System and Method for Using Laser Scan Micrometer to Measure Surface Changes On Non-Concave Surfaces

• US 20160231105A1
• Filed: 02/11/2015
• Published: 08/11/2016
• Est. Priority Date: 02/11/2015
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Liu, Eric, McCubbin, Kerry J., Mitchem, Sean C.
• Granted Patent: US 9,470,514 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01B 11/2433 for measuring outlines by shadow casting
• CPC Class Codes: G01N 21/8901 Optical details; Scanning details per se G02B
• CPC Class Codes: G01N 21/9515 Objects of complex shape, e.g. examined with use of a surface follower device measuring contours and curvatures G01B11/24
• CPC Class Codes: G01N 21/952 Inspecting the exterior surface of cylindrical bodies or wires G01N21/956 takes precedence
• CPC Class Codes: G06F 18/00 Pattern recognition

Abstract

A method of comparing surface profiles of an object, the object being rotatable on an axis, such that the object has a longitudinal dimension and an axial dimension. The object is incrementally scanned with a laser scan micrometer, first in a pre-test scan procedure and then in a post-test scan procedure. The two scan procedures are performed in the same manner, by using the laser scan micrometer to scan the object in a longitudinal direction, rotating the object, re-scanning the object, measuring the scan length thereby obtaining a longitudinal height value, and repeating the preceding steps for a number of incremental rotations thereby obtaining one longitudinal height profile. This process is repeated by incrementally moving the object in an axial direction and acquiring additional longitudinal height profiles, thereby acquiring a set of longitudinal height profiles. The pre-test and post-test sets of profiles are then aligned and compared.

Claims

9-1. The method of claim 1, wherein the incremental rotations are all within the same range, which is equal to or less than 180 degrees.

10. A method of acquiring surface profiles of an object, the object being rotatable on an axis, such that the object has a longitudinal dimension and an axial dimension, comprising:

acquiring a first longitudinal height profile of the object by;

using a laser scan micrometer to scan the object in a longitudinal direction, rotating the object, re-scanning the object, measuring the scan length thereby obtaining a longitudinal height value, and repeating the preceding steps for a number of incremental rotations thereby obtaining a longitudinal height profile; and

repeatedly and incrementally moving the object in an axial direction and acquiring additional longitudinal height profiles, thereby acquiring a set of longitudinal height profiles.

11. A laser scan measurement system for acquiring surface profiles of an object, the object having a physical axis for rotating the object, such that the object has a longitudinal dimension and an axial dimension relative to the axis, comprising:

a laser scan micrometer having scan range;

a first stepper motor operable to rotate the object on the axis in incremental angular positions;

a second stepper motor operable to reposition the object or the laser scan micrometer in incremental axial positions;

a control unit operable to control the angular position and the axial position of the object by generating control signals to the first stepper motor and the second stepper motor;

wherein the control unit and the laser scan micrometer are operable to acquire a set of longitudinal height profiles of the object by;

scanning the object in a longitudinal direction, rotating the object, re-scanning the object, measuring the scan length thereby obtaining a longitudinal height value, and repeating the preceding steps for a number of incremental rotations thereby obtaining a longitudinal height profile;

repeatedly and incrementally moving the object in an axial direction and acquiring additional longitudinal height profiles, thereby acquiring a set of longitudinal height profiles.

12. The system of claim 11, wherein the control unit is further programmed to store data representing a pore-test set of longitudinal profiles and a post-test set of longitudinal height profiles, and to axially and rotationally align one or more pre-test longitudinal height profiles with corresponding post-test longitudinal height profiles.

13. The system of claim 12, wherein the aligning is performed by scanning a non-changing feature on a test object for axial alignment.

14. The system of claim 12, wherein the aligning is performed, for axial alignment. by scanning two non-changing features on a surface of the test object that protrude in the axial direction.

15. The method of claim 12, wherein the control unit is further programmed to compare the difference between the pre-test longitudinal height profiles and the post-test longitudinal height profiles.

16. The system of claim 12, wherein the incremental rotations are all within the same range, which is equal to or less than 180 degrees.

17. The system of claim 12, wherein the second stepper motor moves the object.

18. The system of claim 12, wherein the second stepper motor moves the laser scan micrometer.