JPH08330797A - Lead position detecting device - Google Patents

Abstract

PURPOSE: To protect a lead position detecting device against mis-detection caused by a deterioration in illumination light and the state of leads by a method wherein the threshold level of a binary picture image is obtained from the picture image of a reference pin, and an angle of rotation of a lead arrangement in a reference direction is obtained through a least square method from the center of gravity of many lead picture images. CONSTITUTION: A lead position detecting device is equipped with a camera 3 which picks up the image picture of an electronic component 8, a light source 4 which illuminates the electronic component 8, and a reference pin 6 of the same material as the lead of the electronic component 8 and with a rectangular end face. The image of the end face of the reference pin 6 is picked up by the camera 3, a threshold level is determined from the above image data, the picture image of the lead of the electronic component 8 picked up by the camera 3 at the obtained threshold level is turned into binary data, the center of gravity of a lead is obtained from the binary data of the lead through a picture image processing device 5. Furthermore, an angle of rotation of a lead arrangement in a reference direction and the position of a lead are obtained through a least square method from the center of gravity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead position detecting device for detecting the position of a lead of an electronic component such as a surface mount element, and more particularly to a printed circuit board for correcting variations in the position of the electronic component in an automatic assembly machine for printed wiring boards. The present invention relates to an apparatus for detecting the position of a lead of an electronic component gripped by a robot hand or the like for accurate insertion into a robot hand.

[0002]

2. Description of the Related Art As a conventional lead position detecting device, there is "position correction method of SMD by image processing" in Japanese Patent Laid-Open No. 02-118404.

The conventional lead position detecting device is as follows.

The electronic parts are positioned within the visual field of the camera by the operation of the robot hand holding the electronic parts. The camera captures the image of the electronic component illuminated by the light source and sends it to the image processing apparatus. The image processing device analyzes the image sent from the camera and detects the position of the lead base on the coordinate axis of the camera. A correction value in the rotation direction and correction values in the x and y directions are calculated based on the position of the base of the lead with respect to the coordinate axes on the camera field of view, and used as the positional deviation amount to correct the position of the electronic component mounted by the robot hand.

[0005]

Since the above-described conventional lead position detecting device always recognizes the lead base portion by the image processing including the binarization etc. at the constant threshold level, the image picked up by the camera is There is a drawback that the lead base cannot be accurately identified and the correct lead position cannot be detected when the state of the image changes due to deterioration of illumination light or the like.

[0006]

A lead position detecting apparatus according to the present invention is a reference having a camera for picking up an image of an electronic component, a light source for illuminating the electronic component, and a rectangular end face which is of the same quality as the lead of the electronic component. From the lead image obtained by binarizing the image captured by the camera at the threshold level determined from the image information captured by the camera on the end face of the reference pin illuminated by the light source, the lead barycentric position is determined. The image processing apparatus includes a lead position calculating unit that obtains a rotation angle of the lead array with respect to a reference direction and a lead position from the barycentric position of the lead by using the least squares method.

[0007]

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

In this embodiment, a robot arm 1, a robot hand 2 attached to the robot arm 1 for holding a component, and a one-dimensional CCD camera 3 for capturing an image of an electronic component 8 held by the robot hand 2. A light source 4 for illuminating the electronic component 8 for facilitating imaging, an image processing device 5 for determining the position of the imaged lead of the electronic component 8, and an image processing device attached to the robot hand 2 for processing an image. A reference pin 6 having a rectangular cross section that serves as a reference for
The control unit 7 controls each unit.

The robot hand 2 is attached to the robot arm 1 and is mechanically integrated. A reference pin 6 is attached to the robot hand 2. Reference pin 6
Is made of the same material as the lead of the electronic component to be gripped, and the lower end surface imaged by the one-dimensional CCD camera 3 has a rectangular shape. The robot arm 1 picks up the electronic component 8 from the supply unit (not shown) with the robot hand 2 according to the control signal from the control unit 7, and the one-dimensional CCD camera 3
Within the field of view at a predetermined speed. The image processing device 5
The image pickup result of the one-dimensional CCD camera 3 is fetched in response to a signal from the control unit 7.

FIG. 2 shows a relational diagram of the mounting positions of the electronic component 8 picked up by the robot hand 2 and the one-dimensional CCD camera 3. The one-dimensional CCD camera 3 is attached so that the lead 9 on one side of the electronic component 8 can be imaged. Here, the moving direction of the electronic component 8 is the X axis, and the scanning direction of the one-dimensional CCD camera 3 is the Y axis.

FIG. 3 shows an image pickup signal for one scan when the lead 9 is picked up by the one-dimensional CCD camera 3. FIG. 3A shows a signal when the light source 4 is sufficiently bright,
FIG. 3B shows a signal when the light source 4 is dark. FIG. 4 shows a flowchart of the lead position detection method. FIG. 5 shows a diagram for explaining the position correction of the lead 9.

The electronic component 8 is picked up by the robot hand 2 and carried by the robot arm 1 above the one-dimensional CCD camera 3 at a constant speed. One-dimensional CCD camera 3
Always captures an image and sends image information to the image processing apparatus 5. The control unit 7 measures the time from the start of the constant speed movement of the robot arm 1, determines the timing when the electronic component 8 passes above the one-dimensional CCD camera 3, and sends a signal to the image processing device 5 to start image loading. Send out. The image processing device 5 receives the signal from the control unit 7 and stores the image information sent from the one-dimensional CCD camera 3 in the internal memory.
Further, the control unit 7 measures the time, determines the timing when the electronic component 8 has finished passing above the one-dimensional CCD camera 3, and sends a signal indicating the end of image capture to the image processing device 5. The image processing device 5 receives the signal from the control unit 7 and stops storing the image information sent from the one-dimensional CCD camera 3. As a result, the internal memory of the image processing device 5 has 2
The three-dimensional image information is stored (step f
1).

The image processing device 5 binarizes the image to detect the lead, but the image pickup result by the one-dimensional CCD camera 3 depends on the deterioration state of the light source 4 as shown in FIGS. 3 (A) and 3 (B). The signal level fluctuates. Due to such variations, if the image is always cut out at the same threshold level and the image is binarized, it may be detected in a shape different from the actual lead. Therefore, the robot hand 2 is moved so that the lower end surface of the reference pin 6 is imaged by the camera 3 before the electronic component 8 is imaged, and the image information for one scan when the reference pin 6 is imaged is output from the image processing device 5. Take it out. Since the robot arm 1 is moving at a constant speed, the time for capturing an image, that is, the number of scans, matches the position information. Even if the image capture start timing is slightly deviated from the instability of the robot arm 1 during acceleration, since the image pickup surface of the reference pin 6 has a rectangular shape,
The shape width to be cut out from the extracted image information for one scan is constant. The control unit 7 evaluates the image pickup result and obtains a threshold level at which a correct shape is detected (step f2).

Next, the control section 7 sends the threshold level obtained in step f2 and the signal of the binarization processing to the image processing apparatus 5. The image processing device 5 uses this threshold level to cut out a portion of the level exceeding the threshold level from all the captured imaging results (step f3). Assuming that the cut-out portion is black and the remaining portion is white, the portion displayed in black becomes the image of the lead 9 (see FIG. 5). This image is called a binary image.

Next, the control unit 7 sends to the image processing apparatus 5 a signal for obtaining the barycentric position of each lead of the binary image in order to avoid processing at an unstable edge of the image. The image processing device 5 determines that one block of the black portion of the binary image is one lead, obtains the barycentric coordinates thereof, and sends it to the control unit 7 (step f4). In this way, the barycentric coordinates of all the leads 9 provided on one side of the electronic component 8 are obtained. The control unit 7 controls the plurality of leads 9 sent from the image processing apparatus 5.
A linear equation (y = ax + b) representing the arrangement of the barycentric positions is obtained using the least squares method, and this is a linear equation showing the arrangement of the measurement sides of the electronic component 8 in the measurement coordinate system. From this linear equation, the angle between the measurement side of the electronic component and the measurement coordinate system, that is, the corrected rotation angle θ of the electronic component is obtained (θ = t
an ^-1 (1 / a)) (step f5).

Next, an appropriate barycentric coordinate of the lead 9 is selected, and the position of the electronic component 8 in the x and y directions is obtained. When the centers of gravity of the leads 9 adjacent to each other in the front and rear are compared and the centers of gravity of the leads 9 are separated from each other and the lead spacing is equal to or more than a predetermined amount, it is determined that the lead 9 may be bent, and the lead spacing is determined. The coordinate of the center of gravity of the lead 9 within which a predetermined value is set within the predetermined amount is set as the coordinate of the center of gravity of the appropriate lead, and the difference (x1, y1) from the center of gravity P of the reference pin 6 is obtained. The coordinates of the rotation center S of the robot hand 2 when the position of the reference pin 6 is assumed to be the origin are (x2, y2).

The lead position from the reference pin 6 when the robot hand 2 is rotated by the correction angle θ can be determined by the following equation.

X1 '= (x1-x2) cos θ- (y1
−y2) sin θ + x2 y1 ′ = (x1-x2) cos θ + (y1-y2) si
nθ + y2 The difference between the relative coordinates (x3, x3) of the reference pin 6 and the lead position registered in advance and the relative coordinates (x1 ′, y1 ′) when the measurement result is corrected by the correction angle θ is the correction amount (Δ
x, Δy) (step 6).

Δx = x1'-x3 Δy = y1'-y3 The control unit 7 controls the robot arm 1 and the robot hand 2 with the calculated correction amounts θ, Δx, and Δy to perform position correction in the XYθ directions.

[0021]

Since the lead position detecting device of the present invention obtains the threshold level of image binarization based on the image of the reference pin, erroneous position detection due to deterioration of illumination light is eliminated. Further, since the rotation angle of the lead arrangement with respect to the reference direction is obtained from the barycentric positions of a large number of lead images by using the least squares method, there is an effect of reducing erroneous detection due to the lead state.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram for explaining a relationship between an electronic component 8 picked up by the robot hand 2 shown in FIG. 1 and a one-dimensional CCD camera 3.

FIG. 3 is a diagram showing an image pickup signal of a one-dimensional CCD camera 3 shown in FIG.

FIG. 4 is a flowchart showing a lead position detection method according to an embodiment of the present invention.

5 is a diagram for explaining a method of obtaining a correction amount in the X and Y directions performed in step f6 shown in FIG.

[Explanation of symbols]

 1 robot arm 2 robot hand 3 one-dimensional CCD camera 4 light source 5 image processing device 6 reference pin 7 control unit 8 electronic parts

Claims (1)

[Claims] 1. A camera for picking up an image of an electronic component, a light source for illuminating the electronic component, a reference pin having a rectangular end face of the same quality as the lead of the electronic component, and an end face of the reference pin illuminated by the light source. An image processing device for obtaining the lead barycentric position from the lead image obtained by binarizing the image captured by the camera at a threshold level determined from the image information captured by the camera, and a minimum from the barycentric position of the lead. A lead position detecting device, comprising: a lead position calculating unit that obtains a rotation angle of the lead array with respect to a reference direction and a position of the lead using a square method.