JP2006023624A - Microscope with focusing detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To steadily determine a focused state or adjust a focal point, regardless of the state of the surface of a specimen. <P>SOLUTION: The microscope includes: an observation optical system 2 for observing the image of a specimen face 4a, formed by an objective lens 6; and an illuminating optical system 3 for projecting the image of an index 12 onto the specimen face and causing vertical illuminating on the specimen face. A split prism 8 is disposed in the position where imaging takes place by the objective lens 6. Using the objective lens 6, light reflected from the specimen face 4a and index 12 is imaged onto the split prism 8. The image is observed with the eyepiece lens 7 and focusing is detected. In a focused state, the image of the index 12 is formed on an imaging position on the split prism 8. In a defocusing state, the image of the index 12 is laterally deviated in a wedge direction relative to a separating line of wedge prisms 8a and 8b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microscope provided with a focus detection device for performing focusing on a sample surface in order to measure or observe the height of the sample surface (surface) of the sample, for example.

Conventionally, when focusing an image of a sample for observing the sample with a microscope, a high-magnification microscope can be visually confirmed even if the NA is large and the focus in the Z-axis direction (height direction) is slight, Some of them can adjust the focus shift.
However, in the case of a low-magnification microscope, since the NA is small and the depth of focus is large, it is impossible to accurately detect a shift in the distance in the Z-axis direction (height direction). Therefore, when adjusting the focus, the projection angle of the target light is limited when the target pattern image is projected onto the sample surface, and the target pattern image by the objective lens is converted into a lateral shift at the observation position. The focal position was detected.
Examples of microscopes provided with a focusing device for adjusting the focus of the microscope with respect to the sample surface include those described in Patent Documents 1, 2, and 3, for example.
A microscope equipped with a focusing device described in Patent Document 1 separates a focusing pattern for projecting two objects through a mask, reflects the reflected light by a half mirror, and matches it with the optical path of the object observation optical system. A lens is projected onto the surface of the object. Then, the two focused pattern images are superimposed on the optical path of the observation optical system by the objective lens together with the image of the object plane, and the focus is observed by observing whether or not the images of the two focused pattern images are misaligned. I do.

In the microscope described in Patent Document 2, a split prism provided with a focusing pattern is illuminated to project a light beam divided into two onto a sample surface. Then, an image of the focusing pattern divided into two on the sample surface is formed on the focusing screen by the objective lens, and the presence or absence of lateral shift of the images of the two focusing patterns with respect to the split line is observed.
In Patent Document 3, two focusing patterns illuminated by separate illumination systems in the illumination optical system are guided to the optical path of the observation optical system via the half mirror and projected onto the object plane by the objective lens. Then, images of two in-focus patterns on the object plane are respectively imaged on a focusing screen provided at an imaging position by the objective lens, and the presence or absence of lateral deviation of the two in-focus pattern images on the focusing screen is observed. Whether the in-focus position or the out-of-focus position is detected.

In the focusing apparatus described in each of the above-mentioned Patent Documents 1 to 3, when the focusing pattern located in the illumination optical system is projected onto the object plane, the two focusing patterns are projected onto the sample at different incident angles. ing. When the object plane is displaced in the optical axis direction (the height direction of the object), the imaging positions of the two focusing patterns are shifted in the optical axis direction when viewed from the image observation position, and the plane is substantially orthogonal to the optical axis. It is made to detect as a horizontal shift in.
Therefore, it is preferable that the reflected light of the image of the focusing pattern on the object plane in the optical path of the observation optical system is the same as the angular distribution of the incident light imaged on the object plane.
Japanese Patent No. 291823 British Patent Publication GB 2076176B JP-A-9-127421

However, in the microscope having the focusing device described in each of Patent Documents 1 to 3 described above, the object to be measured has a fine concavo-convex structure such as roughness or grind formed on the object surface by processing. For this reason, the angle of reflected light is often disturbed from the angular distribution of incident light due to irregular reflection on the object surface and light scattering. These irregularly reflected light and scattered light are noises in the observation of the horizontal shift of the two focused pattern images in focus or non-focused at the image formation position by the objective lens, and depending on the degree, the horizontal shift of the focused pattern may occur. There is a drawback that it is difficult to discriminate and the focus detection accuracy is lowered.
In view of such circumstances, an object of the present invention is to provide a microscope including a focus detection device that can stably determine the focus state and adjust the focus regardless of the state of the sample surface. And

A microscope equipped with a focus detection device according to the present invention includes an observation optical system for observing an image of a sample surface formed by an objective lens and an illumination optical system for illuminating the sample surface, and a focusing pattern on the sample surface. In a microscope equipped with a focus detection device that detects whether or not it is in focus by forming an image of the reflected light with an objective lens and observing it, the reflected light from the sample surface passing through the objective lens is condensed. An optical path branching optical member that divides the image of the focusing pattern is disposed on the image side.
In the present invention, since the optical path branching optical member is disposed on the imaging side of the reflected light from the sample surface that forms an image through the objective lens for the focusing pattern on the sample surface, the optical path branching is performed regardless of the state of the sample surface. When the focusing pattern can be stably divided in the optical member, and the image formation position of the reflected light is shifted in the optical axis direction with respect to the optical path branching optical member, the focusing pattern image divided at the boundary of the optical path branching optical member It can be detected as a lateral shift. At that time, even if irregularly reflected light or scattered light is mixed into the reflected light from the sample surface, the reflected light traveling toward the optical path branching optical member is divided to ensure a stable lateral shift of the focused pattern image. And can observe. In the case of out-of-focus, it is possible to adjust the focus by adjusting the distance between the observation optical system and the illumination optical system and the sample surface.
The optical path branching optical member is preferably disposed at the imaging position of the objective lens.
In the present invention, in the case of focusing, the focusing pattern is formed on the optical path branching optical member together with the image of the sample surface, and no deviation occurs. In the case of non-focusing, the imaging position of the sample surface and the reflected light of the focusing pattern is shifted from the optical path branching optical member in the optical axis direction, and the focused pattern image branched on the optical path branching optical member is optical path branching optical Deviation occurs at the parting line.

Further, the focusing pattern is preferably an index image projected onto the sample surface by the illumination optical system.
When the ratio of the regular reflection surface to the sample surface is large, an index image is projected onto the sample surface and reflected as a focusing pattern.
Alternatively, the focusing pattern may be a pattern formed on the sample surface. When the sample surface is, for example, a processed surface formed with a fine uneven pattern, this pattern formed on the sample surface can be used as a focusing pattern without using an index.

Further, the optical path branching optical member is preferably a prism pair composed of two prisms that divide the optical axis of the reflected light from the sample surface passing through the objective lens.
When the sample surface is in an out-of-focus position with respect to the microscope, the reflected light splits the optical path by two prisms, and the image of the focusing pattern split using the boundary between the two prisms as a dividing line causes a shift. It will be.
In this case, the prism pair may be provided on a focusing plate of an eyepiece disposed in the observation optical system. By adopting this configuration, it is possible to add a focusing function at a low cost without changing the microscope system.
Further, the optical path branching optical member may be constituted by an image division reflecting mirror arranged with different inclination angles with respect to the optical axis of the observation optical system.
Even in this configuration, when focused, the reflected light forms an image on the image division reflecting mirror, and a focused pattern without deviation can be obtained. At the time of out-of-focus, the image of the in-focus pattern branched on the image division reflecting mirror is divided by the dividing lines that make up the boundaries of the plurality of reflection mirrors constituting the image dividing reflection mirror, resulting in deviation. The image division reflecting mirror may be composed of first and second reflecting mirrors closely arranged with different inclination angles.

  In the microscope equipped with the focus detection device according to the present invention, the deviation of the image of the focus pattern is caused by the optical path branching optical member arranged on the image forming side through the objective lens of the reflected light reflected by the sample surface. In addition, even if the angle of the reflected light on the sample surface is different from the angle of the incident light, or irregularly reflected light or scattered light is mixed, it will not be a noise with respect to the change of the focused pattern image, and the stable focused pattern It is possible to obtain an image and perform accurate focus determination and adjustment.

Hereinafter, a microscope provided with a focus detection apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing an optical system of a microscope according to the first embodiment, FIG. 2 is a diagram showing an observed index image, (a) is an in-focus state, and (b) is an out-of-focus state.
A microscope 1 shown in FIG. 1 includes an optical system of a focus detection apparatus including an observation optical system 2 and an illumination optical system 3. The observation optical system 2 and the illumination optical system 3 are placed on a stage (not shown) so that the distance from the sample 4 can be adjusted by moving forward and backward relative to the sample 4.
In the observation optical system 2, an objective lens 6 is disposed so as to face the sample 4, and the sample surface 4 a of the sample 4 is located at the in-focus position of the objective lens 6. On the optical axis O of the objective lens 6, an eyepiece lens 7 is provided for observing an image at an imaging position (A position) by the objective lens 6 with respect to the reflected light of the sample surface 4a. A split prism 8 (optical path branching optical member) is positioned substantially orthogonal to the optical axis O at the image forming position on the optical axis O.
The split prism 8 is a prism pair composed of two wedge prisms 8a and 8b. Each wedge prism 8a has, for example, a substantially semicircular shape in plan view, and a substantially wedge shape in which the upper surface is inclined with respect to the lower surface in a side view in the thickness direction. Have. The two wedge prisms 8a and 8b are configured by joining with surfaces having substantially semicircular chords combined in reverse gradient. A straight line that forms the boundary between the two wedge prisms 8a and 8b in plan view is defined as a dividing line 9.

On the other hand, in the illumination optical system 3, a light source 10 and a condenser lens 11 are provided, and an index plate 13 on which an index 12 (focusing pattern) is formed is provided in front thereof. As shown in FIG. 1, the indicator 12 is configured by a line pattern passing through the center of a circular indicator plate 13, for example. In front of the index plate 13, a half mirror 14 is disposed between the objective lens 6 and the split prism 8 on the optical path of the observation optical system 2 so that the illumination light transmitted through the index 12 is directed toward the objective lens 6. The image of the index 12 is projected together with the illumination light on the sample surface 4a by the objective lens 6.
It is assumed that the index 12 is provided at a position conjugate with the sample surface 4a on the optical axis O1 of the optical path from the light source 10 to the sample 4 of the illumination optical system 3 as described above.
In the observation optical system 2, in the focused state, the reflected light of the sample surface 4 a and the image of the index 12 projected thereon is imaged at the position A on the upper surface of the split prism 8 by the objective lens 6. At this time, the images 12a and 12b of the index 12 observed through the eyepiece 7 are divided substantially perpendicularly to the dividing line 9 of the split prism 8, as shown in FIG. It becomes line symmetric.
On the other hand, in the out-of-focus state, the imaging position of the reflected light of the sample surface 4a and the image of the index 12 projected thereon is forward or backward in the optical axis O direction (Z-axis direction) with respect to the A position. Shift. In this case, since the light beam is divided in the direction of the wedge of each wedge prism 8a, 8b by the wedge angle, the images 12a, 12b of the index 12 are shifted in the direction of the wedge with the dividing line 9 as a boundary, and the eyepiece is laterally shifted. It can be observed with the lens 7 (see FIG. 2B).
Therefore, it is possible to perform in-focus determination on the sample surface 4a based on whether or not the images 12a and 12b of the index 12 are laterally shifted.

The microscope 1 provided with the focus detection apparatus according to the present embodiment has the above-described configuration. Next, a focus detection method for the sample 4 will be described.
In the illumination optical system 3 of the microscope 1, the illumination light emitted from the light source 10 is collected by the condenser lens 11 and passes through the index 12. The luminous flux of the image of the index 12 that has passed through the index 12 is bent by the half mirror 14 in the optical path of the observation optical system 2 together with the illumination light, and is projected onto the sample surface 4 a of the sample 4 by the epi-illumination through the objective lens 6. .
Then, the reflected light of the sample surface 4 a and the image of the index 12 projected onto the surface 4 a forms an image through the objective lens 6. In the in-focus state, the image of the sample surface 4 a and the index 12 is formed at the A position that is the upper surface of the split prism 8. At this time, the image of the index 12 is divided into two by the dividing line 9 of the split prism 8, and the divided images 12a and 12b of the index 12 appear in a straight line with the dividing line 9 in between (see FIG. 2A). When the images 12a and 12b of the index 12 shown in FIG. 2A are observed with the eyepiece 7, the focus is determined.

In the out-of-focus state, the reflected light from the sample surface 4a and the index 12 forms an image at a position shifted forward or backward in the optical axis direction (Z-axis direction) from the A position, and therefore the images 12a and 12b of the index 12 Causes a lateral shift in the wedge direction with the dividing line 9 as a boundary on each wedge prism 8a, 8b. As a result, the images 12a and 12b of the index 12 appear laterally shifted at positions shifted in opposite directions with respect to the dividing line 9, as shown in FIG. When such images 12 a and 12 b of the index 12 are observed with the eyepiece 7, it is determined that the image is out of focus.
In addition, when it has shifted | deviated greatly from focusing, the images 12a and 12b of the parameter | index 12 are blurred and observed with the image of the sample surface 4a.
When it is determined that it is out of focus, the stage of the microscope 1 is relatively moved so as to be separated from or approached from the sample 4, and the height is adjusted until the in-focus state shown in FIG. The focus adjustment of the sample surface 4a can be performed by adjusting from the out-of-focus state to the in-focus state. When the value of the amount of movement of the stage from the in-focus position before the relative movement to the in-focus position after the relative movement is obtained, the height difference between the two points before and after the relative movement is obtained.

  As described above, in the microscope 1 according to the present embodiment, the lateral displacement of the images 12a and 12b of the index 12 is caused by the split prism 8 disposed on the imaging side of the reflected light reflected by the sample surface 4a. The reflected light of the image of the index 12 reflected by 4a does not become a noise for focus determination even if irregularly reflected light or scattered light is mixed, and stable focusing and non-focusing are possible even if the incident light and the angular distribution are different. Judgment, measurement, and adjustment.

Next, a microscope according to another embodiment or modification of the present invention will be described. However, the same or similar parts and members as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.
3 and 4 show a modification of the focus detection device of the microscope 1 according to the first embodiment.
In this modification, an eyepiece lens barrel 16 is provided in place of the eyepiece lens 7 and the split prism 8 in the observation optical system 2 of the focus detection apparatus according to the first embodiment shown in FIG. The eyepiece lens barrel 16 shown in FIG. 3 is provided on the optical axis O of the observation optical system 2, and an eyepiece 17 and its focusing screen 18 are provided inside. The focusing screen 18 is provided at the imaging position of the sample surface 4a by the objective lens 6 and forms a substantially annular shape in plan view. A split prism 19 is fitted in the hollow portion 18a inside the focusing screen 18, and the focusing screen 18 and the split prism 19 are arranged coaxially with the optical axis O.
Also in this modification, the reflected light of the image of the sample surface 4a and the index 12 is focused at the position A on the upper surface of the split prism 19 as in the first embodiment. In the out-of-focus state, an image is formed at a position shifted forward or rearward in the optical axis direction (Z-axis direction) with respect to the A position, and the elephant observed through the split prism 19 and the eyepiece 17 is the dividing line 9 The images 12a and 12b of the index 12 appear laterally shifted at positions shifted to both sides in the extending direction of the dividing line 9 with respect to the boundary.
By adjusting the stage up and down so that the images 12a and 12b of the index 12 that have been divided and shifted in two coincide with each other at the position of the dividing line 9, the height of the sample surface 4a and the focus adjustment can be performed.
According to this modification, a focusing function can be added at low cost by simply replacing and mounting the eyepiece lens barrel 16 without changing the microscope system.

Next, a microscope 21 provided with a focus detection device according to a second embodiment of the present invention will be described with reference to FIG.
The microscope 21 shown in FIG. 5 is different from the first embodiment in that an observation optical system 2 is provided with an image division reflecting mirror instead of the split prism 8. That is, in the observation optical system 2, the reflection mirror 22 that bends the optical path having the optical axis O between the objective lens 6 and the eyepiece lens 7, for example, 45 ° is provided, and the A position that is the imaging position on the bent optical path. Is provided with an image division reflecting mirror 23 (optical path branching optical member). The image of the sample surface 4a and the index 12 formed at the A position is observed with the eyepiece lens 7.
The image division reflecting mirror 23 is composed of a pair of a first reflecting mirror 23a and a second reflecting mirror 23b. In the side view shown in FIG. 5, the mirrors 23a and 23b are set at different inclination angles so as to intersect at the A position. Has been. For example, the first reflection mirror 23a is inclined at an angle (45 + θ) ° and the second reflection mirror 23b is inclined at an angle (45−θ) ° with respect to the optical axis O of the optical path bent horizontally by the reflection mirror 22. Yes.

Therefore, in the focused state where the reflected light of the image of the sample surface 4 a and the index 12 is focused at the position A through the objective lens 6, the images 12 a and 12 b of the sample surface 4 a and the index 12 are the second of the image division reflecting mirror 23. An image is formed at the position A on the first and second reflecting mirrors 23a and 23b. At this time, the image of the index 12 is divided into two images 12a and 12b by the dividing line 9 of the first and second reflecting mirrors 23a and 23b, and appears to be in a straight line with the dividing line 9 in between (FIG. 2A). reference). When this is observed with the eyepiece 7, it is determined to be in focus.
In the out-of-focus state, the reflected light of the sample surface 4a and the image of the index 12 forms an image at a position shifted forward or backward in the optical axis O direction (Z-axis direction) from the A position. 12a and 12b appear at positions shifted from the dividing line 9 of the first and second reflecting mirrors 23a and 23b (see FIG. 2B). When this is observed with the eyepiece 7, it is determined that the lens is out of focus.
When it is determined that the in-focus state is not achieved, the stage of the microscope 1 is relatively moved so as to be separated or approached from the sample 4, and the height is adjusted until the in-focus state is achieved. Then, when the amount of movement of the stage between the in-focus positions before and after the movement is obtained, a height difference of two points can be obtained. Moreover, the focus adjustment of the sample surface 4a can be performed by adjusting from the out-of-focus state to the in-focus state.

As described above, according to the present embodiment, the simple structure of the image-splitting reflecting mirror 23 is provided in place of the split prism 8, so that no complicated optical parts are used, so that the manufacturing cost can be reduced.
In the example shown in FIG. 5, in order to observe the image of the sample surface 4 a and the index 12 from above through the eyepiece lens 7, a configuration is adopted in which the optical path is bent twice by the reflection mirror 22 and the image division reflection mirror 23. When observing from the horizontal direction, the reflection mirror 22 may be omitted.

In each of the above-described embodiments, the height of the sample 4 and the focus adjustment are performed using the index 12, but such a configuration has a case where the sample surface 4a of the sample 4 has a large number of regular reflection areas. Is preferred. However, in the case where a fine processing pattern such as a processing grind exists on the sample surface 4a, it is possible to detect whether or not it is in focus by using the processing pattern such as the processing grind on the sample surface 4a without using the index 12. good. In this case, it can be determined whether the processed pattern image on the split prism 8 or the image dividing reflection mirror 23 observed with the eyepiece 7 matches or shifts on both sides of the dividing line 9.
FIG. 6 is a diagram showing a microscope 31 provided with a focus detection device not provided with such an index 12 as a third embodiment. The configuration excluding the index 12 is the same as that according to the first embodiment.

It is a block diagram which shows the optical system of the microscope provided with the focus detection apparatus by 1st embodiment of this invention. It is a figure which shows the image of the parameter | index observed, (a) is a focusing state, (b) is a non-focusing state. It is a figure of the eyepiece part which shows the modification of the microscope by 1st embodiment. FIG. 4 is a perspective view showing a focusing screen and a split prism shown in FIG. 3. It is a block diagram of the optical system of the microscope provided with the focus detection apparatus by 2nd embodiment. It is a block diagram of the optical system of the microscope provided with the focus detection apparatus by 3rd embodiment.

Explanation of symbols

1, 2, 31 Microscope 2 Observation optical system 3 Illumination optical system 4 Sample 4a Sample surface 6 Objective lenses 7, 17 Eyepieces 8, 19 Split prism (optical path branching optical member: prism pair)
12 Indicator (focusing pattern)
12a, 12b Index image (focusing pattern)
18 Focusing plate 23 Reflecting mirror for image division (optical path branching optical member)
23a First reflection mirror (optical path branching optical member)
23b Second reflection mirror (optical path branching optical member)

Claims (6)

An observation optical system for observing an image of the sample surface imaged by the objective lens and an illumination optical system for illuminating the sample surface, and the reflected light of the focused pattern on the sample surface is imaged by the objective lens In a microscope equipped with a focus detection device that detects whether or not it is in focus by observing,
A microscope provided with an in-focus detection device, wherein an optical path branching optical member that divides an image of the in-focus pattern is disposed on an imaging side of reflected light from the sample surface passing through the objective lens.   The microscope provided with the focus detection device according to claim 1, wherein the focus pattern is an image of an index projected on a sample surface by the illumination optical system.   The microscope provided with the focus detection device according to claim 1, wherein the focus pattern is a pattern formed on the sample surface.   4. The focus detection device according to claim 1, wherein the optical path branching optical member is a prism pair including two prisms that divide reflected light from the sample surface that passes through the objective lens. microscope.   The microscope provided with the focus detection device according to claim 4, wherein the prism pair is provided on a focusing plate of an eyepiece disposed in the observation optical system. The microscope provided with the focus detection device according to any one of claims 1 to 3, wherein the optical path branching optical member is an image division reflecting mirror arranged with different inclination angles with respect to the optical axis of the observation optical system.

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