Optics: measuring and testing – Position or displacement – Triangulation
Reexamination Certificate
2001-09-26
2004-04-20
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Position or displacement
Triangulation
C250S559380
Reexamination Certificate
active
06724491
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel visual displacement sensor using a line beam for a measurement light and a two-dimensional imaging device for an imaging device, and in particular to a visual displacement sensor which can freely define the field of view of the imaging device serving as an object for extracting measurement point coordinates.
BACKGROUND OF THE INVENTION
The inventors of this application previously proposed a novel visual displacement sensor using a line beam for a measurement light and a two-dimensional imaging device for an imaging device.
According to such a visual line sensor, several advantages can be gained because a line beam is used as the measurement light, the displacement of a measurement object point can be measured as a line instead of a series of dots.
A visual displacement sensor of this type comprises, as essential elements, a light emitting device (such as a laser diode) for impinging a line beam onto an object to be measured at a prescribed angle, a two-dimensional imaging device (such as a two-dimensional CCD, for monitoring the object to be measured, on which the line beam is impinged, from a different angle, measurement point coordinate determining means for determining a measurement point coordinate according to a reflected line beam light image in an image captured by the two-dimensional imaging device, and displacement measuring means for measuring a desired displacement according to the determined measurement point coordinate.
If the measurement condition is ideal, the number of reflected line beam light image that appears in the, field of view of the two-dimensional imaging device should agree with the expected number. In other words, if the measurement object consists of an opaque member and has no steps on its surface, there should be only one reflected line beam light image in the field of view of the two-dimensional imaging device. When the measurement object consists of a transparent member such as a glass plate or when the measurement object consists of an opaque member but has a step or the like on its surface, the number of the reflected line beam light images that appear in the field of view of the two-dimensional imaging device should agree with the expected number which is determined by the number of laminated glass plates and/or the number of steps.
The displace measurement algorithm for measuring the desired displacement according to the determined measurement point coordinate can function properly and measure the desired displacement only when the sensor is placed under an expected measurement condition. In other words, if the number of reflected line beam light images in the field of view of the two-dimensional imaging device docs not agree with the expected number, the measurement of the desired displacement would run into a serious difficulty.
Also, the measurement point coordinate determining algorithm for determining a measurement point coordinate according to the reflected line beam light image in the image that is captured by a two-dimensional imaging device can function properly only when the sensor is placed under an expected measurement condition. In other words, if the gradation level of the reflected line beam light image does not fall in a prescribed range, the determination of the measurement point coordinate would run into a serious difficulty.
Therefore, according to a visual displacement sensor of this kind, if a spurious reflected line beam light image appears in the field of view of the two-dimensional imaging device due to an improper measurement condition, and the number of measurement point coordinates exceeds the expected number, the displacement measurement algorithm may fail to measure the desired displacement in a normal fashion.
Furthermore, according to a visual displacement sensor of this kind, if the measurement object consists of a transparent member having metallic film having a high reflectivity formed over the back surface thereof as is the case with a glass plate of a CRT or an LCD panel, because in spite of the automatic gradation adjustment function the gradation level for each and every one of the reflected line beam light image that appear in the field of view of the two-dimensional imaging device in a mutually spaced relationship in the direction of displacement measurement may fail to fall within a prescribed range, the measurement point coordinate determining algorithm incorporated in the sensor may fail to determine the measurement coordinates, and the desired displacement the measurement point coordinate may fail to be determined in a normal fashion as a result as far as those reflected line beam light image having gradation levels falling out of the prescribed range are concerned.
Additionally, according to a visual displacement sensor of this kind, when measuring a measurement object consisting of a step by impinging a line beam across the step, if there is a large difference in reflectivity between the upper and lower surfaces of the step, in spite of the operation of the automatic gradation adjustment function, it becomes impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction perpendicular to the direction of displacement measurement within a prescribed range over the entire reflected line beam light image. Therefore, the part of the reflected line beam light image having a gradation level falling out of the prescribed range prevents the measurement point coordinate determining algorithm incorporated in the sensor from properly determining the measurement point coordinate, and the desired displacement fails to be measured in a normal fashion as a result.
The present invention was made in view of such problems of the visual displacement sensor using a line beam for a measurement light and a two-dimensional imaging device for a measurement imaging device, and its primary object is to provide a visual displacement sensor which can determine a measurement point coordinate by using a displacement measurement algorithm incorporated in the sensor so that a desired displacement may be put back into a measurable state by a simple supportive operation of the operator even when a spurious reflective line beam image appears within the field of view of the two-dimensional imaging device due to an improper measurement condition, and the number of measurement point coordinates exceeds an expected number.
Another object of the present invention is to provide a visual displacement sensor which can determine a measurement point coordinate by using a displacement measurement algorithm incorporated in the sensor so that a desired displacement may be put back into a measurable state by a simple supportive operation of the operator even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range when it has become impossible to contain the gradation level of the reflected line beam light image which appears in the field of view of the two-dimensional imaging device as two mutually separated lines in the direction of displacement measurement within a prescribed range over the entire reflected line beam light image, in spite of the operation of the automatic gradation adjustment function, in such a case as when the measurement object consists of a transparent plate having metallic film having a high reflectivity level formed over its back surface as is the case with the glass plate of a CRT or an LCD panel.
Yet another object of the present invention is to provide a visual displacement sensor which can determine a measurement point coordinate by using a displacement measurement algorithm incorporated in the sensor so that a desired displacement may be put back into a measurable state by a simple supportive operation of the operator even with respect to the part of the reflected line beam light image having a gradation level falling out of the prescribed range when it
Kawachi Masahiro
Matsunaga Tatsuya
Barth Vincent P.
Omron Corporation
Rosenberger Richard A.
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