Browse Prior Art Database

Fiber Optic Measurement System

IP.com Disclosure Number: IPCOM000083959D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Schumann, PA: AUTHOR

Abstract

Fiber optic probes have certain features that can be used advantageously for the measurement of the thickness of thin-film layers and other characteristics associated with surfaces. An example of a system in which fiber optic probes are used for thin-film measurement is U. S. Patent 3,751,643.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 61% of the total text.

Page 1 of 2

Fiber Optic Measurement System

Fiber optic probes have certain features that can be used advantageously for the measurement of the thickness of thin-film layers and other characteristics associated with surfaces. An example of a system in which fiber optic probes are used for thin-film measurement is U. S. Patent 3,751,643.

The light emerging from a fiber optic probe has a spread characteristic, that is a function of the diameter of the fiber optics and the index of refraction of the fiber optic material. It, therefore, does not present a single angle of incident for measurement. Since rays are collected in the coaxial light pipe, the fraction of light collected is a function of the height of the probe from the measurement surface.

The distance d(s) that a ray of light is scattered from a surface having a sinusoidal variation of amplitude a and number of cycles n per r is:

(Image Omitted)

The terms and symbols can be best understood with reference to Fig. 1. Phi is the angle of spread of emerging light. r would be the radius of the fiber optic bundle. x is the distance of a single fiber optic strand from the center of the fiber optic bundle. d is the distance between the probe and the base line of the surface being measured. h would be the height or distance from the base line d of a point on the sinusoidal surface.

The fraction of light scattered back into the coaxial pipe when plotted against the distance of the probe from the surface, is shown in Fig. 2.

When...