JP2004156981A - Shape measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape measuring instrument for acquiring uniform light quantity over the whole surface of an inspected object. <P>SOLUTION: This shape measuring instrument is equipped with a lighting optical system for irradiating light from a light source to the inspected object, an objective lens for focusing the light radiated from the light source on the inspected object, an imaging lens for forming an image of the inspected object, and a focusing position changing means for relatively moving the focusing position of the objective lens in the optical axis direction. The diameter of a pupil 41S of the objective lens and that of a pupil 12S of the optical system, being on the pupil 41S of the objective lens, are made larger than the diameter of a pupil 17S of the imaging lens. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a shape measuring device, and more particularly to a shape measuring device suitable for measuring the height of a test object.
[0002]
[Prior art]
[0003]
[Patent Document]
Japanese Patent Application Laid-Open No. 2002-13917
2. Description of the Related Art As a conventional shape measuring device, a device for measuring a three-dimensional shape of a minute object using a confocal optical system is known.
[0005]
This shape measuring device includes a light source, a Nipkow disc, an objective lens, a focusing position changing mechanism for relatively moving the focusing position of the objective lens in the optical axis direction, an imaging lens, and an imaging element. The light condensing position changing mechanism includes a right-angle mirror, a corner cube prism, and a driving unit that drives the corner cube prism.
[0006]
Illumination light emitted from the light source passes through a collector lens, is reflected by a half mirror, and is irradiated on the upper surface of the Nipkow disc. Of the illumination light, only the illumination light that has passed through the pinhole reaches the focusing position changing mechanism, and is focused on the focal plane of the test object by the objective lens.
[0007]
The reflected light from the test object proceeds to the objective lens and the focusing position changing mechanism, and the objective lens focuses on the pinhole of the Nipkow disc. At this time, only light reflected on the focal plane of the test object by the confocal effect passes through the pinhole.
[0008]
After passing through the half mirror, the light beam passing through the pinhole is imaged on the imaging surface of the imaging device by the imaging lens.
[0009]
At this time, the optical path length from the pinhole to the test object is continuously changed by the condensing position changing mechanism, and an image of the test object is acquired at each focal position.
[0010]
[Problems to be solved by the invention]
However, this shape measuring apparatus has the following problems when observing a tilted portion (a portion tilted with respect to the optical axis) of the test object.
[0011]
FIG. 5A is a diagram for explaining the relationship between the illumination light and the reflected light of the conventional shape measuring device, and FIG. 5B is a diagram illustrating the relationship between the illumination light and the reflected light on the pupil of the objective lens shown in FIG. FIG.
[0012]
The illumination light passing through the objective lens 141 is condensed and reflected on the inclined portion of the test object 105 as shown by a solid line in FIG. The reflected light returns to the objective lens 141 while being inclined with respect to the illumination light as shown by a dotted line in FIG.
[0013]
Here, a case is considered where the pupil 112S of the illumination optical system and the pupil 141S of the objective lens 141 have the same diameter on the pupil of the objective lens 141 (see FIG. 5B).
[0014]
Diameter phi ₁₄₁ of the pupil 141S of the objective lens 141 is represented by _{φ 141 = 2 × f × NA} . Here, f is the focal length of the objective lens, and NA is the numerical aperture of the objective lens.
[0015]
The diameter phi _{1 12} pupil 112S of the illumination optical system is represented by _{φ 1 12 = β × φ 1} 3. Here, beta is the ratio of the aperture of the illumination system to the objective pupil, phi _{1 3} is the diameter of the aperture of the illumination system.
[0016]
When the test object 105 has an inclination, the reflected light 105S shifts from the pupil 141S of the objective lens 141 and the pupil 112S of the illumination optical system as shown in FIG. 5B, and does not contribute to the image indicated by oblique lines. A results. Here, the shift amount h is represented by h = f × sin θ. θ is the reflection angle of the principal ray shown in FIG.
[0017]
Therefore, the component contributing to image formation becomes small, and the amount of light in the inclined portion of the test object 105 becomes small, so that detection may not be possible in some cases, and lack of information in the height direction may cause a lack in an image obtained on the imaging surface. May occur.
[0018]
The present invention has been made in view of such circumstances, and an object thereof is to provide a shape measuring device capable of obtaining a uniform light amount over the entire surface of a test object.
[0019]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 includes an illumination optical system that irradiates light from a light source to a test object, and an objective lens that condenses light emitted from the light source on the test object. An imaging lens for forming an image of the test object, and a focusing position changing means for relatively moving a focusing position of the objective lens in an optical axis direction, a pupil diameter of the objective lens and the illumination optical system. Is larger than the pupil diameter of the imaging lens on the pupil of the objective lens.
[0020]
The invention according to claim 2 is an illumination optical system that irradiates the test object with light from a light source, an objective lens that condenses the light emitted from the light source on the test object, and an image of the test object. And a focusing position changing means for relatively moving the focusing position of the objective lens in the optical axis direction, wherein the pupil diameter of the objective lens and the pupil diameter of the imaging lens are the same as those of the objective lens. Is larger than the pupil diameter of the illumination optical system on the pupil.
[0021]
According to a third aspect of the present invention, in the shape measuring apparatus according to the first or second aspect, a first pupil diameter varying unit capable of changing a pupil diameter of the illumination optical system, and a pupil diameter of the imaging lens are set. And a second pupil diameter varying means capable of changing the pupil diameter.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
FIG. 1 is a view showing an entire configuration of a shape measuring apparatus according to a first embodiment of the present invention.
[0024]
The shape measuring device 1 includes a light source 11, a collector lens 12, an aperture 13, a half mirror 14, a first relay lens 15a, a Nipkow disk 20, a right angle mirror 31, a corner cube reflector 32, a corner cube It includes a driving device 33, an objective lens 41, an aperture 16, a second relay lens 15b, an aperture 18, and a detector 50. The first relay lens 15a and the second relay lens 15b form an imaging lens 17 that forms an imaging optical system.
[0025]
The light source 11 emits illumination light. As the light source 11, for example, an arc lamp such as a laser, a Xe lamp, a He lamp, a Ne lamp, and an Ar lamp can be used.
[0026]
The collector lens 12 constitutes the illumination optical system 9 and converts light emitted from the light source 11 into parallel light.
[0027]
The aperture 13 is arranged at a position conjugate with the pupil of the objective lens 41 and changes the pupil diameter of the illumination optical system 9.
[0028]
The half mirror 14 reflects the illumination light but transmits the reflected light from the test object 5.
[0029]
A plurality of pinholes 21 of the same diameter that allow light that is reflected by the half mirror 14 and transmitted through the first relay lens 15a to pass therethrough are formed in the Nipkow disc 20 in a spiral shape at predetermined intervals. The Nipkow disc 20 is driven by a motor 25.
[0030]
The right-angle mirror 31 changes the directions of the illumination light passing through the pinhole 21 and the light reflected from the test object 5.
[0031]
The corner cube reflector 32 is a prism having three mutually perpendicular surfaces and a hypotenuse surface of a right triangle. Light incident on the inclined surface is reflected by the three surfaces, inverted, and emitted from the inclined surface in parallel with the incident light.
[0032]
The test object 5 can be scanned in the optical axis direction by moving the corner cube reflector 32 by the corner cube driving device 33 as shown by an arrow, so that illumination light is selectively directed toward the test object 5. Can be collected.
[0033]
The right angle mirror 31, the corner cube reflector 32, and the corner cube driving device 33 constitute a light condensing position changing unit.
[0034]
The objective lens 41 is a telecentric lens, and the principal ray of the light passing through the objective lens 41 and irradiating the test object 5 is parallel to the optical axis.
[0035]
The diaphragm 16 is arranged at a position conjugate with the pupil of the objective lens 41 and changes the pupil diameter of the imaging lens 17.
[0036]
The pinhole 18a formed in the aperture 18 restricts entry of scattered light and the like.
[0037]
The detector 50 having the aperture 18 is arranged at a position where the pinhole 21 of the Nipkow disc 20 forms an image, and an image corresponding to the intensity of light transmitted through the pinhole 21 is formed on the detector 50.
[0038]
Next, the operation of the shape measuring apparatus having the above configuration will be described.
[0039]
Illumination light emitted from the light source 11 is converted into parallel light by the collector lens 12, and is applied to the upper surface of the Nipkow disk 20 via the stop 13, the half mirror 14, and the first relay lens 15 a.
[0040]
The luminous fluxes that have passed through the plurality of pinholes 21 included in the irradiation range are respectively reflected by the upper reflecting surface 31a of the right-angle mirror 31 and enter the corner cube reflector 32, and after being reflected by the corner cube reflector 32 a plurality of times, The light is returned to the right-angle mirror 31 as illumination light parallel to the incident light, is reflected by the lower reflecting surface 31b of the right-angle mirror 31, enters the objective lens 41, and is condensed on the test object 5 by the objective lens 41. You.
[0041]
The light beams that have passed through the plurality of pinholes 21 of the Nipkow disc 20, respectively, are reflected by the right-angle mirror 31 and the corner cube reflector 32, and are condensed by the objective lens 41 at different positions on the test object 5, respectively.
[0042]
Therefore, a plurality of light spots are formed on the test object 5 by a plurality of light beams from the light source 11.
[0043]
The reflected luminous fluxes from the plurality of light spots of the test object 5 are respectively illuminated by the objective lens 41, the lower reflecting surface 31b of the right-angle mirror 31, the corner cube reflector 32, and the upper reflecting surface 31a of the right-angle mirror 31 in this order. Proceeds in the opposite direction, and the focus is focused on the pinhole 21.
[0044]
At this time, only the light reflected by the light spot due to the confocal effect passes through the pinhole 21, and scattered light and the like are removed because the focus is not focused on the pinhole 21.
[0045]
The reflected light flux passing through the pinhole 21 enters the imaging lens 17. The reflected light flux incident on the imaging lens 17 is condensed on the detector 50 by the first relay lens 15a, the second relay lens 15b, and the stop 16, respectively, and a two-dimensional image is formed on the detector 50.
[0046]
At this time, a plurality of images having different focal positions obtained by driving the corner cube driving device 33 are input to an image processing device (not shown), and the three-dimensional shape of the test object 5 is calculated from the input image data by the image processing device. Is done.
[0047]
FIG. 2 is a diagram showing the relationship between the pupil diameter of the objective lens, the pupil diameter of the illumination optical system, and the pupil diameter of the imaging lens on the pupil of the objective lens of the shape measuring apparatus according to the first embodiment of the present invention; FIG. 2A shows a case where a flat portion of the test object is viewed, and FIG. 2B shows a case where a tilted portion of the test object is viewed.
[0048]
The diameter of the pupil 12S of the illumination optical system 9 is narrowed by the stop 13 (see FIG. 1) so as to match the diameter of the pupil 41S of the objective lens 41.
[0049]
The diameter of the pupil 17S of the imaging lens 17 is narrowed by the stop 16 (see FIG. 1) so as to be smaller than the diameter of the pupil 41S of the objective lens 41 and the diameter of the pupil 12S of the illumination optical system.
[0050]
When the flat part of the test object 5 (see FIG. 1) is viewed, the reflected light 5S returns to the objective lens 41 without tilting with respect to the illumination light. It does not shift from the pupil 12S of the system 9 (see FIG. 2A).
[0051]
When the inclined part of the test object 5 is viewed, the reflected light 5S is inclined with respect to the illumination light and returns to the objective lens 41. Therefore, the reflected light 5S is transmitted from the pupil 41S of the objective lens 41 and the pupil 12S of the illumination optical system 9. Shift (see FIG. 2B).
[0052]
At this time, the entire area of the pupil 17S of the imaging lens 17 is covered with the reflected light 5S, and an image is formed on the detector 50.
[0053]
Here, the angle between the optical axis of the objective lens and the outermost ray of the reflected light from the test object farthest from the optical axis of the objective lens is θ, and the pupil diameter of the objective lens is represented by 2h = f sin θ _max. At this time, all the reflected light having a reflection angle θ from the test object equal to or _smaller than θ _max can be detected without loss of light amount.
[0054]
According to the first embodiment, even when the test object 5 is inclined, there is no component that does not contribute to imaging unlike the related art, so that a uniform light amount can be obtained over a wide range of the test object 5. Obtainable. As a result, it is possible to prevent the amount of light in the inclined portion of the test object 5 from being reduced and the lack of information in the height direction from causing the image obtained on the imaging surface of the detector 50 to be chipped.
[0055]
FIG. 3 is a diagram showing the relationship between the pupil diameter of the objective lens, the pupil diameter of the illumination optical system, and the pupil diameter of the imaging lens on the pupil of the objective lens of the shape measuring apparatus according to the second embodiment of the present invention; FIG. 3A shows a case where the flat part of the test object is seen, and FIG. 3B shows a case where the inclined part of the test object is seen.
[0056]
The diameter of the pupil 57S of the imaging lens 17 is narrowed by the diaphragm 16 (see FIG. 1) so as to match the diameter of the pupil 81S of the objective lens 41.
[0057]
The diameter of the pupil 52S of the illumination optical system is reduced by the aperture 13 (see FIG. 1) so as to be smaller than the diameter of the pupil 81S of the objective lens 41 and the pupil 57S of the imaging lens 17.
[0058]
When the flat part of the test object 5 is viewed, the reflected light 45S returns to the objective lens 41 without tilting with respect to the illumination light, so that the reflected light 45S does not shift from the pupil 52S of the illumination optical system (FIG. )reference).
[0059]
When the inclined part of the test object 5 is viewed, the reflected light 45S is inclined with respect to the illumination light and returns to the objective lens 41, so that the reflected light 45S shifts from the pupil 52S of the illumination optical system (FIG. 3B). reference).
[0060]
At this time, the entire area of the reflected light 45S is covered by the pupil 57S of the imaging lens 17 and the pupil 81S of the objective lens 41, and an image is formed on the detector 50.
[0061]
According to the second embodiment, the same effects as those of the first embodiment can be obtained.
[0062]
FIG. 4 is a view showing the overall configuration of a shape measuring apparatus according to another embodiment of the present invention. The same reference numerals are given to parts common to the above-described embodiments, and the description thereof will be omitted.
[0063]
The shape measuring device 10 includes a first driving device (first pupil diameter varying unit) 13D that drives the stop 13 to change the pupil diameter of the illumination optical system 9 and an imaging lens 17 that drives the stop 16 A second driving device (second pupil diameter varying means) 16D for changing the pupil diameter of the first driving device and a controller 60 for controlling the driving of the first driving device 13D and the second driving device 16D. This is different from the shape measuring device 1 described above.
[0064]
By the way, when the resolution is close to the limit resolution where many components having a high spatial frequency of the test object 5 are large, the contrast of the image becomes high when σ> 1 (incoherent), and when there are many components having a low spatial frequency of the test object, σ It is known that the contrast of an image is increased when <1 (partially coherent).
[0065]
Here, σ = (pupil diameter of illumination optical system) / (pupil diameter of imaging optical system).
[0066]
Therefore, the configuration of the first embodiment has σ> 1 (incoherent), and the configuration of the second embodiment has σ <1 (partially coherent).
[0067]
When the controller 10 determines that there are many components having a high spatial frequency of the test object 5, it outputs a control signal to the first driving device 13D and the second driving device 16D, and the relationship shown in FIG. The first driving device 13D and the second driving device 16D are driven such that (pupil diameter> pupil diameter of the imaging optical system) is established.
[0068]
When the controller 10 determines that there are many components having a low spatial frequency of the test object 5, the controller 10 outputs a control signal to the first driving device 13D and the second driving device 16D, and the relationship shown in FIG. The first driving device 13D and the second driving device 16D are driven such that the pupil diameter of the optical system <the pupil diameter of the imaging optical system) is established.
[0069]
The above determination is performed based on, for example, a frequency analysis of the surface shape of the test object 5.
[0070]
【The invention's effect】
As described above, according to the shape measuring apparatus of the present invention, a uniform light amount can be obtained over the entire surface of the test object.
[Brief description of the drawings]
FIG. 1 is a view showing an entire configuration of a shape measuring apparatus according to a first embodiment of the present invention.
FIG. 2 shows the relationship between the pupil diameter of the objective lens, the pupil diameter of the illumination optical system, and the pupil diameter of the imaging lens on the pupil of the objective lens of the shape measuring apparatus according to the first embodiment of the present invention. FIG.
FIG. 3 shows the relationship between the pupil diameter of the objective lens, the pupil diameter of the illumination optical system, and the pupil diameter of the imaging lens on the pupil of the objective lens of the shape measuring apparatus according to the second embodiment of the present invention. FIG.
FIG. 4 is a diagram showing an overall configuration of a shape measuring apparatus according to another embodiment of the present invention.
5 (a) is a view for explaining the relationship between illumination light and reflected light of a conventional shape measuring device, and FIG. 5 (b) is illumination light on a pupil of an objective lens shown in FIG. 5 (a). FIG. 4 is a diagram for explaining the relationship between the light and reflected light.
[Explanation of symbols]
5 Test Object 11 Light Source 12 Collector Lens 13D First Driving Device (First Pupil Diameter Variable Means)
15 First relay lens 16D Second drive device (second pupil diameter varying means)
17 Image forming lens 31 Right angle mirror 32 Corner cube reflector 33 Corner cube driving device 41 Objective lens

Claims (3)

An illumination optical system that irradiates the test object with light from a light source;
An objective lens for condensing light emitted from the light source on the test object,
An imaging lens for forming an image of the test object,
Light-condensing position changing means for relatively moving the light-condensing position of the objective lens in the optical axis direction,
A pupil diameter of the objective lens and a pupil diameter of the illumination optical system are larger than a pupil diameter of the imaging lens on the pupil of the objective lens. An illumination optical system that irradiates the test object with light from a light source;
An objective lens for condensing light emitted from the light source on the test object,
An imaging lens for forming an image of the test object,
Light-condensing position changing means for relatively moving the light-condensing position of the objective lens in the optical axis direction,
The pupil diameter of the objective lens and the pupil diameter of the imaging lens are larger than the pupil diameter of the illumination optical system on the pupil of the objective lens. First pupil diameter varying means capable of changing a pupil diameter of the illumination optical system;
The shape measuring apparatus according to claim 1, further comprising a second pupil diameter varying unit that can change a pupil diameter of the imaging lens.

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