Phase annulus to carry out a positive phase contrast

Details Phase annulus to carry out a positive phase contrast Phase annulus to carry out a positive phase contrast

1999-11-12

2001-04-03

Spyrou, Cassandra (Department: 2872)

Optical: systems and elements

Diffraction

C359S370000, C359S577000, C359S585000, C359S594000, C428S005000

Reexamination Certificate

active

06212009

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention concerns a phase annulus to produce positive phase contrast. Phase contrast microscopy has been known since Zernike. Accomplishment of this process requires production of “phase rings” by vapor-deposition of one or more thin layers on a substrate, which may be of optical glass, for instance. By skillful selection of the layer thickness, the phase of the direct light, which passes through the vapor-deposited phase, can be delayed relative to the phase of the diffracted light, which is the light that does not pass through the phase annulus, by, for instance, &pgr;/2; or it can be advanced by &pgr;/2. That latter case is “positive” phase contrast.
BRIEF SUMMARY OF THE INVENTION
The objective of this invention is to make available a phase annulus with which one can produce positive phase contrast with essentially constant phase shift and a discrete transmission curve. Another part of the object is to establish each positive phase shift firmly within a certain phase angle interval.


REFERENCES:
patent: 2427689 (1947-09-01), Osterberg et al.
patent: 2616334 (1952-11-01), Zernike
patent: 5144362 (1992-09-01), Kamon et al.
patent: 5461516 (1995-10-01), Kawano et al.
patent: 0180745 (1955-01-01), None
patent: 0187704 (1956-11-01), None
patent: 0045855 (1966-02-01), None
patent: 22 61 780 (1974-01-01), None
patent: 3412958A1 (1985-10-01), None
Pluta, M.: “Stray-Light Problem in Phase Contrast Microscopy or Toward Highly Sensitive Phase Contrast Devices: A Review”; Optical Engineering, vol. 32, No. 12, Dec. 1, 1993, pp. 3199-3214.

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