Method of surface roughness measurement using a fiber-optic probe

• US 5,757,496 A
• Filed: 03/07/1997
• Issued: 05/26/1998
• Est. Priority Date: 03/07/1997
• Status: Expired due to Term

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Yamazaki, Kazuo
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US08/812,598
• Time in Patent Office: 445 Days
• Field of Search: 356/371, 356/373, 356/376, 356/445, 356/446, 250/227.11, 250/227.21, 250/227.23, 250/227.28, 250/227.24, 250/231.1, 385/12
• US Class Current: 356/600
• CPC Class Codes: G01B 11/303 using photoelectric detection means

Abstract

A method of surface roughness measurement is disclosed which uses a fiber-optic probe having a sensor head constituted of a light-emitting fiber and multiple light-receiving fibers disposed coaxially with the light-emitting fiber. The surface roughness measurement includes the steps of: (a) pre-measuring a first correlation between detected intensity and gap distance for each of reference samples obtained under a plurality of different processing conditions; (b) searching a second correlation between maximum intensity and surface roughness for each of the reference samples, based on the first correlation, and storing the second correlation in memory; (c) adjusting the gap distance so as to set the probe in a position at which the maximum intensity is obtained for the reference sample machined under the processing condition to be monitored; and (d) monitoring the maximum intensity of the machined surface at the gap distance set in step (c), and determining the roughness of the machined surface based on the second correlation.

Claims

1. A method of surface roughness measurement using a fiber-optic probe wherein said probe has at least one sensor head constituted of a light-emitting fiber and multiple light-receiving fibers disposed coaxially with the light-emitting fiber, the method comprising the steps of:

(a) directing a light beam from the sensor head onto each of multiple reference samples machined under a plurality of different processing conditions, and pre-measuring a first correlation between detected intensity and gap distance for each of the reference samples, the detected intensity being defined as a sum of outputs of the light-receiving fibers, the gap distance being defined as a distance between the sensor head and a surface of the reference sample;

(b) searching a second correlation between maximum intensity defined as a peak of the detected intensity in a predetermined range of the gap distance and surface roughness, based on the first correlation obtained in step (a), and storing the second correlation in a memory;

(c) adjusting the gap distance so as to set the probe in a position at which the maximum intensity is obtained, based on the first correlation for the reference sample machined under the processing conditions to be monitored; and

(d) monitoring detected intensity obtained at the gap distance set in step (c) for a to-be-measured sample, and determining surface roughness thereof based on the second correlation stored in the memory in advance.

2. The method according to claim 1, wherein

the sensor head comprises the light-emitting fiber and eight light-receiving fibers disposed coaxially therewith, four of the light-receiving fibers being symmetrically disposed on a first axis passing through a light-emitting surface of the light-emitting fiber to lie on opposite sides of the light-emitting fiber and the remaining four of the light-receiving fibers being symmetrically disposed on a second axis perpendicular to the first axis to lie on opposite sides of the light-emitting fiber.

3. The method according to claim 1, wherein

the fiber optic probe is attached to a machine tool, and

the monitoring step (d) is performed during a machining process of the machine tool.