Patent US4887899A successfully refreshed from Google Patents.
US4887899A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus and method for electronic analysis of test objects
Assignee: Individual
•
Filing: 1987-12-07
•
Granted: 1989-12-19
•
Expires: 2007-12-07
Abstract
Abstract A test object is analyzed electronically, i.e. without the use of photographic film. The invention generates a pair of laterally-displaced images of the object which interfere with each other to produce a pattern that can be recorded without a high-resolution detector. The object is illuminated with at least partially coherent light. Reflected light from the object is directed through a birefringent material, a lens system, a polarizer, and then to an image detector, such as a video camera. The birefringent material causes non-parallel beams originating from a unique pair of points on the object to become nearly parallel, and orthogonally polarized. The polarizer modifies the polarization of the parallel beams so that they will interfere with each other. Because the interfering light beams are nearly parallel, the spatial frequency of the interference pattern is sufficiently low that the pattern can be recorded by a low-resolution detector, such as a video camera. Interference patterns due to the superposition of two laterally-displaced images of the same object are recorded while the object is in an undeformed and a deformed state. A computer compares these interference patterns and produces a resultant pattern which depicts the deformation of the test object. Because photographic film is not needed, the invention can analyze objects very rapidly. Also, since the interference pattern is derived from pairs of distinct points on the object, the invention directly provides information on strain.
Inventors
- 👤 Yau Y. Hung
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 08:00
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/16; G01B11/168; G01L; G01L1/00; G01L1/24; G01L1/241
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
105 words
A method for nondestructively analyzing a test object, comprising the steps of: (a) directing coherent radiation onto a test object, (b) passing radiation reflected from the object through a birefringent material and then through a polarizer, (c) directing radiation emerging from the polarizer onto a detector, the birefringent material and the polarizer cooperating to form a random interference pattern on the detector, and storing the random interference pattern thus formed, (d) stressing the object, and repeating steps (a), (b), and (c) while the object is stressed, and (e) electronically comparing the random interference patterns formed while the object is in the stressed and unstressed conditions.
Claim 2
Independent Claim
105 words
A method for nondestructively analyzing a test object, comprising the steps of: (a) directing coherent radiation onto a test object, (b) passing radiation reflected from the object through a birefringent material and then through a polarizer, (c) directing radiation emerging from the polarizer onto a detector, the birefringent material and the polarizer cooperating to form a random interference pattern on the detector, and storing the random interference pattern thus formed, (d) stressing the object, and repeating steps (a), (b), and (c) while the object is stressed, and (e) electronically comparing the random interference patterns formed while the object is in the stressed and unstressed conditions.
Claim 3
Dependent Claim
41 words
The method of claim 1, further comprising the step of displaying a fringe pattern, the fringe pattern being generated as a result of the comparing step, and wherein the comparing step is performed without optical interference between the random interference patterns.
Claim 4
Dependent Claim
11 words
The method of claim 1, wherein the object is continuously vibrating.
Claim 5
Dependent Claim
28 words
The method of claim 1, wherein the comparing step comprises the step of computing the difference of the intensities of each point of the respective random interference patterns.
Claim 6
Dependent Claim
28 words
The method of claim 1, wherein the comparing step comprises the step of computing the sum of the intensities of each point of the respective random interference patterns.
Claim 7
Dependent Claim
28 words
The method of claim 1, wherein the comparing step comprises the step of computing the product of the intensities of each point of the respective random interference patterns.
Claim 8
Dependent Claim
28 words
The method of claim 1, wherein the comparing step comprises the step of computing the quotient of the intensities of each point of the respective random interference patterns.
Claim 9
Independent Claim
107 words
A method for nondestructively analyzing a test object, comprising the steps of: (a) directing light onto a test object, (b) passing light reflected from the object through a birefringent material and then through a polarizer, (c) directing light emerging from the polarizer onto a video camera, the birefringent material and the polarizer cooperating to form a random interference pattern in the camera, and storing the random interference pattern thus formed, (d) stressing the object, and repeating steps (a), (b), and (c) while the object is stressed, and (e) electronically and non-optically comparing the random interference patterns formed while the object is in the stressed and unstressed conditions.
Claim 10
Independent Claim
107 words
A method for nondestructively analyzing a test object, comprising the steps of: (a) directing light onto a test object, (b) passing light reflected from the object through a birefringent material and then through a polarizer, (c) directing light emerging from the polarizer onto a video camera, the birefringent material and the polarizer cooperating to form a random interference pattern in the camera, and storing the random interference pattern thus formed, (d) stressing the object, and repeating steps (a), (b), and (c) while the object is stressed, and (e) electronically and non-optically comparing the random interference patterns formed while the object is in the stressed and unstressed conditions.
Claim 11
Dependent Claim
28 words
The method of claim 8, wherein the comparing step comprises the step of computing the difference of the intensities of each point of the respective random interference patterns.
Claim 12
Dependent Claim
28 words
The method of claim 8, wherein the comparing step comprises the step of computing the sum of the intensities of each point of the respective random interference patterns.
Claim 13
Dependent Claim
28 words
The method of claim 8, wherein the comparing step comprises the step of computing the product of the intensities of each point of the respective random interference patterns.
Claim 14
Dependent Claim
28 words
The method of claim 8, wherein the comparing step comprises the step of computing the quotient of the intensities of each point of the respective random interference patterns.
Claim 15
Dependent Claim
110 words
Apparatus for nondestructive analysis of a test object, comprising: (a) a source of coherent radiation, positioned to direct radiation onto the object so that the radiation is reflected from the object, (b) a birefringent material, disposed to receive radiation reflected from the object, (c) a polarizer, disposed to receive radiation emerging from the birefringent material, (d) image detection means, disposed to receive radiation leaving the polarizing means, the birefringent material and the polarizer cooperating to form a random interference pattern at the detection means, (e) image processing means, the image processing means being programmed to store at least one pair of random interference patterns, and to compare said patterns electronically.
Claim 16
Dependent Claim
110 words
Apparatus for nondestructive analysis of a test object, comprising: (a) a source of coherent radiation, positioned to direct radiation onto the object so that the radiation is reflected from the object, (b) a birefringent material, disposed to receive radiation reflected from the object, (c) a polarizer, disposed to receive radiation emerging from the birefringent material, (d) image detection means, disposed to receive radiation leaving the polarizing means, the birefringent material and the polarizer cooperating to form a random interference pattern at the detection means, (e) image processing means, the image processing means being programmed to store at least one pair of random interference patterns, and to compare said patterns electronically.
Claim 17
Dependent Claim
14 words
The apparatus of claim 13, wherein the image detection means comprises a video camera.
Claim 18
Dependent Claim
31 words
The apparatus of claim 14, wherein the image processing means includes a computer, and wherein the computer is programmed to store and process a plurality of images received by the camera.
Claim 19
Dependent Claim
19 words
The apparatus of claim 13, further comprising a quarter-wave plate disposed between the test object and the birefringent material.
Claim 20
Dependent Claim
20 words
The apparatus of claim 13, further comprising an optical band-pass filter disposed between the test object and the birefringent material.
Claim 21
Dependent Claim
38 words
The apparatus of claim 13, further comprising a quarter-wave plate disposed between the birefringent material and the image detection means, so as to receive radiation leaving the birefringent material, and wherein the orientation of the polarizer is adjustable.
Claim 22
Dependent Claim
21 words
The apparatus of claim 13, further comprising a wide-aperture lens, the lens being disposed between the object and the detection means.
References Cited (Backward Citations)
US3218916A
Cited
US3487227A
Cited
US3373652A
Cited
US3532431A
Cited
US3626753A
Cited
US3849003A
Cited
US3816649A
Cited
US3767308A
Cited
US3829219A
Cited
US3828126A
Cited
US3911729A
Cited
US4118124A
Cited
US4139302A
Cited
US4125314A
Cited
US4427295A
Cited
US4425039A
Cited
US4682892A
Cited
US4620223A
Cited
US4702594A
Cited
US4541280A
Cited
US4523469A
Cited
JPS60231401A
Cited
US4650302A
Cited
US4633715A
Cited
US4690552A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-12-18 | 1993-06-19 | 1993-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-18 | 1997-06-19 | 1997-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-18 | 2001-06-19 | 2001-12-19 | $7700.00 | Window Closed / Lapsed |