U.S. patent application number 15/232579 was filed with the patent office on 2017-02-09 for propagation medium velocity measurement system.
The applicant listed for this patent is Kelvin F. Wright, Selwyn E. Wright. Invention is credited to Kelvin F. Wright, Selwyn E. Wright.
Application Number | 20170038404 15/232579 |
Document ID | / |
Family ID | 53778522 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170038404 |
Kind Code |
A1 |
Wright; Selwyn E. ; et
al. |
February 9, 2017 |
PROPAGATION MEDIUM VELOCITY MEASUREMENT SYSTEM
Abstract
An apparatus measures an electromagnetic signal (e.g., light)
propagation time delay that varies with system speed relative to
its propagation medium. A one-way light propagation time
measurement in the medium between two fixed points moving relative
to the medium is used. The delay is compared with light propagating
in a constant reference path that is independent of motion. A
two-way system is also used, as well as increasing sensitivity
through a light zigzag and fiber optic coil delay. The apparatus is
a compact and extremely sensitive speedometer.
Inventors: |
Wright; Selwyn E.;
(Huddersfield, GB) ; Wright; Kelvin F.; (Saratoga,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wright; Selwyn E.
Wright; Kelvin F. |
Huddersfield
Saratoga |
CA |
GB
US |
|
|
Family ID: |
53778522 |
Appl. No.: |
15/232579 |
Filed: |
August 9, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US15/15063 |
Feb 9, 2015 |
|
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15232579 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01P 3/36 20130101; G01S
11/12 20130101; G01S 11/02 20130101 |
International
Class: |
G01P 3/36 20060101
G01P003/36 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2015 |
US |
PCT/US15/15063 |
Claims
1. A method of measuring a velocity of an apparatus, said method
comprising: while said apparatus is at a reference velocity,
transmitting a first portion of an electromagnetic beam via a first
path on said apparatus to a receiver, wherein a distance said first
portion travels via said first path is dependent on any velocity of
said apparatus; while said apparatus is at said reference velocity,
transmitting a second portion of said beam via a second path on
said apparatus to said receiver, wherein a distance said second
portion travels via said second path is independent of any velocity
of said apparatus; determining a reference phase difference at said
receiver between said first portion traveling via said first path
at said reference velocity and said second portion traveling via
said second path at said reference velocity; while said apparatus
is at said velocity, determining a velocity phase difference at
said receiver between said first portion traveling via said first
path and said second portion traveling via said second path;
determining a total phase difference between said velocity phase
difference and said reference phase difference; and calculating
said velocity of said apparatus using at least said total phase
difference, a frequency of said beam, and the speed of light.
2. The method as recited in claim 1 wherein said reference velocity
is zero relative to the surface of the Earth.
3. The method as recited in claim 1 wherein said first portion
traveling via said first path travels in the direction of said
velocity of said apparatus.
4. The method as recited in claim 1 wherein said first portion
traveling via said first path propagates in a propagation
medium.
5. The method as recited in claim 1 wherein said first path
includes a zigzag portion.
6. The method as recited in claim 1 wherein said first path
includes a solid medium that is longer than the distance between a
source of said beam and said receiver.
7. An apparatus for calculating a velocity of said apparatus, said
apparatus comprising: a receiver; a source that generates an
electromagnetic beam of which a first portion of said beam is
directed toward said receiver via a first path and of which a
second portion of said beam is directed toward said receiver via a
second path, wherein a distance said first portion travels via said
first path is dependent on any velocity of said apparatus, and
wherein a distance said second portion travels via said second path
is independent of any velocity of said apparatus; a phase
comparator coupled to said receiver, said phase comparator being
arranged to determine a reference phase difference between said
first portion traveling via said first path and said second portion
traveling via said second path when said apparatus is at a
reference velocity, said phase comparator being further arranged to
determine a velocity phase difference between said first portion
traveling via said first path and said second portion traveling via
said second path when said apparatus is at said velocity; and a
computing device arranged to calculate said velocity of said
apparatus using at least said reference phase difference, said
velocity phase difference, a frequency of said beam, and the speed
of light.
8. The apparatus as recited in claim 7 wherein said reference
velocity is zero relative to the surface of the Earth.
9. The apparatus as recited in claim 7 wherein said first path is a
straight line.
10. The apparatus as recited in claim 7 wherein said first portion
traveling via said first path propagates in a propagation
medium.
11. The apparatus as recited in claim 7 wherein said first path
includes a zigzag portion.
12. The apparatus as recited in claim 7 wherein said first path
includes a solid medium that is longer than the distance between
said source and said first receiver.
13. The apparatus as recited in claim 7 further comprising: a beam
splitter that splits said beam from said source into said first
portion traveling via said first path and said second portion
traveling via said second path.
14. The apparatus as recited in claim 7 wherein a second receiver
is located in physical contact with said source, said apparatus
further comprising: an electrical conductor that conducts a signal
from said second receiver to said phase comparator.
15. A method as recited in claim 1 wherein a source of said beam,
said second path and said receiver are all contained in a bulk
material having a refractive index greater than 1.
16. A method as recited in claim 1 wherein said second path is a
zig-zag path perpendicular to said velocity of said apparatus.
17. A method as recited in claim 1 wherein said second path travels
through a solid medium which maintains a coherent polarization of
said beam.
18. A method as recited in claim 17 wherein said second path
travels in one or more loops.
19. A method as recited in claim 1 wherein said second path travels
in one or more loops.
20. An apparatus as recited in claim 7 wherein said source, said
second path and a second receiver are all contained in a bulk
material having a refractive index greater than 1.
21. An apparatus as recited in claim 7 wherein said second path is
a zig-zag path perpendicular to said velocity of said
apparatus.
22. An apparatus as recited in claim 7 wherein said second path
travels through a solid medium which maintains a coherent
polarization of said beam.
23. A method as recited in claim 22 wherein said second path
travels in one or more loops.
24. A method as recited in claim 7 wherein said second path travels
in one or more loops.
25. A method as recited in claim 1 wherein said beam at said
reference velocity is a pulse and wherein said beam at said
velocity is a pulse.
26. An apparatus as recited in claim 7 wherein said beam at said
reference velocity is a pulse and wherein said beam at said
velocity is a pulse.
27. A method as recited in claim 1 wherein said second path
includes fiber optic cable having loops that are spaced apart
evenly.
28. An apparatus as recited in claim 7 wherein said second path
includes fiber optic cable having loops that are spaced apart
evenly.
29. A method as recited in claim 1 wherein said first and second
paths are within solid, transparent material.
30. A method as recited in claim 29 wherein said first and second
paths are within fiber optic cable.
31. A method as recited in claim 1 wherein said receiver includes
first and second receivers, wherein said first path ends at said
first receiver and wherein said second path ends at said second
receiver.
32. An apparatus as recited in claim 7 wherein said first and
second paths are within solid, transparent material.
33. An apparatus as recited in claim 7 wherein said first and
second paths are within fiber optic cable.
34. An apparatus as recited in claim 7 wherein said receiver
includes first and second receivers, wherein said first path ends
at said first receiver, wherein said second path ends at said
second receiver, and wherein said phase comparator is coupled to
both said first and second receivers.
35. A method as recited in claim 1 wherein said first path is
orientated in the direction of motion of said apparatus and wherein
said second path is at least one loop of fiber optic cable.
36. An apparatus as recited in claim 7 wherein said first path is
orientated in the direction of motion of said apparatus and wherein
said second path is at least one loop of fiber optic cable.
37. A method as recited in claim 1 wherein a length of said second
path is about ten times a length of said first path.
38. An apparatus as recited in claim 7 wherein a length of said
second path is about ten times a length of said first path.
Description
PRIORITY
[0001] This continuation-in-part claims priority to
PCT/US15/015063, filed Feb. 9, 2015 which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to measuring the
speed of an apparatus on Earth or in outer space. More
specifically, the present invention determines a phase difference
of light beams in order to calculate speed of the apparatus.
BACKGROUND OF THE INVENTION
[0003] It is self evident that all measured motions require a
reference. Although, according to Einstein (1905), there is no
preferred reference frame, that is, no propagation medium or
"ether" required for comparing (measuring) motion of objects or
electromagnetic waves (light). Einstein claimed that only relative
motion between systems was important, not motion relative to a
propagation medium, without specifying any alternative transmission
mechanism in place of the medium (inferring that light does not
require a propagation medium). This claim is in direct conflict
with the basic electromagnetic (EM) wave theory developed by
Maxwell (1865) who established EM wave propagation, predicting the
transmission of light based on a since-measured propagation medium.
Further, an ether-less Universe is not supported by Lorentz's
(1899) motional transform, which is also shown to be based on
Maxwell's propagation medium. Techniques concerning measuring
motion in space relative to such a medium, however, have been
discouraged or believed not possible. Logically (according to these
beliefs), if there is no propagation medium, and space is empty,
then it should be impossible to measure motion in space.
[0004] The Michelson and Morley Experiment (MMX) (1887) designed to
measure the Earth's motion with respect to the propagation medium,
was an insensitive method of measuring motion. Even if there were
relative motion with respect to the medium, at Earth orbital speeds
of 30 km/s (or Mach number M=v/c=10.sup.-4, where v is the system
velocity and c is the speed of light), only a small fraction of an
interference fringe (2.pi. radians) would have been measured, and
at Earth's rotation speed of 480 m/s (M 1.5.times.10.sup.-6)
nothing would have been detected. Because the MMX failed to detect
the relative motion of the Earth through any propagation medium,
this negative result was interpreted as evidence against the
existence of a propagation medium. Even if the system had been
sensitive enough to detect relative motion, no motion would have
been detected, as shown below, because the propagation medium moves
with the Earth.
[0005] To establish motion with respect to the medium at practical
speeds on Earth, as well as at higher speeds in outer space, a more
sensitive measurement system would have been required. The MMX was
insensitive because it was based on a second order velocity term
(M.sup.2) as explained below. The MMX relied on the difference in
the propagation times in each direction in a round trip propagation
measurement, where the propagation differences in each direction
tended to cancel one another. One of the main reasons why the
propagation medium is not readily detectable is that there is no
existing dedicated measurement system sensitive enough to detect
linear motion relative to the medium.
[0006] It is shown that Sagnac (1913) demonstrated rotary motion
relative to the propagation medium. Sagnac split a beam of light
into two beams traveling in opposite directions using a beam
splitter. The beam splitter is used to measure the propagation
delay in and against the direction of rotating mirrors, relative to
the propagation medium. Sagnac reflected light, around a loop
relative to the Earth's surface, using a rotating square of four
mirrors. FIG. 1 shows Sagnac's mirror system 10 including a
rotating frame 20a and 20b, mirrors 31-34 (mirror 31 being a
half-silvered mirror), a radius 42, a side length l 44, and an
angular velocity 46. A light source 50 projects a beam of light
which is split by mirror 31; both beams travel in opposite
directions and end at a detector 55. One light beam propagates in
the medium against the mirror motion, counter-clockwise. The other
light beam propagates in the medium with the direction of mirror
motion, clockwise, through the half-silvered mirror. The mirror
system 10 must have caused the shift in interference fringes as a
consequence of the different distances that light traveled in the
propagation medium (stationary on the Earth's surface) due to the
rotation of the mirror system relative to the propagation medium.
If there had been no medium, or if the medium rotated with the
mirrors, there would have been no effect, no relative motion, and
no Propagation Time Asymmetry (PTA).
[0007] In system 10, light passes around the mirrors having a
peripheral distance d (d=4l) in a propagation time t=.+-.d/c
(depending on the light direction), where c is the speed of light
at the Earth's surface. If the mirror system rotates with an
angular velocity v then the incremental distance travelled in time
t (by the spinning mirrors) is .DELTA.d=vt=.+-.vd/c. The
incremental prediction equation for the propagation time asymmetry
(PTA) is shown below in Equation (1).
.DELTA.t=.DELTA.d/c=vd/c.sup.2=Mt, where M=v/c<<1 (1)
[0008] The incremental time .DELTA.t between the light beams was
measured through interference fringe movement in an interferometer
at the detector. By measuring .DELTA.t and knowing d and c, the
angular velocity of the spinning mirrors at the Earth's surface can
be calculated exactly according to Equation (1) and Maxwell's EM
wave theory, providing the medium is at rest on the Earth's
surface. Although Sagnac demonstrated that his result confirmed the
existence of Maxwell's stationary propagation medium, others
maintained that the Sagnac effect was consistent with special
relativity and that the medium did not exist. This is not possible;
unless Maxwell's wave theory, based on a propagation medium, is
shown to be in error, which is not the case, as it has been
reliably used for over 150 years. Also, any relativistic effects at
these mirror speeds are negligible compared to Sagnac's classical
PTA effect.
[0009] Recent patents for measuring motion in space are, for
example, those of Wang et al. (U.S. Pat. Nos. 6,813,006 and
7,586,587). In the first patent they proposed to measure motion by
measuring the time difference of light passing through two
different media. In the second they proposed to measure motion
using two beams of interfering light. The resulting interference
pattern (standing wave) is used to calculate the system speed. But
these patents do not identify any mechanism by which the
propagation occurs, i.e., whether it is relative to the Earth's
surface, to a vacuum medium or to some other unknown process. A
non-preferred reference is not an option in electromagnetic theory;
it is not a solution of Maxwell's EM wave equation, it is
non-causal (non predictable). If the Earth's surface is assumed to
be the reference then the motion will be defined relative to the
propagation medium stationary on the Earth's surface. Therefore, it
is recognized that improved and consistent techniques for measuring
speed in outer space as well as on Earth are desirable.
SUMMARY OF THE INVENTION
[0010] To achieve the foregoing, and in accordance with the purpose
of the present invention, a technique for measuring speed is
disclosed.
[0011] A system measures a signal (e.g., light) propagation time
delay that varies with system speed relative to its propagation
medium. This velocity measurement system uses a one-way light
propagation time measurement in the medium between two fixed points
moving relative to the medium. The delay is compared with light
propagating in a constant reference path (i.e., there is no
relative motion between the source, transmission path and
receiver), independent of motion, by a phase comparator. A two-way
system and methods of increasing the sensitivity through a light
zigzag and fiber optic coil delay are also described, creating a
compact an extremely sensitive speedometer.
[0012] The system can measure motion with respect to the
propagation medium moving with the Earth, or can measure motion
relative to the propagation medium generally at rest away from
gravitational bodies in outer space. The apparatus can determine
the velocity of spacecraft, probes, satellites, rockets, etc. (even
if they are light years from any object). It can also measure a
system velocity with respect to the ground without the use of
satellites (GPS), by measuring motion relative to the propagation
medium stationary on the Earth's surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention, together with further advantages thereof, may
best be understood by reference to the following description taken
in conjunction with the accompanying drawings in which:
[0014] FIG. 1 shows Sagnac's prior art mirror system.
[0015] FIG. 2 illustrates a propagation medium-based gravitational
entrainment model.
[0016] FIG. 3 illustrates a linear velocity measurement system
based on the Sagnac effect.
[0017] FIG. 4 is a block diagram showing a measurement system with
a velocity v.
[0018] FIG. 5 is a block diagram showing a two-way measurement
system with a velocity v.
[0019] FIG. 6A shows a standard measurement system.
[0020] FIG. 6B shows the propagation path length being increased in
the stationary medium by reflecting the light beam sideways using
mirrors.
[0021] FIG. 6C shows the propagation path length increased in the
stationary medium by passing the light beam through a fiber optic
coil.
[0022] FIG. 7 is a flow diagram describing one specific embodiment
by which the speed of a moving apparatus is measured.
[0023] FIG. 8 is a block diagram of two-way measurement system
comparing phase directly.
[0024] FIG. 9 is a block diagram showing two-way measurement system
using a single laser.
[0025] FIG. 10 illustrates a source, observer, and bulk material
all moving together.
[0026] FIG. 11 illustrates a system that uses a zigzag path to
increase the distance of the reference path.
[0027] FIG. 12 illustrates a system that uses a coil of optical
fiber as an invariant reference path.
[0028] FIGS. 13A and 13B illustrate a computer system suitable for
implementing embodiments of the present invention.
[0029] FIG. 14 illustrates use of a torus as the invariant
path.
[0030] FIG. 15 is a block diagram of a measurement system.
[0031] FIG. 16 is a block diagram of a measurement system using
fiber cable in both paths.
DETAILED DESCRIPTION OF THE INVENTION
[0032] As mentioned above, the MMX relied on the difference in the
propagation times in each direction in a round trip propagation
measurement, where the propagation differences in each direction
tended to cancel one another. Moreover, the null result obtained by
the MMX is now explained by the existence of a boundary layer
propagation medium located between the medium moving with the
rotating surface of the Earth and the surrounding stationary
medium. In other words, the MMX demonstrated that light propagation
on or near the surface of the Earth, through a fixed optical
system, was unaffected by the Earth's motion through the Universe
because the boundary layer rotates with the Earth's surface (on or
near the Earth's surface), i.e., there is no relative motion
between a measuring optical system on the Earth's surface and the
Earth's motion through the Universe.
Propagation Medium
[0033] Others have noted the presence of a propagation medium
(historically, the "ether," "aether" or "luminiferous aether"). The
medium was established by Maxwell in 1865, and the solution of the
EM wave equation (the foundation of all electromagnetic theories)
was based on a propagation medium. If the medium did not exist then
Maxwell's theory and today's EM theories would be in error, which
is not true. Dark Energy and the Higgs Field are both gaining
acceptance based on the notion of a propagation medium; further,
Maxwell's propagation medium and recent investigations (Wright,
2010-2013) have confirmed the medium's existence. Space, it
appears, is not uniformly empty (homogeneous) as Einstein claimed.
The propagation medium is found to be basically at rest in space,
but does move with gravitational bodies (e.g., planets), making EM
propagating disturbances (light) predictable (causal). More
specifically, it appears that a large gravitational body attracts
not only a boundary layer propagation medium rotating with its
surface, but also an orbital medium region above the boundary layer
having a much larger extent; this orbital region is stationary
around and moves with the body in orbit. Whereas Einstein's
non-preferred, homogeneous, uniformly empty space, which
underestimates the complexity, cannot without a medium describe the
situation. A uniformly empty space (no medium) is not a solution of
Maxwell's wave equation, it is non-causal, and it cannot be used to
predict wave propagation or to distinguish between wave propagation
in the various medium motional situations around a gravitational
body (e.g., a planet) or in outer space.
[0034] FIG. 2 illustrates a propagation medium-based gravitational
entrainment model that appears to fit all known data. Shown are
propagation medium profiles around a rotating and orbiting planet
120. A boundary layer propagation medium 122 having width w rotates
with the planet and is thus stationary with respect to the planet
at the planet's surface. Being a boundary layer, there is a
gradient from the planet's surface to the outer edge of the layer
122. At the outer edge the boundary layer is stationary with
respect to the surrounding medium 124; while the inner edge at the
planet's surface is not moving with respect to the planet's surface
(it is rotating with the planet's surface). The layer 122 is
smoothly graded between the two velocities (i.e., there is no
discontinuity). The extent of this boundary layer 122 on Earth is
less than about 10 km (from the Earth's surface), according to
Hafele and Keating's (1972) measurements.
[0035] A propagation medium orbital region 124 is attracted to and
orbits with the planet and is thus stationary with respect to the
orbiting planet (i.e., it is non-rotating, unlike the lower side of
the boundary layer on the planet's rotating surface). This orbital
region surrounding the Earth is confirmed further through Saburi et
al. (1976) satellite communications and GPS (1992) satellite
navigation systems operating in this orbital region. The extent of
this region appears to be controlled by the planet's gravitational
field of dominance (GFOD) in the presence of the Sun's
gravitational field of influence. In the Earth's case, the orbital
region 124 appears to have an extent of approximately W=50 Earth
radii (calculated from the center of the Earth, as illustrated in
FIG. 2. Further, the predicted symmetry in time slowing of atomic
clocks moving relative to the Earth's axis (but not to its rotating
surface) according to Hafele and Keating (1972) confirms that the
orbital region above an altitude of about 10 km is stationary,
i.e., it is not rotating with the Earth's surface.
[0036] The orbital region 124 is shown to move relative to a
propagation medium 126 surrounding the Sun which is stationary with
respect to the Sun and its own gravitational field of dominance.
Medium 126, in turn, is moving relative to a propagation medium at
rest in outer space (e.g., space between solar systems and
gravitational masses within their galaxy. If the planet rotates it
forms a velocity gradient (boundary layer) above the planets'
surface.
[0037] Therefore, the MMX (1887) demonstrated that light
propagation on the Earth's surface, through a fixed optical system,
was unaffected by the Earth's motion through the Universe because
the boundary layer propagation medium on the Earth's surface
separated the effects of Earth orbital motion through the
stationary medium surrounding the Sun from the medium rotating with
the Earth's surface. Sagnac (1913) showed that motion of his
rotating mirrors, relative to the Earth's surface and stationary
medium on the Earth, in and against the light direction, caused
Propagation Time Asymmetry (PTA). Michelson and Gale (1925)
established that the medium clings to the Earth's surface and moves
progressively faster from the poles to the equator. This causes a
measured difference in light propagation time (speed) over the same
distance, at different latitudes on the Earth's surface, revealing
the Earth's rotational speed relative to the surrounding stationary
medium.
[0038] These three experiments establish that a boundary layer
medium immediately above the Earth's surface exists and separates
the Earth's surface from the orbital stationary medium region above
(which surrounds and orbits with the Earth at higher altitudes).
Again, these effects are based on classical physics; the
relativistic effect at these speeds is negligible, unless
integrated over a considerable period of time.
[0039] In the absence of gravitational matter, the propagation
medium in the Universe appears to be stationary, on average,
providing a universal reference for motion. The cosmic microwave
background (CMB) detected by Penzias and Wilson (1965), is shown to
be EM radiation, propagating uniformly in all directions,
throughout the Universe, relative to the propagation medium
basically at rest in space. The stationary medium has also been
confirmed through the Cosmic Background Explorer COBE (1992). Here,
the CMB energy collection increases with system motion relative to
the stationary medium, similar to trawling fish nets catching more
fish than stationary ones. This model, with the stationary medium
surrounding the Earth, is supported by the results from NASA's
Gravity Probe B (2011).
[0040] If the Universe is found to be expanding at an appreciable
rate, then it is believed he propagation medium will expand with
it. Although the exact nature of the propagation medium is not
known, it has measurable properties in a vacuum in space. These
properties are electrical permeability (inductance or "inertia")
.mu.=1.25.times.10.sup.-6 N/A.sup.2 and electrical permittivity
(capacitance or "stiffness")(or .epsilon.)=8.85.times.10.sup.-12
F/m, which enables EM waves to propagate or "bounce" through a
vacuum medium in space.
[0041] Based on these observations, we have realized that the
sensitivity can be increased by many orders of magnitude (e.g.,
10.sup.6) compared with the MMX, by measuring the propagation time
in one direction only, given by Equation (2) below, or in opposite
directions, separately. The proposed method is based on the Sagnac
(1913) effect. Referring back to FIG. 1, the reason why Sagnac's
technique and the prediction equation work, is that it is predicted
through a causal solution of Maxwell's EM wave equation based on
the propagation medium at rest on the Earth's surface. In other
words, Sagnac's rotating mirrors generated a propagation delay
(.DELTA.d) through motion relative to this propagation medium, thus
establishing the medium's presence. There is no other physical
explanation to account for this result. If the medium were not
present, or rotated with the mirrors, there would be no measured
effect.
[0042] Relativistic effects have been offered to explain this
motional effect of Sagnac. But, the relativistic explanation is
lacking; not only do relativistic effects require a medium, but
also these relativistic effects are negligible at the mirror speeds
and small integration times compared to the instantaneous classical
Propagation Time Asymmetry (PTA) calculated by the prediction
Equation (1) above. This is shown in Section 3.5 using equations in
Section 8 in a summary paper of the book Unification of
Electromagnetism and Gravity, by Selwyn E. Wright, published 2014
by Trafford publishing, (included in the U.S. provisional
application referenced above) both are hereby incorporated by
reference.
[0043] Thus, it can be shown that a propagation medium does exist
and that the Sagnac effect is based upon the existence of this
medium. Having made this realization, other conclusions and the
present invention are possible, including applying the invention to
linear motion on and beyond the Earth's surface.
Velocity Measurement System
[0044] FIG. 3 illustrates a linear velocity measurement system 100
based on the Sagnac effect and the realization that a propagation
medium exists. The technique measures the speed of linear motion,
without the need of the rotating mirror system. System 100 has a
velocity, v 141, and includes a source 150 and a receiver 155
separated by distance d 160, a path 180 (through a vacuum or air,
for example), a fiber optic path 182, and a phase comparator 190.
Symbols 151 and 156 illustrate the movement of the system after a
given time. Because the system has a velocity, a first light beam
emitted from source 150 will actually travel a distance equal to d
160 plus .DELTA.d 170 before the light beam reaches the receiver
156. The beam can be split at source 150 and a second beam focused
into, and travels via, a fiber optic path 182 directly to the phase
comparator; this beam will travel a fixed distance because there is
no relative motion on this path. At the comparator, a
photo-electric converter (or first and second converters), for
example, converts the first light beam and the second light beam,
respectively, into electrical signals ready to be compared in the
comparator. The second photo-electric converter can be moved
directly in contact with the light source, with a metal wire
connecting directly to the comparator, so as to eliminate the beam
splitter and fiber optic cable. As is known, the comparator is able
to measure and detect phase differences between two electrical
sinusoidal signals.
[0045] The PTA between the two light beams may then be compared. In
other words, a time measurement of the variable propagation
distance via path 180 (in the direction of motion, via the
propagation medium) is now compared with a fixed (invariant)
propagation distance through the fiber optic cable path 182
connected directly between the light source 150 and the comparator
190 (the comparator being capable of comparing time or phase
changes). There is no relative motion between the light source, the
fiber optic cable and comparator, making this path phase invariant
with respect to the speed of the system. It does not matter what
the fiber optic cable length is as long as it is constant. We are
not comparing exact propagation distances or times, only changes in
times through motion. The actual phase difference is not important
as long as the phase is constant in the fiber optic path,
independent of system motion, which is the case because there is no
relative motion in the source-fiber-comparator path; they all move
together.
[0046] This one-way propagation time measurement is approximately
one million times more sensitive than the round trip propagation
used in the MMX. The invention works on the Earth's surface.
Furthermore, accepting the propagation medium's presence and its
non-homogeneity, allows the invention to measure motion with
respect to the medium anywhere in the Universe, e.g., not only on
gravitational bodies but also in outer space.
[0047] FIG. 4 is a block diagram showing a measurement system 200
having a velocity v, 211. Included is a coherent light source 240,
such as a laser, emitting a narrow light beam 241 in the direction
of the system motion from a source 250 through a vacuum path 280
(or through an air path on Earth). This first light beam is
received at a receiver 252, which may be a photo-electric converter
such as a photo cell, photo diode, PIN diode, PIN photodiode or
equivalent, converting the light into an electrical signal, which
is then transmitted to the comparator 290 through a metal wire.
Distance d 260 is a fixed distance between the source and receiver
within the system. Delta d 270 is the additional distance that the
light beam 241 travels due to the system velocity.
[0048] The light beam is split producing a second beam 243, and a
second light path 282 (a reference signal) connects the laser 240
directly through a fiber optic cable to another receiver at the
comparator 290. The propagation time through the fiber optic cable
will be independent of the system motion because the light source
240, the fiber optic cable and comparator all move together with
the system, i.e., there is no relative motion of the fiber optic
cable with respect to the system 200. The two electrical outputs
from the two receivers are compared at the comparator 290. Graph
292 represents the second light beam via path 282 and graph 294
represents the first light beam via path 280 relative to the second
light beam. Shown is a phase difference 298. The two phases of both
light beams are compared at the comparator 290 and are used to
calculate the system speed v 211 as described below with respect to
FIG. 7. A support tube 288 may be provided for rigidity and
protection for large separation distances d 260. Instead of a beam
splitter, a light siphon may be used to siphon the second light
beam from the first light beam. The comparator may even measure the
phases of the light beams directly from the electrical laser signal
without the need of a photo-electric converter.
[0049] In another embodiment, a fiber optic cable is not needed on
path 282. The reference signal does not have to be sent down the
path 282 as a light beam; it can be an electrical signal. In this
embodiment, the laser source is monitored by a photo-electric
converter at the light source, which converts the received second
light beam into an electrical signal (measuring both the frequency
and phase of the source) and transmits the signal directly to the
phase comparator 290 through a metal wire (for example) to be
compared with the electrical signal from the first light beam. Even
thought there will be a very small air gap between the source of
the second beam and the photo-electric converter at the light
source (which will cause the second light beam to travel an
extremely small distance in addition to d), this air gap will
introduce a negligible error as long as the gap size is a small
fraction of d. For example, if the air gap is 1% of d it will
introduce a 1% error in the speed measurement. Further, the
converter can be in direct contact with the light source, or its
electrical signal derived directly from the light source.
[0050] In yet another embodiment, a mechanism other than a fiber
optic cable may be used if the electromagnetic signal is other than
a visible beam of light. For example, if the electromagnetic signal
uses a microwave source, then path 282 may use metal wire instead
of a fiber optic cable. Or, if the electromagnetic signal has a
frequency higher than that of visible light (e.g., ultraviolet
light), then path 282 may use an optical cable with a UV bandwidth.
One of skill in the art will be able to choose the appropriate
mechanism for transmitting a suitable electromagnetic signal from
source 240 to an appropriate receiver via path 282 in order to
ensure that the distance traveled by the electromagnetic signal on
path 282 is independent of the velocity of system 200.
[0051] FIG. 5 is a block diagram showing a two-way measurement
system 300 having a velocity v, 311. Distance d 360 is the distance
between sources 350a,b and receivers 352a,b. In this embodiment,
two one-way systems, each moving relative to the propagation
medium, are shown facing in opposite directions. This arrangement
creates phase differences in each direction in the two phase
comparators 390a and 390b. The electrical outputs from the two
comparators are transmitted via a communication channel 320 (the
channel being conducting metal, a fiber optic cable, a wireless
signal, etc.). A computing device (computer, laptop, handheld
device, integrated circuit, analog circuit, etc., not shown in this
figure) receives the outputs from both comparators 390a and 390b
via channel 320 and may perform the addition or subtraction of the
two phase differences, as well as calculate the system speed v 311,
as described below.
[0052] The first one-way system includes a laser 340a emitting a
light beam from source 350a in the direction of the system motion,
through a vacuum path (or air path) 380a. The light beam is
received at a receiver 352a. Delta d 370a is the additional
distance that the light beam travels because of the system motion.
The light beam is split, and a second light path 382a connects the
laser 340a directly through a fiber optic cable to the receiver.
The output from the receiver (from both beams of light) is input to
a phase comparator 390a located at the receiver.
[0053] The second one-way system includes a laser 340b emitting a
light beam from source 350b in the opposite direction of the system
motion, through a vacuum path (or air path) 380b. The light beam is
received at a receiver 352b. Delta d 370b is the distance that the
light beam does not have to travel because the beam is moving
against the direction of system motion. The light beam is split,
and a second light path 382b connects the laser 340b directly
through a fiber optic cable to the receiver. The output from the
receiver (from both beams of light) is input to a phase comparator
390b located at the receiver.
[0054] To improve sensitivity, or to keep the separation distance d
small, the propagation path of the light beam (via the air path or
vacuum path in the stationary medium, the variant path) may be
increased over the original distance d, as illustrated in FIGS. 6A,
6B and 6C. The propagation path delay does not have to be in the
direction of motion, as long as the resulting delay causes a
propagation delay in the propagation medium in the direction of
motion. FIG. 6A shows a standard measurement system 410. A light
beam travels from a source 250 to a receiver 252 via a path 280
through the stationary propagation medium, the source and receiver
being separated by a distance d 260. When system 410 has a
velocity, the light beam travels an extra .DELTA.d, 270.
[0055] FIG. 6B illustrates the propagation path length being
increased in the stationary medium by reflecting the light beam
sideways using mirrors 425 forming a light zigzag path 481, all
moving with the system 420 having a velocity v. The source and
receiver are still separated by distance d 260. The propagation
path length traveled by the light beam from source to receiver is
increased over d, not only by the longer zigzag path 481, but also
due to the extra movement of the receiver away from the source
emission point, through the extra propagation delay (distance
traveled in the zigzag), and the velocity of system 420.
[0056] FIG. 6C shows the propagation path length increased in the
stationary medium by passing the light beam through a fiber optic
coil 435, also moving with system 430, for a portion of the
propagation path. The light beam travels on a path 482 through the
stationary medium (e.g., via air or vacuum) before entering coil
435 and after exiting coil 435. In order to maximize the light
transfer from the stationary medium to the fiber coil and from the
fiber coil to stationary medium, light focusing devices 437 (lenses
or equivalent) may be used, also moving with the system. The
propagation path length traveled by the light beam from source to
receiver is increased over d, not only by the longer path through
the fiber optic coil, but also due to movement of the receiver away
from the source emission point because of the velocity of system
through the extra propagation delay (time traveled in the fiber
optic coil), and the velocity of system 430. The fiber coil may be
directly connected to the source as long as there exists an air gap
(or vacuum gap) on the detector side, thus causing the light beam
to travel farther in the medium when it is traveling in the
direction of system motion.
Mode of Operation
[0057] The propagation distance in the propagation medium (whether
in a vacuum in space or in an air path on Earth, for example), as
illustrated in FIG. 4, is d when the system 200 is stationary,
i.e., v=0. The propagation distance becomes d+.DELTA.d with the
system in motion, the light beam moving in the direction of motion,
relative to the propagation medium. This propagation distance
increase (or decrease) produces a propagation time difference and
therefore a phase difference at the phase comparator, compared with
the light beam transmitted directly from the laser (source) to the
phase comparator (receiver), through the fiber optic cable. Of
course, if the system moves in the opposite direction the light
beam will travel a distance d-.DELTA.d because the light beam is
moving against the direction of motion.
[0058] The propagation time t between two stationary fixed points
of separation d, is t=d/c. If the system moves at velocity v, then
the incremental distance travelled by the system in time t' is
.DELTA.d=vt'=v(d+.DELTA.d)/c=M(d+.DELTA.d), i.e.,
.DELTA.d=[M/(1-M)]d Md for M=v/c<<1, M is typically 10.sup.-6
at Earth speeds. The incremental propagation time is then
.DELTA.t=Mt, as shown below in Equation (2):
.DELTA.t=.DELTA.d/c=Md/c=Mt, and phase change
.DELTA..phi.=2.pi.f.DELTA.t, where M=v/c and t=d/c (2)
[0059] If N is the number of interference fringes (2.pi. phase
rotations), f is the frequency and .lamda., the wavelength of the
source (e.g., a laser), then Equation (3) shows:
N=.DELTA..phi./2.pi.=f.DELTA.t=fvd/c.sup.2=fMd/c=Md/.lamda. (3)
[0060] If v=300 m/s (670 miles/hour), c=3.times.10.sup.8 m/s,
M=10.sup.-6, red laser .lamda., =6.times.10.sup.-7 m,
f=c/.lamda.=5.times.10.sup.14 Hz, distance d=3 m, then
N=10.sup.-6.times.3.times.6.sup.-1.times.10.sup.7=5 fringes.
Whereas for the Michelson and Morley Experiment (MMX), the round
trip propagation time, in and against the direction of motion is
t.sub.MMX, where a is the Lorentz contraction factor. The
incremental propagation time is then Lt::M.sup.2t, as shown below
in Equations (4) and (5):
t.sub.MMX=.alpha.dc.sup.-1[{1/(1-M)}+{1/(1-M)}]=.alpha.dc.sup.-12.alpha.-
.sup.-2=.alpha..sup.-12d/c.apprxeq.(1+M.sup.2/2)(2d/c) and
.DELTA.t.apprxeq.M.sup.2t,t=d/c (4)
as
[{1/(1-M)}+{]/(1+M)}]=2/.alpha..sup.2 and
.alpha..sup.2=(1-M)(1-M.sup.2)=(1-M.sup.2) (5)
[0061] Then, the number of expected fringes is shown by Equation
(6):
N=f.DELTA.t=fM.sup.2d/c=M.sup.2d/.lamda.=10.sup.-12.times.3.times.6.sup.-
-1.times.10.sup.7=5.times.10.sup.-6 fringes (6)
[0062] In other words, the MMX system, because of the M.sup.2 term
(rather than the M term in the present invention), is one million
times less sensitive than the present invention at practical
speeds. To increase the sensitivity of the present invention
further, a dual system can be used, as illustrated in FIG. 5.
Measuring the individual phase changes separately (both upstream
and downstream) and adding their magnitudes increases the
sensitivity to motion. The sensitivity can be increased still
further, by increasing the propagation medium path length (thus
increasing the propagation delay) without increasing the overall
dimension d, by inserting a mirror zigzag or a coiled fiber optic
cable, also moving with the system, as illustrated in FIGS. 6A, 6B
and 6C.
Specific Embodiments
[0063] FIG. 7 is a flow diagram describing one specific embodiment
by which the speed of a moving apparatus is measured and is
explained in the context of FIG. 4, although the invention is not
limited to the embodiment of that figure. In general, the system
does not measure absolute velocity; it measures velocity relative
to the propagation medium, whether the medium is stationary on the
Earth's surface or at rest in space. For absolute motion the
velocity of the propagation medium relative to absolute space has
to be taken into account.
[0064] In a first step 504 light from a laser 240 is transmitted
via two different paths from a source 250 to a receiver 252 when
the apparatus is at rest with respect to the stationary medium
(e.g., with respect to the surface of the Earth). The laser may be
split using a conventional beam splitter in order to direct the
beam via two different paths, although other techniques such as a
light siphoning may also be used to direct the laser bean down the
two different paths. As mentioned above, the reference signal may
instead use a photoelectric converter at the source to turn the
light signal into an electrical signal. Preferably, the two beams
are from a common source so if the phase of the source changes it
will change in both paths. Further, although a laser is described
as the light source, any coherent directional electromagnetic
source with a short enough wavelength can be used, such as a
microwave source (e.g., a maser). In general, the smaller the
wavelength of the electromagnetic source (the higher the
frequency), the more accurate the measurement will be.
Electromagnetic radiation having frequencies higher than that of
visible light (e.g., ultraviolet, x-rays and gamma rays) may also
be used in principle.
[0065] The stationary medium path 280 is one of the two paths that
the light beam traverses. On this path, there is relative motion
(between the measurement system and the propagation medium) when
the system is in motion and the light beam will travel a distance
longer than d when the laser is shining in the direction of motion
of the apparatus. When the apparatus is at rest with respect to the
stationary medium (e.g., at rest on the surface of the Earth), then
the light beam will travel a distance d on this path. On this path
the beam may be traveling through air, vacuum, a partial vacuum, a
gas, etc. There will be relative motion between the measurement
system and the propagation medium through which the light travels
when the system is in motion. Via this path 280, the light beam
travels a distance greater than d (when the apparatus is in motion)
because of the relative motion.
[0066] By contrast, the second path, path 282, is a path in which
the beam of light will always travel a fixed distance, regardless
of the velocity of the apparatus. In this example, the beam of
light on path 282 travels the entire distance on a fiber optic
cable between the laser and the receiver. Because the fiber optic
cable is attached to both the laser and the receiver, there is no
relative motion as the beam of light travels from the laser to the
receiver (i.e., the source, fiber cable, and receiver all travel
together). Accordingly, the distance traveled by the light beam
(and the time it takes) is independent of the speed of the system
and this path may be used as a reference. As mentioned previously,
the light source may be converted to an electrical signal on this
second path and transmitted in a metal wire directly to the
comparator.
[0067] In addition, it is not strictly necessary that a light beam
from a laser travel via path 282. Any electromagnetic signal that
originates in conjunction with the laser source may be sent via a
fixed propagation distance through which the electromagnetic signal
can propagate. For example, an electrical signal generated at the
laser source may be sent via a copper wire that connects the laser
directly to the comparator. In this example, the phase comparator
290 would detect the phase difference between the laser beam
arriving via path 280 and photo electric converter and the
electrical signal arriving via path 282. Preferably, the signal has
a very small wavelength making measurement more accurate. As
mentioned above, the electromagnetic signal via path 282 be taken
directly from the laser or a small air gap may be used.
[0068] Preferably, the laser via path 280 is shining in the
direction of motion of the apparatus, that is, in the direction of
velocity 211. Minor variations in the direction of the laser
different from the direction of motion will affect the final speed
calculation, making it appear as if the apparatus is traveling
slower than it actually is. Depending upon the application, this
error in the speed calculation may be within a margin of error that
is acceptable for the application. In an alternative embodiment, it
is contemplated that the laser via path 280 may be shining at a
known angle off of the direction of motion of the apparatus. For
example, the path from the source to the receiver may be at a
45.degree. angle from the direction of motion. A straightforward
mathematical calculation may then be used to adjust for this known
angle in order to obtain the correct speed of the apparatus.
Shining the laser at a known angle, however, will not result in a
final speed calculation that is as accurate as shining the laser in
the direction of motion.
[0069] In another alternative embodiment, the laser via path 280
may be scanned from side to side (or up and down) about a believed
direction of motion in order to determine the actual direction of
motion. Because the largest phase difference (with respect to the
laser via path 282) will occur when the laser via path 280 is
pointed in the direction of motion, the direction of motion can be
determined when the largest phase difference is detected as the
laser is scanned, either manually or automatically. This technique
may be used to orient the laser in the direction of motion.
[0070] In step 508 the phase comparator 290 located at the receiver
measures the phase difference between the two light beams received
via paths 280 and 282 while the apparatus is at rest. As mentioned,
these light signals may be converted to electrical signals through
a photoelectric converter. In the case of electromagnetic radiation
outside the spectrum of visible light other types of converters may
be used. For example, for wavelengths longer than that of visible
light (e.g., a maser) a radio receiver may be used, and for
wavelengths shorter than that of visible light (e.g., for
ultraviolet) a photoelectric converter with UV bandwidth may be
used. For ease of explanation, all of these types of converters
that convert electromagnetic radiation to an electrical signal will
be referred to as "photoelectric converters." It is believed that
most electrical phase comparators only work well up to frequencies
of about 10.sup.9 Hz. As laser light frequencies can be around
10.sup.14 Hz, for frequencies greater than about 10.sup.9 Hz, phase
comparison may use well known optical interference. Although the
phase difference between the two signals may not be measured
directly, the phase difference is measured through an amplitude
variation as a function of phase, using a PIN diode. Of course,
other known techniques for measuring the phase difference of the
two electromagnetic beams (or signals) may also be used. In fact,
later developed technologies for measuring phase difference may
also be used, such as improved electrical phase comparators able to
measure frequencies greater than 10.sup.9 Hz.
[0071] Then, any instrument or dedicated system able to measure
electrical time histories, able to compare and measure different
phases, may be used. Examples of types of phase comparators that
may be used include a dual beam oscilloscope or a computer with a
digital time history capture facility and phase comparison
software. This phase difference is referred to as a reference phase
difference because it measures the phase difference when the
apparatus is at rest or at another known speed. The comparator need
not necessarily be aware of how many times the phase repeats itself
(number of 2.pi. radians), it may simply measure the overall phase
difference.
[0072] The system always measures the velocity of the apparatus
compared to the surrounding propagation medium, i.e., the final
speed calculated in step 524 will be the speed of the apparatus
with respect to the medium. If the medium is moving then its total
(absolute) speed will be the system speed relative to the medium
plus the medium's speed relative to the medium at rest in space
away from any gravitational bodies (Universe). The reference phase
difference (at zero velocity) can be measured while the apparatus
is at rest with the medium on the surface of the Earth, or at rest
with the medium in space. [0053] In step 512 the light beam is
again transmitted via the air path 280 and via the fiber optic path
282 while the apparatus is in motion with respect to the surface of
the Earth (and with respect to the stationary propagation medium)
and has a velocity v. In step 516 a phase difference is measured at
the phase comparator 290 between the two beams that have traveled
along different paths. Because the apparatus is now in motion, the
distance traveled by the light beam over the air path 280 will now
be a distance d plus a distance .DELTA.d (resulting in a phase
difference with respect to the measurement made in step 508).
[0073] Accordingly, in step 520 a total phase difference is
determined between the phase difference measurements in step 508
and the phase difference measured in step 516. In one embodiment,
the reference phase difference from step 508 is subtracted from the
velocity phase difference from step 516 to provide the total phase
difference. For example, if L.sub.V is the light source phase
common to both paths 280 and 282, S.sub.V is the vacuum signal path
delay phase at a velocity v, and R is the reference path phase
independent of v, then the comparator velocity phase difference at
velocity v is given by:
.DELTA..phi..sub.v=(L.sub.v+S.sub.v)-(L.sub.v+R)=S.sub.v-R (7)
[0074] In other words, Equation (7) is independent of light source
L.sub.V phase variations. At zero velocity the reference phase
difference at the comparator will be
(L.sub.V'+S.sub.O)-(L.sub.V'+R) and the phase difference between
this and Equation (7) is:
.DELTA..phi..sub.v=[(L.sub.v'+S.sub.v)-(L.sub.v'+R)]-[(L.sub.v+S.sub.o)--
(L.sub.v'+R)]=S.sub.v-R-(S.sub.o-R)=S.sub.v-S.sub.o (8)
If there is no reference path R then Equation (8) becomes
.DELTA..phi..sub.v=(L.sub.v+S.sub.v)-(L.sub.v'+S.sub.o)=(L.sub.v-L.sub.v-
')+(S.sub.v-S.sub.o).apprxeq.S.sub.v-S.sub.o (9)
providing the light intensity variation (L.sub.V-L.sub.V') is small
compared to S.sub.V-S.sub.O. This is the total phase difference
(step 520) due to the velocity of the system. If the light source
phase (frequency) is ultra stable, i.e., L.sub.V can be considered
to be constant over the two measurements, the reference phase R,
can be discarded. But This is not practical for light frequencies,
where the phase differences that are being measured are very small
indeed.
[0075] Next, in step 524 the speed of the apparatus (with respect
to the surface of the Earth and the stationary propagation medium)
is determined using the total phase difference, the frequency of
the light beam, the speed of light via the air path and distance d
260. Because the phase difference is given by
.DELTA..phi.=2.pi.f.DELTA.t, this means that
.DELTA.t=.DELTA..phi./2.pi.f. And, because
.DELTA.t=.DELTA.d/c=vt/c=vd/c.sup.2, where t=d/c, thus the velocity
of the apparatus v=.DELTA.tc.sup.2/d. Therefore, the velocity of
the apparatus may be determined from the total phase difference,
the light frequency, the speed of light and the fixed distance
d.
[0076] In a similar fashion, the speed of a spacecraft or other
object in outer space may also be calculated. The speed calculated
will be relative to the propagation medium. The system does not
measure absolute velocity; it only measures velocity relative to
the propagation medium, whether the medium is stationary on the
Earth's surface or at rest in space.
[0077] In another specific embodiment, the invention may be
explained in the context of the two-way measurement system of FIG.
5. In this embodiment, phase comparator 390a detects a phase
difference +.DELTA..phi. while the system 300 has a velocity 311,
and phase comparator 390b detects a phase difference -.DELTA..phi.
also while the system has a velocity 311. The two phase differences
may then be used to determine the velocity of system. In this
example, a reference phase difference at each comparator is
measured when the system is at rest as has been described above in
steps 504 and 508. Next, a velocity phase difference is measured as
in step 516 for each comparator. A total phase difference is then
determined for each comparator as in step 520 (i.e., a total phase
difference in the direction of motion and a total phase difference
against the direction of motion). The absolute value of each total
phase difference is taken and half the value of the two values
added together produces a final value, as given in Equation (10)
below. This final total phase difference may then be then be used
in step 524 to determine the velocity of the system.
[0078] A second embodiment of the two-way system measurement is
given in FIG. 8. Because two laser beams are used, and the distance
each beam travels is dependent upon the velocity of the apparatus,
no reference signal that travels a fixed distance is needed. As
long as the two lasers are synchronized (i.e., are in phase) they
may reference to each other. The output from the two photo-electric
converters (PECs) 791a,b are now fed to, and measured by, the same
phase comparator 790. There is now a common ground wire connection
720 between all components to complete the circuit and the two
lasers are now synchronized through a synchronization wire
connection 730 connecting the two lasers. The two lasers may be
synchronized by using a phase-locked loop or equivalent system.
[0079] Using the same terminology as Equation (9), if
|S.sub.V-S.sub.O|U is the modulus or magnitude of source phase with
velocity, minus the source phase with zero velocity, for the
upstream propagation, and |S.sub.V-S.sub.O|D is the value for
downstream propagation, then the total phase with velocity v will
be given by Equation (10):
.DELTA..phi..sub.v={|S.sub.v-S.sub.o|.sub.U+|S.sub.v-S.sub.o|.sub.D}/2={-
|.DELTA..phi..sub.v|.sub.U+|-.DELTA..phi..sub.v|.sub.D}/2 (10)
[0080] A third embodiment of the two-way system measurement is
given in FIG. 9. Here, a single laser 840 supplies the light for
both light paths. Again, because Two beams are used relative to
each other, no reference signal that travels a fixed distance is
needed. The beams are inherently synchronized because they emanate
from the same laser. Laser 840 supplies the downstream path as
usual (through a half-silvered glass 810), and the upstream path is
caused by the half-silvered glass 810 and a mirror 812 to reverse
the direction of the light. A common ground wire 820 is again
provided to complete the connection. Again, the output from the two
photo-electric converters (PECs) 891a,b are now fed to, and
measured by, the same phase comparator 890.
[0081] In other specific embodiments, the invention may be
explained in the context of systems 420 or 430 shown in FIGS. 6B
and 6C. In the context of a system 420, the light beam follows a
zigzag path 481 (or any other type of path other Than a single
linear path from the source to the receiver via air or a vacuum. In
Other words, path 481 is substituted for path 280 in the
measurement system of FIG. 4 and then calculations may be performed
as described in FIG. 7 above. Path 481 may also be substituted for
path 380a or 380b in the measurement system of FIG. 5.
[0082] In the context of system 430, the light beam follows a path
that includes not only an air gap 482 but also a fiber optic path
435. In other words, this path of system 430 may be substituted for
path 280 in the measurement system of FIG. 4 and then calculations
may be performed as described in FIG. 7 above. This path system 430
may also be substituted for path 380a or 380b in the measurement
system of FIG. 5.
Bulk Material as Invariant Reference Path
[0083] In an additional embodiment, a bulk material is used instead
of optical fiber to transmit the light from the source (e.g., a
laser) to the observer along the time-invariant reference path. If
one assumes that there is no relative motion between the source,
observer and optical fiber (they all move together) then there
would be complete light convection, i.e., no phase change with
system motion, giving an invariant propagation time along the
reference path. It is realized, however, that the stationary
propagation medium (whether the propagation medium in outer space
or the medium at rest on the Earth's surface) can dominate, where
the source and optical fiber (having a relatively low transparent
mass), are compared relative to this medium. It is observed that
mass on the order of a small planet may be required for the medium
to dominate. The light may be only partially convected according to
Fresnel (1818) and Fiseau (1851), possibly giving avariant
propagation time for light along the optical fiber reference path
and affecting accuracy of the measurement. For complete convection
(an invariant propagation time) to occur, the source, observer and
optical reference path are best contained within a bulk material
reference path, of refractive index n>1, which allows for
complete light convection.
[0084] FIG. 10 illustrates a source, observer, and bulk material
all moving together. Similar to FIG. 1, system 100 has a velocity,
v 141, and includes a source 150 (such as a laser) and a receiver
155 (such as a pin diode detector) separated by distance d 160, a
stationary medium path 180 (through a vacuum or air, for example),
a bulk material path 602, and a bulk material 604. Bulk material
604 may be any suitable material such as a large mass of a
transparent solid material or transparent liquid material (such as
water) where the refractive index is greater than one. Or, material
604 may be a large mass of a non-transparent liquid or
non-transparent solid (such as lead), as long as its refractive
index is greater than one. Preferably, material 604 is not a gas
(such as air or other) whose refractive index is very close to 1.
The type and mass of the bulk material may be adjusted so that
complete convection occurs along path 602 and the propagation time
is invariant.
[0085] Phase comparison may be accomplished using any of the
techniques discussed above. As is known, phase comparison is used
to detect and measure phase differences between the two signals on
paths 180 and 602. As shown, the source, receiver and path 602 are
all contained within bulk material 604, thus providing for complete
light convection along path 602. The lower stationary medium path
180 (where the refractive index n.apprxeq.1 when the path is
through air or a gas), which has a variant propagation time
depending upon speed, is used to help measure the system velocity v
as has been described above.
Normal Round Trip Propagation Time as Invariant Reference Path
[0086] The invariant property of the round-trip propagation time
(RTPT) normal (perpendicular) to the direction of motion may be
also be used as the invariant reference path in order to measure
the propagation difference through motion in the direction of
motion, instead of using a fiber optic path or a bulk material
path.
[0087] FIG. 11 illustrates a system 610 that uses a zigzag path
with mirrors in order to increase the propagation distance of the
reference path and thus the measurement time (sensitivity). Shown
is a source 620, a receiver 622, and mirrors 625 and 627 used to
create stationary medium path 630, 631. Mirrors 635 and 637 are
used to create the invariant round trip path 640, having a length,
l, 644. The solid line 630 shows the original positions of the
source 620 and receiver 622, while the dotted line 631 shows the
full path traveled by light from the source when the system is in
motion, showing the reception positions 621 and 623 of both the
source and receiver. The two signals that propagate along the upper
and lower paths 640 and 630, 631 arrive at receiver 622 where the
phase difference is measured as has been discussed above.
[0088] Thus, the time t for light to travel the upper invariant
zigzag path, where 1 is the length of the zigzag, and n is the
number of zigzags, is:
t=d/c=n2l/c (11)
The additional distance .DELTA.d travelled in this time tin the
lower path in the direction of motion is:
.DELTA.d=vt,.DELTA.t=.DELTA.d/c=(v/c)t=Mt=Mn2l/c (12)
Here, .DELTA.t may be measured at the receiver (e.g., a pin diode
detector) through interference between the two optical paths. The
number of interference fringes (2.pi.radians) is then:
N=.DELTA.tc/.lamda.=(v/c)(d/c)(c/.lamda.)=Md/.lamda. (13)
[0089] As an example, if l=1 m, n=1, d=2 m, v=30 m/s (67
miles/hour), M=v/c=30/3.times.10.sup.8=10.sup.-7, and
.lamda.=6.times.10.sup.-7, then N=Md/.lamda.=1/3 (120.degree.).
Since 90.degree. corresponds to the first maximum (fringe), speeds
well below 30 m/s may be easily be detected using this
embodiment.
Fiber Optic Coil as Invariant Reference Path
[0090] FIG. 12 illustrates a system 660 using a coil of optical
fiber as an invariant reference path. The optical zigzag system of
FIG. 11 can be prone to vibration and thus alignment issues at
these very small wavelengths, causing a loss in measurement
accuracy. Accordingly, use of a fiber optic coil instead can
improve accuracy because light is not appreciably convected by
moving optical fibers. Although the light is guided in the fiber it
behaves as though it were being transmitted in a vacuum (or in
air).
[0091] System 660 includes a source 670 (e.g. a laser), a receiver
672 (e.g., a PIN diode) and a path 680. Positions 671 and 673 show
positions of the source and receiver after movement of the system
having a velocity, v. Light from the source passes through a
polarizer 676 before traveling along path 680 or along path 690.
Path 680 is the stationary medium path (the variant path), and may
include a path through air, a vacuum or a direct connection. Light
on the invariant path travels through polarizer 676, phase shifter
692 and coupler 694 before entering a coil 696 of optical fiber.
The light is reflected back by mirror 698 before entering coupler
694 where it is passed on to the receiver 672.
[0092] The fixed propagation distance of path 690 is then
d=n2.pi.r, where n is the number of optical turns of single mode
(SM) fiber in coil 696. The light from the source is polarized at
676, for example, through stress created in the fiber using several
tight loops of the optical fiber, or by using a more expensive
magnetic polarizer. The polarized light is bi-refringent, i.e., it
has two orthogonal modes, which, through random variations in fiber
stress (by bending and construction of the fiber), create different
mode speeds (refractive indices) along the fiber, depreciating its
coherence. The polarized light is then split into two paths, the
lower path 680 going directly to the receiver 672. This direct path
is preferably as short as possible, i.e., less than the
polarization coherence length, where the polarization still remains
substantially unaltered. An alternative method is to connect path
680 to the receiver via the coupler 694.
[0093] The upper path 690 passes through a phase shifter 692, for
example, using a paddle wheel of several turns of optical fiber
wound on a disk that can be rotated around the direction of motion,
or by using a magnetic polarizer. The light is then passed through
coupler 694 to the many turns of the optical fiber coil 696. It is
then rotated by 45.degree., reflected back through the coil and
rotated again by 45.degree. by a Faraday rotator mirror 698 (for
example), which rotates the orthogonal modes by 90.degree..
[0094] The light is then returned along the fiber coil to the light
coupler 694 where the signal is passed on to the receiver 672. Use
of this repeated replica path in reverse tends to undo the random
polarization effects in the forward direction, restoring the
coherent polarization of the light. This allows large lengths of
optical fiber to be used in this invariant time delay path 690,
with maintained coherence, so that interference with the
time-variant direct path 680 can be obtained. An alternative to
this embodiment (using the rotator mirror and a repeated replica
path) is to use polarizing maintaining (PM) optical fiber which is
very expensive when hundreds of meters are used in the optical
fiber coil 696. In this alternative, path 690 passes through
coupler 694, through a coil of PM fiber, and then directly into
coupler 694 before being passed to the receiver 672 for
interference with light from path 680.
Additional Embodiments
[0095] 15. The present invention also includes additional
embodiments which are listed below.
[0096] A method of measuring a velocity of an apparatus, said
method comprising:
[0097] while said apparatus is at a reference velocity,
transmitting a first coherent electromagnetic beam via a first path
on said apparatus to a first receiver, wherein a distance said
first beam travels via said first path is dependent on any velocity
of said apparatus;
[0098] while said apparatus is at said reference velocity,
transmitting a second coherent electromagnetic beam via a second
path on said apparatus in a direction opposite to said first beam
to a second receiver, wherein a distance said second beam travels
via said second path is dependent of any velocity of said
apparatus, said second beam being in phase with said first
beam;
[0099] determining a reference phase difference at said receivers
between said first beam traveling via said first path at said
reference velocity and said second beam traveling via said second
path at said reference velocity;
[0100] while said apparatus is at said velocity, determining a
velocity phase difference at said receivers between said first beam
traveling via said first path and said second beam traveling via
said second path;
[0101] determining a total phase difference between said velocity
phase difference and said reference phase difference; and
[0102] calculating said velocity of said apparatus using at least
said total phase difference, a frequency of said first beam, and
the speed of light.
16. The method as recited in claim 15 wherein said first and second
beams originate from different sources, said method further
comprising:
[0103] synchronizing said different sources so that said second
beam is in phase with said first beam.
17. The method as recited in claim 15 wherein said first and second
beams originate from a single source. 18. An apparatus for
calculating a velocity of said apparatus, said apparatus
comprising:
[0104] a first receiver;
[0105] a second receiver;
[0106] a source that generates a coherent electromagnetic beam that
is directed toward said first receiver via a first path and that is
directed toward said second receiver via a second path, wherein a
distance said electromagnetic beam travels via said first path and
via said second path is dependent on any velocity of said
apparatus;
[0107] a phase comparator coupled to said first and second
receivers, said phase comparator being arranged to determine a
reference phase difference between said electromagnetic beam
traveling via said first path and said electromagnetic beam
traveling via said second path when said apparatus is at a
reference velocity, said phase comparator being further arranged to
determine a velocity phase difference between said electromagnetic
beam traveling via said first path and said electromagnetic beam
traveling via said second path when said apparatus is at said
velocity; and
[0108] a computing device arranged to calculate said velocity of
said apparatus using at least said reference phase difference, said
velocity phase difference, a frequency of said electromagnetic
beam, and the speed of light.
19. The apparatus as recited in claim 18 wherein said
electromagnetic beam propagates in a propagation medium. 20. The
apparatus as recited in claim 18 wherein said source includes a
first source that generates a first coherent electromagnetic beam
via said first path and a second source that generates a second
coherent electromagnetic beam via said second path, said apparatus
further comprising:
[0109] a synchronization mechanism for synchronizing said first and
second sources such that said first and second beams are in phase
upon leaving said respective first and second sources.
27. An apparatus as recited in claim 18 wherein said first and
second paths are in opposite directions. 28. A method of measuring
a velocity of an apparatus, said method comprising:
[0110] determining a first reference phase difference between a
first coherent electromagnetic beam traveling via a first path at a
reference velocity and said first beam traveling via a second path
at said reference velocity, wherein a distance traveled via said
first path is dependent upon said velocity, and wherein a distance
traveled via said second path is independent of said velocity;
[0111] determining a second reference phase difference between a
second coherent electromagnetic beam traveling via a third path at
a reference velocity and said second beam traveling via a fourth
path at said reference velocity, wherein a distance traveled via
said third path being dependent upon said velocity, and wherein a
distance traveled via said fourth path being independent of said
velocity;
[0112] while said apparatus is at said velocity, determining a
first velocity phase difference between said first beam traveling
via said first path and said first beam traveling via said second
path;
[0113] while said apparatus is at said velocity, determining a
second velocity phase difference between said second beam traveling
via said third path and said second beam traveling via said fourth
path;
[0114] determining a first total phase difference between said
first velocity phase difference and said first reference phase
difference, and determining a second total phase difference between
said second velocity phase difference and said second reference
phase difference; and
[0115] calculating said velocity of said apparatus using at least
said first total phase difference, said second total phase
difference, frequencies of said first and second light beams, and
the speed of light.
29. A method as recited in claim 28 wherein said reference velocity
is zero relative to the surface of the Earth. 30. A method as
recited in claim 28 wherein said first beam traveling via said
first path travels in the direction of said velocity of said
apparatus, and wherein said second beam traveling via said third
path travels in the opposite direction of said velocity of said
apparatus. 31. A method as recited in claim 28 wherein said first
beam traveling via said first path and said second beam traveling
via said third path propagate in a propagation medium. 32. A method
as recited in claim 28 further comprising:
[0116] adding together the magnitude of said first total phase
difference and the magnitude of said second total phase difference
and using this sum to perform said calculating said velocity.
33. An apparatus for calculating a velocity of said apparatus, said
apparatus comprising:
[0117] a first receiver;
[0118] a second receiver;
[0119] a third receiver;
[0120] a fourth receiver;
[0121] a first source that generates a first coherent
electromagnetic beam that is directed toward said first receiver
via a first path and that is directed toward said second receiver
via a second path, wherein a distance said first beam travels via
said first path is dependent on any velocity of said apparatus, and
wherein a distance said first beam travels via said second path is
independent of any velocity of said apparatus;
[0122] a second source that generates a second coherent
electromagnetic beam that is directed toward said third receiver
via a third path and that is directed toward said fourth receiver
via a fourth path, wherein a distance said second beam travels via
said third path is dependent on any velocity of said apparatus, and
wherein a distance said second beam travels via said fourth path is
independent of any velocity of said apparatus;
[0123] a first phase comparator coupled to said first and second
receivers, said first phase comparator being arranged to determine
a first reference phase difference between said first beam
traveling via said first path and said first beam traveling via
said second path when said apparatus is at a reference velocity,
said first phase comparator being further arranged to determine a
first velocity phase difference between said first beam traveling
via said first path and said first beam traveling via said second
path when said apparatus is at said velocity;
[0124] a second phase comparator coupled to said third and fourth
receivers, said second phase comparator being arranged to determine
a second reference phase difference between said second beam
traveling via said third path and said second beam traveling via
said fourth path when said apparatus is at said reference velocity,
said second phase comparator being further arranged to determine a
second velocity phase difference between said second beam traveling
via said third path and said second beam traveling via said fourth
path when said apparatus is at said velocity; and
[0125] a computing device arranged to calculate said velocity of
said apparatus using at least said first and second reference phase
differences, said first and second velocity phase differences,
frequencies of said first and second beams, and the speed of
light.
Further Embodiment
The Invariant Path
[0126] It is realized that a fiber loop or loops in the invariant
optical path helps create the best invariant reference to the
variant light path which is in the direction of motion. Such fiber
loops may be of any number, and may be wound in a flat fashion,
cylindrical fashion, or other. Such a coil will work with any of
the figures shown having an invariant light path where a coil is
referenced.
[0127] Electromagnetic propagation time asymmetry can be shown to
be present around all moving systems. The instrument of the present
invention reveals motion by recognizing anisotropy in free space.
Propagation in air, a vacuum, or free space is commonly understood.
It is also important to understand how light propagates in bulk
transparent materials or in fiber optic cables compared with a
vacuum (e.g.) through the stationary medium.
[0128] Light traveling in a fiber is only partially convected. The
fiber, however, does not drag the light very much at all as it
moves through the stationary medium, so it can almost be regarded
the same way as propagation in a vacuum. For instance, fiber optic
gyroscopes (FOGs), used in inertial guidance systems work well
because insignificant convection takes place. Fresnel, who
pioneered research in partial convection, and Fizeau who later
added convection in water, found that bulk material convects light
in such a small percentage that it can almost be regarded as
convection in a vacuum for the sake of the operation of modern
instruments.
[0129] Further analysis finds that electromagnetic propagation at
right angles (normal) to the direction of motion does not affect
propagation time at all, whether the instrument is standing still
or in motion. This property is what gave Einstein and contemporary
physicists the idea that there is no change to stationary and
moving systems. If you propagate light in a zig-zag (e.g., as in
FIG. 11), however, propagation time does not vary at all whether
the instrument is standing or moving; this characteristic is used
as the standard invariant time unit to compare and measure
motion.
[0130] The resulting propagation time asymmetry is measured and
calibrated to a speed by comparing phase changes between light
traveling in the two paths, one in the direction of motion vs.
propagation normal to the direction of motion. FIG. 12 illustrates
how the invariant zig-zag optical path may be converted into an
invariant fiber optic path. The invariant loop (or loops) works
because the up and down components of propagation are normal to the
direction of motion and also because the forward and backwards
components in the direction of travel cancel out the asymmetry.
Propagation time in any invariant path may be increased with the
number of zig-zags or loops in the fiber optic cable. The more
zig-zags or the longer the looped fiber optic cable in the
invariant path, the more the instrument can travel horizontally
during the measurement, resulting in an increase in horizontal
phase change, greatly increasing the sensitivity of the
instrument.
[0131] One preferred commercial embodiment is to use dual-mode
telecommunications-grade fiber cable in the embodiment of FIG. 12,
or in any other embodiment where a fiber coil is used. Such a fiber
coil requires a Faraday mirror and reflection back (as shown in
FIG. 12). Use of PM cable does not require a mirror and reflection
back (and can be easier and simpler to implement), but can be
expensive.
Further Embodiment
The Variant Path
[0132] The variant path may be fiber optic cable (preferably PM
cable), a bulk transparent material (as described above) or free
space (e.g., air, vacuum as described above), where the EM
radiation propagates in the direction of motion. Increasing the
path length will improve system sensitivity (as well as in the
invariant path). It has been discovered that there is negligible
convection in fiber optic cable (or in any transparent material),
that is why it may be used instead of free space for the variant
path. Preferably, a linear fiber optic cable is orientated in the
direction of motion for the variant path instead of free space
because it is believed that the instrument will be more stable when
in motion.
Further Embodiment
Invariant Path Coiled Around a Shape
[0133] FIG. 14 shows another embodiment for the invariant light
path. Instead of a straightforward flat or cylindrical fiber coil
in the invariant light path, the fiber optic cable is coiled around
a torus, for example, or similar shape. One coil every 120 degrees
is a minimum configuration, although multiple coils improve
performance. Such coiling has an advantage because it can add more
stability when the instrument travels through a transition zone
(about 10 km above the earth) where the propagation medium
fluctuates as it changes from stationary with respect to the Earth
to orbiting with the Earth, or in the polar regions where the
medium is more turbulent. The torus needs a Faraday mirror at the
end of the coiled cable when using non-PM fiber cable (as
implemented in FIG. 12). When using PM fiber cable then no mirror
at the end is needed and the signal does not need to be reflected
back.
[0134] Of course, the loops on the torus do not have to be 120
degrees apart. For example, there may be four loops that are each
90 degrees apart, or, six loops that are each 60 degrees apart,
etc. In general, a minimum configuration for the torus embodiment
is three wraps 120 degrees apart so that each coil moves or rotates
equally in three-dimensional space. Other configurations beyond
that would also work well. A preferred configuration is to wrap the
torus equally all around (with no spacing between loops) with
whichever length of fiber is specified. In order for the instrument
to have the appropriate sensitivity at least 100 evenly spaced
wraps are preferred. The torus may be orientated in any convenient
direction. In one specific embodiment, 100 meters of fiber cable
(wrapped evenly around the torus) will be sensitive enough to
register "walking speed."
Further Embodiment Using PM Fiber Optic Cable as Invariant Path
[0135] FIG. 15 illustrates a measurement system 1000 using a coil
of polarization maintaining (PM) optical fiber as an invariant
reference path. The system described in FIG. 12 (without PM fiber)
may be more commercially viable due to the lower cost of materials;
however, the system presented in FIG. 15 may be easier to
construct.
[0136] System 1000 uses PM fiber optic cable exclusively in the
invariant path. It includes a source 1100 (e.g., a laser), two
receivers 1101 and 1102 (e.g., PIN diodes). Light from the laser
source 1100 is split into two paths by a 50/50 beamsplitter 1111.
The upper path 1110 is the stationary medium path (the variant
path) and may include a path through air, a vacuum or a direct
connection consisting of a linear (not coiled) fiber optic cable
oriented in the direction of motion of the instrument. Light on the
lower invariant path 1120 travels through a fiber optic cable for
interference with light from path 1110. The two detectors 1101 and
1102 collect the light from the interfering fringes from both paths
in order to double the strength of the signal received. The mirror
1130 is provided to simply guide the light from path 1110 to the
50/50 beamsplitter 1112. Collimators 11140 and 11141 are used to
guide the output from the laser source 1100 into and out of the
fiber optic cable. If path 1110 were to use a fiber optic cable,
there would be no need for the mirror 1130 and the collimators 1140
and 1141, and the 50/50 beamsplitters 1111 and 1112 would be
replaced by two PM fiber optic couplers.
Further Embodiment
Fiber Cable in Both Paths
[0137] FIG. 16 is a block diagram of a measurement system in which
the beam travels in a solid medium in both paths (in this example,
both paths are in fiber optic cable). The variant path is in the
direction of motion and the invariant path travels through any
number of fiber loops. If both paths are in fiber cable, both
cables may end at the same receiver. The receiver/detector may be a
PDA36A-Si Switchable Gain Detector, 350-1100 nm, 10 MHz BW, 13
mm.sup.2, 120 VAC, available from Thor Labs. Also, a pair of
PMC630-50B-APC--1.times.2 PM Coupler, 630 nm, 50:50, FC/APC Aligned
to Slow Axis, also available from Thor Labs, may be used to split
and to combine the variant and invariant fiber optic cable paths
and thus both end at a single detector. Photo diodes are a
component of the PDA36A, the other component of the PDA36A being
additional functionality to output a voltage based on the
brightness of the fringes. Thus, the photo diodes are configured to
output a voltage calibrated to the amount of light detected and are
used to measure the constructive/destructive interference.
Alternatively, CCD/CMOS sensors may be used to compare the outputs
of the two separate paths in order to calculate a velocity. The
collimator may be a Thorlabs F230APC-663 which is used to take the
output from the laser and guide it into the fiber optic cable. The
four, small unlabeled squares are the fiber connectors used to join
the inputs/outputs from each of the other instruments. They are not
strictly necessary and are optional in certain embodiments.
[0138] It has been found that a variant path length in the
direction of motion of about one meter of fiber optic cable and an
invariant path length of about 100 meters of coiled fiber optic
cable works well to calculate speed. A longer invariant path length
increases sensitivity and accuracy of the apparatus. The length of
the fiber coil may be ten times greater than the length of the
cable in the variant path, 50 times greater, 100 times greater or
more. While the variant path length should be in the direction of
motion, the loops of fiber optic cable in the invariant path length
do not need to oriented in any particular direction in
three-dimensional space.
Further Embodiment
Light Pulse
[0139] It is further realized that the instrument may be
implemented by sending a pulse of light in each of the two optical
paths instead of using interferometry with a steady laser beam to
detect the phase differences. Thus, instead of using
interferometry, a CCD/CMOS sensor array on each path may be used to
compare charge accumulation on the array produced by each of the
two signal paths. The pulse of light will be at the frequency and
power that is able to match the design capabilities of the specific
CCD/CMOS sensor. Each CCD/CMOS sensor is used to register a
periodic sampled difference in the accumulated charge (100 times a
second provides a reasonable granularity) and calibrate that to the
speed of the instrument. The variant and invariant pulse paths will
produce different amounts of charge energy: the invariant path
produces the same amount of charge energy at any speed and the
variant path produces successively smaller amounts of charge energy
as the instrument speed increases. Both paths may be aimed at
either two separate single sensor arrays or in different areas of a
single array; comparing the change in charge uses standard
techniques.
[0140] A CCD/CMOS sensor in pulse mode configuration is recommended
as it is believed that a continuous beam of light would overwhelm
the sensor, but a continuous beam may also be used with the
CCD/CMOS sensor. The pulses may be as short as contemporary
technology allows (currently a 250 MHz pulse repetition rate, less
than 100 fs pulse width with a central wavelength in the visible
light spectrum), or as long as it takes to create a measurable
charge at 100 samples or more per second on the CCD/CMOS array. The
calculation is based on contemporary sensor technology. Thus, for
example, in the system of FIG. 4, phase comparator 290 may be
replaced by a CCD array or other light detection device. The CCD
array may be used in any of the above embodiments. When the two
paths (invariant path and variant path) of a laser end at the same
location there may be a single receiver, the CCD/CMOS array, that
compares the two charges.
Further Embodiments
Conclusion
[0141] In general, it is now realized that in all of the
configurations described above that PM fiber may be used and that
the use of PM fiber especially in FIG. 12 will overcome the need
for the forward and back path in the coil involving the Faraday
mirror. It is also realized that a flat coil can be replaced with a
three-dimensional torus (or other shape), that the variant laser
path in free space can be replaced with a linear section of fiber
optic cable (preferably PM fiber) oriented in the direction of of
motion, and that a coil of fiber cable for the invariant path works
well.
Computer System Embodiment
[0142] FIGS. 13A and 13B illustrate a computer system 900 suitable
for implementing embodiments of the present invention. FIG. 13A
shows one possible physical form of the computer system. Of course,
the computer system may have many physical forms including an
integrated circuit, a printed circuit board, a small handheld
device (such as a mobile telephone or PDA), a personal computer or
a super computer. Computer system 900 includes a monitor 902, a
display 904, a housing 906, a disk drive 908, a keyboard 910 and a
mouse 912. Disk 914 is a computer-readable medium used to transfer
data to and from computer system 900.
[0143] FIG. 13B is an example of a block diagram for computer
system 900. Attached to system bus 920 are a wide variety of
subsystems. Processor(s) 922 (also referred to as central
processing units, or CPUs) are coupled to storage devices including
memory 924. Memory 924 includes random access memory (RAM) and
read-only memory (ROM). As is well known in the art, ROM acts to
transfer data and instructions uni-directionally to the CPU and RAM
is used typically to transfer data and instructions in a
bi-directional manner. Both of these types of memories may include
any suitable of the computer-readable media described below. A
fixed disk 926 is also coupled bi-directionally to CPU 922; it
provides additional data storage capacity and may also include any
of the computer-readable media described below. Fixed disk 926 may
be used to store programs, data and the like and is typically a
secondary mass storage medium (such as a hard disk, a solid-state
drive, a hybrid drive, flash memory, etc.) that can be slower than
primary storage but persists data. It will be appreciated that the
information retained within fixed disk 926, may, in appropriate
cases, be incorporated in standard fashion as virtual memory in
memory 924. Removable disk 914 may take the form of any of the
computer-readable media described below.
[0144] CPU 922 is also coupled to a variety of input/output devices
such as display 904, keyboard 910, mouse 912 and speakers 930. In
general, an input/output device may be any of: video displays,
track balls, mice, keyboards, microphones, touch-sensitive
displays, transducer card readers, magnetic or paper tape readers,
tablets, styluses, voice or handwriting recognizers, biometrics
readers, or other computers. CPU 922 optionally may be coupled to
another computer or telecommunications network using network
interface 940. With such a network interface, it is contemplated
that the CPU might receive information from the network, or might
output information to the network in the course of performing the
above-described method steps. Furthermore, method embodiments of
the present invention may execute solely upon CPU 922 or may
execute over a network such as the Internet in conjunction with a
remote CPU that shares a portion of the processing.
[0145] In addition, embodiments of the present invention further
relate to computer storage products with a computer-readable medium
that have computer code thereon for performing various
computer-implemented operations. The media and computer code may be
those specially designed and constructed for the purposes of the
present invention, or they may be of the kind well known and
available to those having skill in the computer software arts.
Examples of computer-readable media include, but are not limited
to: magnetic media such as hard disks, floppy disks, and magnetic
tape; optical media such as CD-ROMs and holographic devices;
magneto-optical media such as floptical disks; and hardware devices
that are specially configured to store and execute program code,
such as application-specific integrated circuits (ASICs),
programmable logic devices (PLDs) and ROM and RAM devices. Examples
of computer code include machine code, such as produced by a
compiler, and files containing higher-level code that are executed
by a computer using an interpreter.
[0146] Although the foregoing invention has been described in some
detail for purposes of clarity of understanding, it will be
apparent that certain changes and modifications may be practiced
within the scope of the appended claims. Therefore, the described
embodiments should be taken as illustrative and not restrictive,
and the invention should not be limited to the details given herein
but should be defined by the following claims and their full scope
of equivalents.
* * * * *