JP2011220912A - Interference objective lens and light interference measuring device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interference objective lens having a structure that can improve the workability by expanding the selection range of an object to be measured which can be measured/observed, and a light interference measuring device including the interference objective lens.SOLUTION: An interference objective lens 30 for irradiating a measurement target W with light from a light emission part 10 includes an interference optical system 100 at an end of the interference objective lens 30. The interference optical system 100 includes a lens group 130 for converging the light from the light emission part 10 to the measurement target W, a reference mirror 120 provided between the light emission part 10 and the lens group 130, and a half mirror 140 provided at the center in an optical axis L direction of the lens group 130 for separating the light from the light emission part 10 into a reference optical path and a measurement optical path and output the reflectance from the reference optical path and the measurement optical path as interfering light. The lens group 130 is structured so that one side and the other side thereof with respect to the optical axis L direction are symmetrical along the half mirror 140.

Description

  The present invention relates to an interference objective lens and an optical interference measurement apparatus including the interference objective lens.

Conventionally, an optical interference measuring device such as a three-dimensional shape measuring device that accurately measures, for example, a three-dimensional shape of an object to be measured using luminance information of interference fringes generated by light interference is known (for example, Patent Documents). 1).
In this optical interference measuring apparatus, a configuration called a mirro type is known as an interference objective lens having a high magnification and a high NA (numerical aperture).

FIG. 6 is a schematic diagram showing a basic configuration of a general mirro type optical system 90.
As shown in FIG. 6, the optical system 90 includes a convex lens 91, a glass plate 93 with a reference mirror 92, and a half mirror 94 in order from the top on the same optical axis L. A measurement object W is placed and placed on the stage S below.
In this optical system 90, the light transmitted through the convex lens 91 and emitted downward is, by the half mirror 94, a reference optical path having a reference mirror 92 (broken line in the figure) and a measurement optical path (in FIG. The reflected light (reference light) from the reference mirror 92 and the reflected light from the measurement object W are combined. When the optical path lengths of the reference light and the reflected light are equal, each light becomes a light wave having a uniform phase and becomes a strengthening interference wave.

JP 2003-148921 A

However, in such a mirro type configuration, a convex lens 91 is provided at the tip of the objective lens, and a glass plate 93 with a reference mirror 92 and a half mirror 94 are arranged between the tip of the objective lens and the measurement object W. Therefore, the working distance is limited to the distance from the half mirror 94 to the measurement object W.
For this reason, there is a problem that the measuring object W that can be measured and observed is limited to those that can be applied within the working distance described above, and that the workability is poor because the working distance is short.

  An object of the present invention is to provide an interference objective lens having a configuration capable of increasing the selection range of measurement objects that can be measured and observed and improving workability, and an optical interference measurement apparatus including the interference objective lens. It is to be.

In order to solve the above-mentioned problem, the invention described in claim 1
In an interference objective lens that irradiates a measurement object with light output from a light source,
An interference optical system for obtaining interference light is provided at the tip of the interference objective lens facing the measurement object,
The interference optical system is
A lens group for converging the light output from the light source with respect to the measurement object;
A reference mirror disposed closer to the light source than the lens group;
The light that is arranged in the center of the optical axis direction of the lens group and is output from the light source is branched into a reference optical path having the reference mirror and a measurement optical path in which the measurement object is arranged, and from the reference mirror A half mirror that outputs reflected light and reflected light from the measurement object as the interference light, and
The lens group is configured such that one and the other in the optical axis direction are symmetrical with respect to the half mirror.

The invention according to claim 2 is the interference objective lens according to claim 1,
The lens group includes a lens body formed by abutting flat surfaces of two identical lenses having a flat surface,
The half mirror is provided on a contact surface of the two lenses in the lens body.

The invention according to claim 3 is the interference objective lens according to claim 1,
The lens group includes the same two lens bodies arranged with a predetermined gap,
The half mirror is arranged in a gap between the two lens bodies.

The invention according to claim 4 is the interference objective lens according to claim 3,
The reference mirror is provided on one surface of the first transparent plate,
The half mirror is provided on one surface of the second transparent plate,
The reference mirror and the half mirror are arranged on the same surface in the optical axis direction with respect to each of the first transparent plate and the second transparent plate.

Further, the invention according to claim 5 is an optical interference measuring apparatus,
The interference objective lens according to any one of claims 1 to 4,
A light source that outputs light to the interference objective lens;
An optical path length variable means for changing the optical path length of either the reference optical path or the measurement optical path;
An imaging means for imaging an interference image by the interference light output from the interference objective lens;
It is characterized by providing.

According to the present invention, since it is not necessary to dispose the reference mirror and the half mirror between the interference objective lens and the measurement object, the working distance can be the distance from the tip of the interference objective lens to the measurement object.
Therefore, since the working distance can be increased as compared with the conventional mill type, the selection range of the measurement object that can be measured and observed can be increased, and workability can be improved.

It is a schematic diagram which shows the whole structure of the three-dimensional shape measuring apparatus as an optical interference measuring apparatus of 1st Embodiment. It is a principal part enlarged view which shows the structure of the interference objective lens in the three-dimensional shape measuring apparatus of FIG. It is a block diagram which shows the control structure of the three-dimensional shape measuring apparatus of FIG. FIG. 10 is an enlarged view of a main part showing a configuration of an interference objective lens of Modification 1; It is a principal part enlarged view which shows the structure of the interference objective lens of 2nd Embodiment. It is a schematic diagram which shows the basic composition of the conventional miro type | mold optical system.

  Hereinafter, a three-dimensional shape measuring apparatus (hereinafter referred to as a shape measuring apparatus) as an optical interference measuring apparatus according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, the configuration will be described.
As shown in FIG. 1, the shape measuring apparatus 1 according to the present embodiment includes a light emitting unit (light source) 10, an optical head unit 20, an objective lens unit (interference objective lens) 30, and an imaging unit (imaging unit) 40. , A drive mechanism section (optical path length varying means) 50, a display section 60, a control section 70, a stage S on which the measurement object W is placed, and the like.

  The light emitting unit 10 is a light source that outputs a wide band light having a large number of wavelength components over a wide band and having a low coherency. For example, a white light source such as a xenon lamp (500 W) is used.

  The optical head unit 20 includes a beam splitter 21 and a collimator lens 22. The light emitted from the light emitting unit 10 is irradiated in parallel to the beam splitter 21 via the collimator lens 22 from the direction perpendicular to the optical axis L of the objective lens unit 30, and along the optical axis L from the beam splitter 21. Light is emitted, and the objective lens unit 30 is irradiated with a parallel beam from above.

The objective lens unit 30 irradiates the measurement object W placed on the stage S below the objective lens unit 30 with light from the tip.
As shown in FIG. 2, an interference optical system 100 for obtaining interference light (interference fringes) is provided at the tip of the objective lens unit 30 facing the measurement target W.

  The interference optical system 100 includes a reference mirror 120 provided on the lower surface of the glass plate 110, a lens group 130 disposed below the reference mirror 120, and a half mirror disposed in the center of the lens group 130 in the optical axis L direction. 140 and the like.

  The reference mirror 120 is disposed on the optical axis L above (the light source side) above the lens group 130, reflects the reference light reflected upward by the half mirror 140 positioned below, and reflects the reference light of the half mirror 140. Advance in the direction.

The lens group 130 converges the light emitted from the optical head unit 20 with respect to the measurement target W.
The lens group 130 includes a half mirror 140 in the center in the vertical direction (optical axis L direction), and is configured so that the upper and lower sides (one and the other in the optical axis direction) are symmetrical with respect to the half mirror 140. Has been.
Specifically, the lens group 130 of the present embodiment includes a lens body 131 formed by abutting flat surfaces of two identical lenses (plano-convex lenses 131a and 131b) having a flat surface.
The two plano-convex lenses 131a and 131b have the same shape, radius of curvature, thickness, material, and the like.
A half mirror 140 is deposited on the contact surface of the two plano-convex lenses 131a and 131b in the lens body 131.

As described above, the half mirror 140 is a thin film disposed on the contact surface of the two plano-convex lenses 131a and 131b in the lens body 131, that is, the center of the lens group 130 in the optical axis L direction.
The half mirror 140 splits light incident from above into a reference optical path having a reference mirror 120 (broken line in FIG. 2) and a measurement optical path in which the measurement object W is arranged (solid line in FIG. 2). The reflected light from the mirror 120 and the reflected light from the measurement object W are combined and output as interference light.

  Here, the interference operation will be described using FIG. 2 on the assumption that light has entered the interference optical system 100 from above the objective lens unit 30 via the optical head unit 20. In addition, although it demonstrates using the optical path along the arrow in FIG.

First, incident light incident on the interference optical system 100 passes through the glass plate 110, then passes through the plano-convex lens 131 a of the lens group 130, and enters the half mirror film 140. Here, the incident light branches into reflected light that travels along the reference optical path and transmitted light that travels along the measurement optical path.
The reflected light is converged and reflected by the reference mirror 120, and then reflected by the half mirror 140. On the other hand, the transmitted light converges and irradiates one point of the measurement object W, is reflected there, and enters the half mirror 140 to be transmitted. Here, the reflected light from the reference mirror 120 and the reflected light from the measurement object W are combined by the half mirror 140 to become a combined wave (interference light), and proceed upward. At this time, interference occurs when the optical path lengths of the reference optical path (optical path 1 + optical path 2) and the measurement optical path (optical path 3 + optical path 4) are equal.
At this time, in the interference optical system 100, the reference mirror 120 is disposed at a position where the reflected light that is reflected by the half mirror 140 and travels through the reference optical path is condensed after passing through the plano-convex lens 131a.
As a result, the light that passes through the half mirror 140 and is collected on the measurement object W and the light that is reflected by the half mirror 140 and collected on the reference mirror 120 have the same optical path length, and interference fringes can be observed. ing.
Thereafter, the combined wave forms an image on the imaging unit 40 to form an interference image. The interference image is captured by the control unit 70 and subjected to image processing.

  The objective lens unit 30 may have any lens configuration above the glass plate 110 (above the tip).

The imaging unit 40 is a CCD camera or the like including a two-dimensional imaging element for constituting an imaging unit. The imaging unit 40 is a composite wave output from the objective lens unit 30 (reflected light from the measurement object W and the reference mirror 120). Reflected light) is captured.
The image data of the interference image captured by the imaging unit 40 is captured as an electrical signal by the control unit 70 and subjected to predetermined image processing and then displayed on the display unit 60.

The drive mechanism unit 50 moves the optical head unit 20 in the direction of the optical axis L in accordance with a movement command from the control unit 70.
The focus position of the objective lens unit 30 is set to a predetermined position on the surface of the measurement object W.
Here, in FIG. 2, if the distance from the half mirror 140 to the reference mirror 120 is d ₁ and the distance from the half mirror 140 to the focus position is d ₂ , the optical path length difference is 0 at the position of d ₁ = d _2. .
Therefore, the drive mechanism unit 50 adjusts the distance d ₂ by moving the optical head unit 20 in the direction of the optical axis L so that the optical path length difference is 0 (d ₁ = d ₂ ).
Incidentally, the above description exemplifies the case of moving the optical head unit 20 may be configured to adjust the distance d ₂ by moving the stage S.
Further, the distance d ₁ from the half mirror 140 to the reference mirror 120 may be variable.
Thus, the drive mechanism unit 50 changes the optical path length of either the reference optical path or the measurement optical path as the optical path length variable means.

  The display unit 60 is, for example, a monitor or the like mounted on a personal computer or the like, and displays image data of an interference image that has been taken into the control unit 70 and subjected to predetermined image processing.

  As shown in FIG. 3, the control unit 70 includes a CPU (Central Processing Unit) 71, a RAM (Random Access Memory) 72, a storage unit 73, and the like.

  The CPU 71 performs various control processes according to various processing programs stored in the storage unit 73, for example.

  The RAM 72 forms a work memory area for storing data calculated by the CPU 71.

  The storage unit 73 is, for example, a system program that can be executed by the CPU 71, various processing programs that can be executed by the system program, data that is used when these various processing programs are executed, and various processing results that are arithmetically processed by the CPU 71. The data etc. are memorized. The program is stored in the storage unit 73 in the form of a computer readable program code.

  Specifically, in the storage unit 73, for example, an imaging data storage unit 731 and a peak position detection program 732 are stored.

The imaging data storage unit 731 stores the image data of the interference image captured by the imaging unit 40 as a plurality of frames.
Note that the image data stored in the imaging data storage unit 731 has its interference intensity value properly corrected by a correction table created in advance in order to eliminate the influence of sensitivity characteristics of the imaging unit 40, for example, Remembered.

The peak position detection program 732 is a program that, for example, causes the CPU 71 to realize a function of detecting a peak position of an interference fringe generated at a position where the optical path difference is zero based on the interference image captured by the imaging unit 40.
Specifically, when an interference fringe is generated, the CPU 71 detects a position indicating the maximum intensity from the intensity change of the interference fringe as a position having an optical path difference of zero.
The CPU 71 functions as a peak position detection unit by executing the peak position detection program 732.

Next, the operation will be described.
As described above, the shape measuring device 1 of the present embodiment and the objective lens unit 30 provided in the shape measuring device 1 are provided with the interference optical system 100 for obtaining interference fringes at the distal end thereof.
For this reason, it is not necessary to arrange a reference mirror or a half mirror between the objective lens unit 30 and the measurement object W as in the conventional mirrow-type objective lens. All the distances up to W can be the working distance.

As described above, according to the objective lens unit 30 of the present embodiment and the shape measuring apparatus 1 including the objective lens unit 30, the interference optical system 100 for obtaining interference light is provided at the tip of the objective lens unit 30. The interference optical system 100 includes a lens group 130 for converging the light output from the light emitting unit 10 with respect to the measurement target W, and an optical axis L closer to the light emitting unit 10 than the lens group 130. The reference mirror 120 disposed above and the center of the lens group 130 in the direction of the optical axis L, the light output from the light emitting unit 10 is branched into a reference optical path and a measurement optical path, and from the reference mirror 120 And a half mirror 140 that outputs the reflected light from the measurement object W as interference light, and the lens group 130 is symmetrical with respect to the half mirror 140 in one direction and the other in the optical axis L direction. Configure to be It has been.
Thereby, since all the distance from the front end surface of the objective lens part 30 to the measuring object W can be made into a working distance, a working distance can be ensured long compared with the conventional mill type.
For this reason, the selection range of the measurement object which can be measured and observed can be increased, and workability can be improved.

Further, according to the objective lens unit 30 and the shape measuring apparatus 1 including the objective lens unit 30 of the present embodiment, the lens group 130 is a plane of the same two lenses (plano-convex lenses 131a and 131b) having a plane. A lens body 131 formed by abutting each other is provided, and a half mirror 140 is provided on a contact surface of the plano-convex lenses 131a and 131b in the lens body 131.
For this reason, compared with the half mirror which formed the film form on the glass substrate, since a glass substrate is not required, it can manufacture at low cost.

(Modification 1)
Next, the configuration of the objective lens unit 30A of Modification Example 1 will be described with reference to FIG.
An interference optical system 200 is provided at the tip of the objective lens unit 30A.
The interference optical system 200 includes a reference mirror 220 provided on the lower surface of the glass plate 210, a lens group 230 disposed below the reference mirror 220, and a half mirror disposed at the center of the lens group 230 in the optical axis L direction. 240 and the like.

  The lens group 230 according to the first modification is provided with a lens body 231 formed by abutting flat surfaces of two identical lenses (plano-concave lenses 231a and 231b), and above and below the lens body 231, respectively. Two convex lenses 232 and 233.

The two plano-concave lenses 231a and 231b are the same in shape, radius of curvature, thickness, material, and the like. In addition, the two convex lenses 232 and 233 having the same shape, radius of curvature, thickness, material, and the like are used.
Further, the distance between the plano-concave lens 231a and the convex lens 232 and the distance between the plano-concave lens 231b and the convex lens 233 are the same.
A half mirror 240 is deposited on the contact surface of the two plano-concave lenses 231a and 231b in the lens body 231.
For this reason, the light that passes through the half mirror 240 and is condensed on the measurement object W and the light that is reflected by the half mirror 240 and collected on the reference mirror 220 have the same optical path length so that interference fringes can be observed. It has become.

In addition to the configuration exemplified in Modification 1, it is needless to say that an optical member can be appropriately provided in the lens group 230.
Also in the first modification, the configuration above the glass plate 210 including the reference mirror 220 (above the tip) may be anything.

(Second Embodiment)
Next, the objective lens unit in the second embodiment will be described focusing on differences from the first embodiment. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment, and the description is abbreviate | omitted.
As shown in FIG. 5, the objective lens unit 80 of the present embodiment includes an interference optical system 300 at the tip.

  The interference optical system 300 includes a reference mirror 320 provided on the upper surface of a glass plate (first transparent plate) 310, a lens group 330 disposed below the reference mirror 320, and the optical axis L direction of the lens group 330. A half mirror 340 provided on the upper surface of a glass plate (second transparent plate) 341 is formed at the center, and the like.

  The reference mirror 320 is disposed on the optical axis L above (the light source side) above the lens group 330, reflects the reference light reflected by the half mirror 340 positioned below and advanced upward, and the half mirror 340. Advance in the direction.

The lens group 330 includes a half mirror 340 at the center in the vertical direction (optical axis L direction), and is configured so that the upper side and the lower side are symmetrical with respect to the half mirror 340.
Specifically, the lens group 330 of the present embodiment includes two identical lens bodies 331 and 332 arranged with a predetermined gap, and a glass with a half mirror 340 is provided in the gap between the lens bodies 331 and 332. A plate 341 is disposed.

More specifically, the lens body 331 includes a first lens 331a having a concave curved surface and a flat surface, and a plano-convex lens 331b in contact with the flat surface side of the first lens 331a.
The lens body 332 includes a second lens 332a having a concave curved surface and a flat surface, and a plano-convex lens 332b in contact with the flat surface side of the second lens 332a.
Here, the first lens 331a and the second lens 332a, and the plano-convex lens 331b and the plano-convex lens 332b have the same shape, radius of curvature, thickness, material, and the like.
The two lens bodies 331 and 332 are arranged with a gap so that their concave curved surfaces face each other, and a glass plate 341 with a half mirror 340 is arranged in the gap between the two lens bodies 331 and 332.
A plano-convex lens 333 is arranged above the lens body 331 so that the plane side is on the lower side, and a plano-convex lens 334 is arranged below the lens body 332 so that the plane side is on the upper side. .
Note that the plano-convex lens 333 and the plano-convex lens 334 also have the same shape, radius of curvature, thickness, material, and the like. Further, the distance between the lens body 331 and the plano-convex lens 333 and the distance between the lens body 332 and the plano-convex lens 334 are the same.

As described above, the lens group 330 is symmetrical with respect to the half mirror 340 in terms of the upper and lower configurations (that is, the configuration of one and the other in the direction of the optical axis L), and passes through the half mirror 340. The light condensed on the top and the light reflected by the half mirror 340 and condensed on the reference mirror 320 have the same optical path length so that interference fringes can be observed.
In the present embodiment, it is described that the reference mirror 320 is provided on the upper surface of the glass plate 310 and the half mirror 340 is provided on the upper surface of the glass plate 341. However, both are provided on the lower surface. Also good.

As described above, according to the objective lens unit 80 and the shape measuring apparatus (not shown) including the objective lens unit 80 according to the present embodiment, the lens group 330 is arranged in the same two with a predetermined gap. Two lens bodies 331 and 332 are provided, and a glass plate 341 provided with a half mirror 340 is disposed in the gap between the two lens bodies 331 and 332.
Thereby, since all the distance from the front end surface of the objective lens part 80 to the measuring object W can be made into a working distance, a working distance can be ensured long compared with the conventional mill type.
For this reason, the selection range of the measurement object which can be measured and observed can be increased, and workability can be improved.

In addition, according to the objective lens unit 80 of this embodiment and the shape measuring device (not shown) including the objective lens unit 80, the reference mirror 320 is provided on one surface of the glass plate 310,
The half mirror 340 and the reference mirror 320 are disposed on the same surface in the optical axis direction with respect to the glass plate 341 and the glass plate 310, respectively.
Thereby, the optical path lengths of the reference optical path and the measurement optical path can be configured to be equal.

In addition to the configuration exemplified in the second embodiment, it is needless to say that an optical member can be appropriately provided in the lens group 330.
Also in the second embodiment, any configuration above the glass plate 310 including the reference mirror 320 may be used.

1. Shape measuring device (optical interference measuring device)
10 Light emitting part (light source)
20 Optical head part 30, 30A, 80 Objective lens part (interference objective lens)
DESCRIPTION OF SYMBOLS 100 Interference optical system 110 Glass plate 120 Reference mirror 130 Lens group 131 Lens body 131a, 131b Plano-convex lens 140 Half mirror film 200 Interference optical system 210 Glass plate 220 Reference mirror 230 Lens group 231 Lens body 231a, 231b Plano-concave lens 232, 233 Convex lens 240 half mirror film 300 interference optical system 310 glass plate (first transparent body)
320 Reference mirror 330 Lens group 331 Lens body 331a First lens 331b Plano-convex lens 332 Lens body 332a Second lens 332b Plano-convex lens 333, 334 Plano-convex lens 340 Half mirror film 341 Glass plate (second transparent body)
40 Imaging unit (imaging means)
50 Drive mechanism (optical path length variable means)
60 Display unit 70 Control unit L Optical axis S Stage W Measurement object

Claims (5)

In an interference objective lens that irradiates a measurement object with light output from a light source,
An interference optical system for obtaining interference light is provided at the tip of the interference objective lens facing the measurement object,
The interference optical system is
A lens group for converging the light output from the light source with respect to the measurement object;
A reference mirror disposed closer to the light source than the lens group;
The light that is arranged in the center of the optical axis direction of the lens group and is output from the light source is branched into a reference optical path having the reference mirror and a measurement optical path in which the measurement object is arranged, and from the reference mirror A half mirror that outputs reflected light and reflected light from the measurement object as the interference light, and
The interference objective lens, wherein the lens group is configured such that one and the other in the optical axis direction are symmetrical with respect to the half mirror. The lens group includes a lens body formed by abutting flat surfaces of two identical lenses having a flat surface,
The interference objective lens according to claim 1, wherein the half mirror is provided on a contact surface of the two lenses in the lens body. The lens group includes the same two lens bodies arranged with a predetermined gap,
The interference objective lens according to claim 1, wherein the half mirror is disposed in a gap between the two lens bodies. The reference mirror is provided on one surface of the first transparent plate,
The half mirror is provided on one surface of the second transparent plate,
The said reference mirror and the said half mirror are distribute | arranged to one surface of the same side of an optical axis direction with respect to each of a said 1st transparent plate and a said 2nd transparent plate. Interference objective lens. The interference objective lens according to any one of claims 1 to 4,
A light source that outputs light to the interference objective lens;
An optical path length variable means for changing the optical path length of either the reference optical path or the measurement optical path;
An imaging means for imaging an interference image by the interference light output from the interference objective lens;
An optical interference measuring apparatus comprising:

Images