US 5,289,267 A · Electro-optical system for gauging surface profile deviations

Abstract

A method and system for gauging deviations of a surface of a test part from a preselected nominal surface profile is disclosed. The system includes a support having a master surface that is substantially a matched or mating surface of the nominal surface profile of the test part and a thin layer of an attenuating medium such as a dye liquid between the master and test surfaces. Electromagnetic radiation is directed through the support and master surface and through the attenuating layer onto the reflective surface of the test part. An image sensor such as a camera is positioned to receive an image of the radiation reflected by the test part surface back through the attenuating layer and support, with the intensity of such radiation across the image varying as a function of the deviation of the test part surface from the nominal surface profile. The sensor output is digitized to form a series of digital signals indicative of the intensity of radiation associated with each location of the reflected image, and the digitized pixel signals are stored in digital electronic memory and/or displayed on a screen. Computer programming corrects the digitized intensity signals for sensor gain, bias and variations in part reflectivity, and presents a quantitative measurement of the deviations in test surface profile from the master surface profile over the entire surface being measured.

Claims31

Dependent claims

A system for gauging deviations of a surface on a test part from a preselected nominal surface geometry using electromagnetic radiation, said system comprising:

(1) a master surface that is substantially a matched surface of the preselected nominal surface geometry and that is essentially transparent to the electromagnetic radiation;
(2) an attenuating medium on the master surface with the test part being supportable on the master surface with the surface of the test part opposed to the master surface such that the attenuating medium substantially fills all space to be gauged between the master surface and the test part surface;
(3) a source of electromagnetic radiation positioned to direct such radiation through the master surface and into the attenuating medium;
(4) an image sensor positioned to receive the electromagnetic radiation transmitted from the test part surface to be gauged and which passes back through the attenuating medium, whereby an image of the test part surface to be gauged is formed, the intensity of the transmitted radiation varying across the image as a function of the deviation of the test part surface from the preselected nominal surface geometry;
(5) a digitizer for converting the image from the image sensor into digital signals indicative to the intensity of the radiation at locations of the image;
(6) digital electronic storage coupled to the digitizer for receiving and storing the digital signals;
and
(7) a calibration arrangement for correcting errors in the image formed by the image sensor, including means for producing a set of correction data and for altering the digital signals in accordance with the correction data.

5 more elements

A method of gauging deviations of a surface on a test part from a preselected nominal surface geometry using electromagnetic radiation and a master surface that is essentially transparent to the electromagnetic radiation and that contains a substantially matched surface of the preselected nominal surface geometry, said method comprising:

(1) forming an attenuating medium layer on the master surface;
(2) placing the test part on the attenuating medium layer such that the surface of the test part is opposed to the corresponding matched surface of the master surface and such that substantially all spaces to be gauged between the test part surface and the master surface are essentially filled with attenuating medium;
(3) passing electromagnetic radiation into the attenuating medium in the direction of the test part surface;
(4) collecting the electromagnetic radiation which is transmitted from the test part surface and which passes back through the attenuating medium to form an image of the transmitted electromagnetic radiation;
(5) digitizing the image of the transmitted electromagnetic radiation;
(6) storing the digitized image in an electronic storage device associated with a computer;
(7) determining the deviations of the surface of the test part from a preselected nominal surface geometry, whereby the intensity of the transmitted electromagnetic radiation varies across the image as a function of the deviation of the test part surface from the preselected nominal surface geometry;
(8) producing a set of correction data related to errors in the digitized image;
and,
(9) altering the digitized image in accordance with the correction data.

7 more elements

Dependencies are inferred from the claim text.

Electro-optical system for gauging surface profile deviations

Life of this patent

Electro-optical system for gauging surface profile deviations

Life of this patent

Abstract

Claims31