US4191476A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical inspection
Assignee: National Research Development Corp UK
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Filing: 1978-03-13
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Granted: 1980-03-04
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Expires: 1998-03-13
Abstract
Abstract In a method of optical inspection of a surface, two patterns of illumination are formed independently on a photosensitive screen respectively by means of light of two different wavelengths. The patterns are formed in the same manner and each results from irradiation of the screen with light derived from a coherent source and consisting of two interfering beams, one of which is constituted by light scattered from the surface under inspection and imaged on to the screen. A video signal is derived from the screen representing the spatial variations in the sum of the intensities in the two patterns.
Inventors
- 👤 Harry C. Pollard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:53
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B9/02001; G01B9/02007; G01B11/00; G01B11/24; G01B11/2441; G01B9/02094
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
110 words
A method of optical inspection of a surface, the method comprising: forming two patterns of illumination independently on a photosensitive screen respectively by means of light of two different wavelengths, said patterns being formed in the same manner and each of them resulting from the irradiation of said screen with light derived from a coherent source and consisting of first and second interfering beams, said first beam for each of said patterns being constituted by light scattered from said surface and imaged on to said screen; and deriving from said screen a video signal representing the spatial variations in the sum of the intensities in said two patterns of illumination.
Claim 2
Independent Claim
110 words
A method of optical inspection of a surface, the method comprising: forming two patterns of illumination independently on a photosensitive screen respectively by means of light of two different wavelengths, said patterns being formed in the same manner and each of them resulting from the irradiation of said screen with light derived from a coherent source and consisting of first and second interfering beams, said first beam for each of said patterns being constituted by light scattered from said surface and imaged on to said screen; and deriving from said screen a video signal representing the spatial variations in the sum of the intensities in said two patterns of illumination.
Claim 3
Dependent Claim
27 words
A method according to claim 1, further comprising processing said video signal to remove its d.c. component and then rectifying the resultant to provide a unidirectional signal.
Claim 4
Dependent Claim
21 words
A method according to claim 2, further comprising utilising said unidirectional signal as a picture signal to generate a television picture.
Claim 5
Dependent Claim
20 words
A method according to claim 1, in which said second beam for each of said patterns has a smooth wavefront.
Claim 6
Dependent Claim
49 words
A method according to claim 1, in which said second beam for each of said patterns is constituted by light scattered from a surface different from, but having a similar form to, said surface and imaged on to said screen in the same manner as for said first beam.
Claim 7
Dependent Claim
30 words
A method according to claim 1, in which said two patterns of illumination are formed successively on said screen, said screen having an integrating characteristic in respect of incident light.
Claim 8
Dependent Claim
19 words
A method according to claim 1, in which said two patterns of illumination are formed simultaneously on said screen.
Claim 9
Independent Claim
155 words
An apparatus for use in optical inspection, the apparatus comprising: a television camera device incorporating a photosensitive screen; an optical system for imaging on to said screen light from surfaces viewed by said camera device; means for causing, in respect of a surface viewed by said camera device, the formation independently on said screen, respectively by means of light of two different wavelengths, of two patterns of illumination which are formed in the same manner and each of which results from the irradiation of said screen with light derived from a coherent source and consisting of first and second interfering beams, said first beam for each of said patterns being constituted by light scattered from said surface and imaged on to said screen by said optical system; and means for operating said camera device to derive a video signal representing the spatial variations in the sum of the intensities in said two patterns of illumination.
Claim 10
Independent Claim
155 words
An apparatus for use in optical inspection, the apparatus comprising: a television camera device incorporating a photosensitive screen; an optical system for imaging on to said screen light from surfaces viewed by said camera device; means for causing, in respect of a surface viewed by said camera device, the formation independently on said screen, respectively by means of light of two different wavelengths, of two patterns of illumination which are formed in the same manner and each of which results from the irradiation of said screen with light derived from a coherent source and consisting of first and second interfering beams, said first beam for each of said patterns being constituted by light scattered from said surface and imaged on to said screen by said optical system; and means for operating said camera device to derive a video signal representing the spatial variations in the sum of the intensities in said two patterns of illumination.
Claim 11
Dependent Claim
30 words
An apparatus according to claim 8, further comprising means for processing said video signal to remove its d.c. component, and means for rectifying the resultant to provide a unidirectional signal.
Claim 12
Dependent Claim
23 words
An apparatus according to claim 9, further comprising means for utilising said unidirectional signal as a picture signal to generate a television picture.
Claim 13
Dependent Claim
36 words
An apparatus according to claim 8, in which said means for causing the formation of two patterns of illumination comprises means for causing said second beam for each of said patterns to have a smooth wavefront.
Claim 14
Dependent Claim
77 words
An apparatus according to claim 8, in which there are provided means for enabling said camera device to view two surfaces having a similar form simultaneously in a similar manner, and in which said means for causing the formation of two patterns of illumination comprises means for causing said interfering beams for each of said patterns to be constituted by light respectively scattered from said two surfaces and imaged on to said screen by said optical system.
Claim 15
Dependent Claim
40 words
An apparatus according to claim 8, in which said means for causing the formation of two patterns of illumination comprises means for causing said patterns to be formed successively, said screen having an integrating characteristic in respect of incident light.
Claim 16
Dependent Claim
29 words
An apparatus according to claim 8, in which said means for causing the formation of two patterns of illuminations comprises means for causing said patterns to be formed simultaneously.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-03-04 | 1983-09-03 | 1984-03-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-03-04 | 1987-09-03 | 1988-03-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-03-04 | 1991-09-03 | 1992-03-04 | $7700.00 | Window Closed / Lapsed |