JP2010008458A - Optical measuring instrument and pattern formed on projection plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical measuring instrument for satisfactorily maintaining focus accuracy. <P>SOLUTION: A plurality of patterns P1 to P3 different in size are formed on a projection plate, and smaller ones of the patterns P1 to P3 are disposed closer to the center axis L of a luminous flux transmitting through the projection plate. Accordingly, at low magnification, the large patterns P3 located in a position away from the center axis L of the luminous flux are used. At high magnification, the small patterns P1 located adjacent to the center axis L of the luminous flux are used. The size change of the patterns P1 to P3 in accordance with zooming can be suppressed, then, the focus accuracy can be satisfactorily maintained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical measurement device and a pattern formed on a projection plate.

FIG. 1 is a diagram showing a configuration of a conventional image measuring apparatus 1, and FIG. 6 is a diagram showing a conventional pattern P projected on a measurement object. FIG. 6 shows a pattern P observed when the imaging lens 4 having an intermediate magnification is used.
2. Description of the Related Art Conventionally, an image measuring apparatus that performs autofocus using a projection plate is known (for example, Patent Document 1).
As shown in FIG. 1, the image measuring apparatus 1 described in Patent Document 1 illuminates light 2 that emits illumination light, and the light from the illumination means 2 is condensed on the object to be measured and reflected by the object to be measured. The objective lens 3 that condenses the light, the focal lengths (magnifications) that are different from each other and can be switched, and a plurality of imaging lenses 4 that image the light condensed by the objective lens 3, and each of these lenses 3 , 4 and an image pickup means 6 such as a CCD (Charge Coupled Device) camera for picking up a picked-up image by picking up an image of the object to be measured placed on the table 5.

  In addition, the image measuring apparatus 1 includes a half mirror 7 that reflects light from the illumination unit 2 toward the objective lens 3 and transmits light from the objective lens 3 toward the imaging lens 4, the half mirror 7, and the illumination unit 2. A plurality of triangular patterns P (FIG. 6) which are provided in between and which block light from the illumination means 2 and which have the same size, and project the pattern P onto the object to be measured; The projection lens 9 provided between the plate 8 and the half mirror 7, the driving means 10 for moving the objective lens 3 in the optical axis L direction of the objective lens 3, and the driving means for controlling the entire image measuring apparatus 1 And control means 11 for controlling the objective lens 3 to a position where the object to be measured is in focus.

  In such an image measuring apparatus 1, the control unit 11 controls the driving unit 10 to change the position of the objective lens 3 in the direction of the optical axis L in the captured image of the object on which the triangular pattern P is projected. Let's get more than one. Then, the control means 11 determines the position where the objective lens 3 is focused on the object to be measured from the contrast difference between the bright part 81 (FIG. 6) and the dark part 82 (FIG. 6) in each captured image. Then, the objective lens 3 is moved to the position. Since such an image measuring apparatus 1 focuses on the basis of the contrast of the pattern P projected onto the object to be measured by the projection plate 8, it can also focus on a low contrast object such as a mirror surface or a glass surface. .

JP 2004-29069 A

FIG. 7 is a diagram showing a conventional pattern P observed when switching to the low-magnification imaging lens 4, and FIG. 8 is a conventional pattern P observed when switching to the high-magnification imaging lens 4. FIG.
However, in the image measuring apparatus 1 described in Patent Document 1, when the imaging lens 4 having a different magnification is switched, the size of the pattern P greatly changes as shown in FIGS. 7 and 8. However, there is a problem that the accuracy of the focus is deteriorated because the edge of the pattern P is blurred.

  An object of the present invention is to provide an optical measurement apparatus capable of maintaining good focus accuracy and a pattern formed on a projection plate.

  An optical measurement apparatus according to the present invention includes an objective lens for condensing light on a measurement object, an observation optical system capable of observing an image of the measurement object based on light emitted from the objective lens, and the observation optics An optical measuring apparatus comprising a driving means for moving the objective lens in the optical axis direction based on the contrast of the image of the object to be measured obtained by a system, including a projection plate on which a pattern is formed. Projection means for projecting the pattern formed on the projection plate onto the object to be measured is provided, and the pattern includes a plurality of patterns having different sizes, and a light flux that passes through the projection plate as a pattern having a smaller size is provided. It is arrange | positioned near the central axis of.

  According to such a configuration, a plurality of patterns having different sizes are formed on the projection plate, and the smaller the pattern, the closer to the optical axis (the central axis of the light beam transmitted through the projection plate). Therefore, when the magnification is low, a large size pattern located away from the optical axis is used, and when the magnification is high, a small size pattern arranged close to the optical axis is used. The change in pattern size can be suppressed, and the focus accuracy can be maintained well.

  In the present invention, the observation optical system includes a plurality of imaging lenses that have different focal lengths and that are switchable, and that image the light condensed by the objective lens. Illuminating means for emitting light, the projection plate through which light from the illuminating means is transmitted, and provided between the objective lens and the imaging lens, and transmits the light from the objective lens to the imaging lens side And a half mirror that reflects the light emitted from the illumination means and transmitted through the projection plate to the objective lens side, and each of the different patterns has a size corresponding to each imaging lens. It is preferable that

  According to such a configuration, each pattern having a different size formed on the projection plate has a size corresponding to each imaging lens having a different focal length, that is, each imaging lens having a different focal length is measured. Since the size is observed at the same level when an object is imaged, a change in pattern size due to zooming can be sufficiently suppressed, and the focus accuracy can be reliably maintained satisfactorily.

In the present invention, the pattern is preferably formed in a triangular shape.
According to such a configuration, since the pattern is formed in a triangular shape, the edge of the object to be measured can be left even if the edge of the object to be measured has directionality. Therefore, it becomes easy to discriminate the edge of the pattern, and the focus accuracy can be reliably maintained good.

  The pattern formed on the projection plate of the present invention projects the pattern formed on the projection plate onto the object to be measured, and moves the objective lens in the optical axis direction based on the contrast of the image of the object on which the pattern is projected. It is a pattern formed on the projection plate in the optical measuring device that moves to the pattern, and the pattern includes a plurality of patterns having different sizes, and the smaller the size of the pattern, the closer to the predetermined point. Features.

  According to such a configuration, the pattern of the present invention includes a plurality of patterns of different sizes, and the smaller the size of the pattern, the closer to the predetermined point, the position of the one point is the optical axis (projection plate). By installing the projection plate on which the pattern is formed in the optical measuring device so that it coincides with the central axis of the light beam that passes through the optical pattern, a large size pattern that is located away from the optical axis at low magnification. When a high magnification is used, a small size pattern arranged close to the optical axis is used. Therefore, by using the projection plate on which the pattern of the present invention is formed in an optical measurement apparatus, it is possible to suppress a change in pattern size due to zooming and maintain a good focus accuracy.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the following, the image measuring apparatus 1 as the optical measuring apparatus of the present embodiment will be described with reference to FIG. 1 used when the conventional image measuring apparatus 1 is described. Since the configuration other than the projection plate 8 of the image measurement device 1 is the same as that of the conventional image measurement device 1, the configuration other than the projection plate 8 will be briefly described below.

  As shown in FIG. 1, the image measuring apparatus 1 includes an illumination unit 2, an objective lens 3 and three imaging lenses 4 (for example, 1X, 2X, 6X), an image pickup means 6 such as a CCD camera for picking up an object to be measured on the table 5 through these lenses 3 and 4, a half mirror 7, and patterns P1 to P3 (see FIG. 2) to be described later in detail. The projection plate 8, the projection lens 9, and the driving lens 10 that moves the objective lens 3 in the direction of the optical axis L of the objective lens 3 and the driving means 10 are controlled to focus the objective lens 3 on the workpiece. The control means 11 to which it moves to the position which suits is provided.

  In the present embodiment, the observation optical system 12 of the present invention that includes the imaging lens 4 and the imaging unit 6 and that can observe the image of the object to be measured based on the light emitted from the objective lens 3 is configured. The projection means 13 of the present invention for projecting the patterns P1 to P3 formed on the projection plate 8 onto the object to be measured includes the half mirror 7, the projection plate 8, and the projection lens 9.

FIG. 2 is a diagram showing patterns P1 to P3 formed on the projection plate 8. As shown in FIG. When the low-magnification imaging lens 4 (1X) is used, the patterns P1 to P3 shown in FIG. 2 are observed.
In such an image measuring apparatus 1, the projection plate 8 shields light from the illumination means 2 by general processing techniques such as electron beam drawing, transfer, etching, and cutting with a dicing saw, as shown in FIG. A plurality of triangular patterns P1 to P3 are formed. The projection plate 8 may be a liquid crystal plate (liquid crystal panel) that displays the patterns P1 to P3.

  These patterns P1 to P3 are formed in three different sizes, and are arranged in the order of patterns P1, P2, and P3 from the smallest size. Pattern P1 corresponds to high magnification imaging lens 4 (6X), pattern P2 corresponds to intermediate magnification imaging lens 4 (2X), and pattern P3 corresponds to low magnification imaging lens 4 (1X). ing. Each of these patterns P1 to P3 is formed in a size that can be observed with the same size when the imaging lens 4 is switched to one having a different magnification.

  The patterns P1 to P3 are formed in the order of the patterns P1, P2, and P3 around the central axis L (optical axis L) of the light beam emitted from the illumination unit 2 and transmitted through the projection plate 8, and each imaging lens. 4 is arranged so that the contrast in the picked-up image picked up using 4 is mainly generated by the patterns P1 to P3 corresponding to the imaging lens 4.

  In this embodiment, the control unit 11 controls the driving unit 10 to change the position of the captured image of the measurement object on which the patterns P1 to P3 are projected in the direction of the optical axis L of the objective lens 3. Get more than one. Then, the control unit 11 determines the position where the objective lens 3 is focused on the object to be measured from the difference in contrast between the bright part 81 and the dark part 82 in each captured image, and places the objective lens 3 at the position. Move. Here, when the object to be measured is imaged using the low-magnification imaging lens 4, a wide area of the measurement surface of the object to be measured is imaged and projected onto the object to be measured as shown in FIG. 2. Since all the patterned patterns P1 to P3 are imaged, the contrast between the bright part 81 and the dark part 82 is mainly caused by the pattern P3 larger than the other patterns P2 and P1.

FIG. 3 is a diagram showing patterns P1 to P3 observed when the imaging lens 4 having an intermediate magnification is used.
Further, when the object to be measured is imaged by the imaging lens 4 having an intermediate magnification, as shown in FIG. 3, among the patterns P1 to P3 projected onto the object to be measured, the medium is centered around the optical axis L. Since the patterns P1 and P2 that fall within the size area (see FIG. 2) are mainly imaged, the contrast between the bright part 81 and the dark part 82 is mainly caused by the pattern P2 having a size larger than the pattern P1. It will be.

FIG. 4 is a diagram showing patterns P1 and P2 observed when the high-magnification imaging lens 4 is used.
Further, when the object to be measured is imaged by the high-magnification imaging lens 4, as shown in FIG. 4, a pattern P <b> 1 that falls within a narrow region (see FIG. 2) centered on the optical axis L is mainly imaged. Therefore, the contrast between the bright part 81 and the dark part 82 is mainly caused by the pattern P1.

  As described above, in this embodiment, the smaller patterns P1 to P3 are formed near the optical axis L on the projection plate 8, so that when the magnification is low, the low magnification is located at a position away from the optical axis L. A large-sized pattern P3 is used. When the magnification is intermediate, a medium-sized pattern P2 arranged around the optical axis L is used. When the magnification is high, the small size is arranged close to the optical axis L. This pattern P1 is used. Therefore, the pattern size can be prevented from changing when the imaging lens 4 is switched to have a different magnification, and the focus accuracy can be maintained well.

  In addition, the size of each pattern P1 to P3 is the size corresponding to the imaging lens 4, that is, the size observed when the object to be measured is imaged using each imaging lens 4 and the same size. Therefore, it is possible to sufficiently suppress the change in the size of the patterns P1 to P3 when switching to the imaging lens 4 having a different magnification, and the focus accuracy can be reliably maintained well.

FIG. 5 is a diagram illustrating the edge of the object to be measured in the captured image.
Moreover, since each pattern P1-P3 is formed in the triangle shape, as shown in FIG. 5, even if the edge of a to-be-measured object has directionality, the edge of to-be-measured object can be left. Therefore, it becomes easy to discriminate the edge of the pattern, and the focus accuracy can be more reliably maintained better.

[Modification of Embodiment]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the above-described embodiment, the observation optical system 12 includes the imaging lens 4. However, the observation optical system 12 may include a zoom lens that can change the focal length and does not move the focus position. .

In the above-described embodiment, the pattern formed on the projection unit is a triangle. However, the pattern formed on the projection unit is not limited to a triangle. Any shape can be used as long as it can determine the in-focus position.
In the above-described embodiment, an example in which the present invention is applied to an image measurement apparatus has been described. However, the present invention may be applied to other optical measurement apparatuses such as a microscope.

  The present invention can be suitably used for an optical measuring device such as an image measuring device or a microscope. Further, the present invention can be suitably used for a pattern formed on a projection plate of an optical measurement device such as an image measurement device or a microscope.

The figure which shows the structure of the image measuring device which concerns on one Embodiment of this invention, and the conventional image measuring device. The figure which shows the pattern currently formed in the projection plate of the said embodiment. The figure which shows the pattern observed when the imaging lens of the intermediate magnification of the said embodiment is used. The figure which shows the pattern observed when using the high magnification imaging lens of the said embodiment. The figure which shows the edge of the to-be-measured object in the captured image of the said embodiment. The figure which shows the conventional pattern projected on the to-be-measured object. A diagram showing a conventional pattern observed when switching to a low magnification imaging lens The figure which shows the conventional pattern observed when switching to the high magnification imaging lens.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image measuring device (optical measuring device), 2 ... Illuminating means, 3 ... Objective lens, 4 ... Imaging lens, 7 ... Half mirror, 8 ... Projection plate, 10 ... Driving means, 12 ... Observation optical system, 13 ... projection means, P1-P3 ... pattern.

Claims (4)

An objective lens for condensing light on the object to be measured;
An observation optical system capable of observing an image of the object to be measured based on light emitted from the objective lens;
An optical measurement apparatus comprising: a driving unit configured to move the objective lens in the optical axis direction based on a contrast of an image of the measurement object obtained by the observation optical system;
Including a projection plate on which a pattern is formed, provided with a projection means for projecting the pattern formed on the projection plate onto the object to be measured,
The optical measurement apparatus, wherein the pattern includes a plurality of patterns having different sizes, and the smaller the pattern, the closer to the central axis of the light beam transmitted through the projection plate. In the optical measuring device according to claim 1,
The observation optical system is provided with a plurality of imaging lenses that have different focal lengths and are installed in a switchable manner to form an image of the light condensed by the objective lens,
The projection means includes
Illumination means for emitting illumination light;
The projection plate through which light from the illumination means is transmitted;
Provided between the objective lens and the imaging lens, transmits light from the objective lens to the imaging lens side, and transmits light emitted from the illumination means and transmitted through the projection plate to the objective lens side. With a reflective half mirror,
Each of the patterns having different sizes has a size corresponding to each of the imaging lenses. In the optical measuring device according to claim 1 or 2,
The optical measurement apparatus, wherein the pattern is formed in a triangular shape. The pattern formed on the projection plate is projected onto the object to be measured, and the objective lens is moved in the direction of the optical axis based on the contrast of the image of the object on which the pattern is projected. Pattern,
The pattern includes a plurality of patterns of different sizes, and a pattern having a smaller size is arranged closer to a predetermined point. The pattern formed on the projection plate.

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