Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
2000-06-29
2004-04-06
Patel, Jayanti K. (Department: 2625)
Image analysis
Applications
Manufacturing or product inspection
C382S151000, C382S298000, C382S305000, C250S491100, C355S055000, C348S095000, C348S142000
Reexamination Certificate
active
06718057
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a position error measurement method and a device that uses a positioning mark, which determines a position of a mark on a workpiece to be machined and performs positioning correction based on the position of this mark. Further, the invention relates to improvement in a machining device which corrects the position of the workpiece based on the result of measuring the position errors using the mark.
BACKGROUND ART
FIG. 7
shows an example of the configuration of a conventional machining device. This device determines a position of a mark on a workpiece to be machined and corrects the position based on the determined position of the mark. Such a device is generally used when drilling holes in a printed board. In this FIG.,
1
is a camera with a lens having a narrow visual field,
5
is an image processing unit which performs image processing to images obtained by the camera
1
,
6
is a display unit which displays the images obtained the camera
1
and the result of processing in the image processing unit
5
,
7
is a workpiece to be machined,
8
is an XY table which performs positioning of the workpiece
7
,
9
is a tool with which the workpiece
7
is machined,
10
is a control unit which provides controls for image processing, positioning correction, and machining, or the like,
11
is a manual pulse generator, and
21
to
24
are positioning marks (that is, marks used for positioning).
Since high-positioning accuracy is required for an operation such as drilling in a printed board, it is required to use any camera with a narrow visual field and high resolution as one used for positioning correction as explained above.
Operation of this device is explained below with reference to FIG.
7
. The workpiece
7
is fixed to the XY table
8
, and positioning is corrected by the XY table
8
before machining is performed. The correction for positioning is performed by positioning the XY table
8
in the X direction and the Y direction by not shown X-axial driving system and Y-axial driving system based on instructions of the control unit
10
. The amount of correction for positioning is determined by moving the camera
1
to the preset reference position of a positioning mark, performing image processing to the mark by the image processing unit
5
, and measuring position errors between the reference position and the positioning mark.
FIG. 8
shows an example of measuring position errors using a positioning mark through image processing. In this
FIG. 3
represents a visual field of the camera
1
. As explained above, the visual field
3
of the camera
1
is narrow because a high-positioning accuracy is required. As shown in
FIG. 8
(
a
), when a positioning mark
21
is not within the narrow visual field
3
of the camera
1
, the positioning mark is not found even when the image processing is performed in the image processing unit
5
, therefore, an error in recognition occurs. On the other hand, if the positioning mark
21
is within the narrow visual field
3
of the camera
1
, the error in recognition does not occur.
In
FIG. 7
, when the positioning mark
21
can not be recognized by the image processing unit
5
, alarm information indicating the error in recognition or the like is transmitted from the image processing unit
5
to the control unit
10
. The control unit
10
generates an alarm or the like so that the operator can easily understand the situation. When the operator hears the alarm he moves the camera
1
at a position such that the positioning mark
21
comes inside the narrow visual field
3
of the camera
1
by using the manual pulse generator
11
of the control unit
10
(see
FIG. 8
(
b
)), and allows the image processing unit
5
to perform image processing again.
FIG. 8
(
c
) shows an example of displaying the result of measuring position errors of the positioning mark on the display unit
6
. The camera
1
is then moved to the position of the next positioning mark, and the position is automatically measured.
The operation of measuring position errors of the positioning mark as explained above is executed some times corresponding to the preset number of points of positioning marks to be measured, position errors of a machining point on the workpiece
7
are determined through operations in the control unit
10
from the data for the measured position errors of the positioning mark, the position errors of the machining point are corrected, and the machining point on the workpiece
7
whose position errors have been corrected is machined with the tool
9
in FIG.
7
. In this type of machining device which corrects the position of the workpiece based on the result of measuring position errors using a positioning mark in the conventional manner, when a positioning mark is not found, an error in recognition occurs in the image processing unit. In this case, a lot of manual operations are required and also a lot of time is spent to correct positioning. That is, the operator has to manually move the camera so that the positioning mark comes inside the visual field of the camera, and image processing is performed again to the mark, and so forth.
As explained above, when the object is not inside the visual field of the camera, the processing is troublesome. To solve the problem, there is a position error measurement device disclosed in JP60-163183A shown in
FIG. 9
as the technology that the processing is performed by changing the size o f the visual field of the camera. In this
FIG. 101
is an object region where an object
102
to be recognized may exist,
103
is a camera with a built-in electric zoom lens
104
that is selectable between a wide visual field and a narrow visual field,
105
is a two-dimensional positioning device which moves the camera
103
to any position within the object region
101
, and
106
is a visual sensor control unit. This visual sensor control unit
106
comprises a zoom lens driving unit
107
that drives the electric zoom lens
104
, a positioning control unit
108
for the two-dimensional positioning device
105
, an image processing unit
109
that processes an image captured from the camera
103
, and a central processing unit
110
that integrally controls these devices.
The camera
103
is positioned at the center of the object region
101
. Further, visual field of the electric zoom lens
104
is set to wide visual field. Therefore, the overall object region
101
is displayed within the image obtained by the camera
103
. The object
102
to be recognized is naturally displayed at a predetermined position within this object range
101
. The two-dimensional positioning device
105
is driven by the positioning control unit
108
and the camera
103
is positioned at the position facing the recognition object
102
based on the data for position errors of the recognition object
102
that has been obtained in the wide visual field. At this stage, the zoom lens driving unit
7
switches the visual field of the zoom lens
104
to narrow visual field. Therefore, the image information obtained in the narrow visual field is processed by the image processing unit
109
to obtain the data for high-accuracy position errors.
Referring to the case that the positioning mark as shown in
FIG. 7
is recognized by using the above explained method, a the image processing is performed to the positioning mark in wide visual field, the camera is moved so that the positioning mark is positioned at the center of the visual field, the visual field is switched to narrow visual field, image processing is performed to the positioning mark, and the positioning correction is performed. Thus, this method is effective only when the most of the positioning marks are not found in the camera with the narrow visual field, but it takes a lot of time to recognize the marks because each of the marks is recognized in wide visual field and then recognized in narrow visual field, which does not allow the method to be applied to any purpose where high productivity is required.
DISCLOSURE OF THE I
Chawan Sheela
Mitsubishi Denki & Kabushiki Kaisha
Patel Jayanti K.
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