe. The interference fringes thus obtained are subjected to fringe analysis by a known method to obtain quantified values. By the first means
The value obtained by the fringe analysis is expanded into an approximate polynomial representing the wavefront aberration by performing least square fitting, and the value (measured value) corresponding to each term is obtained by the second means. In addition to the aberration caused by the surface shape of the surface to be inspected 81 that is originally to be measured, the aberration terms (axisymmetric aberrations) of the fourth and higher order in this approximation polynomial are also measured between the object 8 and the prototype lens 7. Position setting error (defocus) Δ
It also includes the aberration caused by z.

Therefore, the third means calculates the value corresponding to the setting error Δz from the defocus term in this approximation polynomial, that is, the quadratic aberration component caused by the setting error Δz, and corresponds to the calculated Δz. From the value, an even-order aberration (axisymmetric aberration) of 4th order or more caused by the setting error Δz is obtained, and the value (measurement value) of each term of the approximate polynomial is used by using this aberration as a correction value (correction data). to correct.

The interference measuring method of the present invention will be specifically described below. To develop the interference fringe pattern for each aberration,
For example, the Zernike or Seidel coefficient expansion formula is used, and the aberration W (ρ, φ) of the interference fringe pattern is expanded as shown in formula (1) below when only the axially symmetric aberration is considered. To be done. The values corresponding to the respective terms in the following formula (1) are obtained by measuring the surface 81 to be inspected of the object 8 to be subjected to fringe analysis and fitting the analysis data to least squares. Hereinafter, the value after the least-squares fitting will be referred to as a measured value.

[0059]

[Equation 17]

In the expression (1) (approximate polynomial of aberration) shown in the above-mentioned equation 17, each aberration is represented by a different order. For example, spherical aberration is represented by terms of even orders of 4th and higher.

However, in practice, the even-order aberration terms (axisymmetric aberrations) of the fourth or higher order in the above equation (1) are not limited to the aberrations caused by the surface shape of the surface to be measured 81 to be measured, and It also includes aberrations caused by defocus.

That is, the fourth or more terms of the above equation (1) are
The spherical aberration is described as a spherical aberration, but actually, in addition to the spherical aberration generated by the surface 81 to be inspected, a fourth or higher order component of the aberration generated by the defocus is included.

The defocus means the focal point 75 of the prototype lens 7 and the center of curvature 8 of the object 8 shown in FIG.
This is a setting error (deviation) with respect to 5 in the optical axis 73 direction. The magnitude of this setting error, that is, the magnitude of defocus is represented by Δz. In this case, since the reflection system is actually used, Δz is twice the actual deviation amount.

Here, in the converging optical member (condensing lens) that satisfies the sine condition of the prototype lens 7 or the like, the wavefront aberration W _C caused by defocusing is expressed by the following equation (2). Represented by.

[0065]

[Equation 18]

Equation (2) shown in the above equation 18 is given by sin θ = N
When Taylor expansion is carried out with A = h / f, it is expressed by the following equation (3).

[0067]

[Formula 19]

Here, the equation (1) is compared with the equation (3) shown in the equation (19). The first term in the parentheses in the equation (3) above is a quadratic component generated due to the presence of defocus, and is processed as an alignment error.
It does not affect the shape measurement of the test surface 81.

On the other hand, the second and subsequent terms in the parentheses in the equation (3) above are the fourth or higher order components generated by the presence of defocus. The components of the fourth or higher order are included in the fourth and subsequent terms of the equation (1) with respect to the components of the fourth or higher order caused by the original surface shape (shape error) of the surface 81 to be inspected. In order to obtain an accurate aberration, it is necessary to subtract the aberrations of the fourth and higher even-numbered orders generated by defocus from the measured values.

Here, letting NA ₀ (= h _max / f = sin θ _max ) be the numerical aperture of the prototype lens 7, that is, the numerical aperture of the effective light beam incident on the test region of the test surface 81.
Since the third term of the above equation (1) corresponds to the first term of the above equation (3), W ₂₀ is represented by the following equation (4).

[0071]

[Equation 20]

From Expression (4) shown in Expression 20 above, Δz is expressed as Expression (5) shown in Expression 21 below.

[0073]

[Equation 21]

By substituting the numerical aperture NA ₀ of the prototype lens 7 and the W ₂₀ obtained from the above equation (1) as a result of the interference fringe analysis into the equation (5) shown in the above equation 21, the actual set deviation amount is obtained. Δz corresponding to twice the amount is obtained. This △ z
Is substituted into the second and subsequent higher-order (fourth and higher) terms of the above equation (3), the fourth and higher even-order aberrations caused by defocusing can be obtained.

In this way, an even-order aberration of the fourth or higher order generated by defocus is obtained, and this aberration is used as correction data (correction value), and the correction data is subtracted from the measured value to obtain an accurate correction. Obtain the measurement result (corrected measurement value).

For example, when correcting the fourth-order aberration (measurement value), the above-mentioned equation (5) is substituted into the second term of the above-mentioned equation (3), and the fourth-order aberration generated by defocus is calculated. This aberration is used as correction data, and the correction data is subtracted from W ₄₀ of the above equation (1) obtained by fringe analysis. That is, the corrected measurement value A ₄ of the fourth-order aberration is obtained from the equation (6) shown in the following Expression 22.

[0077]

[Equation 22]

When correcting the 6th-order aberration (measurement value), the above-mentioned equation (5) is substituted into the third term of the above-mentioned equation (3), and the 6th-order aberration generated by defocusing is corrected. This 6th-order aberration is used as correction data, and the correction data is subtracted from W ₆₀ of the above equation (1) obtained by fringe analysis. That is, the corrected measurement value A ₆ of the 6th-order aberration is obtained from the equation (7) shown in the following formula 23.

[0079]

[Equation 23]

Similarly, when correcting aberrations (measured values) of 8th or higher even-numbered orders, the aberrations of 8th-order or higher even-orders generated by defocus are obtained in the same manner as described above. Aberrations of even orders are used as correction data,
Each of the correction data is subtracted from the value obtained by the fringe analysis.

As described above, the correction data for the axially symmetric aberrations of the fourth or higher order can be easily obtained from the second-order coefficient W ₂₀ of the aberration developed by analyzing the interference fringes into the approximate polynomial. In addition,
The quadratic coefficient W ₂₀ is called a defocus term in the usual fringe analysis method, and is processed as an alignment error as described above.

In the present invention, as described above, the aberrations of the fourth and higher even-numbered orders obtained by the fringe analysis, that is, the axisymmetric aberrations of the fourth and higher orders are corrected. In this case, the order of the aberration to be corrected is the numerical aperture NA ₀ (sin
The value is determined according to various conditions such as the value of (θ _max ), the target measurement accuracy, etc., but normally, the fourth and sixth orders are sufficient.

Here, as can be seen from the above equation (3),
When the NA ₀ value of the prototype lens 7 is large, the aberration caused by the defocus becomes large, so that the influence of the defocus on the measured value becomes larger. However, according to the present invention, the prototype lens 7 Even if the value of NA ₀ of 7 is large, a highly accurate corrected measurement value can be obtained, for example, by increasing the order of the aberration to be corrected.

Next, how the aberration caused by the defocus changes depending on the magnitude of the NA ₀ value of the prototype lens 7 will be described as a representative of the aberrations of the fourth or higher order caused by the defocus. .

FIGS. 4 and 5 show a condenser lens having a relatively large NA _0, that is, a bright condenser lens (F value = 0.7) and a condenser lens having a relatively small NA ₀ (F, respectively).
It is a figure which shows the structural example of value = 1.4).

The F number (F number) is a value obtained by dividing the focal length (f) of the lens by the effective diameter (d) of the lens,
That is, it means f / d, and in the lens in which the sine condition is corrected, the relationship of NA ₀ = 1 / (2F) is established.

FIG. 6 is a graph (aberration diagram) showing the spherical aberration (SA) and the sine condition (SC) of the condenser lens shown in FIG. 4, and FIG. 7 shows the condenser lens shown in FIG. It is a graph (aberration chart) showing spherical aberration (SA) and sine condition (SC). The horizontal axis of each graph shown in FIGS. 8 and 9 represents the amount of spherical aberration, and the vertical axis represents the incident height of the light beam.

Regarding such two kinds of condenser lenses,
On the surface 81 to be inspected of the object 8 having no shape error, the defocus is reciprocated by 6λ (6 lines) and 12λ, respectively.
When two kinds of (12 lines) are given, the relation between the aberration of the fourth order or higher caused by this defocus and the incident height (h) was obtained by ray tracing.

FIG. 8 is a graph showing the relationship between the fourth or higher-order aberrations caused by defocusing of the condenser lens shown in FIG. 4 and the incident height (h), and FIG.
6 is a graph showing the relationship between the fourth-order and higher-order aberrations caused by defocusing of the condenser lens shown in FIG.

The horizontal axes of the graphs shown in FIGS. 8 and 9 represent the incident height (h) when the maximum incident height (h _max ) is 1, that is, ρ. Further, the vertical axes of the respective graphs shown in FIGS. 8 and 9 represent the amount of aberration of the fourth order or higher due to the defocus obtained by the calculation at the predetermined incident height (h).

A comparison between the graph shown in FIG. 8 and the graph shown in FIG. 9 shows that it is proportional to the square of the brightness of the condenser lens.
It can be seen that the fourth-order aberration generated by defocus increases. Although not shown, regarding the 6th-order aberration generated by the defocus, the aberration amount increases in proportion to the fourth power of the brightness of the condenser lens. In the case of the same brightness (the same F value and the same NA ₀ ), the aberration amount of the 4th order or more generated by the defocus increases in proportion to the defocus amount Δz. The above tendency is in agreement with the tendency of the second term of the equations (6) and (7).

As described above, when a comparatively bright condenser lens is used in the interferometer, the influence of defocus appears remarkably on the measured value. The aberration of even order is corrected by subtracting it from the measurement value, and even when a relatively bright condenser lens is used, for example, by increasing the order of aberration to be corrected, a higher precision correction The measured value is obtained.

Next, the operation of the interference measuring apparatus 1a when measuring the aberration (shape measurement) of the surface 81 to be inspected of the object 8 will be described. The alignment of the test object 8 is performed before the aberration measurement of the test surface 81. As shown in FIG. 1, the test object 8 is fixed to the base of the moving means 9 of the interference measuring apparatus 1a, and the moving means 9 moves the test object 8 in the optical axis 73 direction and the direction perpendicular to the optical axis 73. The inspection object 8 is moved and installed at a predetermined position. In this case, for example, light is emitted from the light source 3 so that interference fringes appear while checking with a monitor device (not shown), that is, the condensing point 75 of the prototype lens 7.
And the object to be inspected 8 are arranged so that the center of curvature 85 of the object to be inspected 8 substantially matches.

The light emitted from the light source 3 in the interference measuring apparatus 1a passes through the objective lens 4 and the collimator lens 5 in order and becomes a parallel light expanded to a desired light beam diameter. The parallel light enters the half mirror 6, and a part of the parallel light passes through the half mirror 6.

The light transmitted through the half mirror 6 is incident on the standard lens 7, and when passing through the standard lens 7, is vertically incident on each part of the reference surface 71, and a part of the light is transmitted through the reference surface 71. However, the remaining portion is reflected by the reference surface 71.

The light reflected by the reference surface 71 passes through the prototype lens 7 to become parallel light again, and is further partially reflected by the half mirror 6 toward the observation lens 10. This reflected light is
It reaches the CCD 17 of the image pickup section 11 through the observation lens 10 and becomes reference light.

On the other hand, the light transmitted through the reference surface 71 is once condensed at the condensing point 75, and then is irradiated on the surface 81 to be inspected of the object 8 to be inspected and reflected by the surface 81 to be inspected. The light is once focused on the center of curvature 85 of the surface 81 or in the vicinity thereof, and then is incident on the reference surface 71 again. Then, the light incident on the reference surface 71 is
After passing through the prototype lens 7, it becomes parallel light again and then enters the half mirror 6, and a part of it is reflected by the half mirror 6 toward the observation lens 10 side. This reflected light is the observation lens 1
After passing through 0, the light reaches the CCD 17 of the imaging unit 11 and becomes the test light.

In this way, the light reflected by the reference surface 71 (reference light) and the light transmitted through the reference surface 71 and reflected by the surface to be inspected 81 (light to be inspected) interfere with each other, whereby an image is picked up. Interference fringes are formed on the CCD 17 of the unit 11.

The image pickup section 11 converts the interference fringe pattern into an analog electric signal. This analog electric signal is converted into a digital signal by the A / D converter of the image processing device 12, and then input to the computing means 13 and the monitor device (not shown).

A monitor device (not shown) performs predetermined signal processing on the input digital signal to project an image corresponding to the pattern of the interference fringes, and the interference fringes can be observed through this image. When there is defocus, the interference fringes are concentric.

As described above, the calculating means 13 drives the standard lens 7 by the driving means 711 by a means (not shown) based on the digital signal input from the image processing device 12, and the well-known phase shift method or the like. The interference fringes are quantified by, that is, fringe analysis is performed. Then, the wavefront aberration of the test surface 81 (including the aberration caused by the surface shape of the test surface 81 and the aberration caused by defocusing) is calculated from the discrete wavefront aberration values obtained by the fringe analysis by calculation such as least square fitting. The wavefront aberration) is calculated and the above-described predetermined correction is performed.

Next, regarding the method of calculating and correcting the aberration of the surface 81 to be inspected of the object to be inspected 8, of the aberrations of the even-numbered orders of 4th and higher, only the 4th and 6th order aberrations are typically corrected. The case will be described.

FIG. 10 is a flowchart showing the operation of the interference measuring apparatus 1a when correcting the aberration of the surface 81 to be inspected of the object 8 and correcting only the 4th and 6th aberrations. . The flowchart will be described below.

First, the operator sets the object to be inspected 8 on the interference measuring apparatus 1a (step 101). Then, the interferometer 2a of the interferometer 1a starts measuring the shape of the surface 81 to be inspected of the object 8 (step 102).

The calculation means 13 performs fringe analysis based on the digital signal input from the image processing device 12, and obtains a value corresponding to the coefficient of each term in the above equation (1), that is,
W ₁₁ , W ₁₂ , W ₂₀ , W ₄₀ , W _60, ... Are calculated (step 103). Note that the calculated W ₁₁ ,
Let W ₁₂ , W ₂₀ , W ₄₀ , W _60, ... Be measured values.

Then, the measured values are stored in predetermined areas of the memory 15 (step 104). Next, the third means of the calculating means 13 is the second means of the above equation (3).
Term, that is, below the number 24 (8), wherein W ₂₀
And other known values are substituted to calculate the fourth-order aberration caused by the defocus, and this value is used as the fourth-order correction data. Then, the fourth-order aberration is corrected by the equation (6).

[0107]

[Equation 24]

The third means of the calculating means 13 is the third term of the above equation (3), that is, (9) shown in the following equation 25.
The above-mentioned W ₂₀ and other known values are substituted into the equation to calculate the 6th-order aberration caused by defocus, and this value is used as the 6th-order correction data. Then, the sixth-order aberration is corrected by the equation (7) (step 105).

[0109]

[Equation 25]

In this way, the corrected aberrations (corrected measurement values) of the 4th and 6th orders, that is, the 4th and 6th order aberrations when there is no defocus are obtained. Note that the odd-order aberrations are not corrected like the fourth-order and sixth-order aberrations, respectively.

Then, the aberration amount is displayed for each aberration of each order (step 106). in this case,
The aberration amount of each order is, for example, the monitor device 1
4 is displayed as an image or is output by a printer (not shown). This is the end of this program.

Next, a second embodiment of the interference measuring apparatus of the present invention will be described. FIG. 2 is a diagram schematically showing a second embodiment of the interference measuring apparatus of the present invention. Interferometer 1 shown in FIG.
Similarly to the interferometer 1a described above, b is a Fizeau interferometer, and the object to be inspected is a lens (lens to be inspected) 2
3, which is a device in the case where the lens 23 to be inspected also serves as a condensing optical member.

The interference measuring apparatus 1b includes a Fizeau interferometer (hereinafter referred to as an interferometer) 2b, an image pickup unit 28 which is an interference fringe detecting unit, and an image processing apparatus (not shown) including an A / D converter and an image memory. , A calculation device, a monitor device, and a memory that is a storage device. In this case, the image pickup unit 28, the image processing device, the calculation means, the monitor device, and the memory of the interference measuring device 1b are respectively the image pickup unit 11, the image processing device 12, and the image processing device 12 of the interference measuring device 1a.
Since it has the same configuration as the computing means 13, the monitor device 14, and the memory 15, the description thereof will be omitted.

The interferometer 2b in the interference measuring device 1b is
Light source 18, objective lens 19, collimator lens 20
, Half mirror 21, and flat prototype 22 as a reference member
And a drive means 222 such as a PZT for moving the plane prototype 22 with high precision with respect to the optical axis 26 and performing the phase shift method.
A reflecting mirror 24 that is a reflecting member, and a moving unit 2 that can move the reflecting mirror 24 in the direction of the optical axis 26 and in the direction perpendicular to the optical axis 26.
5 and an observation lens 27.

In this case, the light source 18, the objective lens 19, the collimator lens 20, the half mirror 21, of the interferometer 2b,
The moving means 25 and the observation lens 27 respectively include the light source 3, the objective lens 4, the collimator lens 5, the half mirror 6, the moving means 9 and the observation lens 10 of the interferometer 2a.
Since the configuration is the same as that of, the description will be omitted.

The flat prototype 22 in the interferometer 2b reflects a part of the incident light and transmits a part thereof. The final surface of the flat prototype 22, that is, the surface of the flat prototype 22 that faces the lens 23 under test constitutes a reference surface 221. The reflecting mirror 24 in the interferometer 2b is formed into a concave curved surface so as to have a predetermined center of curvature, and the surface accuracy is very good.

In the case of the interference measuring apparatus 1b having such a configuration, the moving means 25 moves the reflecting mirror 24 in the direction of the optical axis 26 and in the direction perpendicular to the optical axis 26, and the reflecting mirror 24 is moved.
Are set in place. Alternatively, the lens 23 to be inspected is moved in the direction of the optical axis 26 and the optical axis 26 by a moving means (not shown).
The lens 23 to be inspected is set at a predetermined position by moving the lens 23 in a direction perpendicular to.

The light emitted from the light source 18 in the interference measuring apparatus 1b passes through the objective lens 19 and the collimating lens 20 in order, and becomes a parallel light expanded to a desired light beam diameter. The parallel light enters the half mirror 21, and a part of the parallel light passes through the half mirror 21.

The light transmitted through the half mirror 21 is incident on the flat prototype 22, a part of which is transmitted through the flat prototype 22 (reference surface 221), and the rest is the reference surface 2 of the flat prototype 22.
It reflects at 21.

The light reflected by the reference surface 221 of the flat prototype 22 again enters the half mirror 21, and a part of the light is reflected by the half mirror 21 toward the observation lens 27 side. The reflected light reaches the solid-state image sensor (CCD) 29 of the image pickup unit 28 through the observation lens 27 and serves as reference light.

On the other hand, the light transmitted through the reference surface 221 is
The light enters the lens 23 to be inspected, passes through the lens 23 to be inspected, and is once condensed, and then is irradiated to the reflecting mirror 24.
Reflect on. The light reflected by the reflecting mirror 24 returns to the original path, passes through the lens to be inspected 23, becomes parallel light again, and is incident on the flat plate prototype 22. The light enters the mirror 21, and a part of the light is reflected by the half mirror 21 toward the observation lens 27 side. The reflected light reaches the CCD 29 of the image pickup unit 28 through the observation lens 27 and becomes the test light.

Hereinafter, the operations of the image pickup unit 28, the image processing device, the calculating means, the monitor device and the memory are the same as those of the interference measuring device 1a. In this case, in the interference measurement device 1b, (4) to
The numerical aperture NA ₀ shown in the equation (9) is obtained by the equation (10) shown in the following equation 26, and based on this NA ₀ ,
Similar to the interference measuring device 1a described above, a predetermined calculation is performed.

[0123]

[Equation 26]

The interference measuring apparatus 1b is an apparatus for measuring an object to be inspected (lens 23 to be inspected having a positive power) having a function of condensing a light beam. An apparatus for measuring an object to be inspected (a lens to be inspected having a negative power) having a function of diverging a light beam may be used. In this case, for example, in the interferometer 1b, the curvature of the reflecting mirror 24 may be changed appropriately.

Next, a third embodiment of the interference measuring apparatus of the present invention will be described. FIG. 3 is a diagram schematically showing a third embodiment of the interference measuring apparatus of the present invention. Interferometer 1 shown in FIG.
Reference character c denotes a Twyman-Green type interferometer (hereinafter referred to as an interferometer) 2c, an image pickup unit 41 which is an interference fringe detection unit, an image processing device (not shown) including an A / D converter and an image memory, and an arithmetic unit. , A monitor device and a memory as a storage means. In this case, the image pickup unit 41, the image processing device, the calculation means, the monitor device, and the memory of the interference measurement device 1c are respectively provided in the interference measurement device 1c.
The image pickup unit 11, the image processing device 12, the calculation unit 13, the monitor device 14, and the memory 15 of a have the same configurations, and thus description thereof will be omitted.

The interferometer 2c in the interference measuring apparatus 1c is
Light source 30, objective lens 31, collimator lens 32
A beam splitter 33, a reflecting mirror 34 as a reference member, a drive system 35 for driving the reflecting mirror 34, and a condenser lens (lens having a positive power) as a condensing optical member.
36 and an object 38 which also serves as a reflecting member
It has a moving means 39 capable of moving in the direction of the optical axis 37 and a direction perpendicular to the optical axis 37, and an observation lens 40. In this case, the light source 30, the objective lens 31, the collimator lens 32, the moving means 39, the observation lens 40 and the object 38 of the interferometer 2c are the light source 3 of the interferometer 2a,
Since the objective lens 4, the collimator lens 5, the moving means 9, the observation lens 10 and the test object 8 have the same configuration, the description thereof will be omitted.

The reflecting surface of the reflecting mirror 34 in the interferometer 2c,
That is, the facing surface of the beam splitter 33 in the reflecting mirror 34 constitutes a reference surface 341. Further, in order to utilize the phase shift method or the like for the fringe analysis, a piezo element or the like is used in the drive system 35 for driving the reflecting mirror 34. An aplanatic lens is used as the condenser lens 36 in the interferometer 2c.

In the case of the interference measuring apparatus 1c having such a structure, the moving means 39 moves the test object 38 in the direction of the optical axis 37 and in the direction perpendicular to the optical axis 37 to move the test object 38.
Are set in place.

The light emitted from the light source 30 in the interference measuring apparatus 1c passes through the objective lens 31 and the collimator lens 32 in order and becomes a parallel light expanded to a desired light beam diameter. This collimated light enters the beam splitter 33,
Part of the light is transmitted through the beam splitter 33, and the rest is reflected by the beam splitter 33 toward the reference surface 341.

The light reflected by the beam splitter 33 is applied to the reference surface 341, reflected by the reference surface 341, and incident on the beam splitter 33 again, and a part of the light passes through the beam splitter 33. This transmitted light is
Via the observation lens 40, the solid-state image sensor (CC
D) It reaches above 42 and becomes reference light.

On the other hand, the light transmitted through the collimator lens 32 and further transmitted through the beam splitter 33 is incident on the condenser lens 36, transmitted through the condenser lens 36 and condensed once, and then the object 38 to be inspected. The surface 381 to be inspected is irradiated and reflected by the surface 381 to be inspected. The light reflected by the surface to be inspected 381 returns to the original path, passes through the condenser lens 36, becomes parallel light again, and further enters the beam splitter 33,
A part of the light is reflected by the beam splitter 33 toward the observation lens 40. The reflected light reaches the CCD 42 of the image pickup unit 41 through the observation lens 40 and becomes the test light.

The operations of the image pickup section 41, the image processing device, the calculating means, the monitor device and the memory are the same as those of the interference measuring device 1a, and the illustration and description thereof will be omitted.

Next, a fourth embodiment of the interference measuring apparatus of the present invention will be described. FIG. 11 is a diagram schematically showing a fourth embodiment of the interference measuring apparatus of the present invention. An interference measuring apparatus 1d shown in the figure includes a Twyman-Green type interferometer (hereinafter referred to as an interferometer) 2d, an image pickup unit 54 which is an interference fringe detecting unit,
It has an image processing device (not shown) including an A / D converter and an image memory, a calculation means, a monitor device, and a memory that is a storage means. In this case, the image pickup unit 54, the image processing device, the calculating means, the monitor device, and the memory of the interference measuring device 1d are respectively the image pickup unit 11, the image processing device 12, the calculating device 13, and the calculating device 13 of the interference measuring device 1a.
Since it has the same configuration as the monitor device 14 and the memory 15, the description thereof will be omitted.

The interferometer 2d in the interferometer 1d is
Light source 43, objective lens 44, collimator lens 45
A beam splitter 46, a reflecting mirror 47 as a reference member, a drive system 48 for driving the reflecting mirror 47, and a diverging lens as a diverging optical member (a lens having negative power).
49 and a test object 51 that also serves as a reflection member
It has a moving means 52 capable of moving in the direction of the optical axis 50 and a direction perpendicular to the optical axis 50, and an observation lens 53. In this case, the light source 43 of the interferometer 2d, the objective lens 44, the collimator lens 45, the moving means 52, the observation lens 53, and the test object 51 are the light source 3 of the interferometer 2a,
Since the objective lens 4, the collimator lens 5, the moving means 9, the observation lens 10 and the test object 8 have the same configuration, the description thereof will be omitted.

The reflecting surface of the reflecting mirror 47 in the interferometer 2d,
That is, the facing surface of the beam splitter 46 in the reflecting mirror 47 constitutes a reference surface 471. Further, in order to utilize the phase shift method or the like for the fringe analysis, a piezo element or the like is used in the drive system 48 for driving the reflecting mirror 47. An aplanatic lens is used as the diverging lens 49 in the interferometer 2d.

In the case of the interference measuring apparatus 1d having such a structure, the moving means 52 moves the test object 51 in the direction of the optical axis 50 and in the direction perpendicular to the optical axis 50, and the test object 51 is moved.
Are set in place.

The light emitted from the light source 43 in the interference measuring apparatus 1d passes through the objective lens 44 and the collimator lens 45 in order and becomes a parallel light expanded to a desired light beam diameter. This collimated light enters the beam splitter 46,
A part of the light is transmitted through the beam splitter 46, and the rest is reflected by the beam splitter 46 toward the reference surface 471.

The light reflected by the beam splitter 46 is applied to the reference surface 471, reflected by the reference surface 471, again incident on the beam splitter 46, and part of the light passes through the beam splitter 46. This transmitted light is
Through the observation lens 53, the solid-state image sensor (CC
D) It reaches 55 and becomes a reference light.

On the other hand, the light that has passed through the collimator lens 45 and further through the beam splitter 46 enters the divergent lens 49. The divergent light transmitted through the diverging lens 49 is applied to the test surface 511 of the test object 51 and is reflected by the test surface 511. The light reflected by the surface to be inspected 511 returns to the original path, passes through the diverging lens 49, becomes parallel light again, and is incident on the beam splitter 46. Part of the light is reflected by the beam splitter 46 toward the observation lens 53 side. To do. This reflected light passes through the observation lens 53 and the imaging unit 54.
The light reaches the CCD 55 and becomes the test light.

The operations of the image pickup section 54, the image processing device, the calculating means, the monitor device and the memory are the same as those of the interference measuring device 1a, and the illustration and description thereof will be omitted. Interference measuring device 1d having such a configuration
Is used to measure an object having a concave surface with a relatively large radius of curvature.

Next, a fifth embodiment of the interference measuring apparatus of the present invention will be described. FIG. 12 is a diagram schematically showing a fifth embodiment of the interference measuring apparatus of the present invention. The interference measuring apparatus 1e shown in the figure is an apparatus in the case where the object to be inspected is a lens (lens to be inspected) 62, that is, a modification of the interference measuring apparatus 1b described above. Hereinafter, description of common points with the interference measuring apparatus 1b will be omitted, and different points will be described.

The interference measuring device 1e includes a Fizeau interferometer (hereinafter referred to as an interferometer) 2e, an image pickup unit 66 which is an interference fringe detecting means, an image processing device (not shown) including an A / D converter and an image memory. , A calculation device, a monitor device, and a memory that is a storage device.

The interferometer 2e in the interference measuring apparatus 1e is
Light source 56, objective lens 57, collimator lens 58
, Half mirror 59, and flat prototype 60 as a reference member
And a drive means 602 such as a PZT for accurately moving the plane prototype 60 with respect to the optical axis 64 to perform the phase shift method,
It has a condensing lens (lens having a positive power) 61 which is a condensing optical member, a reflecting mirror 63 which is a reflecting member, and an observation lens 65.

The condenser lens 61 in the interferometer 2e includes:
Use an aplanatic lens. Also, the interferometer 2e
The reflecting surface of the reflecting mirror 63 in FIG.
The surface accuracy is very good.

In the case of the interference measuring apparatus 1e having such a structure, the lens 62 to be inspected is moved in the direction of the optical axis 64 and in the direction perpendicular to the optical axis 64 by the moving means (not shown),
The test lens 62 is installed at a predetermined position.

The light emitted from the light source 56 in the interference measuring apparatus 1e passes through the objective lens 57 and the collimator lens 58 in order, and becomes a parallel light having a desired light beam diameter. The parallel light enters the half mirror 59, and a part of the parallel light passes through the half mirror 59.

The light transmitted through the half mirror 59 is incident on the flat prototype 60, a part of which is transmitted through the flat prototype 60 (reference surface 601), and the rest is the reference plane 6 of the flat prototype 60.
Reflect at 01.

The light reflected by the reference surface 601 of the flat prototype 60 again enters the half mirror 59, and a part of the light is reflected by the half mirror 59 toward the observation lens 65 side. The reflected light reaches the solid-state image pickup device (CCD) 67 of the image pickup unit 66 through the observation lens 65 and serves as reference light.

On the other hand, the light transmitted through the reference surface 601 is
The light enters the condenser lens 61, passes through the condenser lens 61, is condensed once, and then enters the lens 62 to be inspected.
After passing through 2, the light becomes parallel light again, is irradiated onto the reflecting mirror 63, and is reflected by the reflecting mirror 63. The light reflected by the reflecting mirror 63 passes through the lens 62 to be examined, is once focused, then passes through the focusing lens 61 to become parallel light again, and is then incident on the flat plate prototype 60, and a part of it is flat. The light passes through the prototype 60 and enters the half mirror 59, and a part of the light enters the half mirror 59.
Is reflected by the observation lens 65 side. The reflected light reaches the CCD 67 of the image pickup unit 66 through the observation lens 65 and becomes the test light.

In each of the above embodiments, the Fizeau interferometers 2a and 2a are used as the interferometers of the interferometer.
b, 2e and Twyman-Green type interferometers 2c, 2d are used, but the interferometer in the present invention is not limited to these, and other various interferometers may be used to configure the interferometer. .

Further, in each of the above-mentioned embodiments, as the condensing optical member or the diverging optical member of the interferometer, the standard lens 7, the lenses to be inspected 23 and 62, the aplanatic condensing lenses 36 and 61 and the diverging lens are respectively diverged. Although the lens 49 is used, the condensing optical member or the diverging optical member in the present invention is not limited to these, and the condensing optical member or the diverging optical member has a configuration capable of condensing or diverging incident light. It may be any one.

For example, a condensing lens or a diverging lens that does not satisfy the sine condition may be used as the condensing optical member or the diverging optical member of the interferometer. Even if a condensing lens or a diverging lens that does not satisfy the sine condition is used, highly accurate aberration measurement can be performed as compared with the case where the aberration correction is not performed in the present invention.

Further, in the first to fourth embodiments, as the moving means, the moving means 9 for moving the object 8 in the optical axis 73 direction and the moving means for moving the reflecting mirror 24 in the optical axis 26 direction, respectively. The means 25, the moving means 39 capable of moving the test object 38 in the optical axis 37 direction, and the moving means 52 capable of moving the test object 51 in the optical axis 50 direction are used as the moving means in the present invention. Not limited.

That is, the moving means in the present invention is capable of relatively moving the condensing point of the object (reflecting member) and the condensing point of the condensing optical member in the optical axis direction, and the object ( What can move the condensing point of the condensing optical member) and the condensing point of the reflecting member relatively in the optical axis direction, the condensing point of the test object (reflecting member) and the focus of the diverging optical member (virtual image) And those that can be moved relative to each other in the optical axis direction, or those that can move the focal point of the test object (divergent optical member) and the condensing point of the reflection member relative to each other in the optical axis direction. It may have any configuration. Examples of the object to be inspected in the present invention include an optical element such as a lens, a mold, and an output wavefront of an optical disk device.

Further, in each of the above embodiments, only the 4th and 6th order aberrations are corrected, but the order of the aberrations to be corrected in the present invention is not limited to the above respective embodiments. That is, any combination of aberration orders corrected in the present invention is possible as long as it is an even order of four or more. When correcting aberrations of an even number of letters of 8th order or more, for example, the correction may be performed in the same manner as in the case of correcting the 4th order and 6th order aberrations in each of the embodiments.
Although the present invention has been described above based on the illustrated configuration example, the present invention is not limited to this.

[0156]

As described above, according to the interference measuring apparatus and the interference measuring method of the present invention, even when there is a setting error of the test object such as Difukas in the measurement of the aberration of the test object, the setting error is set. It is possible to perform high-precision measurement without performing accurate alignment that eliminates
In particular, when a relatively bright condensing lens or a diverging lens is used as the condensing optical member or the diverging optical member of the interferometer, the measurement accuracy is significantly higher than that in the case where no correction is performed in the present invention. improves.

When a condensing lens or a diverging lens satisfying the sine condition is used as the condensing optical member or the diverging optical member of the interferometer, the aberration caused by the defocus is substantially removed from the measured value. Is possible
Extremely accurate measurement results can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a first embodiment of an interference measuring device of the present invention.

FIG. 2 is a diagram schematically showing a second embodiment of the interference measuring device of the present invention.

FIG. 3 is a diagram schematically showing a third embodiment of the interference measuring apparatus of the present invention.

FIG. 4 is a diagram showing a configuration example of a condenser lens having a relatively large NA ₀ .

FIG. 5 is a diagram showing a configuration example of a condenser lens having a relatively small NA ₀ .

FIG. 6 is a graph (aberration diagram) showing spherical aberration and a sine condition of a condenser lens having a relatively large NA ₀ .

FIG. 7 is a graph (aberration diagram) showing spherical aberration and sine conditions of a condenser lens having a relatively small NA ₀ .

FIG. 8 is a graph showing a relationship between an incident height (h) and a fourth-order or higher-order aberration generated by defocus in a condenser lens having a relatively large NA ₀ .

FIG. 9 is a graph showing the relationship between the fourth-order and higher-order aberrations caused by defocus in a condenser lens having a relatively small NA ₀ and the incident height (h).

FIG. 10 is a flowchart showing the operation of the interference measuring apparatus when correcting only the fourth-order and sixth-order aberrations when performing the aberration measurement of the surface to be inspected of the object to be inspected according to the present invention.

FIG. 11 is a diagram schematically showing a fourth embodiment of the interference measuring device of the present invention.

FIG. 12 is a diagram schematically showing a fifth embodiment of the interference measuring apparatus of the present invention.

[Explanation of symbols]

 1a, 1b, 1c, 1d, 1e Interferometer 2a, 2b, 2e Fizeau interferometer 2c, 2d Twyman-Green interferometer 3 Light source 4 Objective lens 5 Collimator lens 6 Half mirror 7 Standard lens 71 Reference surface 711 Drive Means 73 Optical axis 75 Condensation point 8 Test object 81 Test surface 85 Curvature center 9 Moving means 10 Observation lens 11 Imager 12 Image processing device 13 Computing means 14 Monitor device 15 Data dedicated memory 16 Rays 17 Solid-state image sensor (CCD) ) 18 light source 19 objective lens 20 collimator lens 21 half mirror 22 planar prototype 221 reference surface 222 driving means 23 test lens 24 reflecting mirror 25 moving means 26 optical axis 27 observation lens 28 imaging unit 29 solid-state image sensor (CCD) 30 light source 31 Objective Lens 32 Collimating Lens 3 3 Beam Splitter 34 Reflector 341 Reference Surface 35 Drive System 36 Condenser Lens 37 Optical Axis 38 Test Object 381 Test Surface 39 Moving Means 40 Observation Lens 41 Imager 42 Solid-state Image Sensor (CCD) 43 Light Source 44 Objective Lens 45 Collimate Lens 46 Beam splitter 47 Reflecting mirror 471 Reference surface 48 Driving system 49 Divergence lens 50 Optical axis 51 Test object 511 Test surface 52 Moving means 53 Observation lens 54 Imaging unit 55 Solid-state imaging device (CCD) 56 Light source 57 Objective lens 58 Collimate Lens 59 Half mirror 60 Planar prototype 601 Reference surface 602 Driving means 61 Condensing lens 62 Test lens 63 Reflecting mirror 64 Optical axis 65 Observation lens 66 Imaging unit 67 Solid-state imaging device (CCD) 101 to 106 steps

Claims (23)

[Claims] 1. A light from a light source is divided into two, one is used as a reference light from a reference surface, and the other is used as a test light from a test object, and the reference light and the test light are superposed. An interference measuring device for obtaining a phase difference between the reference light and the test light based on the interference fringe, and obtaining the interference fringe, wherein the interference fringe is an approximate polynomial for specifying the phase difference. The first measuring means and the interference measuring device for the object to be inspected, based on the numerical aperture of an effective light beam that is incident on the object to be inspected or emitted from the object to be inspected. Based on the error information and the numerical aperture obtained by the second means, the second means for calculating error information appearing in the specific term of the approximate polynomial due to the setting position error with respect to The coefficient of the term that specifies the phase difference in the approximate polynomial obtained by An interferometer according to claim 3, characterized in that 2. The interference measuring apparatus according to claim 1, wherein the interference measuring apparatus has a condensing optical member. 3. The interferometer according to claim 2, wherein the focusing optical member satisfies a sine condition. 4. The approximate polynomial in the first means is
The interference measuring apparatus according to claim 2 or 3, which is represented by the following formula (1). [Equation 1] 5. The second means is 2 of the approximate polynomial.
The interferometer according to claim 4, which calculates a coefficient W ₂₀ in the next item. 6. The third means indicates a correction value for correcting a coefficient of a term that specifies the phase difference and a coefficient W _{20 of a} quadratic term of the approximate polynomial, and the following Expression 2 (3). The interference measuring apparatus according to claim 5, wherein the interference measuring apparatus is operated based on the equation. [Equation 2] 7. The third means is 4 of the approximate polynomial.
The interference measuring apparatus according to claim 6, wherein the coefficient W ₄₀ in the next item is corrected by the equation (6) shown in the following Expression 3. [Equation 3] 8. The third means is 6 of the approximate polynomial.
The interference measuring apparatus according to claim 6 or 7, wherein the coefficient W ₆₀ in the next item is corrected by the equation (7) shown in the following Expression 4. [Equation 4] 9. The light from the light source is divided into two, one is used as the reference light from the reference surface, and the other is used as the test light from the test object, and the reference light and the test light are superimposed. An interference measurement method for obtaining a phase difference between the reference light and the test light on the basis of the interference fringes by the first means. It is expanded to an approximate polynomial for specifying the phase difference, and the second means is used to calculate the numerical aperture of the effective light flux that is incident on the test area of the test object or exits from the test area of the test object. The error information appearing in the specific term of the approximate polynomial due to the set position error of the sample with respect to the interferometer is calculated, and the error information and the numerical aperture obtained by the second means are calculated by the third means. The order in the approximate polynomial obtained by the first means based on An interference measurement method, which comprises correcting a coefficient of a term that specifies a phase difference. 10. The interference measuring method according to claim 9, wherein the reference light or the test light passes through a condensing optical member. 11. The interference measuring method according to claim 10, wherein the condensing optical member satisfies a sine condition. 12. The approximation polynomial in the first means is the equation (1) shown in the following equation 5.
The interference measurement method described in 1. [Equation 5] 13. The interference measuring method according to claim 12, wherein the coefficient W ₂₀ of the quadratic term of the approximate polynomial is calculated by the second means. 14. A correction value for correcting a coefficient of a term specifying the phase difference by the third means is shown by a coefficient W _{20 of a} quadratic term of the approximate polynomial and the following Expression 6 (3). The interference measurement method according to claim 13, wherein the calculation is performed based on the equation. [Equation 6] 15. The interference measuring method according to claim 14, wherein the third means corrects the coefficient W ₄₀ of the fourth-order term of the approximate polynomial based on the equation (6) shown in the following Expression 7. [Equation 7] 16. The interference measuring method according to claim 14, wherein the third means corrects the coefficient W ₆₀ of the sixth-order term of the approximate polynomial based on the equation (7) shown in the following Expression 8. [Equation 8] 17. A light from a light source is divided into two, one of which is reflected by a reference surface to be a reference light, and the other of which is converged light or divergent light by an optical member and made incident on a surface to be inspected. As the test light by reflecting on the surface, while obtaining the interference fringes by superimposing the reference light and the test light, the phase difference between the reference light and the test light based on the interference fringes. An interference measuring device for detecting, wherein the interference fringes are expanded into an approximate polynomial for specifying the phase difference, and based on an effective numerical aperture of a light beam incident on a test region of the test surface. Second means for calculating error information appearing in a specific term of the approximate polynomial due to a position error of the surface to be inspected with respect to the interferometer, and the error information obtained by the second means, An approximation obtained by the first means based on the numerical aperture And a third means for correcting the coefficient of the term that specifies the phase difference in the polynomial. 18. The interferometer according to claim 17, wherein the optical member is a standard lens having the reference surface. 19. The interferometer according to claim 17, wherein the optical member is a lens having a positive power. 20. The interferometer according to claim 17, wherein the optical member is a lens having negative power. 21. The interference measuring apparatus according to claim 17, wherein the numerical aperture NA ₀ is obtained by the following equation. NA ₀ = h _max / f = sin θ _max (where, h _max is the maximum incident height from the optical axis when an effective light beam irradiating the test region is incident on the optical member, and f is the optical The focal length of the member, θ _max, is the angle between the outermost ray of the effective luminous flux and the optical axis after passing through the optical member.) 22. The light from the light source is divided into two, one of which is used as a reference light, and the other of which is transmitted as an inspection light by passing through an inspection object having a function of converging or diverging a light beam. An interference measuring device for detecting the phase difference between the reference light and the test light based on the interference fringes, while obtaining the interference fringes by superimposing the test light, the interference fringes, First means for expanding into an approximate polynomial for specifying the phase difference, and a setting position error of the test object with respect to the interferometer, based on the numerical aperture of an effective light beam focused or diverged by the test object. Obtained by the first means based on the error information and the numerical aperture obtained by the second means, the second means calculating the error information appearing in the specific term of the approximate polynomial. Specify phase difference in approximate polynomial And a third means for correcting the coefficient of the term. 23. The interferometer according to claim 22, wherein the numerical aperture NA ₀ is obtained by the following equation. NA ₀ = h _max / f = sin θ _max (where, h _max is the maximum incident height from the optical axis when an effective light beam focused or diverged by the object is incident on the object, f is , Focal length of the test object, θ _max
Is the angle between the outermost ray of the effective luminous flux and the optical axis after passing through the test object. )