JP2011179950A - Measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a common path type measurement system capable of measuring a three-dimensional shape of a subject without contact with the subject.
A measurement system (100A) is arranged adjacent to a test object, a light source unit 11 for emitting a measurement beam (L1) and a reference beam (L2) serving as a reference for the measurement beam, and the reference beam And a reference beam (13) that reflects the light beam and transmits the measurement beam to the object to be measured, and an interference beam in which the measurement beam reflected by the object to be examined and the reference beam reflected by the reference element interfere with each wavelength. A spectroscopic element (20) for spectroscopic analysis, a detection unit (24) for detecting each wavelength dispersed by the spectroscopic element, an optical path length of a measurement beam from the light source unit to the detection unit via the test object and the spectroscopic element, A measurement optical system (12) having a detour that aligns the optical path length of the reference beam from the light source unit to the detection unit via the reference element and the spectroscopic element is provided.
[Selection] Figure 1

Description

  The present invention relates to a measurement system for measuring a three-dimensional surface shape of a test object.

  Conventionally, as a measurement system, an optical coherence tomography (OCT) apparatus has been widely used. Patent Document 1 suggests that a (common path) interferometer having a common optical path in low coherence interference is difficult.

Japanese Patent No. 40385560

  In Patent Document 1, an interferometer having a common optical path (common path type) is realized by placing a subject directly on a reference glass. This makes it very resistant to vibration, but is only effective for samples such as cells. The interferometer described in Patent Document 1 cannot perform non-contact measurement, and cannot measure the shape of a subject having a depth.

  An object of the present invention is to provide a common path type measurement system capable of measuring a three-dimensional shape of a subject without contact with the subject.

  1st aspect of this invention is a measuring system for measuring the unevenness | corrugation of a to-be-tested object. This measurement system is disposed adjacent to the test object and reflects the reference beam, and a light source unit that emits a measurement beam for measuring the unevenness of the test object and a reference beam that serves as a reference for the measurement beam. A flat reference element that transmits the measurement beam to the test object, and a spectroscopic element that splits the interference beam, which is obtained by interference between the measurement beam reflected by the test object and the reference beam reflected by the reference element, into each wavelength, and A detection unit for detecting the intensity of each wavelength dispersed by the spectroscopic element, an optical path length of the measurement beam from the light source unit to the detection unit via the object to be detected and the spectroscopic element, and a reference element and a spectroscopic element from the light source unit. And a measurement optical system having a detour that aligns the optical path length of the reference beam that reaches the detection unit.

  The measurement system of the present invention can measure the three-dimensional shape of a subject without contact with the subject.

It is the figure which showed the whole structure of 1st measurement system 100A of 1st Embodiment, and is the figure which showed the optical path of the light transmission system. It is the perspective view which showed the light source part. (A) is the side view which looked at the light source part 11 from the + Y-axis direction. (B) is the top view which looked at the light source part 11 from the + Z-axis direction. (A) is an enlarged view of the detour part 22 of 1st Embodiment. (B) is the enlarged view which showed the 2nd detour part 32 of another example. FIG. 2A is an enlarged view of a portion surrounded by a broken line A in FIG. (B) is a BB arrow line view of (a). FIG. 4 is a cross-sectional view of a measurement surface Ho of a test object T viewed from the + Z side, and shows scanning of a measurement beam L1 by a scanning mirror 127. It is the figure which showed the whole structure of 1st measurement system 100A of 1st Embodiment, and is the figure which showed the optical path of the light-receiving system. It is a figure for demonstrating the conjugate relationship of the surface Hi and the surface He. It is another figure for demonstrating the conjugate relationship of the surface Hi and the surface He. It is the graph which showed the relationship between the wavelength of the SLD light source 111, and intensity | strength. It is the figure which showed the range of the Z-axis direction which 100A of 1st measurement systems measure. It is the graph which showed the relationship between the wavelength and intensity | strength of the measurement beam L1. It is the graph which showed the measurement result of the one-dimensional (Y-axis direction) to-be-tested object T obtained by carrying out a one-dimensional Fourier transform of a spectrum. 5 is a graph in which the test object T is moved in the Z-axis direction by the electric stage 15 and a one-dimensional measurement result of the test object T is combined for each movement. FIG. 4 is a diagram showing that the light source unit 11 and the measurement optical system 12 move with respect to the XY plane of the reference element 13. It is the figure which showed the measurement range with respect to the wide area | region in XY plane. It is the figure which showed the whole structure of the 2nd measurement system 100B of 2nd Embodiment, and is the figure which showed the optical path of the light transmission system. It is the figure which showed the whole structure of the 2nd measurement system 100B of 2nd Embodiment, and is the figure which showed the optical path of the light-receiving system. It is the figure which showed the whole structure of 3rd measurement system 100C of 3rd Embodiment, and is the figure which showed the optical path of the light transmission system. It is the figure which showed the whole structure of 3rd measurement system 100C of 3rd Embodiment, and is the figure which showed the optical path of the light-receiving system.

(First embodiment)
The first measurement system 100A of the first embodiment is an example to which a Fizeau interferometer in which the measurement beam L1 and the reference beam L2 have a common optical path is applied.

<Configuration of First Measurement System 100A>
First, the light transmission optical system of the first measurement system 100A will be described with reference to FIGS.
<< Configuration of light transmission optical system >>
FIG. 1 is a diagram illustrating an overall configuration of a first measurement system 100A according to the first embodiment. As shown in FIG. 1, the light transmission optical system of the first measurement system 100 </ b> A includes a light source unit 11, a measurement optical system 12, and a reference element 13. In FIG. 1, a plane parallel to the reference element 13 is defined as an XY plane, and a direction perpendicular to the XY plane is defined as a Z direction.

  In FIG. 1, the optical path from the SLD light source 111 of the measurement beam L1 to the measurement surface Ho of the test object T and the optical path from the SLD light source 111 of the reference beam L2 to the Fizeau surface FM of the reference element 13 are shown.

  The light source unit 11 includes a super luminescent diode (SLD) light source 111 (hereinafter referred to as an SLD light source 111), a half-wave plate 112, a planoconvex cylindrical lens 113, and a planoconvex cylindrical lens 114. Has been.

  Specifically, the light source unit 11 will be described with reference to FIGS. 2 and 3. FIG. 2 is a perspective view showing the light source unit 11. FIG. 3A is a side view of the light source unit 11 viewed from the + Y axis direction, and FIG. 3B is a top view of the light source unit 11 viewed from the + Z axis direction.

  2 and 3, the SLD light source 111 irradiates a broadband low-coherent light having a wavelength band of 850 nm to 900 nm or 1250 nm to 1300 nm, for example. The half width of the SLD light source 111 is preferably 30 nm or more. The half-wave plate 112 has a function of causing a half-wave phase difference in incident light. In the first embodiment, for example, the half-wave plate 112 is arranged so as to be rotated with respect to the optical axis, so that the half-wave plate 112 converts the linearly polarized irradiation light from the SLD light source 111 into P-polarized light and S-polarized light. Sort into polarized light.

  As shown in FIG. 2, the planoconvex cylindrical lens 113 is a convex curved surface facing the + X-axis direction when viewed from the + Y side, and the other surfaces are flat surfaces. Therefore, the plano-convex cylindrical lens 113 can collect the incident beam L with the line S1 as shown in FIG. For this reason, for example, the beam L having a circular cross section passes through the plano-convex cylindrical lens 113 and is emitted as an elliptical beam whose cross section is compressed in the Z-axis direction.

  As shown in FIG. 2, the planoconvex cylindrical lens 114 is a convex curved surface facing the + X-axis direction when viewed from the + Z side, and the other surfaces are flat surfaces. Therefore, the plano-convex cylindrical lens 114 can condense the elliptical beam L incident on the plano-convex cylindrical lens 114 in a straight line. That is, as shown in FIG. 3B, the incident beam L can be condensed in a straight line in the Y-axis direction on the line S1. The YZ plane including the line S1 is drawn as the plane Hi.

  Returning to FIG. 1, the measurement optical system 12 has a bypass 22. The bypass unit 22 will be described with reference to FIG. FIG. 4A is an enlarged view of the bypass unit 22 of the first embodiment, and FIG. 4B is an enlarged view showing a second bypass unit 32 of another example.

  The detour unit 22 shown in FIG. 4A includes two block-shaped polarization beam splitters 121 and 122, and a plane mirror 123 disposed away from the polarization beam splitters 121 and 122 by a distance d in the Z-axis direction. , 124. Here, for example, the polarization beam splitters 121 and 122 pass P-polarized light and reflect S-polarized light, and the polarization planes PM11 and PM12 are inclined by 45 degrees with respect to the X-axis direction. The plane mirrors 123 and 124 are also inclined by 45 degrees with respect to the X-axis direction. The polarization plane PM11 of the polarization beam splitter 121 and the reflection plane RM11 of the plane mirror 123 are arranged apart from each other by a distance d. Similarly, the polarization plane PM12 of the polarization beam splitter 122 and the reflection plane RM12 of the plane mirror 124 are arranged apart from each other by a distance d.

  Hereinafter, a detour route by the detour unit 22 will be described. For ease of explanation, only the optical axis of P-polarized light or S-polarized light that has entered the bypass unit 22 will be described. First, at the point A1 of the polarization plane PM11 of the polarization beam splitter 121, for example, the P-polarized light incident on the bypass unit 22 along the + X-axis direction passes through the polarization plane PM11 as it is, and the S-polarized light passes through the polarization plane PM11. Reflect in the direction.

  The P-polarized light that has passed through the polarization plane PM11 exits from the polarization beam splitter 121 in the + X axis direction at the point B1, and enters the polarization beam splitter 122 at the point C1. Further, the light passes through the point D1 on the polarization plane PM12 of the polarization beam splitter 122 as it is and exits from the detour unit 22.

  On the other hand, the S-polarized light reflected by the polarization plane PM11 exits from the polarization beam splitter 121 in the −Z-axis direction at the point E1, and is reflected again in the + X-axis direction at the point F1 on the reflection surface RM11 of the plane mirror 123. The S-polarized light reflected by the reflecting surface RM11 of the plane mirror 123 is also reflected by the point J1 on the reflecting surface RM12 of the plane mirror 124 and is incident on the polarizing beam splitter 122 at the point K1 in the + Z axis direction. The S-polarized light incident on the polarization beam splitter 122 is reflected by the polarization plane PM12 and is emitted from the detour unit 22 in the same direction as the + X axis when entering the detour unit 22.

  Here, in the line segment F1-J1, the point G1 is an intersection of the vertical line from the point B1 to the line segment F1-J1 and the line segment F1-J1, and the point H1 is from the point C1 to the line segment F1-J1. This is the intersection of the vertical line and the line segment F1-J1.

Therefore, the optical path of P-polarized light is as follows.
Distance in glass Distance in air A1-B1 = d2 B1-C1
C1-D1 = d2
---------------------
Total 2 x d2 Total B1-C1

On the other hand, the optical path of S-polarized light is as follows.
Distance in glass Distance in air A1-E1 = d3 E1-F1 = d1
K1-D1 = d3 F1-G1 = d2
G1-H1
H1-J1 = d2
J1-K1 = d1
------------------------------------
Total 2 × d3 Total 2 × (d1 + d2), G1-H1 (= B1-C1)

  Here, from d2 = d3, the difference in the distance in the glass is 0, and the difference in the distance in the air is 2 × (d1 + d2) = 2 × (d1 + d3) = 2 × d. Therefore, the optical path length due to the detouring of the S-polarized light is longer by 2d than the P-polarized light.

  Further, the bypass unit 22 of the measurement optical system 12 may have the configuration of the second bypass unit 32 as shown in FIG. The second bypass 32 is composed of one or two or more glass blocks. The second detour path 32 has polarization planes PM21 and PM22 that pass through one of P-polarized light and S-polarized light and reflect the other, and also have reflective surfaces RM21 and RM22. The polarization planes PM21 and PM22 are inclined 45 degrees with respect to the X-axis direction. The reflective surfaces RM21 and RM22 are also inclined 45 degrees with respect to the X-axis direction. The polarization plane PM1 and the reflection surface RM21 are disposed apart by a distance d, and the deflection surface PM22 and the reflection surface RM22 are disposed apart by a distance d.

  According to the description of the detour unit 22 described above, the length d2 and the length d3 are the same. Therefore, the optical path length detoured in the second detour unit 32 is the line segment C2-D2, the line segment D2-H2, and the line segment H2. -The total length of E2 and line segment E2-F2. That is, the detoured optical path length is twice (d1 + d2). If the length (d1 + d3) is the length d, the detoured optical path length is 2d.

  Returning to FIG. 1 again, the relay lens 125, the half beam splitter 126, and the scanning mirror 127 are sequentially arranged on the + X side of the bypass unit 22, and another relay lens 128 is arranged on the −Z side of the scanning mirror 127. ing. Here, the scanning mirror 127 is vibrated along the arrow AR about the vibration axis O by a driving unit (not shown). The two relay lenses 125 and 128 may be lenses having the same focal length. Both sides are telecentric. Further, the vibration axis O of the scanning mirror 127 is disposed at a position where the + X side focal position of the relay lens 125 coincides with the + Z side focal position of the relay lens 128.

  The reference element 13 may be a wire grid having a Fizeau surface FM, for example. The wire grid is a glass plate on which wires (or grooves) arranged in parallel at intervals sufficiently smaller than the wavelength of the beam L are formed. The wire grid can transmit the measurement beam L1 and reflect the reference beam L2. Here, the Fizeau surface FM of the reference element 13 and the measurement surface Ho are separated by a distance d.

<< Description of optical path of light transmission optical system >>
As shown in FIG. 1, the beam L from the SLD light source 111 is divided into P-polarized light and S-polarized light by the half-wave plate 112. Then, the light passes through the plano-convex cylindrical lens 113 and the plano-convex cylindrical lens 114 and is condensed on a line S1 extending in the Y-axis direction.

  The beam L distributed to the P-polarized light and the S-polarized light is incident on the polarization beam splitter 121 of the measurement optical system 12. Then, for example, the measurement beam L1 which is P-polarized light passes through the polarization beam splitters 121 and 122 and enters the relay lens 125. The reference beam L2 that is S-polarized light is reflected by the polarizing beam splitter 121 in the −Z-axis direction. The reference beam L 2 reflected by the polarization beam splitter 121 is sequentially reflected by the plane mirror 123 and the plane mirror 124 and enters the polarization beam splitter 122. The reference beam L2 incident on the polarization beam splitter 122 is reflected by the polarization beam splitter 122 and enters the relay lens 125 along the same optical path as the measurement beam L1.

  Since the reference beam L2 is detoured in the detour unit 22 as compared with the measurement beam L1, the optical path length of the reference beam L2 in the detour unit 22 is approximately 2d from the optical path length of the measurement beam L1 in the detour unit 22. It is getting longer.

  The measurement beam L1 and the reference beam L2 that have passed through the relay lens 125 pass through the half beam splitter 126 and enter the scanning mirror 127. The axis Ax of the measurement beam L1 and the reference beam L2 is changed from the + X axis direction to the −Z side by reflection of the scanning mirror 127. The measurement beam L1 and the reference beam L2 in which the axis Ax is directed to the −Z side are changed in the −Z axis direction by the relay lens 128 and are incident on the reference element 13.

  Here, as described above, the measurement beam L1 and the reference beam L2 generate a distance difference of about 2d by the bypass unit 22. For this reason, the measurement beam L1 is condensed at a condensing point T1 on the measurement surface Ho which is a distance d away from the Fizeau surface FM of the reference element 13 on the −Z side. On the other hand, the reference beam L2 is condensed at a condensing point T2 on the reference surface Hb that is a distance d away from the Fizeau surface FM of the reference element 13 on the + Z side. In FIG. 1, although it is drawn by the condensing point T1 and the condensing point T2, the measurement beam L1 and the reference beam L2 are condensed in a straight line extending along the Y-axis direction (see FIG. 5). .

  The measurement beam L1 incident on the reference element 13 passes through the reference element 13 and is reflected by the test object T. The reference beam L2 is reflected by the Fizeau surface FM of the reference element 13. The distance d from the condensing point T1 of the measurement beam L1 to the Fizeau surface FM of the reference element 13 is the same as the distance d from the condensing point T2 of the reference beam L2 to the Fizeau surface FM of the reference element 13. The reflected beam from the portion of the measuring beam L1 at the condensing point T1 of the object T and the reflected beam at the Fizeau surface FM of the reference element 13 of the reference beam L2 are emitted from the same location. Since the optical path lengths of the measurement beam L1 and the reference beam L2 are also equal, the measurement beam L1 and the reference beam L2 interfere even with low-coherent light, as will be described later. Specifically, this will be described with reference to FIGS.

  5A is an enlarged view of a portion surrounded by a broken line A in FIG. 1, and FIG. 5B is a view taken along the line BB in FIG. 5A. FIG. 6 is a cross-sectional view of the measurement surface Ho of the test object T viewed from the + Z side, and is a diagram illustrating scanning of the measurement beam L1 by the scanning mirror 127.

  As shown in FIG. 5A, the measurement beam L1 passes, for example, the Fizeau surface FM of the reference element 13 and is separated from the Fizeau surface FM of the reference element 13 by a distance d on the −Z side (measurement point T1 (measurement). Condensed at surface Ho). Further, the reference beam L2 is condensed at a condensing point T2 that is a distance d away from the Fizeau surface FM of the reference element 13 on the + Z side, and then reflected by the Fizeau surface FM of the reference element 13.

  Therefore, the measurement beam L1 reflected from the portion of the test object T at the condensing point T1 and the reference beam L2 reflected from the Fizeau surface FM of the reference element 13 overlap each other, as if the measurement beam L1 and the reference beam L2 Is emitted from the condensing point T1.

  Further, when the measurement beam L1 and the reference beam L2 are viewed from the + X axis direction, they are as shown in FIG. 5B. That is, the measurement beam L1 passes through the reference element 13 and is reflected by the test object T, and the reference beam L2 is reflected by the Fizeau surface FM of the reference element 13.

  Further, as shown in FIG. 6, the first measurement system 100A can measure the test object T more widely in the X-axis direction on the measurement surface Ho by vibrating the scanning mirror 127.

  For example, when the linear measurement beam L1 irradiates the measurement position P1 (x = x0), the height (Z-axis direction) of the test object T at the measurement position P1 can be measured. Further, when the measurement beam L1 irradiates the measurement position P2 (x = + x1) by the vibration of the scanning mirror 127, the height of the test object T at the measurement position P1 can be measured. That is, the measurement beam L1 can measure the region from the measurement position P2 (x = + x1) to the measurement position P3 (x = −x1) by vibrating the scanning mirror 127.

<< Configuration of light receiving optical system >>
Next, the light receiving optical system of the first measurement system 100A will be described with reference to FIG.
FIG. 7 is a diagram showing the overall configuration of the first measurement system 100A shown in FIG. 1, and the optical path from the measurement surface Ho of the test object T of the measurement beam L1 to the detection unit 24 and the reference element of the reference beam L2 It is the figure which showed the optical path from the 13 Fizeau surface FM to the detection part 24.

  As shown in FIG. 7, the relay lens 16 is further provided on the + Z side of the half beam splitter 126. A slit plate 17 in which slit holes are formed so as to remove stray light is provided at the point S2 which is the focal position in the + Z-axis direction of the relay lens 16. Here, the XY plane including the point S2 is defined as a plane He. Further, on the + Z side of the slit plate 17, a relay lens 18 whose focal position is matched with the position of the slit plate 17 (point S2) is disposed.

  A polarizer 19 and a spectroscopic element 20 are sequentially provided in the + Z-axis direction of the relay lens 18. Here, the polarizer 19 transmits a common polarization component from P-polarized light and S-polarized light. The spectroscopic element 20 may be, for example, a reflection type diffractive optical element that diffracts at an angle corresponding to the spectrum of the interfered beam. An imaging lens 21 is disposed on the −X side of the spectroscopic element 20, and a detection unit 24 is disposed at a focal position on the −X side of the imaging lens 21. Here, as the detection unit 24, for example, an InGaAs image sensor, a CCD (Charge Coupled Device) image sensor, and a CMOS image sensor are two-dimensionally arranged.

<< Optical path of light receiving optical system >>
As shown in FIG. 7, the measurement beam L1 reflected by the test object T and the reference beam L2 reflected by the Fizeau surface FM of the reference element 13 are again measured as if they were emitted from the same location. Twelve relay lenses 128 enter. The measurement beam L1 and the reference beam L2 that have passed through the relay lens 128 are reflected by the scanning mirror 127 and enter the half beam splitter 126. Then, the measurement beam L1 and the reference beam L2 are reflected by the half beam splitter 126 and emitted along the + Z-axis direction.

  The measurement beam L1 and the reference beam L2 emitted from the half beam splitter 126 are incident on the polarizer 19. The polarizer 19 transmits a common polarization component from the measurement beam L1 that is P-polarized light and the reference beam L2 that is S-polarized light. Since the optical path length from the surface Hi to the polarizer 19 of the measurement beam L1 and the optical path length from the surface Hi to the polarizer 19 of the reference beam L2 are aligned, the measurement beam L1 and the reference beam L2 are low coherent light. Even they interfere with each other.

  The interfering measurement beam L1 and reference beam L2 are collected by the relay lens 16 and become a straight line extending in the Y-axis direction at the position of the slit hole (surface He) of the slit plate 17. Further, the stray light contained in the measurement beam L1 and the reference beam L2 is removed by the slit plate 17.

  Here, by providing the detour unit 22, the surface Hi and the surface He have a conjugate relationship with respect to both of the optical paths of the measurement beam L1 and the reference beam L2, and the optical path lengths of both are the same. Light can be condensed on the surface He. The conjugate relationship between the surface Hi and the surface He will be described in detail with reference to FIGS.

  The interference beam IL from which the stray light is removed by the slit plate 17 has a wide band (for example, 30 nm or more), and is split at an angle corresponding to the wavelength by the spectroscopic element 20 such as a diffractive optical element.

  The interference beam IL dispersed according to the wavelength passes through the imaging lens 21 and enters the detection unit 24 to form an image. The detection unit 24 detects the interference beams IL spectrally separated by the spectroscopic element 20.

Hereinafter, the projection optical system using the relay lens 125, the relay lens 128, and the relay lens 16 relating to the conjugate relationship between the surface Hi and the surface He will be described in detail.
First, returning to FIG. 1, in order to remove interference and stray light, the optical path length along the measurement beam L1 from the point S1 (showing the line S1) of the surface Hi to the slit plate 17 through the condensing point T1, and the surface It is necessary to make the optical path length along the reference beam L2 from the Hi point S1 through the condensing point T2 to the slit plate 17 equal.

  When the optical path length along the measurement beam L1 from the relay lens 128 to the condensing point T1 is compared with the optical path length along the reference beam L2 from the relay lens 128 to the condensing point T2, the former is 2d longer. For this reason, by adding an extra optical path length of 2d to the S-polarized reference beam L2 by the bypass unit 22 (see FIG. 4A), the surface Hi point S1 in the measurement beam L1 and the reference beam L2 The condensing point T1 and the condensing point T2 become conjugate, and the optical path lengths from the point S1 on the surface Hi to the condensing point T1 and the condensing point T2 are made uniform.

  1 and 7, the optical path length from the condensing point T1 to the slit plate 17 (surface He) is equal to the optical path length from the condensing point T2 to the slit plate 17 (surface He).

  Furthermore, in order to obtain a clear contrast of the interference fringes, the condensing point T1 of the measurement beam L1 and the slit plate 17 (surface He) are conjugate, and the condensing point T2 of the reference beam L2 and the slit plate 17 ( The plane He) is preferably conjugate.

  The conjugate relationship is realized by a relay optical system including the relay lens 125 and the relay lens 128 or a relay optical system including the relay lens 128 and the relay lens 16. However, in order to establish a conjugate relationship with the above-described same optical path length condition at an arbitrary value of d, it is desirable to provide the focal lengths of the relay lens 125 and the relay lens 128 at equal positive values. Further, when the relay lens 125 and the relay lens 128 are each expressed as a thin lens, the arrangement interval between the relay lens 125 and the relay lens 128 and between the relay lens 128 and the relay lens 16 is twice the focal length. It is necessary to be. Hereinafter, the reason will be described with reference to FIGS.

In FIG. 8, the relay lens 125 and the relay lens 128 will be described using the thin lens 700 as an example for the sake of simplicity. For the thin lens 700 having the focal length f shown in FIG. 8, the Newton equation (1) below is established.
x * x '= f ² (1)

  The sign of x is positive when the object point Ob is on the left side of the focal point F, and the sign of x 'is positive when the image point I is on the right side of the focal point F'.

Next, for the sake of simplicity, FIG. 9 also considers a thin lens, and a thin lens 701 having a focal length f and a thin lens 702 having a focal length f are arranged at an interval 2f. For the thin lens 701, the Newton equation (2) is established.
x ₁ * x ₁ '= f ² ... (2)

For the thin lens 702, the Newton equation (3) is established.
x ₂ * x ₂ '= f ² (3)

Here, if the object point Ob is on the left side from the left side focal point F1 of the thin lens 701, 'it is possible to right, not shown x _1' intermediate image by a thin lens 701 is not shown object point Ob focus F1 of The sign satisfies Equation (4).
x ₁ '> 0 ... (4)

Although not shown for the _{x 2,} equation (5) is satisfied.
x ₁ '= −x ₂ (5)

Therefore, if Formula (5) is substituted into Formula (3) and compared with Formula (2), Formula (6) is obtained.
x ₁ = −x ₂ '(6)

  That is, the distance between the object point Ob and the image point I formed by the thin lens 701 and the thin lens 702 is 4f uniformly regardless of the position of the object point Ob.

Next, the projection magnification M between the object point Ob and the image point I is as in Expression (7).
(7)
In other words, the value is equal to 1 regardless of the position of the object point Ob.

  Further, if the principal ray of the object-image projection light beam passes through the focal point F1 ′ or the focal point F2, all the principal ray groups incident on the thin lens 701 from the object point Ob are naturally parallel to the optical axis, and the thin lens 702 All the principal ray groups from the lens to the image point I are also parallel to the optical axis. That is, it becomes both telecentric.

  Here, when the above relationship is applied to the light transmission optical system shown in FIG. 1, the thin lens 701 corresponds to the relay lens 125, and the thin lens 702 corresponds to the relay lens 128.

  Each focal length is set to an equal positive value. In FIG. 1, when the relay lens 125 and the relay lens 128 are expressed as thin lenses, the lens interval is arranged between the relay lens 125 and the relay lens 128. The length of the optical path in the half prism 126 is converted to air, and is equivalently set to twice the focal length. The object point Ob corresponds to the point S1, and the image point I corresponds to the condensing point T1 or the condensing point T2.

  The difference between the optical path length corresponding to x1 in FIG. 9 regarding the optical path length of the measurement beam L1 and the optical path length corresponding to x1 corresponding to the optical path length of the reference beam L2 is the detour distance 2d generated by the detour unit 22 in FIG. Similarly, the difference between x2 ′ for the optical path length of the measurement beam L1 and x2 ′ for the optical path length of the reference beam L2 corresponds to the optical path difference 2d between the condensing points T1 and T2 in FIG. . That is, the optical path length from the point S1 to the condensing point T1 is always equal to the optical path length from the point S1 to the condensing point T2. The projection magnification is always maintained at 1 × regardless of the detour optical path length.

  As described with reference to FIG. 9, if the light beam passing through the point S1 is telecentric, the light beam emitted from the relay lens 128 is also telecentric. As shown in FIG. 3, if the beam L condensed linearly toward the plane Hi including the point S1 is made to be a parallel light beam in the XY plane, any principal ray is parallel to the axis Ax. Therefore, the projection optical system formed by the relay lens 125 and the relay lens 128, or the relay lens 128 and the relay lens 16 are both telecentric. It goes without saying that both telecentricity can be achieved by installing an aperture stop at a common focal position of the relay lens 125 and the relay lens 128, a common focal position of the relay lens 128 and the relay lens 16, or a conjugate position thereof.

  Therefore, the scanning mirror 127 is installed so that the reflection surface and the vibration axis O include the common focus of the relay lens 125 and the relay lens 128. For this reason, even if the angle around the vibration axis O of the scanning mirror 127 changes, the principal ray of the light beam passes through the focal point of the relay lens 128 and therefore remains parallel to the optical axis of the relay lens 128. The telecentricity of the light flux toward T and the reference element 13 is maintained.

<Electric stage 15 of first measurement system 100A>
The first measurement system 100A has a table 14 on which the test object T is placed. The table 14 has an electric stage 15 that can drive the table 14 along the Z-axis direction as indicated by an arrow AR1. Further, a distance sensor device EX for detecting a relative distance between the reference element 13 and the table 14 is further provided.

<Calculation unit 23 of first measurement system 100A>
The calculation unit 23 of the first measurement system 100A calculates the three-dimensional shape of the test object T based on the result of the detection unit 24 detecting the spectrum as the interference signal. As shown in FIG. 7, the calculation unit 23 includes a conversion unit 231 and a distance combination unit 232.

  The conversion unit 231 calculates the position of the test object T in the Z-axis direction by performing a one-dimensional Fourier transform on the detected interference signal of the spectrum. When the table 14 on which the test object T is placed is moved in the Z-axis direction by the motorized stage 15, the distance combination unit 232 and the table detected by the distance sensor device EX and the distance between the unevenness converted by the conversion unit 231. Combined with 14 travel distances. Specifically, this will be described with reference to FIGS.

  FIG. 10 is a graph showing the relationship between the wavelength and intensity of the SLD light source 111. FIG. 11 is an enlarged view showing a range in the Z-axis direction measured by the first measurement system 100A. Here, the measurement range is a measurement range when the measurement beam L1 is at the measurement position P1 (x = x0) shown in FIG. 6, for example.

  As shown in FIG. 10, the SLD light source 111 has a wavelength range of λ0 to λ3, and the relationship graph between the wavelength and the intensity is generally mountain-shaped. The wavelengths λ1 and λ2 belong to the wavelength range λ0 to λ3. FIG. 11 is an enlarged view when irradiating the test object T with the SLD light source 111 as shown in FIG.

  In FIG. 11, the measurement range in the Z-axis direction of the first measurement system 100A is from the measurement surface Ho to the surface H1 that is separated by a minute distance ΔZ in the −Z-axis direction. The minute distance ΔZ from the measurement surface Ho to the surface H1 varies depending on the wavelength resolution of the spectroscopic system including the spectroscopic element 20, the imaging lens 21, and the detection unit 24, and is, for example, about several millimeters at most.

  FIG. 12 is a graph showing the relationship between the intensity distribution with respect to the wavelength at the measurement point T21 or the measurement point T22 of the measurement beam L1. As shown in FIG. 12, the relationship between the wavelength and the intensity distribution is a shape close to a sine waveform. Further, the reason why the whole is a mountain shape is that it reflects the wavelength spectrum of the SLD light source 111 itself shown in FIG. Furthermore, the detection unit 24 detects the relationship between the wavelength and the intensity distribution.

  When detecting the interference beam IL, the detection unit 24 detects an intensity distribution as shown in the graph of FIG. Then, the height of the test object T in the Z-axis direction can be obtained by performing a one-dimensional Fourier transform on the spectrum obtained by the conversion unit 231 (see FIG. 7).

  Therefore, the conversion unit 231 performs a one-dimensional Fourier transform of the spectrum for each of a plurality of measurement points (points in the Y-axis direction including T21 and T22), so that the range within the minute distance ΔZ as shown in FIG. The measurement result in the Y-axis direction (x = x0) is obtained. The range of the minute distance ΔZ varies depending on the wavelength resolution of the spectroscopic system including the spectroscopic element 20, the imaging lens 21, and the detection unit 24, but is, for example, about several millimeters at most. When the height of the test object T (Z-axis direction) is not less than the range of the minute distance ΔZ, the height of the test object T cannot be measured. In FIG. 13, only the height of a part of the test object T can be measured. Therefore, the electric stage 15 moves the table 14 on which the test object T is placed by a distance smaller than the minute distance ΔZ in the Z-axis direction. This moving distance is detected by the distance sensor device EX. The detection unit 24 detects the interference beam IL while the table 14 is moved. The distance combination unit 232 (see FIG. 7) is based on the minute unevenness information converted by the conversion unit 231 and the distance detected by the distance sensor device EX on the YZ plane as shown in FIG. An overall graph of the test object T can be obtained.

  10 to 14, only the case where the measurement beam L1 extending in the Y-axis direction is at the measurement position P1 (x = x0) has been described. However, the measurement beam L1 is measured from the measurement position P2 (x = + x1) by the scanning mirror 127. By scanning to the measurement position P3 (x = −x1), the first measurement system 100A also obtains the height of the test object T in the X-axis direction.

<Wide area measurement on XY plane>
FIG. 15 is a diagram illustrating that the light source unit 11 and the measurement optical system 12 surrounded by a broken line C move in parallel to the XY plane of the reference element 13. FIG. 16 is a diagram illustrating a measurement range with respect to a wide area of the test object T on the XY plane.

  When the test object T is large on the XY plane, the range in which the measurement beam L1 is scanned by the scanning mirror 127 and the relay lens 128 may be exceeded. In such a case, it is preferable to move the light source unit 11 and the measurement optical system 12 integrally in parallel with the XY plane of the reference element 13. The first measurement system 100A shown in FIG. 15 has a plane moving unit 25 that moves the light source unit 11 and the measurement optical system 12 in the X-axis direction indicated by the arrow AR2 or in the X-axis direction indicated by the arrow AR3. is doing. The plane moving unit 25 is a plane drive stage including, for example, a linear guide and a stepping motor.

  In addition, the calculation unit 23 of the first measurement system 100 </ b> A further includes a plane combination unit 233. When the measurement beam L1 and the reference beam L2 are moved on the XY plane, the plane combination unit 233 combines the shapes of the large test object T on the XY plane by combining the distances moved by the plane moving unit 25.

  In the first measurement system 100A, the scanning range of the measurement beam L1 and the measurement beam L2 is also moved by moving the light source unit 11, the measurement optical system 12, and the like along the XY plane by the plane moving unit 25. Therefore, the measurement range in the XY plane of the first measurement system 100A can be made wider. As shown in FIG. 15, the reference element 13 is fixed to, for example, the bottom surface of the electric stage 15, and the relative position between the reference element 13 and the XY plane of the test object T does not change.

  For example, FIG. 16 shows a rectangular test object Tm having a large area. Further, the scanning mirror 127 (FIG. 15) scans the measurement beam L1, so that the first measurement system 100A measures the rectangular measurement area DA shown in FIG.

  When the plane moving unit 25 moves the measurement optical system 12 and the like along the XY plane (see FIG. 15), the entire shape of the test object Tm can be measured. Specifically, when the measurement area DA moves along the arrow AR2, the first measurement system 100A can measure the measurement area DA1. Similarly, when the measurement area DA is moved along the arrow AR2 and measured to the end of the test object Tm, the measurement area DA1 is further moved along the arrow AR3. Then, the first measurement system 100A can measure the measurement area DA2. And then. The plane combination unit 233 can measure the entire test object Tm by superimposing the measurement data corresponding to the measurement areas DA, DA1,.

(Second Embodiment)
<Light Transmitting Optical System of Second Measurement System 100B>
First, the light transmission optical system of the second measurement system 100B will be described with reference to FIG. Here, the same constituent elements as those in the first embodiment will be described with the same reference numerals.
<< Configuration of light transmission optical system >>
FIG. 17 is a diagram illustrating an overall configuration of the second measurement system 100B of the second embodiment. FIG. 17 shows an optical path from the SLD light source 111 of the measurement beam L1 to the measurement surface Ho of the test object T and an optical path from the SLD light source 111 of the reference beam L2 to the Fizeau surface FM of the reference element 13.

  As shown in FIG. 17, the light transmission optical system of the second measurement system 100 </ b> B includes the light source unit 11, the measurement optical system 42, and the reference element 13. In particular, since the measurement optical system 42 is different from the first embodiment, the configuration thereof will be described.

  The measurement optical system 42 includes a half beam splitter 421, two relay lenses 422 and 423 having the same focal length, and a scanning mirror 424. Here, the beam incident on the scanning mirror 424 in the XZ plane can be deflected by causing the scanning mirror 424 to vibrate along the arrow AR about the vibration axis O by a driving unit (not shown).

<< Optical path of light transmission optical system >>
As shown in FIG. 17, the beam L from the SLD light source 111 is divided into P-polarized light and S-polarized light by the half-wave plate 112. Then, the light passes through the plano-convex cylindrical lens 113 and the plano-convex cylindrical lens 114, and is condensed at a point S3 (a straight line extending along the Y-axis direction) on the XZ plane. At this time, the YZ plane including the point S3 is defined as a plane Hi.

  The beam L (measurement beam L1 and reference beam L2) distributed to the P-polarized light and the S-polarized light passes through the half beam splitter 421 and enters the relay lens 422. Then, the beam L is condensed by the relay lens 422 and enters the scanning mirror 424, and is reflected by the scanning mirror 424 as the beam L with the axis Ax directed to the −Z side.

  The beam L emitted from the measurement optical system 42 is incident on the reference element 13 provided on the −Z side. At this time, for example, the measurement beam L1 that is P-polarized light passes through the reference element 13 and enters the test object T, and the reference beam L2 that is S-polarized light is reflected by the Fizeau surface FM of the reference element 13.

  Further, the measurement beam L1 incident on the test object T is focused on the XZ plane of the test object T, which is a distance d away from the Fizeau surface FM of the reference element 13 on the −Z side (along the Y-axis direction). Condensing in a straight line extending For this reason, the optical path length of the measurement beam L1 is formed longer than the optical path length of the reference beam L2 by a distance d.

<Light receiving optical system of second measurement system 100B>
Next, the light receiving optical system of the second measurement system 100B will be described with reference to FIG.
<< Configuration of light receiving optical system >>
FIG. 18 is a diagram illustrating an overall configuration of a second measurement system 100B according to the second embodiment. FIG. 18 shows an optical path from the measurement surface Ho of the test object T of the measurement beam L1 to the detection unit 24 and an optical path of the reference beam L2 from the Fizeau surface FM of the reference element 13 to the detection unit 24.

  As shown in FIG. 18, the measurement optical system 42 further includes a bypass unit 52. In FIG. 18, the detour path 52 includes two polarizing beam splitters 425 and 426 and plane mirrors 427 and 428 arranged at a distance d from the polarizing beam splitters 425 and 426 in the X-axis direction, respectively. Here, the polarization beam splitters 425 and 426 pass, for example, P-polarized light and reflect S-polarized light. Further, the bypass unit 52 of the measurement optical system 42 may have the shape of the second bypass unit 32 that is integrally configured with blocks as shown in FIG. 4 of the first embodiment.

  As shown in FIG. 18, the second measurement system 100B strays to a point S4 (a straight line extending along the Y-axis direction) that is the focal position of the + Z-side relay lens 422 of the bypass unit 52 of the measurement optical system 42. A slit plate 17 is provided so as to remove.

<< Optical path of light receiving optical system >>
As shown in FIG. 18, the measurement beam L <b> 1 reflected by the test object T enters the relay lens 423. Further, the reference beam L <b> 2 reflected by the Fizeau surface FM of the reference element 13 also enters the relay lens 423. Accordingly, the optical path length of the measurement beam L1 is longer than the optical path length of the reference beam L2 by a reciprocal distance 2d from the reference element 13 to the measurement surface Ho. The measurement beam L1 and the reference beam L2 that have passed through the relay lens 422 are reflected to the + Z side by the half beam splitter 421 and enter the detour unit 52.

  The measurement beam L <b> 1 and the reference beam L <b> 2 are incident on the polarization beam splitter 425 of the bypass unit 52, and the measurement beam L <b> 1 that is, for example, P-polarized light passes through the polarization beam splitter 425. The reference beam L2 that is S-polarized light is reflected by the polarization beam splitter 425 in the −X-axis direction. The reference beam L2 reflected by the polarization beam splitter 425 is sequentially reflected by the plane mirror 427 and the plane mirror 428, and enters the polarization beam splitter 426 in the + X axis direction. The reference beam L2 incident on the polarization beam splitter 426 is reflected by the polarization beam splitter 426 and exits the bypass unit 52 along the same direction as the measurement beam L1 that has passed through the polarization beam splitter 426, that is, the + Z axis direction. The measurement beam L1 and the reference beam L2 emitted from the bypass unit 52 are collected at a point S4 that is the focal position of the relay lens 422.

  Here, since the reference beam L2 has been detoured by the distance 2d in the detour part 52, the optical path length is formed in the detour part 52 by a distance 2d longer than the optical path length of the measurement beam L1 (see FIG. 4A). reference). For this reason, as can be seen from the description of the light transmitting optical system and the light receiving optical system described above, by providing the detour unit 52, the surface Hi and the surface He are provided for both the measurement beam L1 and the reference beam L2. And the optical path length of both are equal.

(Third embodiment)
<Light Transmitting Optical System of Third Measurement System 100C>
First, the light transmission optical system of the third measurement system 100C will be described with reference to FIG. Here, the same components as those in the first embodiment are denoted by the same reference numerals.
<< Configuration of light transmission optical system >>
FIG. 19 is a diagram illustrating an overall configuration of a third measurement system 100C according to the third embodiment. FIG. 19 shows the optical path from the SLD light source 111 of the measurement beam L1 to the measurement surface Ho of the test object T and the optical path from the SLD light source 111 of the reference beam L2 to the Fizeau surface FM of the reference element 13.

  As illustrated in FIG. 19, the light transmission optical system of the third measurement system 100 </ b> C includes the light source unit 11, the measurement optical system 62, and the reference element 13. In the third embodiment, the distance from the Fizeau surface FM of the reference element 13 to the measurement surface Ho is 2d, which is particularly different from the first embodiment or the second embodiment.

  The measurement optical system 62 includes a bypass unit 72, two relay lenses 625 and 627 having the same focal length, and a scanning mirror 626. In FIG. 19, the detour 72 includes a half beam splitter 621, a polarizing beam splitter 622, and the half beam splitter 621 and the polarizing beam splitter 622, and plane mirrors 623 and 624 arranged at a distance d in the Z-axis direction. Each has. Here, the polarization beam splitter 622 passes, for example, P-polarized light and reflects S-polarized light. Further, the bypass portion 72 of the measurement optical system 62 may be integrally formed as shown in FIG. 4 of the first embodiment.

  A relay lens 625 and a scanning mirror 626 are sequentially arranged on the + X side of the bypass unit 72. Another relay lens 627 is disposed on the −Z side of the scanning mirror 626. Here, the scanning mirror 626 is vibrated along the arrow AR about the vibration axis O by a driving unit (not shown), thereby deflecting the beam incident on the scanning mirror 626 in the XZ plane.

  Further, the scanning mirror 626 is arranged on the focal plane on the + Z side of the relay lens 627, and the focal plane on the −Z side of the relay lens 627 becomes the measurement plane Ho of the third measurement system 100C.

<< Optical path of light transmission optical system >>
As shown in FIG. 19, the beam L from the SLD light source 111 is divided into P-polarized light and S-polarized light by the half-wave plate 112. Then, the light passes through the plano-convex cylindrical lens 113 and the plano-convex cylindrical lens 114 and is condensed at a point S5 (a straight line extending along the Y-axis direction) on the XZ plane. A YZ plane including the point S5 is defined as a plane Hi.

  The beam L (measurement beam L1 and reference beam L2) distributed to the P-polarized light and the S-polarized light is incident on the half beam splitter 621 of the measurement optical system 62, and a part of the beam L passes through the half beam splitter 621. The remainder of the beam L is reflected to the −Z side by the half beam splitter 621.

  In the beam L (measurement beam L1 and reference beam L2) that has passed through the half beam splitter 621 and entered the polarization beam splitter 622, only the P-polarized component contained therein passes through the polarization beam splitter 622, and the + X axis direction The measurement beam L1 heads toward. The S-polarized component is reflected in the + Z direction and absorbed by a light absorber (not shown). On the other hand, the beam L (measurement beam L1 and reference beam L2) reflected by the half beam splitter 621 is sequentially reflected by the plane mirror 623 and the plane mirror 624 and enters the polarization beam splitter 622 in the + Z-axis direction. Of the beam L incident on the polarization beam splitter 622 from the −Z side, only the S-polarized component contained therein is reflected by the polarization beam splitter 622 and becomes a reference beam L2 directed in the + X-axis direction. The P-polarized component passes in the + Z direction and is absorbed by a light absorber (not shown).

  Here, since the reference beam L2 is detoured in the detour unit 72, the optical path length of the reference beam L2 in the detour unit 72 is longer than the optical path length of the measurement beam L1 in the detour unit 72 by a distance 2d. Yes.

  The measurement beam L1 and the reference beam L2 that have passed through the relay lens 625 are incident on the scanning mirror 626. The axis Ax of the measurement beam L1 and the reference beam L2 is changed from the + X axis direction to the −Z side by reflection of the scanning mirror 626. The measurement beam L1 and the reference beam L2 whose axis Ax is directed to the −Z side are changed in the −Z axis direction by the relay lens 627 and are incident on the reference element 13.

  Here, as described above, the measurement beam L1 and the reference beam L2 have an optical path length difference of 2d by the bypass unit 72. For this reason, the measurement beam L1 is condensed at a condensing point T1 (a straight line extending along the Y-axis direction) on the measurement surface Ho which is a distance 2d away from the Fizeau surface FM of the reference element 13 on the −Z side. L2 is condensed at a condensing point T2 (a straight line extending along the Y-axis direction) of the Fizeau surface FM of the reference element 13. In addition, the measurement beam L1 incident on the reference element 13 passes through the reference element 13 and is reflected by the test object T, and the reference beam L2 is reflected by the Fizeau surface FM of the reference element 13.

<Light receiving optical system of third measurement system 100C>
Next, the light receiving optical system of the third measurement system 100C will be described with reference to FIG.
<< Configuration of light receiving optical system >>
FIG. 20 is a diagram illustrating an overall configuration of a third measurement system 100C according to the third embodiment. FIG. 20 shows an optical path from the measurement surface Ho of the test object T of the measurement beam L1 to the detection unit 24 and an optical path of the reference beam L2 from the Fizeau surface FM of the reference element 13 to the detection unit 24.

  As shown in FIG. 20, the third measurement system 100C has a point S6 (a straight line extending along the Y-axis direction) that is the focal position of the + Z side relay lens 625 of the half beam splitter 621 of the measurement optical system 62. A slit plate 17 is provided so as to remove stray light. An XY plane including the point S6 is defined as a plane He. Further, a relay lens 18 whose focal position is adjusted to the position of the slit plate 17 is disposed on the + Z side of the slit plate 17.

<< Optical path of light receiving optical system >>
As shown in FIG. 20, the measurement beam L <b> 1 reflected by the test object T and the reference beam L <b> 2 reflected by the Fizeau surface FM of the reference element 13 are incident on the relay lens 627 of the measurement optical system 62 again. Here, since the distance from the Fizeau surface FM of the reference element 13 to the measurement surface Ho of the test object T is 2d, the measurement beam L1 is 2d from the reference beam L2 together with the detour of the above-described light transmission optical system. Only a long optical path length. Further, the measurement beam L1 and the reference beam L2 that have passed through the relay lens 627 are reflected to the −X side by the scanning mirror 626 and are incident on the bypass unit 72 again.

  The measurement beam L 1 that is P-polarized light that has entered the bypass unit 72 passes through the polarization beam splitter 622 as it is and enters the half beam splitter 621. On the other hand, the reference beam L2, which is S-polarized light that has entered the bypass unit 72, is reflected by the polarization beam splitter 622, is sequentially reflected by the plane mirror 624 and the plane mirror 623, and enters the half beam splitter 621 in the + Z-axis direction. To do. Then, the measurement beam L1 reflected by the half beam splitter 621 and the reference beam L2 that has passed through the half beam splitter 621 are emitted from the detour unit 72 along the + Z direction. The measurement beam L1 has an optical path length longer than the reference beam L2 by 2d until it enters the detour unit 72. However, when the measurement beam L1 exits the detour unit 72, the optical path length of the reference beam L2 and the optical path length of the measurement beam L1 are (See FIG. 4A).

  The measurement beam L <b> 1 and the reference beam L <b> 2 emitted from the bypass unit 72 are incident on the polarizer 19. In the polarizer 19, for example, a common polarization component is transmitted from the measurement beam L1 that is P-polarized light and the reference beam L2 that is S-polarized light.

  Thereafter, the slit plate 17 provided at the focal position (surface He) of the relay lens 625 becomes a straight shape extending in the Y-axis direction. Further, the stray light contained in the measurement beam L1 and the reference beam L2 is removed by the slit plate 17.

  By providing the detour unit 72, the surface Hi and the surface He have a conjugate relationship with respect to both the optical paths of the measurement beam L1 and the reference beam L2, and the optical path lengths of both are equal.

  The interference beam IL interfered by the polarizer 19 is split at an angle corresponding to the spectrum by a spectroscopic element 20 such as a diffractive optical element.

  The interference beam IL dispersed according to the spectrum passes through the imaging lens 21 and enters the detection unit 24 to form an image. The detection unit 24 detects the interference beams IL spectrally separated by the spectroscopic element 20.

  Also in the third embodiment, the interference between the measurement beam L1 and the reference beam L2 by the polarizer 19 and the splitting of the interference beam by the spectroscopic element 20 are the same as in the first embodiment.

  The optimal embodiment of the present invention has been described above in detail, but as will be apparent to those skilled in the art, the present invention can be implemented with various modifications within the technical scope thereof.

DESCRIPTION OF SYMBOLS 11 ... Light source part 12, 42, 62 ... Measurement optical system 13 ... Reference element 14 ... Table 15 ... Electric stage 16, 18, 125, 128, 422, 423, 625, 627 ... Relay lens 17 ... Slit plate 19 ... Polarizer DESCRIPTION OF SYMBOLS 20 ... Spectroscopic element 21 ... Imaging lens 22, 32, 52, 72 ... Detour part 23 ... Operation part 24 ... Detection part 100A, 100B, 100C ... Measurement system 111 ... SLD light source 112 ... Half-wave plate 113, 114 ... Plano-convex cylindrical lenses 121, 122, 425, 426, 622 ... Polarizing beam splitters 123, 124, 427, 428, 623, 624 ... Planar mirrors 126, 421, 621 ... Half beam splitters 127, 424, 626 ... Scanning mirrors 231 ... Conversion unit 232 ... distance combination 233 ... flat combination part Ax ... shaft FM ... Fizeau surface L1 ... measuring beam L2 ... reference beam T ... object to be detected

Claims (15)

In the measurement system for measuring the unevenness of the test object,
A light source unit that emits a measurement beam for measuring unevenness of the object to be measured and a reference beam serving as a reference for the measurement beam;
A flat reference element that is arranged adjacent to the object to be measured and reflects the reference beam and transmits the measurement beam to the object to be examined;
A spectroscopic element that splits each wavelength of an interference beam in which the measurement beam reflected by the test object interferes with the reference beam reflected by the reference element;
A detection unit for detecting each wavelength dispersed by the spectroscopic element;
The optical path length of the measurement beam from the light source part to the detection part via the object to be examined and the spectroscopic element, and the reference beam from the light source part to the detection part via the reference element and the spectroscopic element Measuring optical system having a detour that aligns the optical path length of
Measuring system. A first surface on the light source unit side in the optical path of the measurement beam, a second surface placed closer to the object to be measured than the reference element, and a third surface on the spectroscopic element side are optically connected to each other. When forming a conjugate relationship,
The measurement system according to claim 1, wherein the first surface and the third surface have an optical conjugate relationship with each other in the optical path of the reference beam.   The light source unit emits the measurement beam and the reference beam, a first convex cylindrical lens for focusing the measurement beam and the reference beam from the light source on the first surface in a one-dimensional direction, and a second The measurement system according to claim 1, further comprising a convex cylindrical lens.   The measurement system according to claim 2, wherein the measurement optical system includes a slit that is disposed on the third surface and removes stray light that is unnecessary for detection of each wavelength. The measurement optical system is disposed on the light source unit side and has a first optical system having a positive refractive power, and has the same positive refractive power as the first optical system, and has two focal points of the first optical system. A second optical system installed with the focal position aligned with the focal point existing on the side opposite to the light source side,
The measurement system according to claim 1, wherein the reference element is installed between the second optical system and the object to be measured.   The measurement system according to claim 5, wherein the first optical system and the second optical system have a bilateral telecentric relationship on the light source side and the reference element side. The second optical system focuses the measurement beam on the object to be examined in a straight line,
The measurement system according to claim 5, wherein the measurement optical system includes a scanning mirror that scans the straight measurement beam in a direction orthogonal to the straight line.   The scanning mirror includes a plane mirror that rotates about a rotation axis, and the plane mirror includes a common focal point of the first optical system and the second optical system in a reflection surface and in the rotation axis. Measuring system.   The measurement system according to any one of claims 1 to 8, wherein the detour path of the measurement optical system is configured by a block-shaped optical prism or a plate-shaped reflecting mirror and has an integral structure. The light source unit includes a light source that emits a light beam having a predetermined band, and a wave plate that rotates a polarization direction of the beam from the light source,
The measurement system according to claim 1, wherein the interference beam has the predetermined band. The measurement beam and the reference beam are linearly polarized beams with different polarization directions,
The measurement system according to any one of claims 1 to 10, wherein the reference element includes a wire grid having a grid interval shorter than a wavelength of the polarized beam. The spectroscopic element includes a diffraction member that diffracts the interference beam to an angle corresponding to each wavelength,
The measurement system according to any one of claims 1 to 11, wherein the detection unit includes a two-dimensional sensor that detects each wavelength diffracted by the diffraction member.   13. The conversion unit according to claim 1, further comprising: a conversion unit that converts the intensity distribution of each wavelength into a distance from the measurement surface on the object side of the measurement beam to each part of the object to be measured. The measurement system according to item. A height variable unit that varies the distance between the test object and the reference element in order to measure the unevenness of the test object when the unevenness of the test object exceeds a range detected by the detection unit. When,
In a state where the distance between the object to be examined and the reference element is changed in the height variable unit, a distance combination unit that combines the uneven distance converted by the conversion unit,
The measurement system according to claim 13. A plane moving unit that moves the light source unit and the measurement optical system along the plane when the object to be detected exceeds a range detected by the detection unit in a plane parallel to the reference element;
A plane combination unit that combines the distance converted by the conversion unit in the plane in a state where the irradiation position of the measurement beam and the reference beam with respect to the object to be examined and the reference element is changed by the plane moving unit;
The measurement system according to claim 13 or 14, comprising: