Image analysis – Pattern recognition
Reexamination Certificate
1998-07-29
2001-10-02
Johns, Andrew W. (Department: 2621)
Image analysis
Pattern recognition
C702S166000, C702S167000, C702S170000, C702S171000
Reexamination Certificate
active
06298152
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image recognition system using the light-section method, in which linear light is projected onto an object to be measured, to form a linear light image on the object and this image is picked up to obtain three-dimensional configuration data on the object.
2. Description of the Related Art
In an image recognition system using the light-section method, an image of linear light which has been projected onto the object by a light projector means must be accurately picked up in order to ensure improved accuracy in the recognition of the configuration of the object. In other words, picking up of a linear light image must be done so as to enable a thinning process by which the linear light is represented by a line having an infinitely small width which is normally the width of one pixel in ordinary image processing.
The image pickup means for picking up an image of an object onto which linear light is projected has a diaphragm mechanism for adjusting the amount of admitted light. If a diaphragm aperture is inappropriate, the above thinning process to express a linear light as a line of one pixel width becomes difficult. More specifically, when picking up an image of the same linear light projected onto an object, if the aperture is small, the picked-up light image becomes thick, so that variations are created in the thinning process, causing zigzag portions on the image of the linear light after thinning. On the other hand, if the aperture is large, the picked-up light image becomes thin, resulting in discontinuous portions in the image of the linear light after thinning. In both cases, the linear light cannot be represented by a line of one pixel width, which causes a defect in the image recognition of the light as a line.
To solve this problem, diaphragm aperture settings are predetermined on the basis of object conditions and illumination intensity.
Such a system, however, has little flexibility and versatility because of preliminarily fixed aperture settings according to object conditions and illumination intensity. In addition, light projection by use of a light projector means needs to be carried out at all times in order to obtain constant illumination intensity, which shortens the service life of the light projector means.
The present invention is directed to overcoming these problems and one of the objects of the invention is therefore to provide an image recognition system using the light-section method, which provides versatility and does not lead to a reduction in the service life of the light projector means.
SUMMARY OF THE INVENTION
The above object can be achieved by an image recognition system using the light-section method according to the invention, in which linear light is projected onto an object to be measured, to form a light image on the surface thereof and the light image is then picked up to obtain three dimensional data associated with the object, the system comprising:
(a) light projector means controlled to be turned ON and OFF to intermittently project a linear light onto the object;
(b) image pickup means for picking up an image of the object onto which a linear light has been projected by the light projector means, the image pickup means including an automatic aperture control mechanism for automatically adjusting diaphragm aperture according to a picked-up image;
(c) image processing means for processing an image picked up by the image pickup means to obtain three-dimensional configuration data on the object; and
(d) controller means for controlling turning ON and OFF of the light projector means such that the light projector means is put in its ON state to project a linear light onto the object between the time when a measuring command is issued and the time just after light has been converged by the automatic aperture control mechanism of the image pickup means or just after a state equivalent to the convergence of light has been established, and controlling the image processing means to process an image picked up by the image pickup means just after the convergence of light by the automatic aperture control mechanism or just after the establishment of the state equivalent to the convergence of light, so as to obtain three dimensional configuration data on the object.
In the invention, firstly, the light projector means is brought into its ON-state, in response to a measuring command, to project a linear light onto an object. According to an image of the object onto which the linear light has been projected, the automatic aperture control mechanism automatically performs aperture adjustment to converge light. Based on an image picked up just after light has been converged by the aperture control or just after establishment of a state equivalent to the convergence of light, image processing for producing three-dimensional configuration data is performed and subsequently, the light projector means is turned off thereby stopping light projection.
Thus, the use of the automatic aperture control mechanism for automatically adjusting the amount of admitted light eliminates the need for fixing not only aperture settings but also object conditions and illumination intensity, which entails improved versatility. Additionally, there is no need to project light by the light projector means at all times as light projection may be carried out between the time when a measuring command has been issued and the time just after light convergence has been caused by the automatic aperture control mechanism or just after establishment of a state equivalent to light convergence. With this arrangement, shortening of the service life of the light projector means can be avoided.
Preferably, the invention further includes aperture holding means for holding the aperture at a value set upon completion of light convergence done by the automatic aperture control mechanism of the image pickup means or upon establishment of the state equivalent to light convergence, from the completion of light convergence or the establishment of the light-convergence-equivalent state until the next release of a measuring command. The provision of such aperture holding means eliminates the need for taking a large action for aperture setting, which in consequence shortens the time required for aperture adjustment operation.
The aperture holding means may be designed to cut off an actuating power source for the automatic aperture control mechanism thereby stopping its aperture adjustment operation to hold the aperture at a value set upon completion of light convergence or upon establishment of the light-convergence-equivalent state. Alternatively, the aperture holding means includes an image storage unit for storing an image picked up by the image pickup means just after light convergence or just after establishment of the light-convergence-equivalent state, at least until the next release of a measuring command. According to this image stored in the image storage unit, the automatic aperture control mechanism performs aperture adjustment operation so as to hold the aperture at the value set upon the completion of light convergence or upon the establishment of the light-convergence-equivalent state, until the next release of a measuring command.
Preferably, the light projector means projects a linear light generated by a single wavelength light source onto the object and the image pickup means picks up the image of the object onto which the linear light has been projected, through an attenuation filter having a pass band centered at the single wavelength of the light emitted by the light source. With this arrangement, lights other than the linear light are not to be picked up so that the resulting three dimensional configuration data is highly accurate.
REFERENCES:
patent: 5270780 (1993-12-01), Moran
patent: 5756981 (1998-05-01), Roustaei et al.
patent: 5949056 (1999-09-01), White
patent: 58-170220 (1983-10-01), None
patent: 61-24616 (1986-02-01), None
Ooenoki Toshiyuki
Ootani Toshiro
Armstrong Westerman Hattori McLeland & Naughton LLP
Azarian Seyed
Johns Andrew W.
Komatsu Ltd.
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