Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1996-07-17
1998-08-18
Font, Frank G.
Optics: measuring and testing
By polarized light examination
With light attenuation
356138, 356153, 356399, 356400, G01B 1114
Patent
active
057964858
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a method for the measurement of off-center rotating components of a measured object, whereby the measured object is supported in a rotatable fashion and rotates about a rotational axis and a measurement plane is defined perpendicular to the rotational axis within which the part of the measured object to be measured is irradiated with a parallel beam emanating from a radiative source, and having a detecting means for recording the silhouette of a cross section through the measured object in the measurement plane produced by the radiative source and the measured object, as well as an apparatus for carrying out the method.
An apparatus and a method of this kind have become known in the art by means of the international publication WO86/07442.
The method and apparatus which are known in the art are suitable for determining the dimensions of an elongated measured object. An optical electronic measuring station is proposed for the automatic dimensional control of outer rotating components by means of which the object to be measured is illuminated from below by an linear radiative source in order to produce an image of two diametrically opposed contour points on two linear photodiode arrays. The resulting intensity discontinuities give the two contour points and the shaft diameter can be determined by the electronically recorded separation between the two diode cells.
FIG. 1 shows the fundamental principle of the measurement in accordance with prior art. A radiative source 1 produces a beam 22 comprising parallel rays which illuminates an object to be measured 2 along an optical axis 8. The elongated measured object 2 rotates about a rotational axis which runs through the center 7 perpendicular to the plane of the drawing. A detecting means 3 comprises two separated detector elements 5, 5' whose separation with respect to each other is movable by means of a positioning means 4. Since the beam 22 comprises parallel rays, the position of the beam on the detector 5 produces a silhouette having an intensity profile. The sampled change in the intensity in the vicinity of the edge of the measured object allows, in concert with the electronically determined separation between the two detector linear photocell arrays 5, 5', for a precise dimensional measurement of the measured object. A repeated measurement of the diameter during the rotation facilitates a determination of the roundness of the measured object. With an apparatus in accordance with prior art the resolution for the diameter measurement assumes a value of one micron and the longitudinal precision assumes a value of 0.002 mm. With this apparatus it is possible to measure shafts in the diameter range from 7 to 100 mm having a length from 200 to 700 mm.
Although the measured diameters and roundnesses can be determined quite precisely, the apparatus and the method in accordance with prior art have the disadvantage that asymmetric measured components can not be measured to the required precision, since the rotation of such a component leads to errors in the measurement.
It is therefore the purpose of the present invention to improve an apparatus and a method of the above mentioned kind in such a fashion that rotating components having an asymmetric stroke support position can be measured sufficiently accurately.
SUMMARY OF THE INVENTION
This purpose is achieved in accordance with the method of the invention in that the rotational axis position is adjusted between the detecting means and the beam in such a fashion that the off-center rotating component which is to be measured is illuminated and initially, with a stationary detecting means, the maximum excursion of a diameter of the off-center rotating component is determined by means of a silhouette projection onto the detecting means, an angle of rotation of the off-center rotating component is determined, and the detecting means is synchronized with the position of the angle of rotation and moved parallel to the beam in such a fashion that the separation, pa
REFERENCES:
patent: 4480918 (1984-11-01), De Fazio
patent: 4880992 (1989-11-01), Niedmayr et al.
Patent Abstracts of Japan, vol. 9, No. 232 (P-389) (1955) 18 Sep. 1985 & JP, A, 60 088 307 (Shingijiyutsu Kaihatsu Jigiyoudan) 18 May 1985.
Dassler Hans-Ulrich
Haas Rudiger
Lang Johann
Font Frank G.
Ratiff Reginald A.
Steinheil Industrielle Messtechnik GMBH
Vincent Paul
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