JPH01257229A - Measuring method of shape of transmission wavefront of substance to be measured and apparatus used for the same - Google Patents

Abstract

PURPOSE:To measure the shape of a transmission wavefront of a substance to be measured, by using interference patterns formed of reflection wavefronts from first and second reflecting surfaces, and the lateral surface of the substance to be measured, etc. CONSTITUTION:Based on an interference pattern formed of a reflection wavefront of a light emitted from an interferometer (not shown) and reflected on first and second reflecting surfaces 1 and 3, an optical path distribution obtained from the shape of the wavefront in a state wherein a substance 6 to be measured is absent in optical paths, is determined. Next, the optical path distribution containing a change in the shape of the reflection wavefront of the reflecting surfaces 1 and 3 in a state wherein the substance 6 to be measured comes into the optical paths, is determined. Moreover, based on an interference pattern formed by the reflecting surface 1 and one side surface 6a of the substance 6 to be measured, the optical path distribution containing the change in the shape of the reflection wavefront caused by the side surface 6a of the substance 6 to be measured is determined. Based on an interference pattern formed by the reflecting surface 3 and the other side surface 6b of the substance 6 to be measured, subsequently, the optical path distribution containing the change in the shape of the reflection wavefront caused by the side surface 6b of the substance 6 to be measured is determined. From these optical path distributions, the shape of a transmission wavefront of the light transmitted through the substance 6 to be measured can be measured accurately.

Description

[Detailed Description of the Invention] Appearance (industrial application field) The present invention aims to improve the homogeneity of the refractive index of an optical material as an object to be measured, that is, the homogeneity necessary for measuring the refractive index distribution. The present invention relates to a method for measuring the shape of a transmitted wavefront of a measured object for measuring the shape of a transmitted wavefront of a measured object, and an apparatus used in the method.

(Prior Art) Conventionally, the homogeneity of the refractive index of an optical material as an object to be measured has been determined using an interferometer according to the procedure described below.

For example, using a Fizeau type interferometer as shown in FIG.
and a second reflecting member 4 having a second reflecting surface 3 are opposed to each other with an interval therebetween, and an object to be measured 6 housed in a container 5 is placed between the opposed members.

The container 5 has a glass plate 7.8 and a top lid 9.8 facing each other with the object to be measured 6 in between. It consists of a lower lid lO, and the gap between the glass plate 7.8 and the object to be measured 6 is filled with a matching liquid 11.

Here, the matching liquid 11 is a liquid having a refractive index substantially equal to the refractive index n of the object to be measured 6, and is prepared by mixing aniline, ethyl alcohol, and glycerin, for example. This matching liquid 11 is used to remove changes in wavefront shape due to irregularities on the side surfaces 68.6b of the object to be measured 6. The refractive index of the medium in which the measuring object 6 is placed and the refractive index n of the measuring object 6
Generally speaking, if the refractive index difference Δn between the side surfaces 6a and 6b is
Optical path length distribution W (x, y) based on the surface shape S (xry) of
Although there is an influence of Δn-8(xey), when the gap is filled with the matching liquid 11 with Δn=o, the unevenness of the side surfaces 6a and 6b of the object to be measured 6 is corrected, and the side surface 6 of the object to be measured 6 is
Changes in the wavefront shape due to the irregularities of a and 6b can be eliminated.

As described above, with the container 5 containing the object to be measured 6 placed between the first reflecting member 2 and the second reflecting member 4 facing each other, the laser light source 12 is driven to emit laser light. , a parallel light beam P as a plane wave is guided to the first reflection member 2 and the second reflection member 4 by the condensing lens 13 and the magnifying lens 14. Then, a part of the plane wave is reflected on the first reflection surface 1 of the first reflection member 2. reflected by. The remaining plane wave that has passed through the first reflective surface 1 of the first reflective member 2 passes through the container 5, reaches the second reflective surface 3 of the second reflective member 4, is reflected by this second reflective surface 3, and is returned to its original state. It reaches the first reflecting surface 1 of the first reflecting member 2 through the optical path, and interferes with the plane wave reflected by the first reflecting surface 1. In this way, interference light is formed by the plane wave reflected by the first reflecting surface 1 and the plane wave reflected by the second reflecting surface. The optical path of this interference light is bent by a half mirror 15 placed between the condensing lens 13 and the magnifying lens 14 in the direction of the imaging lens 16, and an image is formed on the imaging surface 17a of the imaging device 17. , an interference pattern is formed on the imaging surface 17a. This interference pattern is converted into a video signal and sent to a monitor 18 that includes an arithmetic control section.

Now, the geometric surface shape of the first reflective surface 1 is 5x (xty)
, the geometrical surface shape of the second reflective surface 3 is 5t (Xty),
The geometric surface shape of the surface 7a of the glass plate 7 of the container 5 on the side closer to the first reflective surface 1 is 5a(xty), and the geometric surface shape of the surface 8a of the glass plate 8 of the container 5 on the side closer to the second reflective surface 3 is 5a(xty). Assuming that the geometrical surface shape is 84 (x, y), and the shape of the transmitted wavefront transmitted through the object to be measured 6 n (x ty ) - the refractive index of air is 1,
Interference pattern WA when the object to be measured 6 is present in the optical path
(x, y) is expressed by the following formula.

Next, the object 4] 1 is removed from the optical path and the glass plate 7 is removed.
, 8 in close contact with each other.

(xpy) is determined as described below.

That is, as shown in FIG. 13, the first reflecting member 2 and the second reflecting member 3 are made by removing the object 6 from the container 5, sandwiching the matching liquid 11, and bringing the glass plates 7.8 into close contact with each other. While the laser light source 12 is inserted into the optical path between the condenser lenses 13 and 13, the laser light source 12 is driven to emit a laser beam. The magnifying lens 14 guides the parallel light beam P as a plane wave to the first reflecting member 2 and the second reflecting member 4. Then, a part of the plane wave is reflected by the first reflecting surface 1. The remaining plane wave that has passed through the first reflective surface 1 passes through the glass plate 7, the matching liquid 11, and the glass plate 8, reaches the second reflective surface 3, is reflected by the second reflective surface 3, and returns to the original optical path. and reaches the first reflecting surface 1, and interferes with the plane wave reflected by the first reflecting surface 1,
Interfering light is formed. Based on this interference light, an interference pattern W, (x, y) is formed on the imaging surface 17a.

This interference pattern W@(xt V> is expressed by the following equation.

Here, if we solve for H (x, y) using formulas ■ and ■, we get H (xt y) = WA (Xl y) - W, (x, y)
The formula ``...■'' is obtained.

This equation 0 first calculates the interference pattern with the object to be measured 6 interposed in the optical path, then calculates the interference pattern with the object 6 removed from the optical path, and then
This means that the shape of the transmitted wavefront transmitted through the object 6 can be determined by finding the interference pattern with only the object 6 removed from the optical path from the interference pattern with do.

Therefore, the maximum value of the obtained transmitted wavefront shape HCXe y) is Haa(Xs'/), and the minimum value is HM(XI y)
Then, the number of hits is 81! The refractive index distribution δn of the I constant 6 is given by the following formula.

δn=(HMI(X t y) Hum (X +
3')] 'λ/d where λ is the wavelength of the light used for measurement, and d is the thickness of the object to be measured 6.

(Problems to be Solved by the Invention) However, it is difficult and troublesome to manufacture the matching liquid 11 such that the refractive index difference Δn between the object to be measured 6 and the matching liquid U is 0.

Furthermore, when observing the interference pattern, each stitch of the interference pattern moves due to the flow of the matching liquid 11, making it difficult to observe the interference pattern stably.

Furthermore, the matching liquid 11 itself has non-uniformity in refractive index, and the matching liquid 11. Inhomogeneity of refractive index and interference pattern W@
If there is a difference between the inhomogeneity of the refractive index of the matching liquid 11 when determining (XI y), there is also the problem that an error occurs in the shape of the obtained transmitted wavefront.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and its purpose is to obtain the shape of a transmitted wavefront transmitted through an object to be measured without using a matching liquid. An object of the present invention is to provide a method for measuring the shape of a transmitted wavefront of an object to be measured, which can be accurately measured, and an apparatus used in the method.

Example 2 (Means for solving problems) The characteristics of the method for measuring the shape of a transmitted wavefront of a measured object according to the present invention are as follows.

Based on the interference pattern formed by the reflected wavefront reflected by the first reflective surface and the reflected wavefront reflected by the second reflective surface, the optical path includes the wavefront shape in a state where the object to be measured does not enter the optical path. It is formed by a length distribution W□(xty), a reflected wavefront reflected by the first reflecting surface and a reflected wavefront reflected by the second reflecting surface when the object to be measured enters the optical path. Based on the interference pattern, the optical path length distribution W, (x) includes a wavefront shape change due to the presence of the object to be measured.

y) and the interference pattern formed by the reflected wavefront reflected by the first reflecting surface and the reflected wavefront reflected by one side surface of the object to be measured, Optical path length distribution including wavefront shape change due to side surface W)
(Xt y), the other side surface of the object to be measured based on the interference pattern formed by the reflected wavefront reflected by the second reflecting surface and the reflected wavefront reflected by the other side surface of the object to be measured. The optical path length distribution W including the wavefront shape change due to
(x, y), and perform the following calculations based on each of the optical path length distributions to determine the shape H(x) of the transmitted wavefront transmitted through the object to be measured.

y).

H(x, y) = Wt(xty) wx(xty)
(n 1)(Wi(xty)+W4(x-y)
W1 (x, y)] where n is the refractive index of the object to be measured.

The features of the device used in the method for measuring the shape of a transmitted wavefront of a measured object according to the present invention include a first interferometer, a second interferometer, and a device to be measured based on an interference pattern by controlling the first and second interferometers. It has an arithmetic control unit that determines the shape of a transmitted wavefront that has passed through an object.

The first interferometer is provided with a first reflecting member having a first reflecting surface and facing one side of the object to be measured, and the second interferometer is provided with a first reflecting member having a second reflecting surface. and a second reflecting member facing the other side of the object to be measured, the first reflecting member and the second reflecting member facing each other and interposing the object to be measured between them. The arithmetic and control unit configures an optical path, and the calculation control unit causes light to be emitted from the first interferometer and is formed by a reflected wavefront that is reflected by the first reflective surface and a reflected wavefront that is reflected by the second reflective surface. an optical path length distribution W(x, y) including a wavefront shape in a state in which the object to be measured is not entered into the optical path, based on the interference pattern generated by the optical path;
With the object to be measured entering the optical path, light is emitted from the first interferometer side, and a reflected wavefront reflected by the first reflecting surface and a reflected wavefront reflected by the second reflecting surface. Based on the interference pattern formed by the optical path length distribution V/, (x,
y), with the second reflecting member retracted from the optical path, light is emitted from the first interferometer side, and the reflected wavefront reflected by the first reflecting surface and one of the objects to be measured are An optical path length distribution W, (x, y) including a wavefront shape change due to one side surface of the object to be measured based on an interference pattern formed by the reflected wavefront reflected from the side surface, and the first reflecting member Light is emitted from the second interferometer side in a state of being retracted from the optical path, and is formed by a reflected wavefront reflected by the second reflecting surface and a reflected wavefront reflected by the other side of the object to be measured. An optical path length distribution W4 that includes a wavefront shape change due to the other side surface of the object to be measured based on the interference pattern
(Xsy) is determined, and the following calculation is performed based on the respective optical path length distributions to determine the shape H(x, y) of the transmitted wavefront transmitted through the object to be measured.

H (xty) = % (xty) - Wl (x, y) - (
n-t)(Wl (xvy)+W4 (xty)-wx
(xty)] where n is the refractive index of the object to be measured.

(Example) Hereinafter, an example of a method for measuring the shape of a transmitted wavefront of a measured object according to the present invention and an apparatus used in the method will be explained with reference to the drawings. FIG. 2 is an explanatory diagram for explaining a first embodiment of a method for measuring the shape of a transmitted wavefront of a measured object according to the first embodiment, and the method for measuring the shape of a transmitted wavefront of a measured object according to the first embodiment uses a Fizeau type interferometer. Use. Note that in FIGS. 1 to 5, the same components as in the conventional example are given the same reference numerals.

First, as shown in FIG. 1, the first reflecting member 2 and the second reflecting member 4 are arranged facing each other in a relatively slightly inclined state. Second reflective surface 3
Based on the interference pattern fi(Xs y) formed by the reflected wavefront reflected by the optical path length distribution W(
x, y). Here, as in the conventional example, the first reflecting surface 1. The geometric surface shape of the second reflective surface 3 is 5n(
xsy), 52(X, ri), the interference pattern fAx
+y) is given by the following formula 0.

f, (x, y) = Si(xsy) + SR(XIy
) +(A, xs13.y+Ct) ++++++■
Note that the term (Ax+By+C:) is a component that means that reflective surface 1 and reflective surface 2 are tilted relative to each other in order to produce interference fringes, and the coefficients A, B, and C are approximated by plane approximation using the method of least squares. You can seek it by doing. Furthermore, the X-axis component of the surface shape 52 (-x, y) is given a negative sign, but this does not correspond to the sign of the orientation of the second reflective surface 3, as shown in FIG. 5(a). This is because it is oriented in the opposite direction to the first reflective surface 1.

Therefore, by removing the component (A,
3')" f x (Xs y) (A1xs B1
y+C1)...=...■ It is given by the formula.

Next, as shown in FIG. 2, a wavefront is formed by a reflected wavefront reflected by the first reflecting surface 1 and a reflected wavefront reflected by the second reflecting surface 3 when the object to be measured 6 enters the optical path. Based on the interference pattern L(XI y), an optical path length distribution W, (x, y) including a change in wavefront shape due to the presence of the object to be measured 6 is determined.

22, the side surface 6a of the object to be measured 6 on the side closer to the first reflective surface 1
The shape of the side surface 6b of the object to be measured 6 on the side closer to the second reflecting surface 3 is 84 (x, y), and the shape of the transmitted wavefront transmitted through the object to be measured 6 is H(x, y), and the refractive index of the object to be measured 6 is n. Therefore, the refractive index distribution W=(x, y) is W2(x,
y)=L(XI 3')(A4X+82y+CJ
Required by “””■.

Here, the X-axis component of the surface shape S3 (XIY) is given a negative sign, but this is because the direction of the side surface 6a is opposite to that of the first reflective surface 1, as shown in FIG. 5(b). This is because the sign is taken for the direction.

Furthermore, as shown in FIG. An optical path length distribution W3 (x, y) including a wavefront shape change due to one side surface 6a of 6 is determined. The interference pattern is L(
XI y), then fi(xt y)=st(xty
)+si(XIY)+(A3XIB3y+C3)
-...■ Therefore, the refractive index distribution W3 (XI y) is W
l(XI !>=f3CXt y)-(A3XIB3y
+C3) , , , , ・■. Note that the symbols are used as shown in FIG. 5(c).

Finally, as shown in FIG. 4, based on the interference pattern formed by the reflected wavefront reflected by the second reflecting surface 3 and the reflected wavefront reflected by the other side surface 6b of the object to be measured 6, An optical path length distribution W4 (xty) including a change in wavefront shape due to the other side surface 6b of the object to be measured 6 is determined. If the interference pattern is f4(x,・y), then f*(xs y)=St(xsy)+5J-xsy)+
(A4xsB,y+CJ -@1 Therefore, the optical path length distribution W4(x, y) is W4(Key y)=f4(xt
y) - (A, xsB4y+C4) +++
+++■Here, use the ■formula and the 0 formula.

When we calculate W, (x, y) - Wyu(xsy), we get W, (x
, y)-Wl(XI y)=1(x, y)-fx(
Xs y) -■ This 0 formula uses the ■ formula and the 0 formula.

f, (x ty)-f> (x ty)=H(x
ty)+ (n-D (Sl (-xty)+ 84
It can be organized as (x, y)]-@.

On the other hand, by substituting the term on the right side of the interference pattern L(XI y)L[phase] of equation 0, we get W4(x, y)=st(xty)+s4(-xty)
Therefore, W4(xty)=82(xty)+54(xty)
＋＋＋＋＋＋ 0Using this [phase] formula and the 0 formula, W
If we calculate the sum of 3(Xty) and W4(-x, y), then by applying the 0 formula to this 0 formula, By the way, according to the 0 formula and the ■ formula.

W □ (X + y) = Syo (S + y) + 5t (-1
y), the [phase] formula is S3(X+34(Xty)=%(Xs+W4(-
x, y)-Wi(XI y)-@formula.

By substituting this 0 equation into the [phase] equation, the following equation representing the shape H(xt y) of the transmitted wavefront transmitted through the object to be measured 6 is finally obtained.

II (xty) =W2 (xty) -Wx (x
ty) −(n-1) (Wz (xty) +W4
(xty) -Wl (x, y)] Figures 6 to 9 are
FIG. 2 is a diagram showing a second embodiment of the measurement method according to the present invention,
A Twyman Green type interferometer was used.

In the case of this Twyman Green type interferometer, as in the first embodiment, first, as shown in FIG. 6, the interference pattern fi(x
ty), and then, as shown in FIG.
is inserted into the optical path between the beam splitter 19 and the second reflecting member 4 to obtain the interference pattern L (Xty) with the object to be measured 6 present in the optical path, and then as shown in FIG. The interference pattern f3 (XI y) between the first reflecting surface 1 and one side surface 6a of the object to be measured 6 is determined, and finally, as shown in FIG. other side 6
By following the steps of determining the interference pattern f*(xt, y) with b, the shape of the transmitted wavefront transmitted through the object to be measured 6 can be determined.

1O and 11 are diagrams showing an embodiment of an apparatus used in the method for measuring the shape of a transmitted wavefront of a measured object according to the present invention, and as shown in FIG. Total 20
and a second interferometer 21, and an arithmetic control unit 22 that controls the first interferometer 20 and the second interferometer 21 to determine the shape of the transmitted wavefront transmitted through the object to be measured 6 based on the interference pattern. There is. In the first interferometer 20.

A first reflecting member 2 having a first reflecting surface 1 and facing one side surface 6a of the object to be measured 6 is provided, and the second interferometer 21 is provided with a first reflecting member 2 having a second reflecting surface 3 and facing one side surface 6a of the object to be measured 6. A second reflecting member 4 facing the other side surface 6a of the reflecting member 6 is provided. The first reflecting member 2 and the second reflecting member 4 face each other and constitute an interference optical path M in which the object to be measured 6 is interposed between the opposing members.

The arithmetic control section 22 includes a microcomputer 23. It is roughly composed of a memory 24, an operation section 251, and a display section 26. The microcomputer 23 emits light from the first interferometer 20 side and uses an interference pattern formed by a reflected wavefront reflected by the first reflecting surface 1 and a reflected wavefront reflected by the second reflecting surface 3. The optical path length distribution W (x, y
), light is emitted from the first interferometer 20 side with the object to be measured 6 entered into the optical path M, and a reflected wavefront reflected by the first reflecting surface 1 and a reflected wavefront reflected by the second reflecting surface 3 are generated. The optical path length distribution W2 (x, y) including the wavefront shape change due to the presence of the object to be measured 6 is based on the interference pattern formed by the reflected wavefront, and the optical path length distribution W2 (x, y) is 1. Light is emitted from the side of the interferometer 20, and the measured object is measured based on an interference pattern formed by a reflected wavefront reflected by the first reflecting surface 1 and a reflected wavefront reflected by one side surface 6a of the object to be measured 6. The optical path length distribution W3 (XI y) including the wavefront shape change due to one side surface 6a of the object 6, and the light emitted from the second interferometer 21 side with the first reflecting member 2 retracted from the optical path M. The reflected wavefront reflected by the second reflecting surface 3 and the surface 8! The optical path length distribution W4 (x
. The memory 524 stores an arithmetic control program, and the microcomputer 23 executes the arithmetic control program based on commands from the operation unit 25. The measurement results are displayed on the display section 26 together with the interference pattern.

Note that 27 is an A/D converter.

Next, the measurement procedure will be explained with reference to the flowchart shown in FIG.

First, the object to be measured 6 is set on a movable table (not shown) (S
l), Next, the object to be measured 6 is removed from the optical path M by operating the operating section 25 (S2). Next, the laser beam g12 of the interferometer 20 is driven by operating the operating section 25 (S3).
Next, the photoelectric conversion signal of the interference pattern formed on the imaging surface 17a is digitally converted and read as data (S
4). An interference pattern fx (s+y) for display is produced by the microcomputer 23 (S5).

Next, a correction calculation Aix+B, y+G based on the inclination of the first and second reflective surfaces 1.3 is performed (S6), and then the optical path length distribution wz(xty)=ri(xty) A1x+B
, y0C1 is calculated (37).

When the operating unit 25 is operated to drive the movable base, the object to be measured 6
is inserted into the optical path M (S8). driving the laser light source 12 of the interferometer 20 by operating the operation unit 25 (S9);
Data is read in the same way as step S4 (SIO).

Similarly, the interference pattern f, (s+y) is created (
S11), tilt correction calculation A, x+B, y+C,, optical path length distribution w2 (xty) = f z (Xsy) A2X+
Perform calculation to obtain B2y+c (S12.51
3).

Next, when the operating unit 25 is operated to drive the movable base, the second
The reflecting member 4 is retracted from the optical path M (514).

Then, the laser light source 12 of the interferometer zO is driven by operating the operating unit 25 (515). Data is read in the same way as step SIO (S16). And in the same way,
Creation of interference pattern f3 (xty) @ (S17),
Tilt correction calculation A, x+ B3y+ C, optical path length distribution W
3 (X+y) :l: f 3 (xty)-A, x
+B, y+C, are calculated (518, 519
).

Then, as a final step, when the operating section 25 is operated to drive the movable base, the first reflecting member 2 is retracted from the optical path M (520).
The first laser light source 12 is driven (S21).

Next, data is read in the same way as step S16 (S2
2), and similarly, the interference pattern f 4 (X
sy) (S23), slope correction calculation A4X+B4y
+C4-optical path length distribution w4(xty) = t'4(xty)
Perform calculation to obtain A4X+B4V+CI (82
3,524).

After completing these measurements, the microcomputer 23 performs the following calculations (S25).

H(X+y) =% (xsy) -Wt (xty)
-(n-1) ('iMx (xty) +W4 (
xty) -Wx (xty)] Then, it is determined whether the measurement has ended or not, and if it is necessary to measure another object to be measured, the process moves to step Sl to continue that measurement.

According to the apparatus used in the method for measuring the shape of the transmitted wavefront of the object to be measured according to the present invention, the shape H1l of the transmitted wavefront of the object to be measured is
This has the effect that the troublesome procedures involved in setting can be performed with a simple operation.

According to the method for measuring the shape of the transmitted wavefront of the object to be measured according to the present invention, as explained above, the shape of the transmitted wavefront that has passed through the object to be measured can be measured without using a matching liquid. The shape of the transmitted wavefront can be accurately measured, and the shape of the transmitted wavefront can be accurately measured.

Further, according to the apparatus used in the method for measuring the shape of the transmitted wavefront of the object to be measured according to the present invention, the troublesome procedure associated with measuring the shape of the transmitted wavefront of the object to be measured can be performed with a simple operation. .

[Brief explanation of the drawing]

1 to 5 are diagrams showing a first embodiment of a method for measuring the shape of a transmitted wavefront of a measured object according to the present invention, and FIGS. 1 to 4 are diagrams for explaining the measurement procedure. Explanatory diagram, Figure 5 is an explanatory diagram for explaining the coordinate axes of the shape of the transmitted wavefront, and Figure 6 is an explanatory diagram for explaining the coordinate axes of the shape of the transmitted wavefront.
9 to 9 are explanatory diagrams for explaining the second embodiment of the method for measuring the shape of the transmitted wavefront of the object to be measured according to the present invention, and FIG. FIG. 11 is a flowchart showing the measurement procedure when measuring the shape of the transmitted wavefront of the object to be measured using the device shown in FIG. 10, and FIGS. 12 and 13 are conventional FIG. 2 is an explanatory diagram of a method for measuring the shape of a transmitted wavefront of an object to be measured. 1... First reflecting surface, 2... First reflecting member 3...
・Second reflecting surface, 4... Second reflecting member 6... Measured object, 6a, 6b... Side surface 12... Laser light source, 17... Imaging element 20°° "First interferometer ,2
1... Second interferometer 22... Arithmetic control unit, M...
・Light path 1st ward diagram 7

Claims (2)

[Claims] (1) Based on the interference pattern formed by the reflected wavefront reflected by the first reflecting surface and the reflected wavefront reflected by the second reflecting surface, the shape of the wavefront in a state where the object to be measured is not entered into the optical path is determined. the optical path length distribution W_1 (x, y) including the reflected wavefront reflected by the first reflecting surface and the reflected wavefront reflected by the second reflecting surface in a state in which the object to be measured enters the optical path. Based on the interference pattern formed by
_2(x,y), one side of the object to be measured based on an interference pattern formed by a reflected wavefront reflected by the first reflecting surface and a reflected wavefront reflected by one side of the object to be measured. Optical path length distribution W including wavefront shape changes due to side surfaces of
_3 (x, y), the other side of the object to be measured based on the interference pattern formed by the reflected wavefront reflected by the second reflecting surface and the reflected wavefront reflected by the other side of the object to be measured. Optical path length distribution W including wavefront shape changes due to side surfaces of
_4(x, y), and performs the following calculation based on each of the optical path length distributions to determine the shape H(x, y) of a transmitted wavefront transmitted through the object to be measured. A method for measuring the shape of the transmitted wavefront. H(x,y)=W_2(x,y)−W_1(x,y)−
(n-1) [W_3(x,y)+W_4(x,y)-W
_1 (x, y)] where n is the refractive index of the object to be measured. (2) comprising a first interferometer, a second interferometer, and an arithmetic control unit that controls the first and second interferometers to determine the shape of a transmitted wavefront transmitted through the object based on the interference pattern; The first interferometer is provided with a first reflecting member having a first reflecting surface and facing one side of the object to be measured, and the second interferometer is provided with a first reflecting member having a second reflecting surface. and a second reflecting member facing the other side of the object to be measured, the first reflecting member and the second reflecting member facing each other and interposing the object to be measured between them. The arithmetic and control unit configures an optical path, and the calculation control unit causes light to be emitted from the first interferometer and is formed by a reflected wavefront that is reflected by the first reflective surface and a reflected wavefront that is reflected by the second reflective surface. Based on the interference pattern obtained by 1st
A wavefront due to the presence of the object to be measured based on an interference pattern formed by a reflected wavefront reflected by the first reflecting surface and a reflected wavefront reflected by the second reflecting surface after light is emitted from the interferometer side. Optical path length distribution W_2(x
, y), the light is emitted from the first interferometer side with the second reflecting member retracted from the optical path, and the first
an optical path length distribution that includes a wavefront shape change due to one side of the object to be measured based on an interference pattern formed by a reflected wavefront reflected by the reflective surface and a reflected wavefront reflected by one side of the object to be measured; W_3(x, y), a reflected wavefront that is reflected by the second reflective surface by emitting light from the second interferometer side with the first reflecting member retracted from the optical path, and the measured object. Based on the interference pattern formed by the reflected wavefront reflected from the other side of the object, an optical path length distribution W_4 (x, y) including a change in wavefront shape due to the other side of the object to be measured is determined, and each of the above-mentioned An apparatus used in a method for measuring the shape of a transmitted wavefront of a measured object, characterized in that the shape H(x, y) of a transmitted wavefront transmitted through the measured object is determined by performing the following calculation based on the optical path length distribution. H(x,y)=W_2(x,y)−W_1(x,y)−
(n-1) [W_3(x,y)+W_4(x,y)-W
_1 (x, y)] where n is the refractive index of the object to be measured.