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Claims  |
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I claim:
1. A method for determining the refractive index of an object between two
locations in mid object, wherein said object is a partially energy
transparent object with a known path length between, first and second
locations in said object, by measuring the difference between two energy
path lengths, said method comprising:
spatially filtering confocally and 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 said illuminating energy beam
through a second coherent energy guide to an energy exit port denoted the
second exit;
wherein said first and second portions of said illuminating energy beam are
at least partly coherent and respect to one another on emerging from said
first and second exits respectively;
focussing coherently at least a portion of illuminating energy emerging
from said first exit into a first spot intersecting said object;
coherently directing at least a portion of a first coherent signal energy
beam resulting from interaction between said illuminating energy beam in
said first spot and said object to an interferometer, said first signal
beam being coherent with respect to said illuminating energy beam;
focussing coherently at least a portion of illuminating energy emerging
from said second exit into a second spot intersecting said object;
coherently directing at least a portion of a second coherent signal energy
beam resulting from interaction between said illuminating energy beam in
said second spot and said object to said interferometer; said second
signal beam being coherent with respect to said illuminating energy beam;
wherein said first spot is at a first location in said object, said second
spot is formed by focussing through said object via said first location to
a second location in said object;
whereby said first and second signal beams interfere thereby producing an
output signal;
calculating from said output signal said energy path length difference
between said first energy path from said energy source, through said first
energy guide to the intersection of said first spot with said object to
said interferometer and said second energy path from said energy source,
through said second energy guide to the intersection of said second spot
with said object to said interferometer; and
determining the refractive index of said object between said first and
second locations in said object by comparing said energy path length
difference with said known path length.
2. A method for determining the path length between two locations in an
object, wherein said object is a partially energy transparent object with
known refractive index between first and second locations in said object
by measuring the difference between two energy path lengths, said method
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 said illuminating energy beam
through a second coherent energy guide to an energy exit port denoted the
second exit:
wherein said first and second portions of said illuminating energy beam are
at least partly coherent with respect to one another on emerging from said
first and second exits respectively;
focussing coherently at least a portion of illuminating energy emerging
from said first exit into a first spot intersecting an object;
spatially filtering confocally and coherently directing at least a portion
of a first coherent signal energy beam resulting from interaction between
said illuminating energy beam in said first spot and said object to an
interferometer, said first signal beam being coherent with respect to said
illuminating energy beam;
focussing coherently at least a portion of illuminating energy emerging
from said second exit into a second spot intersecting said object;
coherently directing at least a portion of a second coherent signal energy
beam resulting from interaction between said illuminating energy beam in
said second spot and said object to said interferometer, said second
signal beam being coherent with respect to said illuminating energy beam;
wherein said first spot is at a first location in said object, said second
spot is formed by focussing through said object via said first location to
a second location in said object;
whereby said first and second signal beams interfere thereby producing an
output signal; and
calculating from said output signal said energy path length difference
between said first energy path from said energy source, through said first
energy guide to the intersection of said first spot with said object to
said interferometer and said second energy path from said energy source,
through said second energy guide to the intersection of said second soot
with said object to said interferometer; and
determining the path length between said first and second locations from
said energy path length difference with said known refractive index.
3. A method for determining refractive index of an object with known path
length between first and second locations in said object, comprising:
(a) coherently directing a portion of an illuminating energy beam from a
coherent energy source through a first coherent energy guide an energy
exit port denoted the first exit;
(b) coherently directing a second portion of said illuminating energy beam
through a second coherent energy guide to an energy exit port denoted the
second exit;
wherein said first and second portions of said illuminating energy beam are
at least partly coherent with respect to one another on emerging from said
first and second exits respectively;
(c) focussing coherently at least a portion of illuminating energy emerging
from said first exit into a first spot intersecting said object at a first
location;
(d) coherently directing at least a portion of a first coherent signal
energy beam resulting from interaction between said illuminating energy
beam in said first spot and said object at said first location to an
interferometer, said first signal beam being coherent with respect to said
illuminating energy beam;
(e) directing coherently at least a portion of said first portion of said
illuminating energy beam, denoted the first reference beam, from said
first exit to said interferometer whereby said first reference beam and
said first signal beam interfere thereby producing a first output signal;
(f) calculating from a first output signal said first energy path length
difference between a first energy path from said energy source, through
said first energy guide to the intersection of said first spot with said
object at said first location and from said first location to said
interferometer and a second energy path from said energy source, through
said second energy guide to said interferometer;
(g) repeating steps (a) and (b);
(h) focussing coherently at least a portion of illuminating energy emerging
from said first exit through said object via said first location into a
second spot intersecting said object at a second location;
(i) coherently directing at least a portion of a second coherent signal
energy beam resulting from interaction between said illuminating energy
beam in said second spot and said object at said second location to the
interferometer, said second signal beam being coherent with respect to
said illuminating energy beam;
(j) directing coherently at least a portion of said second portion of said
illuminating energy beam, denoted the second reference beam, from said
second exit to said interferometer whereby the second reference beam and
said second signal beam interfere thereby producing a second output
signal; and
(k) calculating from said second output signal said second energy path
length difference between a third energy path from said energy source,
through said first energy guide to the intersection of said second spot
with said object at said second location and from said second location to
said interferometer and a fourth energy path from said energy source,
through said second energy guide to said interferometer;
(l) determining the refractive index of said object between said first and
second locations in said object by comparing said first and second energy
path length differences with said known path length.
4. A method for determining path length between two locations in an object,
wherein the object is a partially energy transparent object with known
refractive index between first and'second locations in the object,
comprising;
(a) 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;
(b) 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;
(c) focussing coherently at least a portion of illuminating energy emerging
from the first exit into a first spot intersecting the object at a first
location;
(d) coherently directing at least a portion of a first coherent signal
energy beam resulting from interaction between the illuminating energy
beam in the first spot and the object at the first location to an
interferometer, the first signal beam being coherent will respect to the
illuminating energy beam;
(e) directing coherently at least a portion of the first portion of the
illuminating energy beam, denoted the first reference beam, from the first
exit to the interferometer whereby the first reference beam and the first
signal beam interfere thereby producing a first output signal; and
(f) calculating from the first output signal a first energy path length
difference between a first energy path from the energy source, through the
first energy guide to the intersection of the first spot with the object
at the first location and from the first location to the interferometer
and a second energy path from the energy source, through the second energy
guide to the interferometer;
(g) repeating steps (a) and (b);
(h) focussing coherently at least a portion of illuminating energy emerging
from the first exit through the object via the first location into a
second spot intersecting the object at a second location;
(i) coherently directing at least a portion of a second coherent signal
energy beam resulting from interaction between the illuminating energy
beam in the second spot and the object at the second location to said
interferometer, the second signal beam being coherent with respect to the
illuminating energy beam;
(j) directing coherently at least a portion of the second portion of the
illuminating energy beam, denoted the second reference beam, from the
second exit to the interferometer whereby the second reference beam and
the second signal beam interfere thereby producing a second output signal;
and
(k) calculating from the second output signal the second energy path length
difference between a third energy path from the energy source, through the
first energy guide to the intersection of the second spot with the object
at the second location and from the second location to the interferometer
and a fourth energy path from the energy source, through the second energy
guide to the interferometer;
(l) determining the path length between the first and second locations in
the object by comparing the first and second energy path length
differences with the known refractive index.
5. The method of any one of claims 1-4 further comprising:
scanning the object by moving the spot(s) relative to the object.
6. The method of any one of claims 3 or 4 wherein the signal energy beam(s)
is spatially filtered confocally before the interferometer.
7. A microscope for measuring the difference between two energy path
lengths comprising:
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 exit;
an energy focusser operatively associated with the first exit for focussing
coherently at least a portion of illuminating energy emerging from the
first exit into a spot intersecting an object;
a first energy director operatively associated with the first exit and the
focusser for spatially filtering confocally and coherently directing at
least a portion of a 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;
a second energy director operatively associated with the second exit and
the interferometer to direct 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
a calculator operatively associated with the interferometer to calculate
from the output signal the energy path length difference between a first
energy path from the energy source, through the first energy guide to the
intersection of the spot with the object via the focusser and from the
intersection to the interferometer via the first energy director and a
second energy path from the energy source, through the second energy guide
to the interferometer via the second energy director.
8. A microscope for measuring the difference between two energy path
lengths comprising:
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;
a first energy focusser operatively associated with the first exit for
focussing coherently at least a portion of illuminating energy emerging
from the first exit into a first spot intersecting an object;
a first energy director operatively associated with the first exit and the
first focusser for spatially filtering confocally and coherently directing
at least a portion of a first signal energy beam resulting from
interaction between the illuminating energy beam in the first spot and the
object to an interferometer, the first signal beam being coherent with
respect to the illuminating energy beam;
a second energy focusser operatively associated with the second exit for
focussing coherently at least a portion of illuminating energy emerging
from the second exit into a second spot intersecting said object;
a second energy director operatively associated with the second exit and
the second focusser for coherently directing at least a portion of a
second signal energy beam resulting from interaction between the
illuminating energy beam in the second spot and the object to the
interferometer, the second signal beam being coherent with respect to the
illuminating energy beam;
whereby the first and second signal beams interfere thereby producing an
output signal; and
a calculator operatively associated with the interferometer to calculate
from the output signal the energy path length difference between a first
energy path from the energy source, through the first energy guide to the
intersection of the first spot with the object via the first focusser and
from the intersection of the first spot with the object to the
interferometer via the first energy director and a second energy path from
the energy source, through the second energy guide to the intersection of
the second spot with the object via the second focusser and from the
intersection of the second spot with the object to the interferometer via
the second energy director.
9. The microscope of claim 8 wherein the first and second focussers are the
same focusser.
10. The microscope of claim 7 or 8 wherein the first and second coherent
energy guides are the same coherent energy guide and the first and second
directors are the same director.
11. The microscope of claim 8 wherein the second director comprises at
least one energy guide and at least one energy focusser for collecting the
second signal beam the energy focusser(s) being operatively associated
with the second energy guide to image the core of the second energy guide
at its entrance onto the second spot whereby the numerical apertfore NA,
of the second signal beam originating from the central portion of the
second spot, the wavelength of the second signal beam, .lambda., and the
average diameter, d, of the energy guiding core of the second energy guide
at its entrance are related by the equation:
NA<or.apprxeq.0.6.times..lambda./d.
12. The microscope of claim 7, 8 or 11 wherein the first director comprises
at least one energy guide and at least one energy focusser for collecting
the first signal beam said energy focusser(s) being operatively associated
with said first energy guide to image the core of the first energy guide
at its entrance onto the first spot whereby the numerical aperture NA of
the first signal beam origination from the central portion of the first
spot, the wavelength of the first signal beam, .lambda., and the average
diameter, d, of the energy guiding core of the first energy guide at its
entrance are related by the equation:
NA<or.apprxeq.0.6.times..lambda./d.
13. The microscope of claim 7, 8 or 11 wherein the first and second energy
directors comprise portions of the first and second energy guides.
14. The microscope of claim 7, 8 or 11 wherein the first and second exits
are coupled so as to be fixed relative to one another and further
comprising a scanner operatively associated with the exits to move the
spot(s) relative to the object.
15. The microscope of claim 7, 8 or 11 wherein the first or second energy
path includes an energy path length changer and the calculator is
operatively associated with the energy path length changer to enable
quadrature operation of the interferometer.
16. The microscope of claim 7, 8 or 11 wherein the microscope further
comprises:
a third coherent energy guide operatively associated with the energy
source;
a first energy splitter operatively associated with the third coherent
energy guide and the first and second energy guides whereby coherent
illuminating energy emanating from the energy source is coupled coherently
into the third energy guide to guide coherently a portion of the
illuminating energy to the first energy splitter wherein a portion of the
energy is coupled coherently into the first energy guide and another
portion of the illuminating energy is coupled coherently into the second
energy guide.
17. The microscope of claim 7, 8 or 11 further comprising a scanner
operatively associated with the microscope to move the spot(s) relative to
the object.
18. The microscope of claim 7, 8 or 11 wherein the energy source is a
source of electromagnetic radiation with a wavelength in the range of and
including far UV to far IR, the energy guide(s) is a multimode optical
fibre(s), single mode optical fibre(s) or coherent fibre brindle(s).
19. A microscope for measuring the difference between two light path
lengths comprising:
a light source which emanates an illumination light beam having at least
one wavelength in the range of far UV to far IR wherein at least a portion
of the illuminating light beam is substantially coherent;
a first optical fibre operatively associated with a first light splitter to
receive coherently a first portion of the coherent illuminating light
beam, the first optical fibre having a second light splitter and a light
exit port denoted the first exit;
a second optical fibre operatively associated with the light source to
receive coherently a second portion of the coherent illuminating light
beam via the first light splitter, the second optical fibre having a light
exit port denoted the second exit and having a light path length changer;
wherein the illuminating light beams are coherent with respect to one
another on emerging from the first and second exits;
a light focusser operatively associated with the first exit for focussing
coherently at least a portion of illuminating light emerging from the
first exit into a diffraction limited spot intersecting an object;
wherein the focusser is operatively associated with the first exit for
coherently directing at least a portion of a signal light beam resulting
from interaction between the spot and the object to the first exit and
thereby to the first light splitter which acts as an interferometer, via
the first optical fibre and the second light splitter, the signal beam
being coherent with respect to the illuminating light beam;
wherein the numerical aperture NA, of the signal beam originating from the
central portion of the spot, the wavelength of the signal light beam,
.lambda., and average diameter, d, of the light guiding core of the first
optical fibre at the first exit are related by the equation:
NA<or.apprxeq.0.6.times..lambda./d
a light reflector operatively associated with the second exit and the
interferometer to direct coherently at least a portion of the second
portion of the illuminating light beam, denoted the reference beam, to the
first light splitter via the second exit and the second optical fibre
whereby the reference beam and the signal beam interfere thereby producing
an output signal;
a first detector operatively associated with the first splitter to detect
the output signal;
a scanner operatively associated with the first and second exits whereby
the first and second exits are movable relative to the focusser and the
reflector, which focusser and reflector are stationary with respect to the
object, but which exits are not movable with respect to each other;
a second detector operatively associated with the second splitter to detect
signal light from the first optical fibre; and
a calculator operatively associated with the light path length changer, the
first detector and the first light splitter to maintain the interference
between the reference and signal beams in quadrature, to calculate the
light path length difference between a first light path from the light
source, through the first optical fibre to the intersection of the spot
with the object via the first exit and the focusser and from the
intersection back to the first light-splitter via the focusser, the first
exit and the first optical fibre and a second light path from the light
source, through the second optical fibre back to the first light splitter
via the second exit, the light reflector and the second exit and back
through the second optical fibre, and determine via the second detector
when the spot is substantially focussed on the surface of the object.
20. A microscope for measuring the difference between two light path
lengths comprising:
a light source which emanates an illuminating light beam having at least
one wavelength in the range of far UV to hr IR wherein at least a portion
of the illuminating light beam is substantially coherent;
a first optical fibre operatively associated with a first light splitter to
receive coherently a first portion of the coherent illuminating light
beam, the first optical fibre having a second light splitter and a light
exit port denoted the first exit;
a second optical fibre operatively associated with the light source to
receive coherently a second portion of the coherent illuminating light
beam via the first light splitter, the second optical fibre having a light
exit port denoted the second exit and having a light path length changer;
wherein the illuminating light beams are coherent with respect to one
another on emerging from the first and second exits;
a light focusser operatively associated with the first exit for focussing
coherently at least a portion of illuminating light emerging from the
first exit into a first diffraction limited spot intersecting an object;
wherein the focusser is operatively associated with the first exit for
coherently directing at least a portion of a first signal light beam
resulting from interaction between the first spot and the object to the
first exit and thereby to the first light splitter which acts as an
interferometer, via the first optical fibre and the second light splitter,
the first signal beam being coherent with respect to the illuminating
light beam;
wherein the numerical aperture NA, of the first signal beam originating
from the central portion of the first spot, the wavelength of the first
signal light beam, .lambda., and average diameter, d, of the light guiding
core of the first optical fibre at the first exit are related by the
equation:
NA<or.apprxeq.0.6.times..lambda./d
said light focusser being operatively associated with the second exit for
focussing coherently at least a portion of illuminating light emerging
from the second exit into a second diffraction limited spot intersecting
the object;
wherein the focusser is operatively associated with the second exit for
coherently directing at least a portion of a second signal light beam
resulting from interaction between the second spot and the object to the
second exit anti thereby to the first light splitter which acts as an
interferometer, via the second optical fibre, the second signal beam being
coherent with respect to the illuminating light beam:
wherein the numerical aperture NA, of the second signal beam originating
from the central portion of the second spot, the wavelength of the second
signal light beam, .lambda., and average diameter, d of the light guiding
core of the second optical fibre at the second exit are related by the
equation:
NA<or.apprxeq.0.6.times..lambda./d
whereby the first and second signal beams interfere thereby producing an
output signal;
a first detector operatively associated with the first splitter to detect
the output signal:
a scanner operatively associated with the first and second exits whereby
the first and second exits are movable relative to the focusser, which is
stationary with respect to the object, but are not movable with respect to
each other;
a second detector operatively associated with the second splitter to detect
signal light from the first optical fibre; and
a calculator operatively associated with the light path length changer, the
first detector and the first light splitter to maintain the interference
between the first and second signal beams in quadrature, to calculate
light path length difference between a first light path from the light
source, through the first optical fibre to the intersection of the first
spot with the object via the first exit and the focusser and from the
intersection back to the first light splitter via the focusser, the first
exit and the first optical fibre a the second light path from the light
source, through the second optical fibre back to the first light splitter
via the second exit, the focusser and from the intersection back to the
first light splitter via the focusser, the second exit and the second
optical fibre, and determine via the second detector when the first spot
is substantially focussed on the surface of the object. |
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Claims |
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Description |
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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 the first exit for focussing
coherently at least a portion of illuminating energy emerging from the
first exit into a spot intersecting an object;
a first energy director operatively associated with the first exit and the
focusser for coherently directing at least a portion of a 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;
a second energy director operatively associated with the second exit and
the interferometer to direct 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
a calculator operatively associated with the interferometer to calculate
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 via the focusser and from the
intersection to the interferometer via the first energy director and the
second energy path from the energy source through the second energy guide
to the interferometer via the second energy director.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing of an interference microscope according to
the present invention;
FIG. 2 is a schematic drawing of a refractive index profiler according to
the present invention;
FIG. 3 is a schematic drawing of a memory read head according to the
present invention;
FIGS. 4, and 4a are a schematic drawings of a surface profiler according to
the present invention;
FIG. 5 is a schematic drawing of a microscope for measuring the difference
between two energy paths according to the present invention; and
FIG. 6 is a schematic drawing of a differential interference microscope
according to the present invention.
Objects of this invention are to provide methods and microscopes for
measuring the difference(s) between at least two energy path lengths.
DESCRIPTION OF PREFERRED EMBODIMENTS
For a discussion of "interfere" and "interferes" in accordance with the
intended meaning in this specification reference is made to Principles of
Optics, Max Born and M.L. Wolf, Pergamon Press, 6th Corrected edition,
reprinted 1984 Chapters VII and X, the contents of which are incorporated
herein by cross reference.
Throughout the specification the word "spot" used in the context of energy
being focussed into a spot refers to the three dimensional volume defined
by the high energy density surrounding what is commonly termed the point
of focus. Throughout the specification the words "intersection" and
"intersecting" used in the context of a spot intersecting an object refers
to a surface or intersection between the spot and the object, the surface
being located on or in the object. Where reference is made herein to a
coherent energy source it is intended to include a partially coherent
energy source such as that produced by an LED, for example.
According to a first embodiment of this invention there is provided a
method 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 or 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 tire
first and second exits respectively;
focussing coherently at least a portion of illuminating energy emerging
from tire 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.
According to a second embodiment of this invention there is provided a
method 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 first spot intersecting an object:
coherently directing at least a portion of a first coherent signal energy
beam resulting from interaction between the illuminating energy beam in
the first spot and the object to an interferometer, the first signal beam
being coherent with respect to the illuminating energy beam;
focussing coherently at least a portion of illuminating energy emerging
from the second exit into a second spot intersecting the object:
coherently directing at least a portion of a second coherent signal energy
beam resulting from interaction between the illuminating energy beam in
the second spot and the object to the interferometer, the second signal
beam being coherent with respect to the illuminating energy beam;
whereby the first and second signal beams 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 first spot with the object to the
interferometer and the second energy path from the energy source, through
the second energy guide to the intersection of the second spot with the
object to the interferometer.
According to a third embodiment of this invention there is provided a
method for determining refractive index of an object between two locations
in the object, comprising the method of the second embodiment wherein the
object is a partially energy transparent object with known path length
between first and second locations in the object and wherein the first
spot is at the first location in the object, the second spot is formed by
focussing through the object via the first location to the second location
in the object, and wherein the method further comprises:
determining the refractive index of the object between the first and second
locations in the object by comparing the energy path length difference
with the known path length.
According to a fourth embodiment of this invention there is provided a
method for determining the path lengt | | |
