Optics: measuring and testing – By polarized light examination – With light attenuation
Reexamination Certificate
1999-11-18
2001-04-03
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By polarized light examination
With light attenuation
C029S759000, C382S151000
Reexamination Certificate
active
06211958
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for mounting an electronic component on a substrate and an apparatus for implementing the method, and particularly to an electronic component mounting apparatus provided with a recognizing means of inexpensive construction which is capable of recognizing electronic components of various sizes during they are moved.
A known conventional electronic component mounting apparatus is constructed such that a mounting head driven for movement by a driver holds an electronic component at a feed station, and pauses at a particular position of a recognition station where the electronic component is monitored with a recognizing camera before being moved to a mounting station, where the electronic component is precisely positioned and mounted on a substrate.
However, in such a construction, the mounting head has to be paused each time at the particular position of the recognition station for recognition of the electronic component, thus increasing the mounting tact and limiting the improvement of productivity.
For overcoming such a drawback, a modified electronic component mounting apparatus employs a line camera with a one-dimensional CCD array as the recognition camera, with which an image of electronic component held with the mounting head being moved is picked up for recognition of their held location.
Another modified apparatus is known which employs a shutter camera for taking a two-dimensional image of electronic component held with the mounting head being moved to monitor their location.
Line cameras having a one-dimensional CCD array has an advantage of high resolution in comparison with other types of cameras and thus are suitable for taking images and recognizing components of large size with high accuracy. When taking images with a line camera, in order to maintain the ratio of length to breadth of the image, it is necessary to move an object of which image is being picked up in a direction vertical to the lengthwise direction of the arrangement of the CCD by a distance which is equivalent to a length of the object assigned to each pixel of CCD during the scanning action of one line. The higher the resolution is needed, the shorter the distance of moving the object within a period of transfer of one line is decreased. Moreover, as the transfer of an image data with thousands of pixels from the CCD takes a considerable length of time, the moving speed of the electronic component above the line camera cannot be increased.
Theoretically, shutter cameras may have better capacity of taking images at a high speed due to the emission of a light with high brightness in a short time by utilizing their shutter function. However, since a common two-dimensional CCD array which is applicable to image taking at a high speed comprises about 500×500 pixels and has a field of view bound in extension, the size of electronic component as the object to be monitored is limited in order for maintaining the resolution power above a certain level.
There are actually high-speeded line cameras or cameras of high resolving power having a sensor with 2000×2000 pixels and being capable of scanning at 60 MHz, but their prices are exorbitant and thus they cannot be applied to such a field as the electronic component mounting devices.
In view of the foregoing, it is an object of the present invention to provide an electronic component mounting method and an apparatus of inexpensive construction for implementing the method, by which it is possible to accurately recognize various sizes of electronic components which are being moved for precise mounting on to a substrate.
SUMMARY OF INVENTION
An electronic component mounting apparatus according to one aspect of the present invention is characterized by having a mounting head for holding and moving an electronic component to a mounting location and for mounting it on a substrate, and a recognizing means disposed below a movement path of the mounting head for recognizing the electronic component held on the mounting head, wherein the recognizing means comprises a line camera having a one-dimensional CCD array, a shutter camera having a shutter function, and a selecting means for selecting either the line camera or the shutter camera depending on the size or shape of the electronic component so that the electronic component can be recognized before being mounted by an image data obtained through picking up an image thereof while being moved by the mounting head. Since the image pick-up is selectively made either by the line camera or the shutter camera depending on the size or shape of the electronic component, it is possible to recognize the electronic component of both large and small size precisely at a high moving speed with an image of a necessary level of resolving power. Efficient and precise mounting of electronic component of various sizes can be thereby performed.
Also, by projecting the image of the electronic component held and moved by the mounting head simultaneously via a light path dividing means to both the line camera and the shutter camera which are focused to the same location on the path of movement of the electronic component held on the mounting head, the electronic component can be recognized while being moved along the identical path of movement irrespective of their size or shape.
Preferably, the electronic component is illuminated by an illuminating means comprised mainly of groups of LEDs as a light source, and the duration and intensity of the illumination from the LEDs are controlled in accordance with the size of the electronic component or selected type of the cameras. The illumination can be performed for a short moment with a high intensity of light when picking up images by the shutter camera and for a longer time with a lower intensity of light when picking up images by the line camera, whereby an image data can be achieved properly.
Also, by controlling an amount of electric current supplied to the LEDs by means of a switching function of semiconductor switching elements joined in plurality in parallel to each other, the illumination with a high intensity of light can be achieved by causing a large amount of current to flow to the LEDs by conducting all the semiconductor switching elements for a short time.
Preferably, the LEDs are aligned in two groups, one for directing light to illuminate the focusing point of the line camera linearly and the other for directing light to illuminate a field of view at the focusing point of the shutter camera, and the controlling means selectively activates the two groups of the LEDs. The illumination with a sufficient intensity of light can be thereby effectively achieved.
Also, by providing a reflection plate such as to locate above the electronic component held on the mounting head as well as an illuminating means for illuminating the electronic component from behind when picking up its image including a halogen lamp arranged as a light source for emitting light to the reflection plate, a transmitting image of the electronic component can be taken while being moved.
Preferably, the electronic component is illuminated by an illuminating means including a group of LEDs as a light source for directly illuminating the electronic component and a halogen lamp for emitting light to a reflection plate provided above the electronic component, and the illumination with the LEDs is controlled by semiconductor switching elements while the illumination with the halogen lamp is controlled by a mechanical shutter means provided across the light path of the halogen lamp. The switchover between the image pick-up with the illumination by the reflected light and by the transmitting light can be instantly achieved with higher response.
REFERENCES:
patent: 4628464 (1986-12-01), McConnell
patent: 4812666 (1989-03-01), Wistrand
patent: 5260779 (1993-11-01), Wasserman
patent: 5420691 (1995-05-01), Kawaguchi
patent: 5741114 (1998-04-01), Onodera
patent: 5839186 (1998-11-01), Onodera
patent: 0449481A1 (1991-10-01), None
patent: 05965
Hachiya Eiichi
Noudo Akira
Tanabe Atsushi
Jordan and Hamburg LLP
Matsushita Electric - Industrial Co., Ltd.
Pham Hoa Q.
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