The present invention relates to a calibration jig for calibrating a component recognition device picking up images of components, and a component recognition calibration method using the calibration jig, and a component mounting apparatus handling the calibration jig. Electronic components are an example of the above component.
These days, electronic circuit boards are required to be improved in mount quality with electronic components mounted correctly.
An example of a conventional electronic component mounting apparatus will be described hereinbelow with reference to FIGS. 15-20. A conventional electronic component mounting apparatus is shown in FIG. 15 and includes a board transfer device 42 for carrying in and out circuit boards 41, a component feed device 44, an XY robot 45 which is equipped with a nozzle 46 and a board recognition camera 49 and movable in X, Y directions, and an electronic component recognition camera 47.
The structure of the component recognition camera 47 is indicated in FIG. 16. It is a calibration jig 51 that is held at a leading end of the nozzle 46. The component recognition camera 47 is equipped with, for the purpose of picking up images of components, an LED illuminator 52 for illuminating a component held by the nozzle 46, a mirror 54 and a lens 55 arranged on an optical path of the LED illuminator 52 reflected by the component, and a CCD camera 56 for receiving a light passing through the lens 55. In FIG. 16, a light of the LED illuminator 52 reflected by the calibration jig 51 is condensed by the lens 55 via the mirror 54, so that an image of the calibration jig 51 is picked up by the CCD camera 56. The reference numeral 53 represents an optical axis.
A resolution of the component recognition camera 47, and at the same time, how to measure an inclination of the component recognition camera 47 to the X, Y directions in which the XY robot 45 moves, and a center position of the component recognition camera 47 will be explained below. Since the nozzle 46 is rotatable about its axis, the center position of the camera is easily detected by the following method. That is, each of the images of the calibration jig 51 is obtained by rotating the jig 51 every 90° through the rotation of the nozzle 46 every 90° about the axis, and then four centroids corresponding to the respective images are taken and thus a center of the four centroids is considered as a rotational center of the nozzle 46. For the resolution and inclination of the camera, as shown in FIG. 17, the calibration jig 51 is moved in X, Y directions in the vicinity of an outline of a recognition view field 47a of the component recognition camera 47, thereby measuring the resolution and inclination from a move amount of the calibration jig 51 over the recognition camera 47 and a move amount of the XY robot 45.
The operation of the conventional electronic component mounting apparatus 1, constituted as above, will be described below. The circuit board 41 is carried to a mount position by the board transfer device 42. The XY robot 45 moves the board recognition camera 49 to a position above the circuit board 41 and seeks a position 43 where an electronic component is to be mounted on the circuit board 41. Then, the XY robot 45 moves the board recognition camera 46 to a position above the component feed device 44 to recognize the electronic component to be held, and lets the nozzle 46 hold the electronic component 48. An attitude of the component 48 held by the nozzle 46 is picked up by the component recognition camera 47. The position of the component is corrected on the basis of the obtained image information, and then the electronic component 48 is mounted onto the circuit board 41.
The electronic component 48 held by the nozzle 46 of the XY robot 45 is moved in X, Y directions by the XY robot 45. Meanwhile, X, Y directions of a coordinate system in the image obtained by the component recognition camera 47 recognizing the attitude of the electronic component 48 held by the nozzle 46 are different from the X, Y directions as the movement directions of the XY robot 45. Although the component recognition camera 47 is set so that the X, Y directions of the coordinate system of the component recognition camera 47 agree with the X, Y directions of the XY robot 45, a slight offset is actually present between the directions. Thus, the electronic component 48 held by the nozzle 46 cannot be mounted correctly to the circuit board 41 unless the offset is calibrated. In other words, the measurement of the resolution, inclination and center position of the component recognition camera 47, i.e., calibration of the board recognition camera 49 is important in order to correctly mount the electronic component 48 onto the circuit board 41.
FIG. 18 shows a state where the calibration jig 51 is picked up by the board recognition camera 49. FIG. 19 indicates a luminance level of an image obtained by slicing an image of FIG. 18 in the X direction, while FIG. 20 is a luminance level of an image obtained by slicing the image of FIG. 18 in the Y direction.
As is shown in FIG. 16, the LED illuminator 52 irradiates a flat face 57 of the calibration jig 51, and therefore the component recognition camera 47 picks up the flat face 57. It is important for the calibration of the component recognition camera 47 to clearly and stably photograph an outline of the flat face 57. At this time, an edge part of the flat face 57 photographed by the component recognition camera 47, namely, a perpendicular part 50 extending in a direction orthogonal to the flat face 57 is not always in parallel to the photographed optical axis 53. While the calibration jig, 51 is manufactured to make the perpendicular part 50 as small as possible, the calibration jig 51 is easy to break if its shape is minimal. As such, the perpendicular part 50 is given a certain margin of length. The light projected from the LED illuminator 52 irradiates the perpendicular part 50 as well and a faint light reflected at the perpendicular part 50 is picked up by the CCD camera 56 which is represented by a reference numeral 58 in FIG. 18. As shown in FIGS. 19 and 20, an intensity of the reflecting light at the flat face 57 of the calibration jig 51 is high, and therefore the flat face 57 is photographed with a high gain by the CCD camera 56, assuming a high luminance level. A shape of the flat face 57 is accordingly detected clearly. On the other hand, the perpendicular part 50 with a low intensity of the reflecting light assumes a low luminance level and is not clear in contrast as designated by luminances 59, 60 in FIGS. 19 and 20. As a result, the outline of the calibration jig 51 is not clear in the image obtained by the component recognition camera 47.
In the above state with the luminances 59 and 60 brought about, a position of the calibration jig 51 when rotated for measuring the center position of the camera, or a position of the calibration jig 51 when held by the nozzle 46 cannot be recognized easily, thus hindering stable measurement of the resolution, inclination and center position of the component recognition camera 47.
As discussed hereinabove, the offset of the component recognition camera 47 cannot be correctly measured according to the conventional calibration jig 51, and consequently the component recognition camera 47 cannot be calibrated correctly, whereby the electronic component. 48 cannot be correctly and stably mounted to the circuit board 41.