Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1993-07-26
1996-02-13
Turner, Samuel A.
Optics: measuring and testing
By particle light scattering
With photocell detection
356360, 25022727, G01B 902
Patent
active
054915503
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods and microscopes for measuring the difference(s) between at least two energy path lengths.
2. Description of the Related Art
Conventional microscopes have a large depth of field or axial resolution compared to their lateral resolution. Confocal microscopes have approximately 30% better lateral resolution and much better axial resolution than conventional microscopes. To get high lateral resolution surface profiles of objects it is common to use an interference microscope. It would be advantageous to combine the properties of an interference microscope with those of a confocal microscope. Standard confocal microscopes suffer from alignment problems and require large numbers of components precisely located with respect to each other on an optical bench arrangement. Confocal interference microscopes also have severe stability problems due to such things as air currents and minor temperature fluctuations. In addition, a normal interference confocal microscope has a very limited depth of field and is difficult to scan rapidly.
SUMMARY OF THE INVENTION
The present invention is directed to a method and an interference microscope for measuring energy path length differences, path length between two locations and for determining the refractive index of a material.
According to the present invention, a method is provided for measuring the difference between two energy path lengths, comprising:
coherently directing a portion of an illuminating energy beam from a coherent energy source through a first coherent energy guide to an energy exit port denoted the first exit;
coherently directing a second portion of the illuminating energy beam through a second coherent energy guide to an energy exit port denoted the second exit;
wherein the first and second portions of the illuminating energy beam are at least partly coherent with respect to one another on emerging from the first and second exits respectively;
focussing coherently at least a portion of illuminating energy emerging from the first exit into a spot intersecting an object;
coherently directing at least a portion of a coherent signal energy beam resulting from interaction between the illuminating energy beam in the spot and the object to an interferometer, the signal beam being coherent with respect to the illuminating energy beam;
directing coherently at least a portion of the second portion of the illuminating energy beam, denoted the reference beam, from the second exit to the interferometer whereby the reference beam and the signal beam interfere thereby producing an output signal; and
calculating from the output signal the energy path length difference between the first energy path from the energy source, through the first energy guide to the intersection of the spot with the object and from the intersection to the interferometer and the second energy path from the energy source, through the second energy guide to the interferometer.
Other methods for measuring the difference between two energy path lengths are described herein below.
The present invention further provides a microscope for measuring the difference(s) between two or more energy path lengths.
The microscope comprises:
an energy source which emanates an illuminating energy beam wherein at least a portion of the illuminating energy beam is substantially coherent;
a first coherent energy guide operatively associated with the energy source to receive coherently a first portion of the coherent illuminating energy beam, the first coherent energy guide having an energy exit port denoted the first exit;
a second coherent energy guide operatively associated with the energy source to receive coherently a second portion of the coherent illuminating energy beam, the second coherent energy guide having an energy exit port denoted the second exit;
wherein the illuminating energy beams are coherent with respect to one another on emerging from the first and second exits;
an energy focusser operatively associated with t
REFERENCES:
patent: 4627731 (1986-12-01), Waters et al.
patent: 4928527 (1990-05-01), Burger et al.
patent: 5177566 (1993-01-01), Leuchs et al.
Commonwealth Scientific and Industrial Research Organization
Turner Samuel A.
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