JP5354254B2 - Shape measuring apparatus and method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a shape of an object to be inspected without moving the object to be inspected along an optical axis of an objective lens. <P>SOLUTION: An MLA 12 is disposed on a pupil plane or an image plane of the objective lens 11. An image sensor 13 is installed behind the MLA 12, and captures an image of the object to be inspected by the objective lens 11. An arithmetic processing circuit 34 generates a plurality of measurement images from an output of the image sensor 13, uses correction information of the measurement images as a reference image obtained from pixels at a location for intersecting a main light beam of the objective lens 11 among pixels for composing imaging areas of the image sensor 13 corresponding to a plurality of MLs two-dimensionally arrayed in the MLA 12, and measures the three-dimensional shape of the object to be inspected. The invention can be applied to the shape measuring apparatus for measuring the three-dimensional shape of the object to be inspected. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a shape measuring apparatus and method, and a program.

  While moving the test object along the optical axis of the objective lens, obtain multiple images with different focal positions, and select the image with the maximum focus measure for each point on the test object from the multiple images. It is known that the focus position in the image is the height of the point and the shape of the test object is measured from these pieces of information.

This is generally a technique such as SFF (Shape From Focus).
Japanese Patent No. 2960684

  However, in such a conventional technique, it is necessary to acquire an image while moving the test object along the optical axis of the objective lens, and the measurement takes time.

  The present invention has been made in view of such a situation, and makes it possible to measure the shape of a test object without moving the test object along the optical axis of the objective lens.

The shape measuring apparatus according to one aspect of the present invention includes an objective lens, an optical element having a plurality of lenses arrayed two-dimensionally behind the objective lens, and a two-dimensional imaging element disposed behind the optical element. And image generating means for generating a plurality of measurement images having different focal planes from the output of the image sensor, the objective lens among the pixels constituting the image sensor region of the image sensor corresponding to each of the plurality of lenses, and the A position in the optical axis direction of the objective lens of the test object obtained from the correlation between a reference image obtained by focusing on all the pixels and the plurality of measurement images obtained from predetermined pixels according to the optical arrangement with the optical element using, characterized in that it comprises a three-dimensional shape measurement means for measuring the three-dimensional shape of the test object.

  The optical element is conjugate with an exit pupil of the objective lens, and the three-dimensional shape measuring means is arranged on the imaging surface of the imaging element by a lens at the optical axis position of the objective lens among the plurality of lenses. An image obtained from the image formed in the above is used as the reference image.

  The image pickup surface of the image pickup device is conjugate with the exit pupil of the objective lens, and the three-dimensional shape measuring unit obtains the reference image from pixels constituting the image pickup region of the image pickup device where chief rays of the objective lens intersect. It is characterized by forming.

The three-dimensional shape measuring means has the most significant correlation between the edge position of interest and the pixel signal in the vicinity thereof among the plurality of measurement images and the contrast signal of the edge position obtained from the reference image and the pixels in the vicinity thereof. The test object using the position in the optical axis direction of the test object obtained by obtaining the best focus position at each edge position from the virtual focal position of the image. The three-dimensional shape is measured.

The three-dimensional shape measurement means detects an edge position in the plurality of measurement images using the reference image, and based on a change in defocus amount obtained by a predetermined filter process at the edge position, A three-dimensional shape of the test object is measured using a position in the optical axis direction of the test object obtained by obtaining a best focus position at each edge position.

  Projecting means for projecting a predetermined pattern onto the object to be examined is further provided, and the imaging element is a reflected light of the pattern projected onto the object to be examined, and images an object image by the objective lens. The three-dimensional shape measuring means measures the three-dimensional shape of the test object based on an image signal obtained from the reflected light of the pattern output from the imaging device.

  If you want to increase the measurement aperture by increasing the lens aperture when you want to increase the measurement sensitivity and the lens aperture that is located at the pupil plane of the objective lens or at a position conjugate with the pupil plane, The apparatus further comprises lens diaphragm control means for controlling the lens diaphragm so as to increase the F value by narrowing the lens diaphragm.

The shape measuring method or program according to one aspect of the present invention is a shape measuring method or program corresponding to the shape measuring apparatus according to one aspect of the present invention described above.

In one aspect of the present invention, a plurality of measurement images having different focal planes are generated from the output of the image sensor, and the objective lens and the optical element among the pixels constituting the imaging region of the image sensor corresponding to each of the plurality of lenses Using the position in the optical axis direction of the objective lens of the test object obtained from the correlation between a reference image obtained by focusing on all the pixels and a plurality of measurement images obtained from predetermined pixels corresponding to the optical arrangement of The three-dimensional shape of the specimen is measured.

  According to the present invention, the shape of the test object can be measured without moving the test object along the optical axis of the objective lens.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate.

In the present invention, the amount of blur (including directionality) (hereinafter also referred to as focus information) from a plurality of virtual object planes (Z ₁ , Z ₂ ,...) Is calculated without moving the lens. In addition, an omnifocal image without blur can be obtained at the same time. Thereby, in this invention, it becomes possible to perform the distance measurement using those information.

  Specifically, from the distance a between the lens and the imaging surface (hereinafter also referred to as the lens position a) and the focal length f of the lens, the measurement point of the object to be measured is calculated according to the Gauss formula of the following equation (1). The distance b can be known.

  1 / b = 1 / f−1 / a (1)

In the measurement according to the present invention, in addition to the lens position a determined mechanically, the pixel signal on the image sensor that has passed through a microlens array (hereinafter referred to as MLA) is recombined and added to virtually add the lens. The imaging plane intervals a ₁ , a ₂ , a ₃ ,..., _An are constructed. A value string of values b obtained by substituting these values into the value a in the equation (1) is the position of a plurality of object planes (Z ₁ , Z ₂ , Z ₃ ,... Z _n ). That is, in such measurement, it is possible to reconstruct an image at that time and obtain focus information on the assumption that light beams emitted from different object surfaces have reached the imaging surface by such reconstruction.

  In this way, the same information as in the conventional SFF method can be obtained without moving the test object along the optical axis of the lens.

  In addition, since the position in such focus detection can be executed by the number of MLAs, how finely the test object can be measured (spatial resolution) is determined by the arrangement of the MLA. In other words, the larger the number of MLA, the higher the spatial resolution of the measurement.

  Next, details of the shape measuring apparatus for measuring the shape of the test object using the above principle will be described for each component.

[1. Optical system]
First, an outline of an optical system of a shape measuring apparatus to which the present invention is applied will be described with reference to FIG.

  As shown in FIG. 1, the optical system is configured to include an objective lens 11, an MLA 12, and an image sensor 13.

  FIG. 1 shows the configuration of the two optical systems shown in FIGS. 1a and 1b. In the configuration shown in FIG. 1a, the focal point of the objective lens 11 that captures an image of the test object (object plane (P plane)) is shown. The MLA 12 is placed at a position separated by a distance, and the image sensor 13 is placed at a position separated by the focal length of the MLA 12. In FIG. 1a, the imaging surface of the imaging device 13 is conjugate with the object plane (P plane), and an image of the test object is formed.

  The MLA 12 is an optical element in which a plurality of microlenses (hereinafter referred to as ML), such as 7 × 7, are arranged in a two-dimensional manner, similar to the above-described MLA (in FIG. 1, seven in the vertical direction are arranged). Shown). A region where an image formed by each ML can be formed, that is, an image signal obtained from the ML region 13ML is an image of a different viewpoint of the test object, that is, an image having a parallax according to the position of each ML region. Yes.

  On the other hand, in the configuration of FIG. 1b, the MLA 12 is placed on the surface where the object plane P at a predetermined position forms an image with the objective lens 11, and the image sensor 13 is placed at a position separated by the focal length of ML. In this case, the surface of the image sensor 13 is conjugate with the pupil plane of the objective lens 11, and the image signal in each ML region is an image obtained by dividing the pupil. In other words, in FIG. 1b, the imaged rays are distributed into rays at different angles as seen from the lens pupil.

  In the present invention, it is possible to obtain a plurality of images with different focal planes by reconstructing light rays from different angles from either of the above-described configurations of FIG. 1a or FIG. 1b. Measure the shape of the specimen. Therefore, in the following description, the description will focus on the configuration of FIG. 1a, but the same applies to the configuration of FIG. 1b.

Then, with reference to FIG.2 and FIG.3, the further detailed structure of the optical system of FIG. 1a is demonstrated next. In FIG. 2, three MLs of microlens ML _a , microlens ML _b , and microlens ML _c (hereinafter referred to as ML _a , ML _b , and ML _c , respectively) as a part of MLA 12 composed of a plurality of MLs. For illustrative purposes).

In Figure 2, the light from point P1 on the object plane (P-plane), is refracted after passing through the objective lens 11 as a parallel to the optical axis direction of the light (solid line in the drawing), captured by ML _b element 13 light ray group is focused on a point P1 _b of the ML area on the imaging surface of the (solid line in the figure) and, after passing through the center of the objective lens 11, the ML _c, the ML area on the imaging surface of the imaging device 13 and the like light ray group is focused on the point P1 _c (dotted line in the figure).

In this way, each ML placed on the pupil plane of the objective lens 11 forms an object image independently on the imaging plane. At this time, the ML region point P1 _b and the ML region point P1 _c on the imaging surface receive light rays emitted from the same point P1 on the object surface (P surface) at different angles. .

Similarly, the light beam from point P2 on the object plane (P-plane), passes through the refractive objective lens 11 by injection in the direction indicated by the dashed line in the figure, on the imaging surface of the image sensor 13 by the ML _a as shown in rays that are imaged on a point P2 _a ML-region, with a solid line in the figure, after passing through the objective lens 11 is injected in a direction parallel to the optical axis of the objective lens 11, imaging by ML _b element 13 rays imaged at the point P2 _b of ML areas on the imaging surface, and as shown by a dotted line in FIG refracted after passing through the objective lens 11 is injected in downward direction, the image pickup device by ML _c rays imaged is shown at point P2 _c of ML areas on the imaging surface 13. Further, the light rays from point P3 on the object plane (P-plane), is refracted after passing through the objective lens 11 is injected upward, as shown by a chain line in the figure imaged by ML _a device 13 light is imaged on a point P3 _a ML-region on the imaging surface of, and exit in the direction parallel to the optical axis of the objective lens 11 as shown by the solid line in the figure, the imaging surface of the imaging device 13 by the ML _b The rays that are imaged at point P3 _b in the upper ML region are shown.

Here, if it is assumed that the imaging system includes only the objective lens 11, for example, light emitted from the point P <b> 2 is condensed at one point by the objective lens 11. That is, in the optical system of FIG. 2, the light intensity from all directions emitted from the point P2 such as the points P2 _a , P2 _b , and P2 _c is added, and this becomes a pixel signal. This means that in the optical system of the present invention as shown in FIG. 2, the light emitted from one point on the test object can be sorted and captured by each ML by the ML of the MLA 12. ing.

  FIG. 3 shows that an image viewed from one ML is an image of the P plane composed of light rays emitted from the same direction and emitted from the P plane. This shows that images viewed from different directions by the number of MLs can be obtained. That is, as many as the number of MLs can be used, but this means that light emitted from the P plane enters the corresponding ML and forms an image of the P plane. In other words, parallax images that differ by the number of MLs are obtained.

  Among the light rays shown in FIGS. 3a to 3c, in FIG. 3b, the image by ML in the central portion that collects the light entering perpendicularly to the objective lens 11 is an image obtained by capturing the P plane from the front. 3a and 3c show that the image by ML located toward the end where the light incident obliquely on the objective lens 11 is collected is an image obtained by viewing the P surface from the angle direction of the light emitted from the P surface. Become.

  The pupil plane of the objective lens 11 is divided into the size of each ML of the MLA 12, and each ML forms the same object image. At this time, the image in the ML near the edge is blurred in the vicinity (where the object cannot be seen) and a part of the visual field near the edge is blocked, but basically, the image by each ML is blocked. Is an image obtained by viewing the object plane (P plane) from a different angle at a position conjugate with the object plane (P plane).

  The NA (open angle) of each of the N MLA images is reduced to 1 / N by an opening determined by the aperture of each ML. What should be noted here is that each ML image has a small angle of view from the image forming side and a small amount of light, but the depth of field (depth of focus) becomes very deep. Therefore, regardless of the depth on the object side, the image is almost in focus, that is, a so-called omnifocal image.

Further, an image formed by ML (corresponding to ML _b in FIG. 2) on the optical axis of the objective lens 11 in FIG. 3B (corresponding to the center of the MLA 12 in FIG. 2) has an object position in the optical axis direction. Even if it moves, the image stays in focus and does not move. That is, the image hardly changes even if the position of the object in the optical axis direction changes.

On the other hand, when the ML deviated from the center in FIGS. 3a and 3c (corresponding to ML _a and ML _c in FIG. 2) is viewed, the object position is away from the objective lens 11 as shown by the left arrow in the figure. When moving away, the image to be imaged is shifted in the direction of the upward arrow in FIG. 3a and shifted in the direction of the downward arrow in FIG. 3c. In other words, the pixel position where the light beam strikes shifts in a direction away from the optical axis. Conversely, when the object position is close, the pixel positions of these images are shifted in the direction approaching the optical axis.

  The optical system of the present invention is configured as described above.

[2. Focused image generation procedure]
(2-1) When the MLA 12 is used as the pupil plane of the objective lens 11 Next, referring to FIGS. 4 and 5, the object plane at a plurality of different positions when the optical system of the present invention is employed. A method for detecting the focus information at each point of the object by forming the image or signal will be described. In the present embodiment, as described with reference to FIG. 1, regardless of the configuration of FIG. 1a or FIG. 1b, a plurality of beams having different focal planes are reconstructed by reconstructing rays incident from different angles. It is possible to generate images. Therefore, first, (1) the case where the MLA 12 is placed on the pupil plane of the objective lens 11 will be described, and then (2) the case where the MLA 12 is placed on the imaging plane of the objective lens 11 will also be explained.

  FIG. 4 shows a ray tracing diagram of the objective lens 11 and the MLA 12, and FIG. 5 shows a part of the pixel array on the surface of the image sensor 13 imaged by the MLA 12 and a selection for signal processing for each MLA region. A pixel is shown.

  By the way, the image pickup device 13 disposed on the rear side of the MLA 12 is, for example, a CCD (Charge Coupled Device) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, or the like, and receives a predetermined light that passes through each ML of the MLA 12. The pixel array is arranged in an arrangement pattern corresponding to ML. The number of pixels in the vertical direction and the horizontal direction of this pixel array is appropriately set so that, for example, partial light beams individually transmitted through MLs such as 7 × 7 can be individually received. Here, an example in which a CCD is used as the image sensor 13 will be described.

In FIG. 5, 21 × 21 squares indicate pixels arranged on the imaging surface when the imaging device 13 is viewed from the optical axis direction of the objective lens 11, and 7 × surrounded by a thick line among them. Each of the seven square areas represents one ML area. In FIG. 5, 3 × 3 ML regions are representatively shown in the 7 × 7 ML regions. Therefore, the center area among the ML areas surrounded by the thick line in the figure is the ML area formed by the ML at the center of the objective lens 11 (corresponding to ML _b in FIG. 2).

Figure 4a is a ray diagram in the case where the object plane P0 (the same as the focal plane Z ₀ are focused) is in the focus position. Here, the object plane P0 is uniquely determined by the focal length f of the optical system and the distance a between the objective lens 11 and the imaging surface of the imaging element 13, and specifically, the Gaussian equation of the optical system described above. This is the position of the distance b determined by (1).

  The light emitted from the position that coincides with the optical axis of the objective lens 11 on the object plane P0 is the ML of each MLA 12, and the center of each ML area on the CCD (imaging device 13) surface (coincides with the optical axis of each ML). Condensed to Therefore, as shown in FIG. 5 (as already described, only the pixel area corresponding to each ML region around the ML at the position corresponding to the optical axis of the objective lens 11 is shown), Since the light emitted from the point P02 at the center of the object plane P0 (which coincides with the optical axis of the objective lens 11) is focused on the central pixel (black square in FIG. 5) in each ML region, each pixel area The total luminance of the point P02 on the object plane P0 can be obtained by selecting and adding the outputs of the center pixel.

Light from a position deviating from the point P02 on the object plane P0 is incident on the MLA 12 in parallel at an angle corresponding to the amount of deviation from the point P02, so that these lights have the same amount from the center and in the same direction in each ML region. It will shift. Therefore, selecting the pixel of the same position in each ML regions, by adding, it is possible to reproduce an image of the object plane P0 in the focal plane Z _0.

4b shows an object plane P1 closer to the objective lens 11 than the object plane P0 (actually, as indicated by the dotted object plane P0 in FIG. 4b, the object plane P0 and the imaging plane of the image sensor 13 as in FIG. 4a). Is a light ray diagram from Light emitted from a position that coincides with the optical axis of the objective lens 11 on the object plane P1 is incident on each ML of the MLA 12 at an angle slightly shifted outward from the optical axis of each ML toward the end of the lens. Is done. In this case, the light emitted from the point P12 at the center of the object plane P1 (which coincides with the optical axis of the objective lens 11) is imaged by the center ML region (ML _{b in} FIG. 2) as shown in FIG. In the other ML region, the pixels in the other ML regions are left as they are, and the pixels on the object plane P0 shown in FIG. The total luminance of the point P12 on the object plane P1 can be obtained by selecting and adding the pixels.

  Since light from a position deviating from the point P12 on the object plane P1 enters the MLA 12 in parallel at an angle corresponding to the amount of deviation from the point P12, these lights are the same amount from the center and in the same direction in each ML region. It will shift. Therefore, by selecting and adding pixels at the same position in each ML region, the image of the object plane P1 can be reproduced.

4c shows an object plane P2 that is farther from the objective lens 11 than the object plane P0 (actually, as indicated by the dotted object plane P0 in FIG. 4c, the object plane P0 and the imaging plane of the image sensor 13 are similar to FIG. 4a. Is a light ray diagram from Light emitted from a position that coincides with the optical axis of the objective lens 11 on the object plane P2 is incident on each ML of the MLA 12 at an angle that slightly shifts inward from the optical axis of each ML toward the end of the lens. Is done. In this case, the light emitted from the point P22 at the center of the object plane P2 (which coincides with the optical axis of the objective lens 11) is imaged by the center ML region (ML _{b in} FIG. 2) as shown in FIG. The pixels in the other ML regions are left as they are, and in the other ML regions, the pixels on the inner side of the pixel position on the object plane P0 shown in FIG. Since the light is condensed into a square, the total luminance of the point P22 on the object plane P2 can be obtained by selecting and adding the pixels.

  Since light from a position deviating from the point P22 on the object plane P2 enters the MLA 12 in parallel at an angle corresponding to the amount of deviation from the point P22, these lights are the same amount from the center and in the same direction in each ML region. It will shift. Therefore, by selecting and adding pixels at the same position in each ML region, an image of the object plane P2 can be reproduced.

In FIG. 4, the rectangle 40 on the right side of the image sensor 13 schematically represents 13ML ₁ to 13ML ₇ that are part of the ML region, and the light condensing position in each ML region is black. By filling in, the above description in FIG. 5 is supplemented and conceptually described. That is, in the present embodiment, since an example of 7 × 7 ML areas is taken up, each of the ML areas 13ML ₁ to 13ML ₇ in the vertical direction is schematically shown, and the light is condensed in each ML area. The state of the (imaged) light is shown. In FIG. 4a, the line from the object plane P02 is focused (imaged) at the center of each ML region on the CCD (image sensor 13). Also, as shown in FIG. 4b, the light from the object plane P1 closer to the objective lens 11 than the object plane P0 is collected in the center in the central ML region (although not completely imaged, the ML aperture) In other ML regions, the light is condensed outward as compared with the case of FIG. 4a. Furthermore, as shown in FIG. 4c, the light from the object plane P2 farther from the objective lens 11 than the object plane P0 is collected in the center in the central ML region (although it is not completely imaged, the ML aperture) In other regions, the light is condensed inward compared to the case of FIG. 4a.

  If further captured, in the present embodiment, the front object plane P1 and the rear object plane P2 are actually the object plane P0 determined by the position of the objective lens 11 (the object plane P0 in FIG. In other words, it is a virtual focusing surface that can be obtained without moving the objective lens 11 other than the light receiving surface.

As described above, as in the object plane P0, P1, P2, even when changing the position of the optical axis direction of the object from the object plane P0, (corresponding to the Figure 2 ML _b) the center of the ML of the objective lens 11 As a result, the position of the image does not shift while the image is focused.

That is, (corresponding to P2 _b in FIG. 2) image formed by the ML of lens center of the optical system configuration (corresponding to ML _b in FIG. 2) shown in Figure 3b, the objective lens 11 It consists of light rays that enter vertically, and it is an image that captures the object from the front. Therefore, even if the object position moves in the optical axis direction, the image does not shift. And since it is the image from the divided | segmented small pupil, F value is large and the depth of field (depth of focus) becomes very deep. That is, even if the position of the test object in the optical axis direction changes, the image hardly changes. Therefore, regardless of the depth on the object side, the image is almost in focus, that is, a so-called omnifocal image.

(2-2) When the MLA 12 is placed on the imaging surface of the objective lens 11 By the way, in the above (2-1), an example in which the configuration of FIG. The case where it is set on the pupil plane of the lens 11 has been described. The method of acquiring the omnifocal image always in focus is not limited to the method (2-1), and as shown in FIG. 1B, the MLA 12 is placed on the focal (imaging) plane of the objective lens 11, ie, the object The same effect can be obtained even when the position is conjugate to the surface. Therefore, next, as a second example of a method for acquiring an omnifocal image, (2-2) a case where the MLA 12 is set on the image plane of the objective lens 11 will be described. In this case, since the procedure for creating an image on a different object plane is different from that of the method (2-1), here, the procedure for creating the image will be mainly described with reference to FIGS.

  6 to 8, in order to make the explanation easy to understand, each light ray (the center of the corresponding microlens ML is incident on each of the five pixels a, b, c, d, and e aligned on the straight line in the image sensor 13. Only the chief ray passing through). Further, each element in each drawing is given a suffix (1, 2, 3,...) For indicating coordinates in a plane perpendicular to the optical axis.

That is, as shown in FIG. 6, an image of a test object by an objective lens 11 (not shown) is imaged on the MLA 12 (Z = 0) (regions incident on each ML are indicated by broken lines, and the coordinates of the center are X ₁ to X ₇ ), rays r ₁ , r ₂ , r ₃ , r ₄ , and r ₅ from an objective lens 11 (not shown) are image planes (on the Z = 0 plane), that is, ML. Gather at one point on the surface. Each region indicates the center coordinates in X ₁ to X X _7, since subject to the same action, will be described below the central region. The light exiting from the center X ₄ in the central region corresponds to each pixel on the surface of the image sensor 13 by the lens action of the microlens ML ₄ , and a ₄ , b ₄ , c ₄ , d ₄ , e ₄ pixel signals. Therefore, each image signal on the imaging plane (Z = 0) is the sum of these. That is, if the image signal is L, L can be obtained by the following equation (2).

L (i) = (a _i + b _i + c _i + d _i + e _i ) (2)

However, as described above, i represents the coordinate in the X direction (i = 1 to 7) in the plane perpendicular to the optical axis. For example, in the case of the coordinate X ₄ , L (4) = (a ₄ + B ₄ + c ₄ + d ₄ + e ₄ ). Actually, since it is necessary to think two-dimensionally, it is necessary to consider the Y direction in addition to the X direction, but only the X direction will be described here in order to simplify the description.

On the other hand, as shown in FIG. 7, the image signal of the center coordinate X ₄ of the central region at the position of Z = h ₁ where the imaging plane is displaced from the surface of each ML is obtained from the following equation (3). Can do. However, i = 1 to 7 and a value in which the coordinate suffix is outside 1 to 7 is a value that is not used.

L (i) = (a _i−2 + b _i−1 + c _i + d _{i + 1} + e _{i + 2} ) (3)

In the case of the coordinate X ₄ , since i = 4, L (4) = (a ₂ + b ₃ + c ₄ + d ₅ + e ₆ ). As is clear from this, the central pixel signal c _i (c _{4 in} this example) in each region of the imaging surface of the imaging device 13 always exists regardless of the focal position. That is, an image obtained by collecting only these signals is a constant image regardless of the position on the object side, and is an image without defocusing.

  Therefore, as shown in FIG. 8, an image composed of signals having the relationship expressed by the following equation (4) has a constant image plane regardless of the image plane (in other words, the image plane is constant). It will always be an all-in-focus image (wherever the inspection is). However, FIG. 8 is a diagram in which a field lens (hereinafter referred to as FL) is added to FIGS. By disposing the FL, the angle of the light beam incident on the ML disposed at a high image height can be suppressed. Therefore, although not described in the above-described example, it is preferable to provide the FL.

L (i) = c _i (4)

That is, for example, in FIG. 8, an image obtained by collecting central pixel signals c ₁ , c ₂ , c ₃ , c ₄ , c ₅ , c ₆ , and c ₇ in each area of the imaging surface of the image sensor 13 is This results in a focused omnifocal image.

  As described above, by adopting the configuration of FIG. 1a or 1b, the procedure for generating a focus image is different, but a plurality of images having different focal planes are generated by reconstructing rays from different angles. .

[3. Measurement signal processing procedure]

Next, signal processing executed to obtain image data for measurement from the image group at the virtual focal position generated by the above procedure will be described. Such signal processing is characterized in that an omnifocal image that is always in focus is used, and by performing edge processing on each acquired image data while shifting the focal plane little by little in the optical axis direction, focusing is achieved. Select an image.

(3-1) Multi-Focus Sequential Processing Method Although several methods can be considered as the above-described edge processing, first, a case where a multi-focal sequential processing method is used as a method for detecting an edge of an image will be described. To do. Further, a case where a Fourier transform (wavelet transform) method is used as an edge process in the multifocal sequential process will be described as an example.

  Above [2. After a group of images on a plurality of different object planes is formed by the procedure for generating a focus image, the focus information is obtained by the following method at the same pixel area position of each image by the same process as SFF described above. Can be detected.

That is, in such signal processing, as shown in FIG. 9, FFT (Fast Fourier) is performed on image groups of a plurality of object planes (..., Z ₋₁ , Z ₀ , Z ₁ ,. The image signal is subjected to Fourier transform (or wavelet transform) by Transform, and only high-frequency components are extracted in the spatial frequency space (on the Fourier plane) with a high pass filter, and then inverse Fourier transform (or inverse wavelet transform). ) By this processing, an image of only the edge (contour) portion is obtained. Next, paying attention to the position (X _i , Y _i ) of each point having an edge in these images, a plurality of object planes (..., Z ₋₁ , Z ₀ , Z ₁ ,...) An image having the sharpest edge (the highest inclination component) is selected from the image group as the best focus.

  FIG. 10 is a graph of the slope component of the edge of the sampling point in the image group of each focal plane. In FIG. 10, the horizontal axis Z represents the position of the object plane (distance from the test object), and the vertical axis α represents the inclination component of the edge, and the value increases in the upward direction in the figure (the focal point). (The degree of focus is high).

  As shown in FIG. 10, the sampling points in the Z direction are discrete because they are values for each object plane. However, as shown by the curve in the figure, the function approximation is used. By obtaining the peak (dotted line in the figure), a position Z having a value after the decimal point is obtained by interpolation processing, and the accuracy is improved.

  However, although the position of Z can be obtained by this procedure, the following problems remain.

  That is, when an edge is detected from an image with a different focus, there are places where the focus (focus) is in focus and places where it is not in accordance with the distance of the object. At this time, if edges with extremely different brightness (signal intensity) are adjacent to each other, the bright edge that is not in focus covers the adjacent dark edge that is in focus, and the position of the edge is erroneously recognized. There is a fear.

  In order to solve such a problem, it is only necessary to obtain a differential value for each pixel using an image in which all edges are in focus, and to detect a correct edge position first.

Therefore, in the present embodiment, even when the image of the center (on the axis) of the objective lens 11 formed in the ML at the center of the MLA 12 (corresponding to ML _b in FIG. 2) changes the position of the object plane. It is an image that does not change (even if the direction of Z changes), has a deep depth of field, is almost completely in focus regardless of the distance on the object side, no image shift, and no blur Focusing on the fact that there is no image (omnifocal image), this image is used.

In the signal processing of the present invention, using this omnifocal image, the Fourier transform and high-pass filter processing are performed as described above to obtain the correct edge position (X _i , Y _i ), and at the same time the neighboring image The contrast signal (image density value) is registered. Next, with respect to those edges, the edge position (X _i , Y _i ) of _interest and its edge are selected from among a group of images of a large number of object planes (..., Z ₋₁ , Z ₀ , Z ₁ ,. The Z in the image in which the neighboring image signal has the highest correlation with the registered contrast signal is obtained.

That is, for each edge position (X _i , Y _i ) obtained from the omnifocal image, the edge position of the same coordinate (X _i , Y _i ) is obtained from a plurality of (including blurred) images having different object positions (Z). The object position (Z) having the highest similarity (correlation) with the edge signal of the unfocused omnifocal image is obtained. Thereby, Z at each edge point (X _i , Y _i ) can be detected.

Specifically, first, the target edge position (X _i , Y _i ) that is the target edge position and the signal intensity f _{i, j} of the neighboring pixels are detected. Next, with respect to those edges, the same edge position (X _i , Y _i ) from the image group of a large number of object planes (..., Z ₋₁ , Z ₀ , Z ₁ ,. Z is obtained when the neighborhood signal g _{i, j} (Z) has the highest correlation with f _{i, j} .

As a method of obtaining this correlation, it is preferable to use a well-known normalized correlation method that absorbs the difference in brightness and contrast at each point. Other methods may be used as long as the correlation can be obtained, such as a method of obtaining the sum of squares .

  Then, for example, Z is obtained when the value of the following formula (5) or formula (6) is the smallest.

Thus, the edge coordinates of the object (X _i, Y _i) is Z at position sought.

  Although an example in which image processing is directly performed on the image signal output from the image sensor 13 has been described here, image preprocessing may be performed for the purpose of highlighting edge signals and reducing detection errors. Good. For example, each image is processed by combining a Fourier transform and a high-pass filter, or by image processing such as a digital differential filter called a Sobel filter or a Laplacian filter, thereby obtaining a so-called edge image in which only the contour portion is emphasized. After that, the above correlation process may be performed.

  Further, when calculating the correlation, it is also possible to obtain the correlation using the interpolation processing as shown in FIG.

  As described above, in the multifocal sequential processing method, when an edge position is specified only by the intensity of an image signal (an image that is in focus in the optical axis direction) is to be specified, the original edge to be specified is caused by strong blur light. Since there are cases where it cannot be detected, in order to avoid this, correlation processing using an omnifocal image is performed.

(3-2) Omnifocal Edge Extraction Method Next, a case where the omnifocal edge extraction method is used as a method for detecting an edge of an image will be described.

In the multi-focal sequential processing method (3-1) described above, processing such as Fourier transform is performed after a large number of focused image groups are formed once, so processing time is inevitably required. Also, as an image for detecting an edge, in the image group of the previous object plane (..., Z ₋₁ , Z ₀ , Z ₁ ,...), There is a focal plane somewhere, and from that focal point. The deviated portion is blurred and it becomes difficult to detect all edges. Therefore, in the all-focus edge extraction method, focusing on the fact that the edge position can be specified on the two-dimensional image in advance by the all-focus image formed by the ML at the center of the MLA 12, the edge position in the optical axis direction is determined only by the specified edge position. Search for. That is, the feature (edge) in the omnifocal image is detected first, only the image of the object plane at the position corresponding to the detected edge position is generated, and Z that is the best focus at that position is determined. If detected, the number of processing points can be reduced, and not only the calculation burden is reduced, but also the calculation time can be shortened, contributing to rapid measurement.

Specifically, using an omnifocal image formed in the center ML of the MLA 12, a 3 × 3 matrix (generally called a differential operator) for contour extraction, which is well known in image processing, is used. The edge extraction calculation process is performed. For example, an edge in an image is detected in the X direction or the Y direction using a Sobel filter or the like. This method is particularly effective for line edge detection. Further, a Laplacian filter corresponding to a second derivative may be used for detection of points such as spots and intersections. These are due to a difference in some structure, color, reflectance, etc., such as a step of the test object. In the all-focus edge extraction method, the values processed by these filters at the detected edge and point positions (X _i , Y _i ) are calculated as defocus amounts.

In the omnifocal edge extraction method, paying attention to each point (position) having an edge of the image, as in (3-1), the above-described many object planes (..., Z ₋₁ , Z ₍₀ , Z ₁ ,...) Corresponding to this defocus amount change is calculated. Since the value obtained by this is the same data as in FIG. 10, the peak of the signal, that is, Z that is the best focus is obtained from this.

As described above, each edge coordinate (X _i , Y _i ) position of the object is obtained by edge processing such as the above-described multifocal sequential processing method (3-1) or the all-focus edge extraction method (3-2). Z at is detected. Thereafter, a distance measurement process using the detected value is performed. The process is described in [4. Distance measurement procedure].

[4. Distance measurement procedure]
(4-1) Method for obtaining object position from multiple focus images Distance measurement using Z at each edge coordinate (X _i , Y _i ) position of the object obtained by the above procedure is performed. There are several methods for the procedure, but here we first generate a number of focus images (a number of images with different focal plane positions, that is, a number of virtual focal plane images), and the best focus among them is generated. A method for obtaining the position will be described.

Here, the value of the position (..., Z ₋₁ , Z ₀ , Z ₁ ,...) Of the object plane on the object image side conjugate with the virtual focal plane is based on the expression (1). It is uniquely determined by the distance a between the lens 11 and the imaging surface of the imaging device 13 or the distance (a ₁ , a ₂ , a ₃ ,..., _An ) between the objective lens 11 and the virtual focal plane.

Therefore, if the position of the focal plane (including the case where it is on the imaging plane (that is, a ₁ , a ₂ , a ₃ ,..., _An )) is determined, the test object to be focused on that position. And the distance b to that part can be obtained using the equation (1). As a result, the coordinate (X, Y, Z) of the portion of the test object, ie, the coordinate (X, Y) information of the two-dimensional image output from the image sensor 13 together with the obtained distance b, that is, Three-dimensional spatial coordinates can be determined.

(4-2) Method for Obtaining Object Position from Image Information of Two Different Focal Planes In the above method (4-1), a large number of focus images (images obtained when a number of different focal planes are assumed) are obtained. The distance to each part of the test object can be accurately measured by generating and detecting the best focal position from each focus image. For that purpose, for example, a procedure of detecting peaks from multipoint information as shown in FIG. 10 is required. In FIG. 10, the horizontal axis Z indicates the distance to the test object, and the vertical axis α indicates the degree of focus (degree of focus). From this figure, it can be seen that the distance to the in-focus portion of the test object at a certain coordinate (X, Y) of the two-dimensional image can be obtained as the value of Z that is the maximum value of α. However, there are many processing procedures, and there is a high possibility that processing will take time.

  Therefore, here, as another method, a measurement procedure for speeding up with a small amount of processing will be described. In this method, a large number of images are generated and peaks are not detected from the multipoint information as shown in FIG. 10, but the difference signal between the two is obtained using image information of at least two different focal planes. That is, the position of Z is obtained from the difference in the defocus amount at the two positions. Since this Z corresponds to the distance b from the objective lens 11 to the test object, the coordinate (X, Y) information of the two-dimensional image of the image sensor 13 is combined with this value and the coordinate (X, Y) of the test object. X, Y, Z), that is, a three-dimensional shape can be measured.

  However, there is a high possibility that the difference in local reflection intensity of the test object is affected only by the value calculated by this method. That is, the signal intensity varies depending on the brightness distribution of the original illumination light and the difference in reflectance depending on the position of the test object. In particular, if there is a portion where the difference in brightness is significant in the adjacent region, both signals are mixed in the defocused state, so that there is a possibility that an edge peak is erroneously detected.

Therefore , the calculation value obtained by such calculation processing is divided by each pixel value of the image formed by the ML at the center of the MLA 12 and normalized so that brightness (light intensity) is obtained for each local area. Therefore, it is possible to obtain a standardized defocus blur amount.

  As described above, in the present embodiment, for example, the distance measurement process is performed by the method (4-1) or (4-2), so that the coordinates (X, Y, Z) is determined and the three-dimensional shape is measured.

  Thus, in the present embodiment, since the three-dimensional shape of the test object can be measured using the image signal obtained by one imaging, a plurality of imaging operations are required as in the conventional SFF. Compared to the case, measurement can be performed at high speed.

[5. Shape measuring device]
Next, the configuration of the shape measuring apparatus according to the present embodiment that performs the above-described distance measurement process and measures the three-dimensional shape of the test object will be described with reference to FIG.

  As shown in FIG. 11, the shape measuring apparatus includes an objective lens 11, an MLA 12, an image sensor 13, a control circuit 31, a user interface 32, a drive circuit 33, an arithmetic processing circuit 34, and a memory 35. In FIG. 11, the objective lens 11 to the imaging element 13 correspond to the objective lens 11 to the imaging element 13 of FIG.

  The control circuit 31 controls the drive circuit 33, the arithmetic processing circuit 34, and the memory 35 in accordance with instructions input from the user via the user interface 32. Further, the control circuit 31 controls the operation of each part of the shape measuring apparatus of FIG.

  The drive circuit 33 drives the image sensor 13. Further, the drive circuit 33 outputs the image signal from the image sensor 13 to the arithmetic processing circuit 34.

  The arithmetic processing circuit 34 performs predetermined arithmetic processing based on the image signal from the drive circuit 33. Then, the arithmetic processing circuit 34 stores the calculation result in the memory 35.

  The arithmetic processing circuit 34 measures the three-dimensional shape of the test object from image data obtained by imaging the image formed by each ML of the MLA 12 by the imaging device 13. Details of this processing will be described together with the description of the operation of the arithmetic processing circuit 34 of FIG.

  The shape measuring apparatus is configured as described above.

  Next, the three-dimensional shape measurement process performed by the arithmetic processing circuit 34 of FIG. 11 will be described with reference to the flowchart of FIG.

  The arithmetic processing circuit 34 acquires the image signal from the drive circuit 33 in step S11, and generates a focus image in step S12. Specifically, the above-mentioned [2. As described in [Procedure for generating a focus image], the arithmetic processing circuit 34 uses the method (2-1) in the case of the configuration of FIG. 1a and (2-2) in the case of the configuration of FIG. 1b. By this method, light rays from different angles are reconstructed to generate a plurality of images having different focal planes.

In step S13, the arithmetic processing circuit 34 performs measurement signal processing. Specifically, the above [3. As described in the “Signal processing procedure of measurement”, the arithmetic processing circuit 34 performs the edge processing such as the “multifocal sequential processing method” in (3-1) or the “all-focus edge extraction method” in (3-2). The Z at each edge coordinate (X _i , Y _i ) position of the object is obtained using an omnifocal image that is always in focus.

  Then, the arithmetic processing circuit 34 performs a distance measurement process in step S14, measures the three-dimensional shape of the object in step S15, and the process ends. Specifically, the above-mentioned [4. As described in the “distance measurement procedure”, the arithmetic processing circuit 34 selects the “image information of two different focal planes” in (4-1) “Method for obtaining an object position from a large number of focus images” or (4-2). The method of determining the object position from the “coordinates (X, Y, Z) of the surface of the test object is determined, and the three-dimensional shape is measured.

As described above, in the shape measuring apparatus in FIG. 11, the arithmetic processing circuit 34 [2. Procedure for generating focus image], [3. Measurement signal processing procedure], [4. The distance measurement procedure] is sequentially executed, thereby performing signal processing using an omnifocal image obtained from the image formed by the ML at the center of the MLA 12, and each edge coordinate (X _{i) of the} object obtained thereby. , Y _i ), the coordinates (X, Y, Z) of the surface of the test object, that is, the three-dimensional shape is measured from Z at the position.

That is, as shown in FIG. 1a, when the MLA 12 is arranged so as to be conjugate with the exit pupil of the objective lens 11, the arithmetic processing circuit 34 determines the position of the optical axis of the objective lens 11 among the plurality of MLs. The multifocal image (reference image) obtained from the image formed on the imaging surface of the imaging device 13 by the ML at the center of the MLA 12 and a plurality of images (measurement images) having different focal planes obtained from the output of the imaging device 13 The three-dimensional shape of the test object is measured using the Z position of the test object obtained from the correlation with ( ).

In the present embodiment, the configuration shown in FIG. 1a is mainly described. However, as shown in FIG. 1b, the imaging surface of the imaging device 13 is arranged so as to be conjugate with the exit pupil of the objective lens 11. In this case, the arithmetic processing circuit 34 includes an omnifocal image (reference image) obtained from the pixels constituting the imaging region of the imaging element 13 where the principal rays of the objective lens 11 intersect, and a focal plane obtained from the output of the imaging element 13. The three-dimensional shape of the test object is measured using the Z position of the test object obtained from the correlation with a plurality of different images (measurement images).

[6. Pattern projection illumination system]
By the way, in the shape measuring apparatus of FIG. 11, the passive method (natural light) and the active method (Active) are used as the illumination method when executing the shape measurement process of the test object, depending on the measurement object and purpose. (Use of auxiliary light) can be used properly depending on the measurement object and application.

  The passive method is the method described so far. In other words, this method uses the reflected light or scattered light from the test object and outputs the edge (contour, etc.) signal from the captured image when the test object has a pattern, edge, or contrast change. It is to detect. Further, in the shape measuring apparatus, even when the distance to the test object is long, the auxiliary light does not reach, so the measurement is performed by the passive method.

  Here, the details of the active method, which is another illumination method, will be described.

  In the shape measuring apparatus of FIG. 11, when the three-dimensional shape measuring process is executed, if the object to be examined does not have an edge signal or a sufficient contrast signal, illumination having a structure such as texture or pattern projection And the focus change is detected.

  FIG. 13 is a schematic diagram of an example of the configuration of an optical system in the case of the active method.

  In FIG. 13, only the optical system is illustrated among those constituting the shape measuring apparatus of FIG. 11. Actually, as described above, the image sensor 13 is connected to the drive circuit 33 and obtained by imaging. The obtained image signal is output. Further, in the optical system of FIG. 13, in addition to the objective lens 11 to the imaging element 13 described above, a light source 51 and an illumination lens system for realizing an active illumination method for irradiating a measurement auxiliary light to a test object. 52, a pinhole pattern 53, and a half mirror 54 are arranged.

  As the light source 51, for example, a white light source such as a halogen lamp, an LED (Light Emitting Diode) composed of RGB three colors, or the like is used. The illumination lens system 52 is actually composed of a plurality of lenses, and collects the illumination light emitted from the light source 51 (advancing from the lower side to the upper side in the figure). This condensed illumination light illuminates the pinhole pattern 53.

  The pinhole pattern 53 is formed in a flat plate shape and is disposed so as to intersect perpendicularly with the optical axis of the illumination lens system 52. The pinhole pattern 53 is provided with a plurality of pinholes that are opened at regular positions at regular intervals in the front-rear and left-right directions on the surface that intersects the optical axis of the illumination lens system 52. As a pattern to be projected onto the test object, for example, a lattice pattern or other patterns such as vertical stripes and horizontal stripes may be used instead of pinholes.

  The half mirror 54 is disposed between the objective lens 11 and the MLA 12 in a state inclined by 45 degrees with respect to the optical axis of the illumination lens system 52.

  Illumination light emitted from the light source 51 and traveling toward the illumination lens system 52 (upward in the drawing) enters the illumination lens system 52 and is collected, and then reaches the pinhole pattern 53. Part of the illumination light that has passed through the pinhole of the pinhole pattern 53 is reflected by the half mirror 54, turned 90 degrees, and incident on the objective lens 11, and the pinhole pattern is projected onto the test object. .

  As shown in FIG. 13, in the illustrated example, the pinhole pattern is 5 × 3 dots. A part of the illumination light irradiated on the surface of the test object becomes reflected light on the surface of the test object, enters the objective lens 11, passes through the half mirror 54, and further passes through the MLA 12, An image is formed on the image sensor 13. The reflected light imaged by the imaging device 13 is received by each light receiving portion of the pixel area formed on the imaging surface, and is output to the drive circuit 33 shown in FIG. Then, as illustrated in FIG. 11, the arithmetic processing circuit 34 performs a three-dimensional shape measurement process based on the image signal from the drive circuit 33.

  Since this example is an active method, the arithmetic processing circuit 34 detects changes in edges and contrast at intersections and spots of illuminated projection patterns. At this time, since the position of the pattern is known, the arithmetic processing circuit 34 has only to detect the edge contrast of that portion. Then, the arithmetic processing circuit 34 obtains a multifocal image, detects the best focus position from the focal point change of each point, and obtains the distance from the test object, in the same manner as the processing described above. In addition, the distance between separated points such as pinholes or lattice points is the spatial resolution of the measurement.

  In the present embodiment, a laser scanning illumination system can be employed instead of the pattern projection illumination system. That is, when the laser scanning illumination system is employed, the shape measuring apparatus applies a slit or a linear beam with laser light or the like, and scans the beam in a direction perpendicular thereto, or two-dimensional scanning with a condensed spot light. It consists of the structure of the laser microscope which performs.

  As described above, in the shape measuring apparatus shown in FIG. 11, the passive method and the active method can be properly used as the illumination method depending on the measurement object and application.

  Furthermore, in the optical system of FIGS. 1 and 13 and the like, only the basic elements of the optical system have been illustrated and described, so that the functions are actually equivalent and various modifications can be considered. For example, although the field lens FL may be placed in front of the MLA 12 as described above, it is needless to say that a relay lens may be placed between the MLA 12 and the image sensor 13.

[7. Lens aperture (F value) variable mechanism]
In the present embodiment, a method for measuring an image by changing the F value of the optical system (lens) or a supporting function thereof may be provided.

  In general, the depth of field of an optical system varies depending on the F value of the lens. In order to adjust this, it is necessary to install a lens diaphragm (aperture) at the position of the pupil plane of the lens or at a position conjugate with the pupil plane, and to change the size of the lens diaphragm.

  By providing this variable mechanism, for example, it can be effectively used in the following two applications.

(7-1) Adjustment according to measurement application If the measurement object is imaged by increasing the aperture and decreasing the F value, the depth of field becomes shallow and the sensitivity of image focus measurement increases. At this time, however, the measurable range is narrowed. Conversely, if the F value is increased by narrowing down, the depth of field becomes deeper and the measurement sensitivity is lowered, but the measurement range is expanded. By utilizing this, it is possible to adjust to an optimum value according to the measurement application and the required accuracy and range. Specifically, in the shape measuring apparatus of FIG. 11, a lens diaphragm (not shown) is arranged at the position of the pupil plane of the objective lens 11 or a position conjugate with the pupil plane. For example, when it is desired to increase the measurement sensitivity. In a case where the lens aperture is increased by a drive system (not shown) controlled by the control circuit 31 to reduce the F value and the measurement range is to be expanded, the lens aperture is reduced by the drive system to increase the F value. Will do.

(7-2) Aberration Measurement It is also possible to use as an auxiliary means in the aberration measurement of the objective lens 11 or as a means for evaluating the variation of each lens element of the MLA 12. In other words, when the F value of the lens is sufficiently narrowed, the depth of field is deepened and only the center portion of the lens is used, so that an optical image with greatly reduced aberration (substantially no aberration) can be obtained. The image signal from the image sensor 13 obtained by the optical system of the present invention is influenced by the optical characteristics of the MLA 12 together with the objective lens 11. Therefore, when optical characteristics such as aberration are evaluated using this image signal, the influences of both appear overlappingly. Therefore, after capturing the image in which the influence of this aberration is eliminated by reducing the F value of the objective lens 11, the image is taken with the aperture opened (F value is minimized), and the difference between the two is taken. Aberrations or individual optical characteristics of each ML are known. Then, by subtracting the characteristics of the obtained MLA 12, the characteristics of only the objective lens 11 can be understood. This is an effective function when, for example, measuring the aberration of the objective lens 11.

  As described above, according to the present invention, an object is processed along the optical axis of the objective lens by performing image processing using a focused omnifocal image obtained from the ML at the center of the MLA. The shape of the test object can be measured without moving.

  The series of processes described above can be executed by hardware, or can be executed by software. When a series of processing is executed by software, a program constituting the software may execute various functions by installing a computer incorporated in dedicated hardware or various programs. For example, it is installed from a recording medium in a general-purpose personal computer or the like.

  This recording medium is not only composed of a computer, but also a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory or the like on which the program is recorded, which is distributed to provide a program to users. It is configured by a hard disk drive or a ROM (Read Only Memory) in which a program is recorded, which is provided to the user in a state of being preinstalled in the computer.

  In addition, a program for executing the above-described series of processing is installed in a computer via a wired or wireless communication medium such as a local area network, the Internet, or digital satellite broadcasting via an interface such as a router or a modem as necessary. You may be made to do.

  In the present specification, the step of describing the program stored in the recording medium is not limited to the processing performed in chronological order according to the described order, but is not necessarily performed in chronological order. It also includes processes that are executed individually.

  The embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

It is a figure explaining the outline | summary of the optical system to which this invention is applied. It is a figure explaining the further detailed structure of an optical system. It is a figure which shows that the image seen from a certain ML is the image seen for every direction comprised with the light ray from the same direction. It is a figure which shows the tracking result of the light ray by an objective lens and MLA. It is a figure which shows the pixel arrangement | sequence in the image pick-up element surface imaged by MLA. It is a figure which shows the example of a structure when MLA is made into the image plane of an objective lens (Z = 0). The MLA is a diagram illustrating an example of a configuration when the image plane of the objective lens (Z = h _1). It is a figure which shows the example of an omnifocal image. It is a figure which shows the flow of the signal processing using the Fourier-transform method of an image group. It is the figure which graphed the inclination component of the edge of a sampling point. It is a figure which shows the structure of one Embodiment of the shape measuring apparatus to which this invention is applied. It is a flowchart explaining a three-dimensional shape measurement process. It is the schematic of the example of a structure of the optical system in the case of an active system.

Explanation of symbols

  11 objective lens, 12 MLA, 13 image sensor, 31 control circuit, 32 user interface, 33 drive circuit, 34 arithmetic processing circuit, 35 memory, 51 light source, 52 illumination lens system, 53 pinhole pattern, 54 half mirror, ML micro Lens, FL field lens

Claims (9)

An objective lens;
An optical element having a plurality of lenses arranged two-dimensionally behind the objective lens;
A two-dimensional image sensor disposed behind the optical element;
Image generating means for generating a plurality of measurement images having different focal planes from the output of the image sensor;
A reference image in which all the pixels are focused, obtained from predetermined pixels corresponding to the optical arrangement of the objective lens and the optical element among the pixels constituting the imaging region of the imaging element corresponding to each of the plurality of lenses. comprising the, using the position of the optical axis of the objective lens of the object obtained from the correlation between the plurality of measurement images, and a three-dimensional shape measurement means for measuring the three-dimensional shape of the test object A shape measuring apparatus characterized by that. The optical element is conjugate with an exit pupil of the objective lens;
The three-dimensional shape measuring means uses, as the reference image, an image obtained from an image formed on the imaging surface of the imaging element by a lens located at the optical axis of the objective lens among the plurality of lenses. The shape measuring apparatus according to claim 1. The imaging surface of the imaging element is conjugate with the exit pupil of the objective lens,
The shape measurement apparatus according to claim 1, wherein the three-dimensional shape measurement unit forms the reference image from pixels that form an imaging region of the imaging element where chief rays of the objective lens intersect. The three-dimensional shape measuring means has the most significant correlation between the edge position of interest and the pixel signal in the vicinity thereof among the plurality of measurement images and the contrast signal of the edge position obtained from the reference image and the pixels in the vicinity thereof. The test object using the position in the optical axis direction of the test object obtained by obtaining the best focus position at each edge position from the virtual focal position of the image. The shape measuring device according to any one of claims 1 to 3, wherein the three-dimensional shape is measured. The three-dimensional shape measurement means detects an edge position in the plurality of measurement images using the reference image, and based on a change in defocus amount obtained by a predetermined filter process at the edge position, The three-dimensional shape of the test object is measured using the position of the test object in the optical axis direction obtained by obtaining the best focus position at each edge position. The shape measuring apparatus according to any one of 3. A projection unit for projecting a predetermined pattern onto the test object;
The imaging element is reflected light of the pattern projected onto the test object, and captures a test object image by the objective lens,
The three-dimensional shape measuring means measures a three-dimensional shape of the test object based on an image signal obtained from the reflected light of the pattern output from the imaging device. shape measuring device according to any one of the 5. A lens diaphragm arranged at a position conjugate with the pupil plane of the objective lens or the pupil plane;
A lens that controls the lens aperture so that the lens aperture is increased to decrease the F value when it is desired to increase measurement sensitivity, and the lens aperture is decreased to increase the F value when the measurement range is to be expanded. shape measuring apparatus according to any one of claims 1, characterized by further comprising a diaphragm controller 6. An objective lens;
An optical element having a plurality of lenses arranged two-dimensionally behind the objective lens;
In a shape measuring method of a shape measuring apparatus comprising: a two-dimensional image sensor disposed behind the optical element;
Generating a plurality of measurement images having different focal planes from the output of the image sensor;
A reference image in which all the pixels are focused, obtained from predetermined pixels corresponding to the optical arrangement of the objective lens and the optical element among the pixels constituting the imaging region of the imaging element corresponding to each of the plurality of lenses. When using the position of the optical axis of the objective lens of the object obtained from the correlation between the plurality of measurement images, characterized in that it comprises the step of measuring the three-dimensional shape of the test object Shape measurement method. An objective lens;
An optical element having a plurality of lenses arranged two-dimensionally behind the objective lens;
A program for causing a computer to control a device including a two-dimensional image sensor disposed behind the optical element,
Generating a plurality of measurement images having different focal planes from the output of the image sensor;
A reference image in which all the pixels are focused, obtained from predetermined pixels corresponding to the optical arrangement of the objective lens and the optical element among the pixels constituting the imaging region of the imaging element corresponding to each of the plurality of lenses. When using the position of the optical axis of the objective lens of the object obtained from the correlation between the plurality of measurement images, characterized in that it comprises the step of measuring the three-dimensional shape of the test object program.

Images