JP3954378B2 - Image processing method and component mounting apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing method for apparently improving the resolution of a component recognition camera in a component mounting apparatus for mounting electronic components on a circuit board, and a component mounting apparatus using the image processing method.
[0002]
[Prior art]
Conventionally, a component mounting apparatus that automatically mounts a large number of electronic components (hereinafter simply referred to as components) such as ICs, resistors and capacitors on a circuit board (hereinafter simply referred to as a substrate) that is automatically carried into the device. There is.
[0003]
FIG. 5 (a) is a perspective view showing the external appearance of such a component mounting apparatus, and FIG. 5 (b) is a perspective view schematically showing the internal configuration by removing the upper and lower protective covers. A component mounting apparatus (hereinafter also referred to as a main body apparatus) 1 shown in FIGS. 1A and 1B includes a monitor apparatus 2 composed of a CRT display above a ceiling cover and an alarm lamp 3 for informing the operating state. . In addition, on the front surface of the upper protective cover 4, a small display input panel 5 that includes a liquid crystal display and a touch panel and can input various instructions by external operations is disposed.
[0004]
On the lower base 6, a pair of parallel and fixed board guide rails 7 and 7 are arranged in the center in the transport direction (X-axis direction, diagonally right in the figure) of the circuit board (hereinafter simply referred to as the board). It is arranged to extend horizontally in a diagonally upper left direction from the bottom. A loop-shaped conveyor belt (conveyor belt) is disposed so as to be able to travel in contact with the lower part of the substrate guide rails 7. The conveyor belt is driven by a belt drive motor with the side of the belt of several millimeters in width, viewed from below the substrate guide rail 7 and driven by the belt drive motor, and supports both sides of the back side of the substrate from below. Then, the board before component mounting is carried into the apparatus main body from the upstream side of the line, and the board on which the component has been mounted is carried out to the downstream side of the line.
[0005]
The base 6 is provided with a substrate positioning device, a substrate fixing mechanism for fixing the substrate between the two substrate guide rails 7, a control device for controlling each part, etc., although not particularly shown. ing.
Further, on the base 6, a pair of left and right fixed rails (Y-axis rails) straddling the pair of substrate guide rails 7 and extending in parallel to a direction (front-rear direction) perpendicular to the substrate transport direction. 8 and 8 are arranged. A movable rail (X-axis rail) 9 is slidably engaged with the Y-axis rail 8 along the Y-axis rail 8, and an electronic component (hereinafter simply referred to as a component) is mounted on the board on the X-axis rail 9. A work head 10 for working is suspended along the X-axis rail 9 so as to be slidable.
[0006]
Although not clearly shown in FIGS. 1A and 1B, the X-axis rail 9 has an X-axis (not shown) for freely moving the work head 10 along its longitudinal direction (X-axis direction). A motor is disposed, and a Y-axis motor (not shown) that moves the X-axis rail 9 back and forth (Y-axis direction) along the Y-axis rail 8 is also disposed on the base 6. When these X-axis motor and Y-axis motor rotate freely in both forward and reverse directions according to instructions from the control circuit, the work head 9 moves freely in the X-axis direction and the Y-axis direction.
[0007]
Component supply stages 11 and 11 are disposed on the front and rear portions of the base 6, respectively. Although not particularly shown in the drawings, these component supply stages 11 are provided with a plurality of cartridge-type component supply devices provided with reels around which tapes containing components are wound, corresponding to a plurality of types of components. A tray-type component supply device equipped with a plurality of pallets corresponding to different types of components engages.
[0008]
The work tower 10 is a base of the apparatus main body 1 through a plurality of signal cords (not shown) that are protected and accommodated in a belt-like chain body 12 (12-1, 12-2) that is bendable and hollow inside. 6 is electrically connected to a central control unit disposed on the motherboard. The work tower 10 is supplied with electric power and a control signal from the central control unit via these signal codes, and transmits image data indicating information on the component mounting position on the board to the central control unit.
[0009]
FIG. 6 is a perspective view of the working head 10. As shown in the figure, the work head 10 is connected to the central control unit of the apparatus main body by the flexible belt-like cord 12-1 (and the belt-like cord 12-2 shown in FIG. 5B) as described above. At the tip, two mounting heads 13 and 13 and a substrate recognition camera 14 are provided. Each of the two mounting heads 13 can be moved up and down in the Z-axis direction (vertical direction), and a lighting device 15 and a suction nozzle 16 are mounted at the tip of the head, respectively. The suction nozzle 16 includes a light diffusion plate 16-1 and a nozzle 16-2, and is rotatable in the θ-axis direction (360 ° direction).
[0010]
The working head 10 is freely moved back and forth and left and right by the two Y-axis rails 8 and the one X-axis rail 9 described above, and is not shown on the component supply stage 11 shown in FIG. The component is picked up by the suction nozzle 16 from the component supply device and moved onto the component recognition camera 17 shown in FIG. 5B arranged on the base 6 side.
[0011]
Then, the illumination device 15 illuminates the light diffusing plate 16-1 from above to diffuse the background light of uniform brightness from the light diffusing plate 16-1, and the components that appear in the background light are detected by the component recognition camera 17. The image is picked up to detect a holding position deviation of the component, and the mounting position data is corrected based on the detected holding position deviation.
[0012]
Further, the position of the board (not shown) positioned by the board guide rail 7 shown in FIGS. 5A and 5B is confirmed by the board recognition camera 14, and the above components are placed at a predetermined position on the board. Is installed.
Normally, a CCD camera is used as the component recognition camera 17. Image recognition is performed after analog image data output from the CCD camera is converted to digital image data by an A / D converter. Therefore, the resolution of the captured image depends on the density of the CCD camera pixels (CCD elements) used for imaging.
[0013]
FIGS. 7A and 7B are diagrams illustrating examples of captured images obtained when the resolution of the component recognition camera is relatively coarse with respect to the size of the component. In FIGS. 4A and 4B, the vertical axis indicates the intensity of light reflected from the component surface to be imaged, that is, the output of the CCD element.
FIG. 6A is a diagram showing CCD outputs for the background image 21 and the component image 22 when the image formed on the CCD element surface of the CCD camera is assumed to be continuously analog scanned.
[0014]
However, as described above, the image data captured by the CCD camera is image data at a sampling interval depending on the density of the CCD elements (element arrangement interval S shown in FIGS. 7A and 7B). It is not imaged data by continuous analog scanning.
Generally, from the sampling theorem, if the sampling interval is T, only 1 / 2T frequency components can be acquired as sampled data. Therefore, it is difficult to obtain a resolution higher than the arrangement interval of the CCD elements. For this reason, for example, the data of the portion with a steep inclination shown in FIG. 7A is converted into data with a gentle inclination as shown in FIG.
[0015]
In the example shown in FIG. 5A, the pixel density, that is, the arrangement interval S of the CCD elements is larger than the edges E1 and E2 of the parts. The actual output of the CCD camera cannot correctly capture the edges E1 and E2 of the component, and is based on the arrangement interval S (= sampling interval S) of the CCD elements as shown in FIG. Thus, it is recognized as edge imaging data having a large tolerance, such as the edges E1 ′ and E2 ′ acquired by the sampling theorem.
[0016]
[Problems to be solved by the invention]
By the way, in recent years, as the size of components has been reduced and many small components are included in the mounted components, a finer resolution is often required for the resolution of the component recognition camera.
[0017]
Otherwise, that is, if the resolution is small for a small part, when the part is image-recognized as described above, the tolerance of the part edge position becomes large as shown in FIG. The position cannot be recognized correctly. Then, the position recognition for the entire part becomes inaccurate and correct position correction cannot be performed. If the correct position cannot be corrected, the substrate cannot be correctly mounted at the mounting position, and a defective substrate unit is produced, resulting in a decrease in yield.
[0018]
In order to cope with this problem, that is, to recognize a part having a very small size, it is necessary to increase the magnification of the lens of the camera or to use a CCD camera having a larger number of CCD elements.
However, the method of increasing the magnification of the lens of the camera has a problem that a large part cannot be recognized because the field of view of the entire captured image is narrowed. On the other hand, the method of increasing the number of CCD elements is not preferable because it causes various problems such as an increase in captured image data, an increase in transfer time of the image data, and an increase in the cost of the CCD camera.
[0019]
In view of the above-described conventional situation, an object of the present invention is to provide an image processing method for improving the recognition accuracy of a component without increasing the number of CCD elements of the camera, and a component mounting apparatus using the image processing method.
[0020]
[Means for Solving the Problems]
First, an image processing method according to the first aspect of the present invention includes a step of capturing an object with a depth of focus shallower by a predetermined range than an actual depth of focus and acquiring a defocused image data with a poor focus, and the acquired defocused image. A step of converting the data into digital image data, a step of interpolating the converted digital image data to generate interpolated image data, and a filter operation step of approximating the actual image data based on the interpolated image data. Composed.
[0021]
Next, a component mounting apparatus according to a second aspect of the present invention is a method of taking an electronic component from a component supply device and holding it and recognizing the position of the electronic component on the way of transferring the held electronic component onto a circuit board. A component mounting apparatus for correcting and mounting the position-corrected electronic component at a predetermined position on the circuit board, wherein the electronic component is imaged at a focal depth shallower than the actual focal depth by a predetermined range, and a defocused image with a poor focus Out-of-focus image data acquisition means for acquiring data, image data conversion means for converting out-of-focus image data acquired by the out-of-focus image data acquisition means into digital image data, and digital image data converted by the image data conversion means Image data interpolation means for generating interpolated image data by interpolation, and based on the interpolated image data generated by the image data interpolation means A filtering unit to approximate the captured image data with the actual depth of focus, and includes a.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram schematically illustrating a configuration of a mechanism main part of a component mounting apparatus according to an embodiment. In the component mounting apparatus 20 shown in the figure, the external appearance and the structure of the internal mechanism portion are the external appearance of the component mounting apparatus 1 shown in FIG. 5 (a) and the internal mechanism portion shown in FIG. 5 (b) and FIG. This is almost the same as the configuration.
[0023]
An XYZθ robot 21 shown in FIG. 1 includes a work head 22 and a support unit 23 that supports the work head 22 so as to be movable in the horizontal X-axis direction and the horizontal Y-axis direction as indicated by arrows X and Y in the figure. A mounting head 24 that is provided on the work head 22 and can be moved up and down as indicated by an arrow Z, and a suction nozzle 25 that is attached to the tip of the mounting head 24 and is rotatable in a horizontal 360 degree direction as indicated by an arrow θ. Consists of.
[0024]
The movement of the work head 22 in the X-axis direction and the Y-axis direction, the movement of the mounting head 24 in the Z-axis direction, and the rotation of the suction nozzle 25 in the 360-degree direction are performed by dedicated actuators (not shown).
In addition, on the path on which the work head 22 sucks a component 26 from a component supply device (not shown) with a suction nozzle 25 and moves the suctioned component 26 to be transferred onto a substrate (not shown), A CCD camera 27 for picking up an image of 26 from below is disposed on the component mounting apparatus main body side. The CCD camera 27 includes a lens 28 and an imaging unit 29 in which a CCD is disposed. The CCD camera 27 is a normal CCD camera in which the density of the CCD pixels provided in the image pickup unit 29 is normal, that is, the number of pixels is not particularly large.
[0025]
FIG. 2 is a flowchart for explaining image recognition processing for the component 26 controlled by a central control unit (not shown) in the above configuration. In the figure, first, a part is imaged (S1). This process is a process in which the work head 22 sucks the component 26 from the component supply device by the suction nozzle 25 and acquires an image of the bottom surface of the component 26 by the CCD camera 27 when passing over the CCD camera 27.
[0026]
At this time, the component 26 at the tip of the suction nozzle 25 is movable by the XYZθ robot 21, so that the distance from the CCD camera 27 can be set arbitrarily. In a normal case, imaging is performed such that the distance between the component 26 and the CCD camera 27 is a distance between the focal point of imaging and the CCD pixel surface.
[0027]
In this example, the case where the part 26 is a small-sized part is taken as an example. In the processing in S1 described above, the distance between the part 26 and the CCD camera 27 is slightly shortened and the focus is not achieved (the focus is not adjusted). Take a picture in a shallow state. That is, in the imaging processing of this example, out-of-focus out-of-focus image data is acquired.
[0028]
FIGS. 3A and 3B are diagrams for explaining the state of data obtained as CCD image data of an out-of-focus image. As shown in FIG. 3A, in the case of a captured image in focus, the light reflected from one point of the component forms an image on one point on the CCD element.
[0029]
However, in the case of a captured image that is out of focus (not in focus), the light reflected from one point of the component diffuses along the δ function 30 as shown in FIG. An image is formed on the CCD element.
Therefore, even if the same part shown in FIG. 7A is imaged, a blurred image in which the diffused light is integrated on each element is formed on the CCD.
[0030]
FIG. 4A shows an example of such out-of-focus image data, and FIG. 4B shows out-of-focus image data after data interpolation, which will be described later. Note that the captured image data of the component acquired in the process S1 of FIG. 2 is the out-of-focus image data shown in FIG.
[0031]
However, the out-of-focus image data shown in FIG. 4 (a) is diffused to eliminate the high-frequency component of the image, and apparently even at the same sampling interval. Sampling is faithful to changes in image components. However, although the sampling is faithful to the change of the image component, the out-of-focus image data is a discrete value because it is an acquired value by the CCD camera.
[0032]
Next, an approximation process is performed on the out-of-focus image data composed of the discretized sampling values (S2). In this process, interpolation data between sampling points is calculated by using Fourier transform or the like for the above-mentioned out-of-focus image data, the apparent number of pixels is increased, and the process approximates discrete data to continuous data. It is.
[0033]
Following the above, prediction of inter-pixel data is performed (S3). This process is a process of predicting data between pixel data (discrete values output from the CCD element) by interpolation data obtained by the above approximation process (filling between pixel data with interpolation data). As a result, as shown in FIG. 4B, the interpolation data 32 obtained by the approximation process is added between the sampling points 31 of the out-of-focus image data captured at the sampling interval S and the values of the sampling points 31. In addition, the out-of-focus image data that is interpolated so as to appear as if it was sampled at a sampling interval that is ½ of the sampling interval S is generated.
[0034]
A defocused image can be thought of as having undergone a δ function transformation on an in-focus image, so if an inverse δ function transformation is applied to a defocused image, the in-focus image will be restored. Can do.
Therefore, next, the interpolated out-of-focus image data is converted using an inverse δ function filter (S4). In this processing, the out-of-focus image data shown in FIG. 4 (b) can be considered as out-of-focus image data along the δ function sampled at a sampling interval of 1/2 of the sampling interval S by the above interpolation. Is apparently restored as data approximated to image data sampled in focus at a sampling interval ½ of the sampling interval S.
[0035]
Since the variable of the inverse δ function varies depending on the degree of focus shift, it is preferable to measure the degree of focus shift in advance. As a result, an image as if it was sampled at a sampling density twice as high as the actual sampling is always restored.
The position is detected using the restored image data (S5). As described above, the restored image data approximates to the image data sampled by focusing at a sampling interval that is half the sampling interval S as described above. The position of can also be accurately captured. That is, it is possible to accurately recognize the position of the component held by the suction nozzle.
[0036]
Based on this recognition, the actuator is controlled (S6). In this process, the central control unit calculates the positional deviation from the part table data, that is, the NC program parameters, based on the recognition result, and corrects the position of the part based on the calculation result. The correction value is notified to an actuator control unit (not shown), and each actuator of the XYZθ robot 21 is controlled by the actuator control unit.
[0037]
Thereafter, it is determined whether or not there is a part to be imaged next (S7), and if there is (S7 is Yes), the process returns to S1 and the processes of S1 to S7 are repeated. On the other hand, when there is no part to be imaged next (S7 is No), the process is terminated.
In this way, the resolution of the component recognition camera is apparently improved from the actual level, and the position of the component can be recognized with higher accuracy, so that the image data of the component with higher resolution than the number of CCD elements can be obtained. Processing can be performed, and the position and angle of the component can be calculated more accurately and corrected.
[0038]
【The invention's effect】
As described above in detail, according to the present invention, an image in a defocused state with few high-frequency components is intentionally acquired when imaging a component, an approximate expression of this image data is established, and a minimum sampling interval is obtained. The data value is predicted, and the defocused image data interpolated by this predicted value is restored to the focused image by the filter, so that an image with a resolution higher than the number of CCD elements can be obtained by the amount of interpolation, As a result, it is possible to perform highly accurate component recognition at low cost without replacing the CCD camera.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a mechanism main part of a component mounting apparatus according to an embodiment.
FIG. 2 is a flowchart illustrating image recognition processing for a component controlled by a central control device of the component mounting device according to the embodiment.
FIGS. 3A and 3B are views for explaining the state of data obtained as CCD image data of an out-of-focus image. FIG.
4A is a diagram showing an example of out-of-focus image data, and FIG. 4B is a diagram showing out-of-focus image data after data interpolation.
5A is a perspective view showing an external appearance of a conventional component mounting apparatus, and FIG. 5B is a perspective view schematically showing an internal configuration by removing the upper and lower protective covers.
FIG. 6 is a perspective view of a working head of a conventional component mounting apparatus.
FIGS. 7A and 7B are diagrams illustrating examples of captured images obtained when the resolution of a component recognition camera is relatively coarse with respect to the size of a component in a conventional component mounting apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Component mounting apparatus 2 Monitoring apparatus 3 Alarm lamp 4 Upper protective cover 5 Display input panel 6 Base 7 Board | guide guide rail 8 Y-axis rail 9 X-axis rail 10 Work head 11 Component supply stage 12-1, 12-2 Strip | belt-shaped code 13 Mounting head 14 Substrate recognition camera 15 Illumination device 16 Adsorption nozzle 16-1 Light diffusion plate 16-2 Nozzle 17 Component recognition camera 21 XYZθ robot 22 Work head 23 Support section 24 Mounting head 25 Adsorption nozzle 26 Component 27 CCD camera 28 Lens 29 Imaging unit

Claims (2)

A step of setting the position of the CCD camera and the imaging object so that the focal depth is shallower than the actual focal depth by a predetermined range;
By imaging the imaging Target object in the set position, a step of acquiring the blurred image data obtained at the sampling intervals corresponding to the CCD camera resolution in accordance with the change of the sweet image components focal,
Converting the acquired out-of-focus image data into digital image data;
Calculating interpolation data of the sampling interval of the converted digital image data ;
A step of generating interpolated image data by “interpolating the sampling interval by the calculated interpolation data and increasing the apparent sampling number”;
A filter calculation step for converting the “out-of-focus” interpolation image data with an inverse δ function filter to approximate the actual image data;
An image processing method comprising: In the process of taking out and holding the electronic component from the component supply device and transferring the held electronic component onto the circuit board, the electronic component is image-recognized by a CCD camera to correct the position, and the position-corrected electronic component is moved to the circuit board. A component mounting device mounted at a predetermined position of
A position setting means between camera electronic components for setting the position of the CCD camera and the electronic component so that the focal depth is shallower than the actual focal depth by a predetermined range;
The electronic component is imaged at a position set by the position setting means between the electronic components of the camera, and defocused image data obtained at a sampling interval corresponding to the resolution of the CCD camera according to a change in an image component with a poor focus is acquired. Out-of-focus image data acquisition means;
Image data conversion means for converting the out-of-focus image data acquired by the out-of-focus image data acquisition means into digital image data;
Interpolation means for calculating interpolation data of the sampling interval of the digital image data converted by the image data conversion means ;
A defocused interpolated image data generating means for generating defocused interpolated image data in which the apparent sampling number is increased by interpolating the sampling interval with the interpolation data calculated by the interpolating means;
Filter arithmetic means for converting the interpolated out-of-focus image data generated by the out-of-focus interpolated image data generation means with an inverse δ function filter and approximating the image data captured at the actual depth of focus;
A component mounting device characterized by comprising:

Images