Optics: measuring and testing – Shape or surface configuration – By focus detection
Reexamination Certificate
2000-05-16
2001-12-11
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Shape or surface configuration
By focus detection
C382S145000, C382S151000, C250S559220, C356S624000
Reexamination Certificate
active
06330066
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a height measuring apparatus and method for measuring heights of an object for imaging such as electronic components as well as to a testing apparatus for testing an object and measuring its heights by using such a height measuring apparatus.
2. Description of the Prior Art
Conventionally, after electronic components have been mounted on a mounting circuit board, the mounting of the electronic components is tested visually according to the following method.
For example, as for a mounting circuit board
1
, each electronic component to be tested is imaged by an imaging section
3
by using a lens
2
having a relatively high magnification as shown in FIG.
9
A and is visually tested while an operator looking at an imaged picture taken by the imaging section
3
(see FIG.
9
B).
In this case, since individual electronic components have different surface heights, the heights of the respective electronic components are detected by imaging the electronic components by using a separately provided measuring instrument such as a laser measuring instrument or by utilizing what is called an overall focusing method.
The overall focusing method is a method for obtaining an imaged picture that is in focus in the entire range by imaging the electronic components with the imaging section
3
while moving an imaging means, that is, the lens
2
and the imaging section
3
, in the height direction with respect to the electronic components with a moving means by a very small distance at a time and then synthesizing a picture by picking up portions including in-focus components of imaged pictures at the respective heights.
This method allows recognition of the heights of the respective components based on the movement distances of the imaging section
3
that is moved by the moving means.
However, in recent years, the integration density of electronic components etc. has increased and a video camera has come to be used to test minute components visually.
As shown in
FIGS. 10A and 10B
, in the case of using a video camera
4
a lens
5
having a relatively small magnification and a large depth of field is used because a wide region of a mounting circuit board
1
needs to be tested. Therefore, in appearance a wide area is in focus and hence the above-mentioned overall focusing method cannot be utilized.
Therefore, the heights of the respective components cannot be measured simultaneously with testing. To measure the heights of the respective components, a separately provided height measuring instrument is needed. This causes a problem of increase in equipment cost.
OBJECT AND SUMMARY OF THE INVENTION
In view of the above, an object of the present invention is to provide a height measuring apparatus and method which make it possible to perform height measurement based on imaged pictures of an object member such as an electronic component as well as to a testing apparatus which makes it possible, by utilizing such a height measuring apparatus, to perform imaging and height measurement of an object member simultaneously.
According to a first aspect of the invention, there is provided a height measuring apparatus comprising imaging means provided so as to be movable in a Z direction that is perpendicular to an object, for imaging the object; moving means for moving the imaging means in the Z direction with adjustment; and control means for measuring a height of the object by causing the imaging means to image the object sequentially while causing the moving means to move the imaging means in the Z direction by a very small distance at a time, calculating focus values through image processing based on respective imaged pictures, and detecting a focus position from a Z-direction variation of the focus values.
According to a second aspect of the invention, there is provided a testing apparatus comprising imaging means provided so as to be movable in a Z direction that is perpendicular to an object, for imaging the object; moving means for moving the imaging means in the Z direction with adjustment; and control means for measuring a height of the object by causing the imaging means to image the object sequentially while causing the moving means to move the imaging means in the Z direction by a very small distance at a time, calculating focus values through image processing based on respective imaged pictures, and detecting a focus position from a Z-direction variation of the focus values, and for performing a shape test on the object by combining a plurality of imaged pictures of the object.
According to a third aspect of the invention, there is provided a height measuring method comprising a first step of imaging an object sequentially at individual movement positions with imaging means while moving the imaging means in a Z direction that is perpendicular to the object by a very small distance at a time; a second step of calculating focus values based on respective imaged pictures taken by the imaging means; a third step of detecting a focus position from a Z-direction variation of the focus values, and employing the focus position as a height of the object.
In the first and third aspects of the invention, in a case where a wide region of an object is to be imaged, the object is imaged at each position while the imaging means is moved in the Z direction by a very small distance at a time, whereby object imaging can be performed by utilizing what is called an overall focusing method.
The control means calculates focus values, for example, spatial frequencies, at respective positions by performing image processing on imaged pictures at the respective positions, detects a focus position based on a Z direction variation of the focus values, and employs the focus position as a Z direction height of the object.
Therefore, the height of the object can be measured based on imaged pictures of the object taken by the imaging means without the need for using a separately provided height measuring means.
Where the imaging means comprises a lens having a large depth of field, the invention makes it possible to measure the height of an object by detecting a focus position from a Z-direction variation of focus values that are calculated through image processing. This is in contrast to a conventional case where the use of such a lens disables measurement of the height of an object based on imaged pictures because of a wide focus range.
In the second aspect of the invention, similarly, in a testing apparatus which images an object and tests the object based on imaged pictures, the testing and height measurement of the object are performed simultaneously because the height of the object is measured by utilizing the imaged pictures for the testing.
The focus value is a numerical representation, such as a spatial frequency, of the degree of focusing of a focusing-attempted portion (hereinafter referred to as “focused region”) of an object. A larger numerical value of the focus value means a high degree of focusing.
The spatial frequency is a quantity representing a spatial repetition frequency. In this case, a numerical value representing luminance per unit length is used as the spatial frequency.
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patent: 5305092 (1994-04-01), Mimura et al.
patent: 5448360 (1995-09-01), Wakai et al.
patent: 5543918 (1996-08-01), Abraham et al.
patent: 5780866 (1998-07-01), Yamamura
Takeuchi Kuniyoshi
Tanaka Minoru
Kananen Ronald P.
Pham Hoa Q.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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