Image analysis – Applications – Surface texture or roughness measuring
Reexamination Certificate
1998-09-15
2001-02-06
Mehta, Bhavesh (Department: 2721)
Image analysis
Applications
Surface texture or roughness measuring
C356S340000, C702S166000
Reexamination Certificate
active
06185315
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to the general field of interferometric profilometry. In particular, it provides a technique for improving the resolution of an interferometric profilometer by reducing the field of view of its objective and combining multiple overlapping images to form a composite profile.
2. Description of the Prior Art
The optical resolution of the objective of an interferometer is an important parameter in the overall performance of the instrument. The spatial resolution can be enhanced by reducing the field of view of the objective, but that also reduces the capability of the instrument with respect to the area of sample being tested. If, on the other hand, the field of view is enlarged to cover a larger test surface, the optical (and therefore also spatial) resolution of the resulting image is adversely affected. Therefore, a practical balance is normally struck between the optical resolution of the profilometer and the size of the test surface that it can handle.
As interferometric technology progresses, it has become very desirable to provide some flexibility with regard to the surface size of the samples suitable for testing. This invention provides a procedure for enhancing the resolution or, alternatively, for increasing the x-y profiling range of a conventional interferometer.
BRIEF SUMMARY OF THE INVENTION
It is therefore an objective of this invention to provide a procedure that effectively increases the field of view of a given interferometric profiler without modifications to its optics.
Another object of the invention is a procedure for increasing the field of view of a given interferometric profiler without affecting its optical resolution.
Another objective of the invention is a computationally efficient method to achieve the above goals, so that computer processing time is minimized.
Another goal of the invention is a method that is computationally stable, repeatable and consistent with measured data.
A further objective of the invention is a procedure capable of implementation in real time for on-line applications.
Another goal of the invention is its general application to increasing the x-y scanning range of conventional interferometric profilers without limitation to any specific field of testing.
Finally, another goal is the realization of the above mentioned objectives in a system that can be implemented with existing sensory, computing, and other hardware devices.
In accordance with these and other objectives, the preferred embodiment of the method and apparatus of this invention consists of taking successive measurements of adjacent sections of the surface of a test sample by sequentially placing them within the field of view of the instrument and independently profiling each section by phase shifting or vertical scanning interferometry. The x-y translation of the microscope between successive measurements from one section to the next adjacent section of the surface being profiled is carried out by maintaining a region of overlap between sections, so that spatial continuity is retained between measurements. The height data generated for each section are then combined to form a larger image corresponding to the entire surface tested and discontinuities and/or errors introduced by the x-y translation process are corrected by normalizing the overlapping portions to a common reference plane. A plane is fitted through each set of measured heights in the overlapping regions and the tip, tilt and offset of one of the fitted planes are corrected to produce matching overlapping height data in adjacent sections. The measured height data for the balance of each section are then also corrected by the same difference in tip, tilt and offset to obtain a continuous normalized image.
Various other purposes and advantages of the invention will become clear from its description in the specification that follows, and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose only some of the various ways in which the invention may be practiced.
REFERENCES:
patent: 4641972 (1987-02-01), Halioua et al.
patent: 4869593 (1989-09-01), Biegen
patent: 5469259 (1995-11-01), Golby et al.
patent: 5471303 (1995-11-01), Ai et al.
patent: 5555471 (1996-09-01), Xu et al.
patent: 5633715 (1997-05-01), Ai et al.
patent: 5710631 (1998-01-01), Bou-Ghannam et al.
patent: 5712890 (1998-01-01), Spivey et al.
patent: 5717782 (1998-02-01), Denneau, Jr.
patent: 5726754 (1998-03-01), Andrews et al.
patent: 5760901 (1998-06-01), Hill
patent: 5784163 (1998-07-01), Lu et al.
patent: 5831736 (1998-11-01), Lichtman et al.
patent: 5926266 (1998-11-01), Dorundo et al.
patent: 6011624 (2000-01-01), De Groot
patent: 6011625 (2000-01-01), Glass
patent: 6014166 (2000-01-01), Guerra
Becker Brian W.
Schmucker Mark A.
Durando Antonio R.
Mehta Bhavesh
Patel Kanji
Wyko Corporation
LandOfFree
Method of combining multiple sets of overlapping... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of combining multiple sets of overlapping..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of combining multiple sets of overlapping... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2604706