JP2006234553A - Visual inspection device and visual inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a visual inspection device capable of performing accurate inspection using an inexpensive device, and a visual inspection method. <P>SOLUTION: A stage part 21 is constituted so as to form a stage surface on which a thin plate-shaped inspection target having flexibility is placed to hold one main side of the placed inspection target and the stage surface in a close contact state. An imaging camera 31 takes the image of the inspection target held to the stage surface in the close contact state. An X-axis direction drive mechanism 35, a Y-axis direction drive mechanism 23 and a Z-axis direction drive mechanism 36 are constituted so as to relatively move at least on of the stage surface and the imaging camera 31 in the respective directions of them. A control part 4 controls the X-axis direction drive mechanism 35, the Y-axis direction drive mechanism 23 and the Z-axis direction drive mechanism 36 on the basis of the displacement data at a plurality of positions on the stage surface while holding an equal distance between the imaging camera 31 and the stage surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an appearance inspection apparatus and an appearance inspection method, and more specifically to an appearance inspection apparatus and an appearance inspection method for inspecting an appearance by imaging a flexible thin plate member such as a printed circuit board or a film mask with a camera. .

  On the surface of a printed circuit board or the like on which electronic components or the like are mounted, a conductor wiring necessary for constituting a predetermined circuit is formed in a pattern. Then, using a visual inspection apparatus, the visual inspection is performed for the presence or absence of defects in the wiring pattern formed on the printed circuit board. For example, the printed circuit board is placed on the stage surface of the appearance inspection apparatus with the surface on which the pattern is formed as the upper surface. The appearance inspection apparatus has an imaging camera such as a CCD (Charged Coupled Device) camera in a space on a printed board placed on a stage surface. The appearance inspection apparatus moves the stage surface horizontally in the main scanning direction, and images the printed circuit board that has passed under the imaging camera. The appearance inspection apparatus sequentially shifts the imaging camera in the sub-scanning direction every time scanning in the main scanning direction is completed, and finally captures the entire inspection area of the printed circuit board to obtain image data. Thereafter, the appearance inspection apparatus performs a pattern matching process or the like on the obtained image data to detect a pattern defect.

  In addition, a mask may be used when a pattern such as a conductor wiring is formed on the surface of a printed board or the like. The mask is made of glass, film, or the like, and serves as an original pattern to be transferred to the substrate. The appearance of the pattern formed on such a mask is also inspected by the method using the appearance inspection apparatus as described above.

  In such an appearance inspection apparatus that uses a printed circuit board or mask as an inspection object, it is important that the focus of the imaging camera serving as the imaging means coincides with the upper surface of the inspection object when increasing the accuracy of detecting a pattern defect. Become. This becomes more prominent as the inspection resolution increases, and generally, a technique is used in which an imaging camera having an autofocus function is used to inspect while focusing on the upper surface of the inspection object in real time. For example, the autofocus method is premised on non-contact with the object to be inspected, and uses the information on the height of the object to be inspected obtained using a laser displacement sensor or the amount of blur of the captured image itself. The focus is adjusted.

An apparatus that changes the focal position of an imaging camera using information on the height and shape of an object to be inspected is disclosed (for example, see Patent Documents 1 to 3). The visual inspection apparatus disclosed in Patent Document 1 detects a height displacement amount of a reference surface of a printed circuit board by a height sensor while the printed circuit board is being conveyed, and relatively moves the imaging camera in the focal direction based on the displacement amount. Focus by moving to. The apparatus disclosed in Patent Document 2 captures images by changing the focus position based on a focus map created by detecting the shape of a sample. The defect inspection apparatus disclosed in Patent Document 3 detects height information of a plurality of points including two points sandwiching an imaging position on the surface of an object to be inspected, and focuses the imaging apparatus using the height information. . In this way, the height and shape of the inspection object placed on the stage surface before the inspection is measured, or the displacement of the inspection object is measured, and the imaging camera is moved up and down in the focal direction according to the measurement result. For example, a method of scanning the inspection object while optimally adjusting the focal length is employed.
JP 2000-266991 A JP 2002-42706 A Japanese Patent Laid-Open No. 2003-177101

  However, in the above-described appearance inspection apparatus, the method of focusing using the blur amount of the captured image itself of the imaging camera is not suitable for high-speed appearance inspection because a long calculation time is required.

  Further, in the method of measuring the upper surface of the object to be inspected using the displacement sensor as described above, particularly in the inspection of a transparent thin plate member such as a film mask, the surface (upper surface) and the rear surface (lower surface) of the mask surface. Separation becomes difficult. Generally, a displacement sensor irradiates a film mask with light or a laser, and detects the displacement of the upper surface of the film mask based on the reflection. However, the resolution of the film mask is limited because of its limited resolution. Misrecognize front and back during scanning. In order to prevent such erroneous detection, it is necessary to use a displacement sensor having a sufficiently high resolution, but this is expensive and increases the price of the appearance inspection apparatus itself. The devices disclosed in Patent Documents 1 to 3 are all techniques for obtaining a height on an object to be inspected and automatically performing focusing using this height information. Therefore, it is necessary to obtain height information in advance for each inspection object.

  Therefore, an object of the present invention is to provide an appearance inspection apparatus and an appearance inspection method that can perform an accurate inspection using an inexpensive apparatus.

In order to achieve the above object, the present invention has the following features.
1st invention is an external appearance inspection apparatus which test | inspects the thin plate-shaped member which has flexibility as a to-be-inspected object. The appearance inspection apparatus includes a stage unit, a close contact unit, an imaging unit, a relative movement unit, a storage unit, and a control unit. The stage portion forms a stage surface on which the inspection object is placed. The close contact means holds the one main surface of the placed inspection object in close contact with the stage surface of the stage portion. The imaging means images the object to be inspected that is held in close contact with the stage surface. The relative movement means relatively moves at least one of the stage surface and the imaging means. The storage means stores displacement data at each of a plurality of positions on the stage surface. The control unit controls the relative movement unit based on the displacement data so that at least one of the stage surface and the imaging unit relatively moves while maintaining an equal distance between the imaging unit and the stage surface.

  According to a second aspect, in the first aspect, the distance between the imaging unit and the stage surface that the control unit keeps at an equal distance is the other of the inspected object in which the focal position of the imaging unit is closely held on the stage surface. The distance on the main surface.

  In a third aspect based on the first aspect, the relative movement means includes an imaging direction movement means and a horizontal direction movement means. The imaging direction moving means relatively moves at least one of the stage surface and the imaging means in the imaging direction of the imaging means. The horizontal direction moving means moves at least one of the stage surface and the imaging means in a direction perpendicular to the imaging direction. The displacement data is data indicating the displacement of the height in the imaging direction at other positions on the stage surface with reference to the height in the imaging direction from the imaging means to the reference point set on the stage surface.

  In a fourth aspect based on the first aspect, the storage unit stores displacement data with respect to intersection points of the lattices arranged at predetermined intervals in two directions orthogonal to each other set on the stage surface. Remember.

  In a fifth aspect based on the fourth aspect, the control unit converts the displacement data of the intersection point of the lattice that coincides with the intersection point of the straight line connecting the principal point that is the optical center of the imaging means and the gazing point and the stage surface. Based on this, the relative movement means is controlled. When the intersection of the straight line and the stage surface does not coincide with the intersection of the grid, the control unit uses the displacement data for the intersection of the plurality of grids set near the intersection of the straight line and the stage surface, The displacement data at the intersection with the surface is interpolated and the relative movement means is controlled based on the interpolated displacement data.

  A sixth invention is an appearance inspection method for inspecting a thin plate member having flexibility as an object to be inspected. The appearance inspection method includes a placement step, a contact step, an imaging step, and a control step. In the placing step, the inspection object is placed on the stage surface. The contact step holds the one main surface of the placed inspection object and the stage surface in close contact. In the imaging step, the object to be inspected and held on the stage surface is scanned and imaged by the imaging means. The control step scans the object to be inspected while maintaining an equal distance between the imaging means and the stage surface based on displacement data at each of a plurality of positions on the stage surface.

  According to the first aspect, the stage surface can be scanned using the displacement data of the stage surface while keeping the distance between the imaging means and the stage surface at an equal distance. If the flexible thin plate-like member such as a film mask is an inspection object, the inspection object adheres along the stage surface. Therefore, the imaging unit can perform imaging while always maintaining an equal distance from the object to be inspected, and can perform accurate imaging in scanning the object to be inspected to increase the inspection resolution. In the appearance inspection apparatus, when the positional relationship between the stage unit and the imaging unit is fixed, it is not necessary to create the displacement data again once the displacement data is stored. Therefore, conventionally, a step for obtaining height information for each object to be inspected is not required, so that the time required for appearance inspection can be shortened. Further, a sensor for obtaining the displacement is not required for the appearance inspection apparatus, and the apparatus cost can be reduced.

  According to the second aspect of the invention, since the scanning of the imaging means can always be adjusted to the upper surface of the object to be inspected using the displacement data of the stage surface, in the inspection of a transparent thin plate member such as a film mask. Even with an inspection object in which separation of the upper surface and the lower surface is difficult, it is possible to perform imaging with the upper surface accurately focused.

  According to the third aspect, since the displacement data is created with the height in the moving direction (imaging direction) of the imaging direction moving unit, the displacement data can be used as it is for the movement control of the imaging direction moving unit, Control becomes easy.

  According to the fourth aspect of the invention, since the displacement data is stored only for the intersection of the lattice set on the stage surface, the amount of data to be stored can be limited. Further, it becomes easy to detect the position where the displacement data is set on the stage surface.

  According to the fifth aspect, the distance between the imaging means and the stage surface can be kept constant even at a position where displacement data is not set on the stage surface.

  Further, according to the appearance inspection method of the present invention, the same effect as the above-described appearance inspection apparatus can be obtained.

  An appearance inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a top view and a front view schematically showing the overall configuration of the appearance inspection apparatus. Here, for the sake of specific explanation, a case where a film mask on which a wiring pattern is drawn is inspected as an object to be inspected will be described as an example. The present invention is not limited to a film mask, but is effective for an inspection using a flexible thin plate-like member such as a glass mask, a printed board, a flexible thin board, or the like as an inspection object.

  In FIG. 1, an appearance inspection apparatus 1 generally includes a stage transport mechanism unit 2, an imaging mechanism unit 3, and a control unit 4 (see FIG. 2). The stage transport mechanism unit 2 includes a stage unit 21, a turning unit 22, a Y-axis direction drive mechanism 23, and a base unit 24. The imaging mechanism unit 3 includes an imaging camera 31, a support member 32, an X-axis direction drive member 33, a camera support member 34, an X-axis direction drive mechanism 35, and a Z-axis direction drive mechanism 36.

  The stage unit 21 has a glass plate mounted horizontally on the uppermost surface, and the stage surface is constituted by the upper surface of the glass plate. Then, the film mask that is the object to be inspected is placed in close contact with the stage surface of the stage unit 21. Any method may be used as the method of bringing the film mask and the stage surface into close contact with each other. For example, the film mask is pressed against the stage surface by a roller, the pressure between the stage surface and the film mask is suctioned and fixed, the electrostatic fixing is performed between the stage surface and the film mask, and air is blown from the upper surface of the film mask. The film mask is brought into close contact with the stage surface by a method such as fixing the end of the film mask with a clamp. In addition, as long as the object to be inspected is in close contact with the stage surface by its own weight, the object to be inspected may be naturally placed on the stage surface and brought into close contact therewith. Note that the contact means of the present invention corresponds to a mechanism for bringing these objects into close contact with the stage surface.

  The lower part of the stage unit 21 is supported by the turning unit 22, and the stage unit 21 is configured to be rotatable in the θ direction in the figure by the turning operation of the turning unit 22. The base portion 24 is extended and fixed in the illustrated Y-axis direction parallel to the stage surface so as to pass below the imaging mechanism portion 3. The Y-axis direction drive mechanism 23 slides along a guide provided in the Y-axis direction on the upper surface of the base portion 24, and the turning portion 22 is fixed on the upper surface thereof. The Y-axis direction drive mechanism 23 includes a Y-axis drive motor 231 and a Y-axis NC driver 232 described later (see FIG. 2). As a result, the Y-axis direction drive mechanism 23 can be moved in the Y-axis direction (main scanning direction) along the guide of the base portion 24 by the driving force from the Y-axis drive motor 231 and supported by the turning portion 22. The horizontal movement of the stage unit 21 in the main scanning direction is also possible. The stage transport mechanism unit 2 has a transmission illumination light source (not shown) below the glass plate of the stage unit 21. This light source for transmitted illumination irradiates the lower surface of the film mask with illumination light through a glass plate.

  The support member 32 is installed in the upper space of the stage unit 21 that horizontally moves on the base unit 24. An X-axis direction drive mechanism 35 is provided on the support member 32, and the X-axis direction drive member 33 is parallel to the stage surface and in the illustrated X-axis direction (sub-scanning direction) perpendicular to the Y-axis direction. Move. Note that the X-axis direction drive mechanism 35 includes an X-axis drive motor 351 and an X-axis NC driver 352 described later (see FIG. 2). The X-axis direction drive member 33 is provided with a Z-axis direction drive mechanism 36, and moves the camera support member 34 in the illustrated Z-axis direction perpendicular to the X-axis and Y-axis directions. The Z-axis direction drive mechanism 36 includes a Z-axis drive motor 361 and a Z-axis NC driver 362 described later (see FIG. 2).

  The imaging camera 31 is constituted by, for example, a CCD camera, and is supported by the camera support member 34 so that the imaging direction is a downward direction in the Z axis in the figure. The imaging camera 31 converts incident light into an electric signal indicating its color and intensity. In the example of the appearance inspection apparatus 1 shown in FIG. 1, two imaging cameras 31a and 31b are provided and supported by the camera support member 34 so that their imaging directions are in the downward direction of the Z axis in the figure. For example, the imaging camera 31a for obtaining image data for pattern matching processing in the appearance inspection apparatus 1 and the imaging camera 31b for obtaining image data for visual inspection by the user of the appearance inspection apparatus 1 are configured. The transmitted light irradiated to the film mask from the light source for transmitted illumination is received. In the present invention, a plurality of imaging cameras 31 may be fixed to the camera support member 34, or only one imaging camera 31 may be fixed to the camera support member 34.

  With such a configuration, the imaging camera 31 is movable in the illustrated X-axis direction (sub-scanning direction) and Z-axis direction (imaging direction). Then, main scanning is performed by moving the stage unit 21 in the main scanning direction (Y-axis direction) while the position of the imaging camera 31 in the X-axis direction is fixed. Next, every time main scanning from one end to the other end of the inspection area of the film mask is completed, the imaging camera 31 moves by a predetermined distance along the sub-scanning direction (X-axis direction). As a result, image data for the entire inspection area of the film mask is obtained from the imaging camera 31. Furthermore, the imaging camera 31 can be moved in the Z-axis direction (imaging direction) by the Z-axis direction drive mechanism 36. As will be described later, the Z-axis direction drive mechanism 36 appropriately moves the camera support member 34 in the Z-axis direction according to the height of the stage surface of the stage unit 21 in the Z-axis direction. In the present embodiment, the film mask is brought into close contact with the stage surface of the stage portion 21 and the thickness of the film mask is uniform. Therefore, as long as data on the height of the stage surface of the stage portion 21 in the Z-axis direction and data on the thickness of the film mask are obtained, the Z-axis direction driving mechanism 36 can focus the imaging camera 31 while scanning the film mask. The position of the imaging camera 31 in the Z-axis direction can be controlled so that the position is always on the upper surface of the film mask. The relative movement means of the present invention corresponds to the X-axis direction drive mechanism 35, the Y-axis direction drive mechanism 23, and the Z-axis direction drive mechanism 36. The horizontal movement means of the present invention corresponds to the X-axis direction drive mechanism 35 and the Y-axis direction drive mechanism 23. The imaging direction moving means of the present invention corresponds to the Z-axis direction drive mechanism 36.

  Next, with reference to FIG. 2, a schematic configuration of the control function in the appearance inspection apparatus 1 will be described. FIG. 2 is a block diagram showing the control function of the appearance inspection apparatus 1.

  In FIG. 2, the appearance inspection apparatus 1 includes a control unit 4 including a main control unit 41, a focus control unit 42, and a storage unit 43. The main control unit 41 and the focus control unit 42 are constituted by, for example, a CPU board and are connected to each other. A storage unit 43 is connected to the main control unit 41 and the focus control unit 42. The storage unit 43 is used as a storage area when the main control unit 41 and the focus control unit 42 perform processing, and stores a data group necessary for processing. The storage unit 43 stores a stage height table 431.

  The main control unit 41 mainly controls operations of the X-axis NC driver 352 and the focus control unit 42. The X-axis NC driver 352 drives the X-axis drive motor 351 according to the control of the main control unit 41. Then, the X-axis drive motor 351 moves the X-axis direction drive member 33 in the X-axis direction (sub-scanning direction; see FIG. 1), and moves the imaging camera 31 in the X-axis direction. With these configurations, the main control unit 41 can control the operation of the imaging camera 31 in the sub-scanning direction.

  The focus control unit 42 mainly controls the operations of the Y-axis NC driver 232 and the Z-axis NC driver 362. The Y-axis NC driver 232 drives the Y-axis drive motor 231 according to the control of the focus control unit 42. The Y-axis drive motor 231 moves the stage unit 21 horizontally in the Y-axis direction (main scanning direction; see FIG. 1). With these configurations, the focus control unit 42 can control the operation of the stage unit 21 in the main scanning direction. The Z-axis NC driver 362 drives the Z-axis drive motor 361 according to the control of the focus control unit 42. Then, the Z-axis drive motor 361 moves the camera support member 34 in the Z-axis direction (imaging direction; see FIG. 1) to move the imaging camera 31 in the Z-axis direction. With these configurations, the focus control unit 42 can control the operation of the imaging camera 31 with respect to the imaging direction (focal direction).

  Here, the focus control unit 42 creates a stage height table 431 in advance and stores the stage height table 431 in the storage unit 43 before visual inspection of the inspection object. At that time, the displacement sensor 5 is attached to the appearance inspection apparatus 1. The displacement sensor 5 detects the displacement of the stage surface at each detection point of the stage surface with reference to the height of the reference point set on the stage surface of the stage unit 21. For example, a laser displacement sensor, a light A displacement sensor, an ultrasonic sensor, a mechanical sensor that contacts the stage surface, or the like is used. The displacement sensor 5 is fixed to the imaging camera 31 and the camera support member 34 with the displacement detection direction being the Z-axis direction (see FIG. 1) toward the upper surface of the stage unit 21 in the same manner as the imaging direction of the imaging camera 31. As will be apparent from the description below, the displacement sensor 5 detects the displacement in the Z-axis direction of the region on the top surface where the object to be inspected is placed with reference to a reference point set on the top surface of the stage unit 21. Therefore, as long as the displacement can be detected while being able to move in the X-axis direction and the Y-axis direction relative to the stage portion 21, it may be fixed to another part.

  When creating the stage height table 431, the displacement sensor 5 outputs displacement information DL on the upper surface of the stage unit 21 to the focus control unit 42. The relative positional relationship between the displacement sensor 5 and the stage unit 21 in the Y-axis direction is determined by the focus control unit 42 by outputting a feedback pulse PF output from the Y-axis drive motor 231 to the focus control unit 42. Can be detected. Furthermore, the relative positional relationship between the displacement sensor 5 and the stage unit 21 in the X-axis direction is obtained by obtaining from the main control unit 41 a control amount for moving the X-axis direction drive member 33 in the X-axis direction. 42 can be detected. That is, the focus control unit 42 is on the stage surface of the stage unit 21 detected by the displacement sensor 5 based on the relative positional relationship between the displacement sensor 5 and the stage unit 21 in the X-axis direction and the Y-axis direction. The position of can be obtained. Then, the focus control unit 42 can obtain the displacement information DL for the position on the stage surface detected by the displacement sensor 5.

  Next, with reference to FIG. 3 and FIG. 4, the operation | movement which measures the displacement of the upper surface of the stage part 21 by the displacement sensor 5 is demonstrated. FIG. 3 is a schematic diagram illustrating an operation in which the displacement sensor 5 measures the displacement of the upper surface of the stage unit 21 in the Y-axis direction. FIG. 4 is a schematic diagram illustrating the position of the displacement sensor 5 that measures the displacement by scanning the upper surface of the stage unit 21.

  In FIG. 3, the displacement sensor 5 measures the displacement of the upper surface of the stage unit 21 for each pitch Yp in the Y-axis direction with reference to the reference point P0 set on the upper surface of the stage unit 21. For example, it is assumed that the distance in the Z-axis direction from the displacement sensor 5 to the reference point P0 is Z0. Then, the Z-axis direction distance from the displacement sensor 5 at each point on the upper surface of the stage portion 21 for each pitch Yp from the reference point P0 in the Y-axis direction is Z1, Z2,..., Zn (n is a natural number), respectively. . In this case, the displacement sensor 5 detects the displacements Z1-Z0, Z2-Z0,..., Zn-Z0 in order for each point on the upper surface of the stage portion 21 for each pitch Yp from the reference point P0 in the Y-axis direction. And output to the focus control unit 42. In FIG. 3, the displacement sensor 5 is described as moving in the Y-axis direction, but this indicates a relative positional relationship. 1 and 2, the displacement sensor 5 is fixed on the stage surface, and the stage unit 21 is moved in the Y-axis direction so that the displacement sensor 5 sequentially shifts the displacement of the stage surface from the reference point P0. Measure for each Yp. In this way, the stage unit 21 moves in the main scanning direction (Y-axis direction) with the position of the displacement sensor 5 in the X-axis and Z-axis directions fixed, so that the displacement of the upper surface of the stage unit 21 with respect to the main scanning direction is changed. It is measured.

  In FIG. 4, every time the displacement measurement in the Y-axis direction from the one end to the other end of the displacement measurement region is completed on the upper surface of the stage unit 21, the X-axis direction drive mechanism 35 moves the X-axis direction drive member 33 in the sub-scanning direction. It moves by the pitch Xp along (X-axis direction). By this movement, the position at which the displacement sensor 5 measures the displacement also moves in the X-axis direction by the pitch Xp. Then, the stage unit 21 moves in the Y-axis direction opposite to the previous time while the position of the displacement sensor 5 in the X-axis and Z-axis directions is fixed, so that the stage unit 21 moves in the main scanning direction away from the previous time by the pitch Xp. The displacement of the upper surface is measured. By repeating such an operation, the displacement of the entire displacement measurement region on the upper surface of the stage unit 21 is obtained from the displacement sensor 5. At this time, in the displacement measurement area, the displacement in the Z-axis direction with respect to the reference point P0 is measured with respect to the position of the lattice-shaped intersection having the pitch Xp in the X-axis direction and the pitch Yp in the Y-axis direction. In FIG. 4, a line for measuring the displacement of the displacement sensor 5 is indicated by a solid line, and movement for each pitch Xp along the sub-scanning direction (X-axis direction) is indicated by a broken line. The focus control unit 42 creates the stage height table 431 using the displacement information DL from the displacement sensor 5 measured and output by such an operation. Note that it is preferable to measure the displacement in the main scanning direction with respect to the sub-scanning direction at shorter intervals (that is, Yp <Xp).

  FIG. 5 is a diagram illustrating an example of the stage height table 431. Note that the stage height table 431 shown in FIG. 5 is data relating to the height of the stage surface of the stage portion 21 in the Z-axis direction. The pitch Xp = 10 mm and the pitch Yp = 0.5 mm, and the reference point P0 (X-axis). The displacement of each measurement point with respect to the direction position: 0 mm and the Y-axis direction position: 0.0 mm is described in units of μm.

  In FIG. 5, the stage height table 431 is measured by the displacement sensor 5 on the upper surface of the stage portion 21 with respect to the position of the grid-like intersection point having the pitch Xp in the X-axis direction and the pitch Yp in the Y-axis direction. Each displacement is described. As described above, the focus control unit 42 is on the stage surface measured by the displacement sensor 5 based on the relative positional relationship between the displacement sensor 5 and the stage unit 21 in the X-axis direction and the Y-axis direction. Gaining position. The focus control unit 42 derives a displacement amount from the displacement sensor 5 using the displacement information DL with the reference point P0 as a reference. Therefore, the focus control unit 42 can create the stage height table 431 by describing the displacement amount corresponding to the position on the stage surface measured by the displacement sensor 5. The stage height table 431 is data representing the height and undulation (flatness) of the stage surface with respect to the imaging direction (Z-axis direction) of the imaging camera 31. The focus control unit 42 stores the created stage height table 431 in the storage unit 43.

  Next, with reference to FIG. 6, the operation when the imaging camera 31 of the appearance inspection apparatus 1 images the inspection object will be described. FIG. 6 is a schematic diagram illustrating an operation in which the imaging camera 31 images the inspection object placed on the upper surface of the stage unit 21 in the Y-axis direction. In FIG. 6, the inspection object (film mask) placed on the upper surface of the stage unit 21 is omitted.

  In FIG. 6, the imaging camera 31 is movable in the X-axis direction (sub-scanning direction) and the Z-axis direction (imaging direction). Then, main scanning is performed by moving the stage unit 21 in the main scanning direction (Y-axis direction) while the position of the imaging camera 31 in the X-axis direction is fixed. For example, the focus control unit 42 controls the Z-axis direction drive mechanism 36 so that the imaging camera 31 is focused on the upper surface of the film mask placed on the reference point P0 on the stage surface. The position in the Z-axis direction is the reference height. Regarding the derivation of the reference height, the reference height at which the imaging camera 31 is focused on the upper surface of the film mask can be calculated from the distance from the stage surface to the imaging camera 31 and the thickness of the film mask to be placed. In addition, after moving the imaging camera 31 in the Z-axis direction to a height (reference height) that can be adjusted by the focusing function provided in the imaging camera 31, the focusing function focuses on the upper surface of the film mask. It doesn't matter if they match.

  Here, the film mask as the object to be inspected is in close contact with the stage surface of the stage portion 21, and the thickness of the film mask is sufficiently uniform as compared with the depth of focus. That is, the upper surface of the film mask forms the same undulation as the stage surface of the stage portion 21. Therefore, in the present invention, the focus control unit 42 uses the stage height table 431 so that the focus position of the imaging camera 31 is always on the upper surface of the film mask while scanning the film mask on the stage surface. The drive mechanism 36 is controlled to move the position of the imaging camera 31 in the Z-axis direction.

  As shown in FIG. 6, the focus control unit 42 uses the reference height at the reference point P0 as a reference, and the position of the imaging camera 31 in the Z-axis direction for each pitch Yp in the Y-axis direction based on the stage height table 431. To change. For example, it is assumed that the stage surface of the stage unit 21 is displaced as described with reference to FIG. That is, in the stage height table 431, displacements Z1-Z0, Z2-Z0,..., Zn-Z0 are sequentially described with respect to each point on the upper surface of the stage portion 21 for each pitch Yp in the Y-axis direction from the reference point P0. Has been. Then, the focus control unit 42 moves the scanning of the imaging camera 31 for each pitch Yp when the stage unit 21 moves and scans in the main scanning direction (Y-axis direction) with the position of the imaging camera 31 in the X-axis direction fixed. The position in the Z-axis direction is raised or lowered by the amount of displacement described in the stage height table 431. When the displacement amount is described in the stage height table 431, the focus control unit 42 moves from the reference height by displacements Z1-Z0, Z2-Z0,..., Zn-Z0 for each pitch Yp in the Y-axis direction. The imaging camera 31 is moved up and down in the Z-axis direction. As a result, the distance between the imaging camera 31 and the upper surface of the film mask (the stage surface of the stage unit 21) is constant, so that the focal position of the imaging camera 31 is always controlled to be the upper surface of the film mask.

  Next, the main control unit 41 controls the X-axis direction driving mechanism 35 to move the imaging camera 31 in the sub-scanning direction (X-axis direction) every time main scanning from one end to the other end of the film mask inspection region is completed. ) Along a predetermined distance (for example, pitch Xp). Then, the focus control unit 42 performs scanning by moving the stage unit 21 in the Y-axis direction opposite to the previous time while the position of the imaging camera 31 in the X-axis direction is fixed. At this time, the focus control unit 42 shifts the position of the imaging camera 31 in the Z-axis direction for each pitch Yp, as described in the stage height table 431 according to the X-axis direction and Y-axis direction position of the imaging camera 31. Move up and down by the amount. Thereby, the upper surface of the film mask is scanned in the main scanning direction that is a predetermined distance away from the previous time. By repeating such an operation, while scanning the film mask, the position of the imaging camera 31 in the Z-axis direction is controlled so that the focal position of the imaging camera 31 is always on the upper surface of the film mask. The entire image data is output from the imaging camera 31.

  In addition, the exact X-axis direction and Y-axis direction positions of the imaging camera 31 in the above description are straight lines connecting the principal point that is the optical center of the lens of the imaging camera 31 and the gazing point (hereinafter referred to as the viewing direction). ) And the stage surface of the stage portion 21. As described above, since the imaging camera 31 is supported by the camera support member 34 so that the imaging direction is the Z-axis downward direction, the line-of-sight direction is also fixed in the Z-axis downward direction. Therefore, the X-axis direction and Y-axis direction positions where the principal point of the imaging camera 31 is located are the X-axis direction and Y-axis direction positions of the imaging camera 31. On the other hand, the displacement amount described in the stage height table 431 is described with respect to the X-axis direction and Y-axis direction positions at the positions of the lattice-like intersections having the pitch Xp in the X-axis direction and the pitch Yp in the Y-axis direction. Is done. Therefore, the X-axis direction and Y-axis direction positions of the imaging camera 31 may not match the X-axis direction and Y-axis direction positions described in the displacement amount in the stage height table 431. For example, when the position in the X-axis direction where imaging starts and the position in the X-axis direction described in the stage height table 431 do not match, the X-axis direction drive mechanism 35 is controlled to move the imaging camera 31 in the X-axis direction. Inconsistency occurs when the distance for movement is different from the pitch Xp. At this time, the focus control unit 42 calculates the displacement amount by performing interpolation with respect to the X-axis direction in order to obtain the displacement amount for each pitch Yp described in the stage height table 431 with respect to the Y-axis direction.

FIG. 7 is a diagram for explaining the interpolation processing in the X-axis direction. For example, it is assumed that the imaging camera 31 is scanning in the Y-axis direction at a position separated by a distance Xof (Xof <Xp) in the X-axis direction with respect to the position in the X-axis direction described in the stage height table 431. At this time, when the imaging camera 31 is placed at one of the positions in the Y-axis direction described in the stage height table 431 (point Ps shown in FIG. 7), the stage height table 431 is moved to the left and right in the X-axis direction. There are a point P1 and a point P2 where the amount of displacement is described. The focus control unit 42 uses the displacement amount at the point P1 and the displacement amount at the point P2 to calculate the displacement amount at the point Ps, for example, by performing a linear interpolation process. For example, in the case of the example shown in FIG.
Zps = Zp1 + (Zp2-Zp1) * (Xof / Xp)
It becomes. Here, Zps: displacement amount at the point Ps, Zp1: displacement amount at the point P1, and Zp2: displacement amount at the point P2. In the above example, the interpolation processing between two points is described, but the same calculation can be performed when four-point interpolation is performed within a four-point grid.

  In the above-described operation in which the imaging camera 31 captures an object to be inspected, the imaging camera 31 is focused on the upper surface of the film mask placed at the reference point P0 to obtain the reference height of the imaging camera 31. The reference height of the imaging camera 31 may be set at the position. Even if the imaging camera 31 is focused on the upper surface of the film mask placed at a position other than the reference point P0, the reference height is similarly set in consideration of the difference in displacement between the position and the reference point P0. Needless to say, it can be set.

  As described above, the appearance inspection apparatus 1 uses the data relating to the height of the stage surface of the stage unit 21 measured in advance in the Z-axis direction, while keeping the distance between the imaging camera 31 and the stage surface equal. The stage surface can be scanned. If the flexible thin plate-like member such as a film mask is an inspection object, the inspection object adheres along the stage surface. Therefore, the imaging camera 31 can perform imaging while always maintaining the same distance from the upper surface of the inspection object, and once the focus is on the upper surface of the inspection object, the entire inspection area of the inspection object can be scanned. The focus can always be accurately adjusted to the upper surface, and the inspection resolution of the appearance inspection apparatus 1 can be increased. Even if the line-of-sight direction of the imaging camera 31 and the displacement detection direction of the displacement sensor 5 are slightly tilted from the vertical with respect to the stage surface, the displacement amount described in the stage height table 431 is measured including the tilt. Therefore, the imaging camera 31 can be focused on the upper surface of the object to be inspected according to the inclination. In the appearance inspection apparatus 1, when the positional relationship between the stage unit 21 and the imaging camera 31 in the Z-axis direction is fixed, once the stage height table 431 is created, the stage height table 431 is created for each inspection. do not have to. Therefore, conventionally, a step for obtaining height information for each object to be inspected is not required, so that the time required for appearance inspection can be shortened.

  Note that the stage height table 431 may be measured and stored in the storage unit 43 only when the stage unit 21 is manufactured, or the timely timing (e.g., every day or Measurement may be performed according to each inspection lot) and stored in the storage unit 43. In addition, when measuring and creating only immediately after manufacture, since it is not necessary to create the stage height table 431 again, the displacement sensor 5 becomes unnecessary in the appearance inspection apparatus 1, and apparatus cost can be reduced. On the other hand, when the stage height table 431 is created for each timely timing immediately before inspecting the inspection object, even if the positional relationship in the Z-axis direction between the stage unit 21 and the imaging camera 31 changes after manufacturing, The focal position can be appropriately adjusted according to the change.

  In the above description, an example in which a plurality of imaging cameras 31a and 31b are supported by one camera support member 34 is shown. In this case, scanning may be performed by the same operation as described above using the principal point position of one representative imaging camera 31 among the principal point group of the plurality of imaging cameras 31. Further, when a plurality of imaging cameras 31 perform scanning while simultaneously capturing images, even if scanning is performed in the same manner as described above using neutral positions (for example, average) in the principal point group of the plurality of imaging cameras 31. It doesn't matter. Further, when the plurality of imaging cameras 31 perform scanning while simultaneously imaging, the same operation as described above is performed by fixing the gazing points of the plurality of imaging cameras 31 to the camera support member 34 so that they are at the same position on the stage surface. You can scan with.

  In the above description, the imaging camera 31 receives the transmitted light irradiated to the object to be inspected from the transmitted illumination light source provided below the glass plate of the stage unit 21. However, the light source is the stage unit. It may be provided at the top of 21. In this case, the imaging camera 31 receives the reflected light reflected by the object to be inspected from the light source provided on the upper part of the stage unit 21.

  In the present embodiment, the main scanning is performed by moving the stage unit 21 in the Y-axis direction. However, the present invention is not limited to this, and the main scanning is performed by moving the imaging camera 31 in the main scanning direction. You may do it. Similarly, instead of moving the imaging camera 31 in the sub-scanning direction, the stage unit 21 may be moved in the sub-scanning direction.

  The visual inspection apparatus and method according to the present invention can perform a high-accuracy inspection using an inexpensive apparatus, and have a flexible thin plate-like member placed on the stage surface as an inspection object. It is useful as a device, an appearance inspection method, and the like.

The top view and front view which show typically the whole structure of the external appearance inspection apparatus which concerns on one Embodiment of this invention The block diagram which shows the control function of the external appearance inspection apparatus 1 of FIG. FIG. 2 is a schematic diagram illustrating an operation in which the displacement sensor 5 in FIG. 2 measures the displacement of the upper surface of the stage unit 21 in the Y-axis direction. Schematic which shows the position of the displacement sensor 5 which scans the upper surface of the stage part 21 and measures a displacement. The figure which shows an example of the stage height table 431 of FIG. FIG. 1 is a schematic diagram illustrating an operation in which the imaging camera 31 of FIG. The figure for demonstrating the interpolation process regarding the X-axis direction of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Appearance inspection apparatus 2 ... Stage conveyance mechanism part 21 ... Stage part 22 ... Turning part 23 ... Y-axis direction drive mechanism 231 ... Y-axis drive motor 232 ... Y-axis NC driver 24 ... Base part 3 ... Imaging mechanism part 31 ... Imaging Camera 32 ... Support member 33 ... X-axis direction drive member 34 ... Camera support member 35 ... X-axis direction drive mechanism 351 ... X-axis drive motor 352 ... X-axis NC driver 36 ... Z-axis direction drive mechanism 361 ... Z-axis drive motor 362 ... Z-axis NC driver 4 ... Control part 41 ... Main control part 42 ... Focus control part 43 ... Storage part 431 ... Stage height table 5 ... Displacement sensor

Claims (6)

An appearance inspection apparatus for inspecting a flexible thin plate-shaped member as an inspection object,
A stage portion on which a stage surface on which an object is placed is formed;
A close contact means for closely holding one main surface of the placed inspection object and the stage surface of the stage portion;
Imaging means for imaging an object to be inspected and held in close contact with the stage surface;
Relative movement means for relatively moving at least one of the stage surface and the imaging means;
Storage means for storing displacement data at each of a plurality of positions on the stage surface;
A control unit that controls relative movement means based on the displacement data so that at least one of the stage surface and the imaging means relatively moves while maintaining an equal distance between the imaging means and the stage surface; An appearance inspection apparatus comprising:   The distance between the imaging unit and the stage surface that the control unit keeps at an equal distance is a distance at which the focal position of the imaging unit is on the other main surface of the inspection object held in close contact with the stage surface. The appearance inspection apparatus according to claim 1, wherein The relative moving means is
An imaging direction moving means for relatively moving at least one of the stage surface and the imaging means in the imaging direction of the imaging means;
Horizontal direction moving means for relatively moving at least one of the stage surface and the imaging means in a direction perpendicular to the imaging direction;
The displacement data is data indicating the displacement of the height in the imaging direction at other positions on the stage surface with reference to the height in the imaging direction from the imaging means to a reference point set on the stage surface. The appearance inspection apparatus according to claim 1, wherein the appearance inspection apparatus is provided.   The storage unit stores the displacement data for intersections of lattices arranged at predetermined intervals respectively in two directions orthogonal to each other set on the stage surface. 1. An appearance inspection apparatus according to 1. The control unit controls the relative movement unit based on the displacement data of the intersection of the lattice that coincides with the intersection of the straight line connecting the principal point that is the optical center of the imaging unit and the gazing point and the stage surface. ,
When the intersection between the straight line and the stage surface does not coincide with the intersection of the lattice, the control unit uses displacement data for the intersection of the plurality of lattices set near the intersection of the straight line and the stage surface. 5. An appearance inspection apparatus according to claim 4, wherein the displacement data at the intersection of the straight line and the stage surface is interpolated and the relative movement means is controlled based on the interpolated displacement data. A visual inspection method for inspecting a flexible thin plate-like member as an inspection object,
A placing step for placing an object to be inspected on the stage surface;
A close contact step for tightly holding the one main surface of the placed inspection object and the stage surface;
An imaging step of scanning and imaging an object to be inspected and held on the stage surface by an imaging means;
A visual inspection method including a control step of scanning the inspection object while maintaining an equal distance between the imaging unit and the stage surface based on displacement data of each of a plurality of positions on the stage surface.

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