JP2008175682A - Detailed shape height measuring device and measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device for obtaining two-dimensional information and three-dimensional information of a body to be inspected, so that measuring errors due to the aberrations of a usage lens will not occur, and to provide a measurement method. <P>SOLUTION: The measuring device for measuring irregular shape on the surface of a substrate and the height of a foreign matter includes: a stage for mounting to arrange and horizontally conveying an article to be inspected, forming irregularities on the surface of a flat plate-like substrate, and an article of the shape known in which the same as the article to be inspected and its shape are known; light sources irradiating the article to be inspected and the shape known articles with illumination light, respectively; an imaging means for using a line sensor camera installed, in a state where the light axis is inclined at 45 degrees to the surface of the shape known article and the article to be inspected; an optical distribution element for integrating the optical paths of each reflected light from the article of the shape known and the article to be inspected into one; a shutter means installed among the optical distribution element, the article to be inspected and the article of the shape known, respectively; and a means for processing images by storing image data captured by the imaging means. The measuring method is also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for accurately and rapidly measuring in-plane height information such as minute foreign matters and defects on an inspected product.

  In recent years, the size of various electronic devices such as televisions has increased significantly. For example, taking a liquid crystal television as an example, the panel size is 700 × 400 mm even for the 32 type, which is highly competitive in the market, and 1430 × 800 mm for the largest 65 type.

  These panels are composed of one million or more cells, and the size of one cell is several hundred μm. The cell having a size of several hundreds μm is managed so as not to have a dust or a defect having a size of several tens of μm.

  However, for example, the screen size of a liquid crystal screen used in a mobile phone is mainly QVGA of 2.2 to 4 inches, and the size of one cell is about 100 μm. It is said that the VGA will be shifted to 2 inches in the future, so that the size of the cell will be about several tens of μm, and the detection accuracy of defects and the like will be insufficient at the conventional level.

  Further, as the panel is made thinner, short-circuiting due to foreign matter is likely to occur, and the height of the foreign matter itself has become a cause of defects. In the inspection of liquid crystal screens used in mobile phones, the required detection accuracy is 10 μm or less.

  The method currently used for such inspection is to pick up an image of the object to be inspected with a line sensor camera, obtain an image of the object to be inspected, and perform some kind of image processing on the image to detect a foreign object or a defect. That's it. The configuration of the apparatus used in such an inspection includes a camera and a lens that are an image acquisition system, a stage for moving an object to be inspected, and an irradiation light source.

  As the camera, a line sensor camera is mainly used, and imaging is performed by combining it with a lens having a specification that realizes a desired resolution. Image data acquired by the camera is taken into image processing and storage means such as a personal computer via an image processing board, and recording and predetermined processing are performed.

  Since the line sensor camera is a one-dimensional image acquisition device, it cannot obtain two-dimensional image data by itself. Therefore, two-dimensional image data is obtained by moving the object to be inspected or the camera itself.

  As described above, the line camera can obtain the two-dimensional information, but the method of simply taking an image with the camera can obtain the two-dimensional information and cannot obtain the three-dimensional information.

  When it is desired to inspect the height of a foreign object or the height of a product shape, it is necessary to obtain not only two-dimensional information but also three-dimensional information.

  For example, in the measuring apparatus according to Patent Document 1, while acquiring a two-dimensional image of an inspection object with a line sensor camera, information on the height of each point of the inspection object is acquired with a laser beam and an optical position detection element. It is characterized by doing.

Japanese Patent No. 3379928

  However, in the measuring apparatus according to Patent Document 1, although the line sensor camera and the optical position detection element have the same objective lens, lenses other than the objective lens are used individually. For this reason, there is a problem that measurement errors may occur due to aberrations of lenses other than the objective lens being different.

  The present invention has been made in view of such circumstances, and a measurement apparatus capable of obtaining two-dimensional information and three-dimensional information of an object to be inspected while preventing measurement errors due to aberration of a lens to be used. An object is to provide a measurement method.

The invention corresponding to claim 1 is a measuring device for measuring the uneven shape on the surface of a flat substrate and the height of a foreign material,
An inspected product in which irregularities are formed on the surface of a flat substrate, and a transport stage that carries the same shape of the inspected product and the known shape of the surface of the inspected product side by side and transports them horizontally,
A first illumination light source for illuminating the inspected product with illumination light;
A second illumination light source for irradiating illumination light to a known shape product;
An imaging means including a line sensor camera and a lens, which is installed with its optical axis inclined at 45 ° with respect to the surfaces of the known shape product and the inspected product;
A light distribution element that is installed between the imaging means and the transfer stage and integrates the optical paths of the reflected lights from the known shape product and the inspected product into one;
First shutter means installed between the light distribution element and the product to be inspected;
Second shutter means installed between the light distribution element and the known shape product;
Means for storing and processing image data captured by the imaging means;
It is a shape measuring apparatus provided with these.

The invention corresponding to claim 2 is a measuring method for measuring the uneven shape on the surface of the flat substrate and the height of the foreign matter,
An inspected product in which irregularities are formed on the surface of a flat substrate, and a transporting stage for horizontally placing and transporting a known product having the same shape as the inspected product and the shape of the surface;
A first illumination stage for illuminating the inspected product with illumination light;
A second illumination stage for irradiating illumination light to a known shape product;
An imaging stage by an imaging means equipped with a line sensor camera and a lens, which is installed in a state where its optical axis is inclined by 45 ° with respect to the surfaces of the known shape product and the inspected product,
An optical path integrating step of integrating the optical paths of the reflected light from the known shape product and the inspected product into one by the light distribution element installed between the imaging means and the transport stage;
An imaging target selection step of selecting an imaging target by a first shutter means installed between the light distribution element and the product to be inspected and a second shutter means installed between the light distribution element and the known shape product. When,
Storing and processing image data captured by the imaging means;
It is a shape measuring method characterized by comprising.

  By taking the above measures, the known shape product and the product to be inspected are installed in the same relative position with respect to the camera. An optical system capable of acquiring each image is formed. Imaging is performed by alternately linking a known product and a product to be inspected in conjunction with one camera and two shutters. By synthesizing two types of images from the positional relationship between the camera, the known product, and the inspected product, and analyzing the difference value of the pixels at the same position, it becomes possible to obtain the shape information of the inspected product.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram schematically showing an example of a known shape product 9 to be imaged in the present embodiment.
On a flat substrate 3, a plurality of square pillars 2 having a square with a length p of one side and a height of h are arranged two-dimensionally with an interval s.

  It is assumed that the known shape product 9 is known in advance in terms of dimensions, including the height shape, among the products to be inspected. That is, it becomes a master product for product inspection in the same lot. In the present embodiment, it is assumed that whether or not the height h is within the standard value is inspected.

FIG. 2 is a diagram showing a schematic configuration of a measurement unit according to an embodiment of the present invention.
The known shape product 9 and the product 10 to be inspected are placed on a horizontal stage 12 and illuminated by the illumination lamp 11 from directly above. The illuminating lamp 11 provides illumination with an equivalent illuminance to the known shape product 9 and the inspected product 10, and a fluorescent lamp, LED, halogen light source, metal halide light source, or the like can be used.

  The camera 4 is installed so that the known shape product 9 and the inspected product 10 can be imaged through the cubic type half mirror 7. The cubic half mirror 7 as a light distribution element is generally a cube formed by joining two right-angled isosceles triangular prisms having the same shape, and light is distributed at the joint surface. Therefore, in order to equalize the optical path length between the camera 4 and the known shape product 9 and the product to be inspected 10, the angle between the optical axis of the camera 4 and the horizontal plane is 45 °.

  As the lens 5 of the camera 4, it is preferable to use a telecentric lens or the like so that contrast can be obtained and only parallel light can be received. Further, the ND filter 6 may be disposed in front of the lens 5 so that the amount of light received from the imaging target can be adjusted.

  The camera 4 captures an image of the known shape product 9 and the product to be inspected 10 arranged at the same optical position with respect to the camera 4. At this time, the shutter mechanisms 8a and 8b are arranged between the cubic type half mirror 7, the product 9 to be inspected, and the product 10 having a known shape in order to alternately and continuously capture images. The shutter mechanisms 8a and 8b are synchronized with the camera 4, and when the known product 9 is imaged, the shutter 8b is opened and the shutter 8a is closed. Further, when the inspected product 10 is imaged, the shutter 8a is opened and the shutter 8b is closed.

  The camera 4 is a line sensor camera that captures image data for each column. It should be noted that the lens 5 is adjusted or the distance between the camera 4 and the stage 12 so that the image of the luminance value comparison region 1 of the known shape 9 and the inspected product 10 is formed on the line sensor element of the camera 4. It is necessary to adjust. The stage 12 stops when the camera 4 captures an image, and moves a predetermined distance while the image is not captured.

  By repeating this process, the camera 4 alternately captures the known shape product 9 and the inspected product 10 and acquires respective image data. These two image data are captured and recorded in image processing and storage means such as a personal computer via an image board.

  After preprocessing that removes noise in the image data is performed, it is possible to analyze the height information of the inspected product by comparing the luminance values of the pixels at the same position in the two image data Become.

Hereinafter, an example of the analysis of the height information of the inspected product 10 will be shown.
First, as shown in FIG. 3, a plurality of feature points 13 are extracted from the image data of the inspected product 10. From the coordinate position of the feature point 13, the angle θ formed by the pixel array direction of the line sensor element of the camera 4 and the array direction of the quadrangular prism 2 is calculated. Then, affine transformation as shown in FIG. 4 is performed to convert the image data of the inspected product 10 into rectangular coordinates.

  3 and 4, for the sake of explanation, the angle formed by one of the pixel array direction (X direction in FIG. 4) of the line sensor elements of the camera 4 and the array direction of the quadrangular prism 2 is θ (θ ≠ 90 °) and the angle formed by the other is schematically 0 ° (same as the X direction in FIG. 4). Actually, it may take a value other than 0 °, but even in that case, affine transformation is possible.

  The same processing is performed on the image of the known shape product 9 and converted into rectangular coordinates. Image data obtained by this processing will be referred to as an affine transformation image below.

  Next, the shape of the luminance value comparison region 1 in FIG. 1 is extracted from the affine transformation images of the known product 9 and the product to be inspected 10. By calculating the coordinate value of the end of the luminance value comparison area 1 of each square column 2, the shape can be known. At that time, between the known product 9 and the product to be inspected 10, the image of the corresponding quadrangular prism 2 is labeled and recognized by the labeling process.

  Since the shape of the known shape product 9 is known, the coordinate value in the affine transformation image of the point 14 from which the height information of each square shape 2 of the known shape shape product 9 is obtained, and the height of each square shape 2 of the product 10 to be inspected. By comparing the coordinate values in the affine transformation image of the point 14 from which information is obtained, the dimensions of the inspected product 10 are obtained.

  The height distribution in the surface of the luminance value comparison region 1 can be estimated from the luminance value for each pixel in the luminance value comparison region 1. In order to compare the luminance values of the pixels in the luminance value comparison region 1 between the known shape product 9 and the inspected product 10, the luminance value of the known shape product 9 is subtracted from the luminance value of the inspected product 10. This value is the difference value.

  When an object illuminated from directly above is imaged from an oblique direction, the difference value takes a positive value when the inspected product 10 is higher than the known shape product 9, and takes a negative value when it is lower. Therefore, the defect may be caused when the difference value takes a positive value.

  When the pixel size is small with respect to the luminance value comparison region, the shape distribution can be known in more detail. Although this difference value is different from the actual dimension, it is desirable to predict and determine it in correlation with the actual height information.

  In order to obtain the height shape information from the substrate surface, the height information obtained from the coordinate value of the point 14 from which the height information is obtained and the difference value may be obtained in a total form. By providing a threshold for the height shape information from the substrate surface, it is possible to determine whether the product to be inspected is acceptable.

  As described above, according to the present invention, for example, in the inspection of an electronic component, if the height information of a minute foreign matter can be a defect that causes an electrical short circuit or the like, the known product and the inspected object whose height information is known in advance. By imaging and comparing the product optically at the same position, it is possible to obtain height information with high accuracy without being greatly affected by accuracy degradation due to lens aberration.

The schematic diagram of the shape known goods which concern on one Embodiment of this invention. The schematic diagram which shows schematic structure of the measurement part which concerns on one Embodiment of this invention. The schematic diagram which shows the point from which height information is obtained in the diagonal image which imaged the to-be-inspected goods. Explanatory drawing which shows the coordinate transformation of an oblique image typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Luminance value comparison area 2 ... Square pillar 3 ... Product board 4 ... Line sensor camera 5 ... Lens 6 ... ND filter 7 ... Light distribution element (cubic type half mirror)
8a ... Shutter mechanism 8b ... Shutter mechanism 9 ... Product with known shape 10 ... Product to be inspected 11 ... Illumination light source 12 ... Transport stage p ... Length of one side of the bottom of a square column s ... Distance between adjacent square columns h ... Square column height

Claims (2)

A measuring device for measuring the uneven shape on the surface of a flat substrate and the height of a foreign object,
An inspected product in which irregularities are formed on the surface of a flat substrate, and a transport stage that carries the same shape of the inspected product and the known shape of the surface of the inspected product side by side and transports them horizontally,
A first illumination light source for illuminating the inspected product with illumination light;
A second illumination light source for irradiating illumination light to a known shape product;
An imaging means including a line sensor camera and a lens, which is installed with its optical axis inclined at 45 ° with respect to the surfaces of the known shape product and the inspected product;
A light distribution element that is installed between the imaging means and the transfer stage and integrates the optical paths of the reflected lights from the known shape product and the inspected product into one;
First shutter means installed between the light distribution element and the product to be inspected;
Second shutter means installed between the light distribution element and the known shape product;
Means for storing and processing image data captured by the imaging means;
A shape measuring apparatus comprising:
It is a measuring method for measuring the uneven shape on the surface of a flat substrate and the height of foreign matter,
An inspected product in which irregularities are formed on the surface of a flat substrate, and a transporting stage for horizontally placing and transporting a known product having the same shape as the inspected product and the shape of the surface;
A first illumination stage for illuminating the inspected product with illumination light;
A second illumination stage for irradiating illumination light to a known shape product;
An imaging stage by an imaging means equipped with a line sensor camera and a lens, which is installed in a state where its optical axis is inclined by 45 ° with respect to the surfaces of the known shape product and the inspected product,
An optical path integrating step of integrating the optical paths of the reflected light from the known shape product and the inspected product into one by the light distribution element installed between the imaging means and the transport stage;
An imaging target selection step of selecting an imaging target by a first shutter means installed between the light distribution element and the product to be inspected and a second shutter means installed between the light distribution element and the known shape product. When,
Storing and processing image data captured by the imaging means;
A shape measuring method comprising: