Optics: measuring and testing – By light interference – For dimensional measurement
Reexamination Certificate
1999-02-04
2001-05-08
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By light interference
For dimensional measurement
C356S477000
Reexamination Certificate
active
06229617
ABSTRACT:
BACKGROUND OF THE INVENTION
Inspection of manufactured articles is of great importance, particularly to manufacturers of critical equipment whose failure can produce catastrophic results. However, some of the articles in this category defy close inspection because the geometry of the article makes inspection extremely difficult for conventional inspection techniques.
Fiber optical devices are extensively used to view objects that normally would be considered inaccessible. The optical fiber elements for this purpose are typically smaller than 50 &mgr;m in diameter, including protective layers. Optical fibers such as these can be bent into radii as short as 3 cm, allowing their infiltration into areas that normally preclude direct imaging techniques.
The medical community has made extensive us of such optical fibers for endoscopic applications, such as the real-time imaging of internal organs to provide guidance for microsurgical techniques. Fiber-optic technology also has been applied in many other areas, such as opto-mechanical applications for numerous industrial and medical applications.
The primary problem with prior art, fiber optic imaging is that it is difficult to achieve acceptable measurement of surface tolerances or roughness through a single port or single optical fiber. Conventional fiber optic imaging also does not provide any quantitative measurement of the interior region being imaged. This is because prior art systems generally must rely on interferometry concepts requiring multiple fibers.
It is therefore an object of the present invention to provide profilometer apparatus for inspecting the interior surfaces of tanks and other device under tests, including medical implants and any enclosure having a single access port.
It is therefore an object of the present invention to provide apparatus for inspecting interiors of tanks and other device under tests that is capable of accurate quantitative measurement of interior surface imperfections with a high degree of resolution.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects, apparatus for inspecting the interior of a device under test through a single port in the device under test comprising laser means for producing laser energy, with beam splitter means for directing the laser energy to a first direction and to a second direction. Delay means receive the laser energy from the second direction for introducing a predetermined delay to the laser energy from the second direction and outputting the delayed laser energy from the second direction. Optical routing means receive the laser energy from the first direction of at a first input for directing the laser energy from the first direction to ones of a first at least one optical fibers that enter the device under test through the port, and for transmitting laser energy reflected from interior surfaces of the device under test to ones of a second at least one optical fibers. Interferometer means receive the laser energy reflected from the interior surfaces of the device under test and the delayed laser energy from the second direction for interfering said laser energy reflected from the interior surfaces of the device under test with the delayed laser energy from the second direction and outputting interference patterns, wherein the interference patterns are representative of the interior surfaces of the device under test.
In a further aspect of the present invention, and in accordance with its objects and principles, a method for inspecting the interior surfaces of a device under test having a single entry port comprises the steps of launching laser energy into the device under test; receiving light reflected from the interior surfaces of the device under test; interfering the light reflected from the interior surfaces of the device under test with reference laser energy, creating an interference pattern; analyzing the interference pattern to discern information about the interior surfaces of the device under test; and outputting the information about the interior surfaces of the device under test.
REFERENCES:
patent: 4857748 (1989-08-01), Takiguchi
patent: 6002480 (1999-12-01), Izatt et al.
Leeches Gerald W.
Nierop John Van
Patterson R. Alan
Piltch Martin S.
Teti John J.
Font Frank G.
Lee Andrew H.
The Regents of the University of California
Wyrick Milton D.
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