USH230H - Apparatus for non-destructive inspection of blind holes - Google Patents
Apparatus for non-destructive inspection of blind holes Download PDFInfo
- Publication number
- USH230H USH230H US06/689,115 US68911585A USH230H US H230 H USH230 H US H230H US 68911585 A US68911585 A US 68911585A US H230 H USH230 H US H230H
- Authority
- US
- United States
- Prior art keywords
- detector
- light
- reflected
- light source
- housing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000001066 destructive effect Effects 0.000 title description 3
- 238000007689 inspection Methods 0.000 title description 3
- 239000000835 fiber Substances 0.000 claims abstract description 7
- 238000011109 contamination Methods 0.000 claims description 6
- 238000009659 non-destructive testing Methods 0.000 claims 1
- 230000003287 optical effect Effects 0.000 claims 1
- 238000012360 testing method Methods 0.000 abstract description 3
- 230000006978 adaptation Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000010363 phase shift Effects 0.000 description 2
- 230000003746 surface roughness Effects 0.000 description 2
- 230000001594 aberrant effect Effects 0.000 description 1
- 238000004026 adhesive bonding Methods 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000000572 ellipsometry Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/954—Inspecting the inner surface of hollow bodies, e.g. bores
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/21—Polarisation-affecting properties
- G01N21/211—Ellipsometry
Definitions
- the solution to the problem lies in the development of NDI tools that can detect deviations from an acceptable surface condition norm.
- the first step involves characterization of an acceptable surface, i.e., identification of the boundaries of signals from various surface tools for which the surface is acceptable.
- the second step involves establishing which tools can detect which deviations from the acceptable surface.
- the third step involves scanning of surfaces with the surface tools to identify regions that deviate from the acceptance band (i.e., that are contaminated).
- Ellipsometry is one NDI reflective technique wherein the sample is not touched by the instrument.
- a beam of polarized monochromatic light is reflected from the surface.
- the incident beam is plane polarized at an azimuth of 45° with respect to the plane of incidences (POI)
- the reflected beam is elliptically polarized.
- the parameters measured by the ellipsometer are the phase shift ⁇ of light polarized perpendicular to the POI with respect to that polarized parallel to the POI and ⁇ , the arctangent of the reflection coefficients for these components.
- An advantage of the ellipsometer is that ⁇ and ⁇ are absolute values that are not dependent on the absolute light intensities but only on the ratio of the intensities.
- phase shift ⁇ can be used to detect as little as 0.1 ⁇ to as much as 5000 ⁇ of oxide or hydroxide on a properly anodized aluminum surface or a film of contamination on top of the oxide with the same resolution.
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
A miniaturized ellipsometric testing device having a laser for precisely impinging a prescribed beam of light upon a surface to be tested and a detector for capturing the reflected impinged beam only within prescribed limits. The value of the reflected impinged beam, which is transmissible to the detector, is used in determination of the validity of the surface tested; the miniaturized device is couplable to the laser light source and the detector by fiber optic cables.
Description
The present invention relates to contamination testers, and more particularly, to an apparatus for non-destructive inspection of blind holes.
In order to achieve maximum efficiency of performance in high technology products--such as airfoils, engines, etc.--special non-destructive inspection (NDI) discipline has developed. To date, NDI tools have been developed which are very sensitive to surface contamination. These tools include surface potential difference, photoelectron emission and ellipsometric testers.
The problem is to develop NDI tools which can perform in even the closest of areas. This arsenal should be one that can inspect all areas of surface-treated panels or parts. The need for sophisticated equipment that can scan curved or shaped parts is characterized by the critical nature of and the great number of parts to be inspected.
The solution to the problem lies in the development of NDI tools that can detect deviations from an acceptable surface condition norm. The first step involves characterization of an acceptable surface, i.e., identification of the boundaries of signals from various surface tools for which the surface is acceptable. The second step involves establishing which tools can detect which deviations from the acceptable surface. The third step involves scanning of surfaces with the surface tools to identify regions that deviate from the acceptance band (i.e., that are contaminated).
Ellipsometry is one NDI reflective technique wherein the sample is not touched by the instrument. In one embodiment, a beam of polarized monochromatic light is reflected from the surface. Although the incident beam is plane polarized at an azimuth of 45° with respect to the plane of incidences (POI), the reflected beam is elliptically polarized. The parameters measured by the ellipsometer are the phase shift Δ of light polarized perpendicular to the POI with respect to that polarized parallel to the POI and ψ, the arctangent of the reflection coefficients for these components. An advantage of the ellipsometer is that Δ and ψ are absolute values that are not dependent on the absolute light intensities but only on the ratio of the intensities. Although ψ is very sensitive to surface roughness, it is relatively insensitive to the thickness of dielectric (e.g., oxide) films on the surface. In contrast, Δ is extremely sensitive to film thickness and relatively insensitive to surface roughness. The phase shift Δ can be used to detect as little as 0.1 λ to as much as 5000 λof oxide or hydroxide on a properly anodized aluminum surface or a film of contamination on top of the oxide with the same resolution.
The present invention is an adaptation of a hand-holdable contamination tester employing an off-null ellipsometric technique which is disclosed in my U.S. Pat. No. 4,381,151, and reference should be made thereto for further background information.
This device and other known ellipsometric devices fail, however, to be operable in regions such as small "blind holes". In many instances it is necessary to prepare surfaces for painting, adhesive bonding, electroplating, etc., in blind holes that are difficult or impossible to reach with normally used surface tools.
It is therefore an object of the present invention to provide an off-null ellipsometric device which is operable in hard to reach regions such as blind holes.
The present invention comprises a miniaturized ellipsometric testing device comprising first means for precisely impinging a prescribed beam of light upon a surface to be tested and second means for capturing the reflected impinged beam only within prescribed limits. The value of the reflected impinged beam, which is transmissible to a detector, enable determination of the validity of the surface tested; the miniaturized device is couplable to a laser light source and said detector by means of respective fiber optic cables.
The invention will be more clearly understood by reference to the following detailed description of a preferred embodiment thereof in conjunction with the accompanying drawing, which is a schematic diagram of the present invention.
The presently disclosed miniaturized ellipsometer 10 is shown in FIG. 1 inside a blind hole 36, and having a small frame 12 (shown in dashed-line) which houses miniaturized, optically alligned, ellipsometric components, comprising mirrors 14 and 16, plane polarizer 18, compensator (quarter wave plate) 20, and analyzer (polarizer) 22. The first mirror 14 is coupled to a light source such as laser 24 by means of fiber optic cable 26 and the second mirror 16 is coupled to a detector (such as a photodector) 28 by means of fiber optic cable 32. Feet are provided to precisely orient the sensor to the surface to be tested.
Fiber optic cables 26 and 32 are affixed to housing 12 in a manner which assures a fixed angle of reflection at mirrors 14 and 16, as will be appreciated by those of ordinary skill in the art. Preferrably polarizer 18 and analyzer 22 each comprise a Glan-Thompson prism.
In operation, the sensor housing 12 is entered into a blind hole 36 and is oriented against the surface to be tested 38 by means of feet. The light signal from laser 24 enters the fiber optic cable 26 and is reflected by fixed mirror 14 through element 18, plane polarizing the beam of light L thereat. Thence, the light beam L is directed through quarter wave plate compensator 20 to impinge upon surface 38 at an angle of incidence θ. The reflected beam LR under ideal conditions will be reflected also at angle θ through polarizing analyzer 22 to mirror 16. Element 22 and mirror 16 cooperate to transmit via cable 32 to detector 28 only that sample of light which is acceptabley reflected by surface 38. Where surface 38 is aberrant, reflections of beam L will result in beam LR at other than at angle θ, with possible less coherent characteristics, all as will result in a diminished amount of light power being present in the beam delivered to detector 28. The value of the beam which is detected can then represent the reflective (i.e., contamination) characteristics of the surface under test.
While the present invention has been described in connection with rather specific embodiments thereof, it will be understood that many modifications and variations will be readily apparent to those of ordinary skill in the art and that this application is intended to cover any adaptation or variation thereof. Therefore, it is manifestly intended that this invention be only limited by the claims and the equivalents thereof.
Claims (7)
1. An appartus with a light source and a detector for the non-destructive testing for contamination of surfaces in blind holes, comprising:
a miniaturized housing which is placeable in a blind hole, separate from said source and detector, having means of impinging a beam of light of a known value from said light source upon said surface to be tested,
and means for transmitting to said detector only that portion of said impinged light beam which is reflected within a prescribed optical path by said surface.
2. The apparatus of claim 1, wherein said first means comprises a mirror, a polarizer, and a compensator for directing said beam onto said surface at a prescribed angle.
3. The apparatus of claim 1, wherein said second means comprises a polarizing analyzer and a mirror.
4. The apparatus of claim 1 wherein said housing is couplable to said light source and to said detector by means of respective fiber optic cables.
5. The apparatus of claim 1, wherein said housing further comprises at least one foot for orienting said housing against said surface.
6. The apparatus of claim 2, wherein said polarizer comprises a Glan-Thompson prism.
7. The apparatus of claim 3, wherein said analyzer comprises a Glan-Thompson prism.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/689,115 USH230H (en) | 1985-01-07 | 1985-01-07 | Apparatus for non-destructive inspection of blind holes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/689,115 USH230H (en) | 1985-01-07 | 1985-01-07 | Apparatus for non-destructive inspection of blind holes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| USH230H true USH230H (en) | 1987-03-03 |
Family
ID=24767106
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US06/689,115 Abandoned USH230H (en) | 1985-01-07 | 1985-01-07 | Apparatus for non-destructive inspection of blind holes |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | USH230H (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5329357A (en) * | 1986-03-06 | 1994-07-12 | Sopra-Societe De Production Et De Recherches Appliquees | Spectroscopic ellipsometry apparatus including an optical fiber |
| US5963327A (en) * | 1998-03-03 | 1999-10-05 | J.A. Woollam Co. Inc. | Total internal reflection electromagnetic radiation beam entry to, and exit from, ellipsometer, polarimeter, reflectometer and the like systems |
| US5969818A (en) * | 1998-03-03 | 1999-10-19 | J. A. Woollam Co. Inc. | Beam folding optics system and method of use with application in ellipsometry and polarimetry |
| US9134232B1 (en) * | 2012-11-15 | 2015-09-15 | Industrial Optical Measurement Systems, LLC | Laser inspection system |
| US9581556B1 (en) * | 2012-11-15 | 2017-02-28 | Industrial Optical Measurement Systems, LLC | Laser probe for use in an inspection system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3699350A (en) | 1970-12-28 | 1972-10-17 | Ibm | Radiant energy mark sensor |
| US3761186A (en) | 1972-01-17 | 1973-09-25 | Itt | Apparatus for optically inspecting the condition of a surface having known variations in the condition |
| US4315688A (en) | 1979-08-08 | 1982-02-16 | Diffracto Ltd. | Electro-optical sensor systems for thread and hole inspection |
| US4381151A (en) | 1980-10-23 | 1983-04-26 | The United States Of America As Represented By The Secretary Of The Air Force | Hand-holdable contamination tester |
-
1985
- 1985-01-07 US US06/689,115 patent/USH230H/en not_active Abandoned
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3699350A (en) | 1970-12-28 | 1972-10-17 | Ibm | Radiant energy mark sensor |
| US3761186A (en) | 1972-01-17 | 1973-09-25 | Itt | Apparatus for optically inspecting the condition of a surface having known variations in the condition |
| US4315688A (en) | 1979-08-08 | 1982-02-16 | Diffracto Ltd. | Electro-optical sensor systems for thread and hole inspection |
| US4381151A (en) | 1980-10-23 | 1983-04-26 | The United States Of America As Represented By The Secretary Of The Air Force | Hand-holdable contamination tester |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5329357A (en) * | 1986-03-06 | 1994-07-12 | Sopra-Societe De Production Et De Recherches Appliquees | Spectroscopic ellipsometry apparatus including an optical fiber |
| US5963327A (en) * | 1998-03-03 | 1999-10-05 | J.A. Woollam Co. Inc. | Total internal reflection electromagnetic radiation beam entry to, and exit from, ellipsometer, polarimeter, reflectometer and the like systems |
| US5969818A (en) * | 1998-03-03 | 1999-10-19 | J. A. Woollam Co. Inc. | Beam folding optics system and method of use with application in ellipsometry and polarimetry |
| US9134232B1 (en) * | 2012-11-15 | 2015-09-15 | Industrial Optical Measurement Systems, LLC | Laser inspection system |
| US9581556B1 (en) * | 2012-11-15 | 2017-02-28 | Industrial Optical Measurement Systems, LLC | Laser probe for use in an inspection system |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| AS | Assignment |
Owner name: UNITED STATES OF AMERICA AS REPRESENTED BY THE SEC Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. SUBJECT TO LICENSE RECITED.;ASSIGNOR:SMITH, TENNYSON;REEL/FRAME:004451/0675 Effective date: 19841120 |
|
| STCF | Information on status: patent grant |
Free format text: PATENTED CASE |