Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
1998-08-28
2001-06-12
Boudreau, Leo (Department: 2723)
Image analysis
Applications
Manufacturing or product inspection
Reexamination Certificate
active
06246789
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a component mounting apparatus and method for mounting such components as electronic components, optical components and mechanical components onto a circuit board or other member onto which the components should be mounted. More specifically, the invention relates to an improvement in the positional calibration of the component and the circuit board due to any shift of the optical axis of an image recognition optical system used in the component mounting apparatus or method.
Conventionally, in an electronic component mounting apparatus, an electronic component is mounted onto a circuit board after position recognition of the electronic component and the circuit board is executed by an image recognition optical system for enhanced mounting precision. Then, calibration operation of the image recognition optical system is performed in order to suppress any shift of the mounting position due to distortion of the image recognition optical system or the like caused by changes in environmental temperature around the electronic component mounting apparatus.
Hereinbelow, an example of the electronic component mounting apparatus according to the prior art is described with reference to
FIGS. 16 and 17
. Referring to
FIG. 16
, reference numeral
921
denotes an electronic component, which is stored on a tray
922
. Reference numeral
923
denotes a head, which sucks up and conveys the electronic component
921
. Reference numeral
924
denotes a circuit board, which is sucked up and held to a bonding stage
925
. The bonding stage
925
and the tray
922
are fixed on a slide base
926
. Reference numeral
927
denotes an image recognition optical system, which performs position recognition of the circuit board
924
and the electronic component
921
. Further, the head
923
is movable in an X direction, the slide base
926
is movable in a Y direction and the image recognition optical system
927
is movable in both X and Y directions.
Referring to
FIG. 17
, reference numeral
928
denotes a CCD camera of the image recognition optical system
927
, with a magnifying lens
929
coupled thereto. Reference numeral
930
denotes a prism frame in which a prism
931
is fixed, and the magnifying lens
929
is coupled to this prism frame
930
. An image of the electronic component
921
sucked up and held to the head
923
or the circuit board
924
sucked up and held to the bonding stage
925
is taken by the CCD camera
928
via the prism
931
and the magnifying lens
929
. Then, the image recognition optical system
927
takes the image of either the electronic component
921
or the circuit board
924
through a switching of the field of view.
With respect to the electronic component mounting apparatus constructed as described above, its operation is described below. First, after the head
923
and the slide base
926
have moved to specified positions, the head
923
moves down to pick up the electronic component
921
on the tray
922
. Subsequently, the head
923
and the slide base
926
move again so that a coarse positioning for mounting the electronic component
921
onto the circuit board
924
is performed. Subsequently, for checking the position of the circuit board
924
, the image recognition optical system
927
moves to such a position as to bring a feature point on the circuit board
924
into the field of view, performing image recognition of the feature point. Next, for checking the position of the electronic component
921
, the image recognition optical system
927
moves to such a position as to bring a feature point on the electronic component
921
into the field of view, performing image recognition of the feature point. Then, position correction between the circuit board
924
and the electronic component
921
is performed based on the image recognition results of the circuit board
924
and the electronic component
921
, and on an offset amount (optical-axis shift amount) between a field of view “e” on the electronic-component image recognition side and a field of view “f” on the circuit-board image recognition side which are inputted as previously measured and fixed values. After that, the head
923
moves down to mount the electronic component
921
onto the circuit board
924
.
However, with the constitution as described above, even when the image-pickup positions of the electronic component
921
and the circuit board
924
have changed because of distortion of the holding portion of the image recognition optical system
927
due to changes in the room temperature or heat generation inside the apparatus so that the inclination of the optical axis has changed, the position correction would be performed based on a decision that merely the position of the electronic component
921
or the circuit board
924
has changed. As a result, the mounting position of the electronic component
921
is shifted causing change in the inclination of the optical axis.
SUMMARY OF THE INVENTION
In view of the above issues of the prior art, an object of the present invention is therefore to provide an electronic component mounting apparatus and method in which the mounting position of the electronic component does not shift even when an offset amount between fields of view on the electronic-component image recognition side and the circuit-board image recognition side has changed due to a change in the room temperature or heat generation inside the apparatus. In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a component mounting apparatus comprising a component holding and conveying device for holding and conveying a component and mounting the component onto a circuit board; a circuit board holding device for holding the circuit board; an image recognition optical system for performing position recognition of the component and the circuit board with different fields of view, respectively; and a control section for repeatedly determining an optical-axis shift amount using the two fields of view between a position of the component and a position of the circuit board recognized by the image recognition optical system. Based on those results, an optical-axis shift amount is determined for calibration.
Calibration of the image recognition optical system is performed based on the optical-axis shift amount for calibration determined by the control section, and then the component is mounted onto the circuit board.
According to a second aspect of the present invention, there is provided a component mounting apparatus according to the first aspect, wherein the control section determines the optical-axis shift amount between the two fields of view of the image recognition optical system three or more times. If a plurality of shift amounts are left after excluding an upper-limit shift amount and a lower-limit shift amount from the determined shift amounts, a mean value of the remaining shift amounts is determined and taken as the optical-axis shift amount for calibration. If only one shift amount is left after excluding the upper-limit shift amount and the lower-limit shift amount, the remaining shift amount is taken as the optical-axis shift amount for calibration. Based on the determined optical-axis shift amount for calibration, the control section performs the calibration of the image recognition optical system.
According to a third aspect of the present invention, there is provided a component mounting apparatus according to the first aspect, wherein the control section determines the optical-axis shift amount between the two fields of view of the image recognition optical system three or more times. If a difference of one shift amount from any other shift amount exceeds a threshold value, the mean value of the shift amounts except the one shift amount is determined and taken as the optical-axis shift amount for calibration (i.e., the one shift amount is dropped). Based on the determined optical-axis shift amount for calibration, the control section performs
Hosotani Naoto
Minamitani Shozo
Morita Koichi
Nishino Kenichi
Onobori Shunji
Boudreau Leo
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
Werner Brian
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