US 20050057756A1
(19) United States
(12) Patent Application Publication (10) Pub. No.: US 2005/0057756 A1
(43) Pub. Date:
Fang-Yen et al.
(54)
SYSTEMS AND METHODS FOR PHASE
MEASUREMENTS
(52)
U.S. c1. ............................................................ .. 356/497
(57)
(75) Inventors: Christopher M. Fang-Yen, Somerville,
MA (US); Gabriel Popescu, Brighton,
MA (US); Changhuei Yang, Pasadena,
CA (US); Adam Wax, Chapel Hill, NC
(US); Ramachandra R. Dasari,
Lexington, MA (US); Michael S. Feld,
Newton, MA (US)
Mar. 17, 2005
ABSTRACT
Preferred embodiments of the present invention are directed
to systems for phase measurement Which address the prob
lem of phase noise using combinations of a number of
strategies including, but not limited to, common-path inter
ferometry, phase referencing, active stabilization and differ
ential measurement. Embodiment are directed to optical
devices for imaging small biological objects With light.
These embodiments can be applied to the ?elds of, for
Correspondence Address:
WEINGARTEN, SCHURGIN, GAGNEBIN &
LEBOVICI LLP
example, cellular physiology and neuroscience. These pre
ferred embodiments are based on principles of phase mea
surements and imaging technologies. The scienti?c motiva
tion for using phase measurements and imaging
technologies is derived from, for example, cellular biology
TEN POST OFFICE SQUARE
BOSTON, MA 02109 (US)
at the sub-micron level Which can include, Without limita
(73) Assignee: Massachusetts Institute of Technology,
Cambridge, MA
neuronal transmission and implementation of the genetic
(21) Appl. No.:
10/823,389
code. The structure and dynamics of sub-cellular constitu
ents cannot be currently studied in their native state using the
(22) Filed:
Apr. 13, 2004
existing methods and technologies including, for example,
Related US. Application Data
(63) Continuation-in-part of application No. 10/024,455,
?led on Dec. 18, 2001.
(60)
tion, imaging origins of dysplasia, cellular communication,
Provisional application No. 60/479,732, ?led on Jun.
19, 2003.
x-ray and neutron scattering. In contrast, light based tech
niques With nanometer resolution enable the cellular
machinery to be studied in its native state. Thus, preferred
embodiments of the present invention include systems based
on principles of interferometry and/or phase measurements
and are used to study cellular physiology. These systems
include principles of 10W coherence interferometry (LCI)
using optical interferometers to measure phase, or light
scattering spectroscopy (LSS) Wherein interference Within
the cellular components themselves is used, or in the alter
native the principles of LCI and LSS can be combined to
Publication Classi?cation
(51)
Int. Cl? ..................................................... .. G01B 9/02
result in systems of the present invention.
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interface
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Placing sample interfaces as the end /126
re?ectors of a signal interferometer
arm
l
Scanning the reference mirror in the
/12s
reference interferometer arm
l
Combining the re?ections from the
—>
/130
signal and reference arms and
separating them by wavelength
l
Detecting the heterodyne
/132
oscillations in the intensities of the
combined light
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Extracting the phases of the
/134
heterodyne signals
l
Evaluating a difference phase for
/136
the entire scan
l
Repeating the scan with the
/137
wavelength of the light being
slightly detuned
To Fl+G.6B
FIG. 6A
Patent Application Publication Mar. 17, 2005 Sheet 6 0f 74
US 2005/0057756 A1
From FIG. 6A
i
Superposing the two difference
phases found from the two scans
/138
1
Determining the locations of the
/140
sample interfaces by the phase
crossing points
i
Determining the optical separation
between the interfaces by counting
/142
the number of times the heterodyne
signal associated with the CW light
wraps over by 21: between the two
crossing points
i
Re?ning the separation distance by /144
measuring the difference phase at
the crossing points
FIG. 6B
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Patent Application Publication Mar. 17, 2005 Sheet 8 0f 74
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/
184
Placing sample interfaces as the end /186
re?ectors of a signal interferometer
arm
1
Scanning the reference mirror in the /138
reference interferometer arm
1
Combining the re?ections from the
/190
signal and reference arms and
separating them by wavelength
Further separating the LC
wavelength-with ?lters
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Detecting the heterodyne
/196
oscillations in the intensities of the \
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combined light
Detecting the heterodyne
i
oscillations with three
detectors
Extracting the phases of the
/198
heterodyne signals
1
Evaluating a difference phase for
each LC signal with the CW signal
/2oo
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To FIG. 88
FIG. 8A
Patent Application Publication Mar. 17, 2005 Sheet 9 0f 74
US 2005/0057756 A1
From FIG. 8A
l
Superposing the two difference
/202
phases
Determining the locations of the
/204
sample interfaces by the phase
crossing points
Determining the optical separation
between the interfaces by counting /206
the number of times the heterodyne
signal associated with the CW light
wraps over by 2n between the two
crossing points
i
Re?ning the separation distance by
measuring the difference phase at
the crossing points
FIG. 8B
208
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phase crossing system
using low coherence
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phase crossing system
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