Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1993-09-29
1995-04-04
Rosenberger, Richard A.
Optics: measuring and testing
By polarized light examination
With light attenuation
33707, G01B 1114
Patent
active
054042267
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for determining the position of a positioning body relative to a reference body wherein the positioning body has a scale with marks of constant distances and the, reference body has a scanner onto which the marks of the scale are projected, and devices to implement the respective process.
Such methods serve, e.g., to acquire during the control of measurement and production machines the distances between longitudinally moveable objects such as measuring heads, gripping arms or assembling arms. In so doing, the accuracy with which these distances can be determined is a decisive factor for the machining accuracy of the automatic device.
A process, which enables high accuracy of measurement independently of an exact guide of the scanner, is already known from the DE-OS 39 09 856. At the same time three marks of a scale are evaluated by a scanner. With two marks the angle of projection formed between a projection center and these marks would still depend on how far the center of projection is above the marks and how far it is moved sideways. With three marks it is possible to exactly determine the center of the projection by way of another angle of projection formed between the center of projection, the third mark and one of the other two marks. For a combination of two angles there exists only one place where the center of projection can be located.
Furthermore, it is well-known from the book by G. Konecny and G. Lehmann: Photogrammetry, 4th edition, de Gruyter, Berlin, N.Y., 1984, pp. 48-55, to utilize a projective relationship to determine the coordinates and to consider a tilt angle between a projection area and a pre-image plane.
SUMMARY OF THE INVENTION
The present invention is based on the problem of not only acquiring measurements of the position of a positioning body relative to a reference body in the direction of a scale axis and vertically thereto but also the tilt angle between the positioning body and the reference body. This problem is solved by a process, and a device to carry out the process, to determine the position of a positioning body relative to a reference body, wherein the positioning body includes a scale having marks of constant spacing therebetween and wherein the reference body includes a scanner with a projection area onto which the marks of the scale are projected and imaging optics, the process comprising the steps of trigonometrically calculating coordinates of a projection center of the imaging optics from projection angles between the projection center and three marks, arranged on the scale, and from the constant spacing of the marks, and trigonometrically calculating a tilt angle of the positioning body with respect to the reference body, the tilt angle calculating step including determining coordinates of the projection center, determining distance of the projection center from the projection area of the scanner, and determining image coordinates of a plumb line base point of the projection center on the project area.
In a first alternative, the coordinates are determined first in the longitudinal direction of the scale and then the coordinates that note the distance from the scale. Subsequently these variables are evaluated in connection with the chamber constants, i.e. the distance between the projection center and the projection area of the scanner and the plumb line base point of the projection center on the projection area, the results of which are finally the tilt angle.
The tilt angle can be calculated in a simple manner with the concrete formula of calculation so that one can make do with a single scanner in order to determine three degrees of freedom. A second, alternative embodiment is a process to determine the position of a positioning body relative to a reference body, wherein the positioning body includes a scale with marks of constant spacing and the reference body includes a scanner with a projection area, onto which the marks of the scale are projected, and imaging optics, the process compris
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E.M.S. Technik GmbH
Eisenberg Jason D.
Rosenberger Richard A.
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