Systems and methods for phase measurements
First Claim
1. A method for measuring phase of light passing through a portion of a medium comprising the steps of:
- providing a first wavelength of light;
directing light of the first wavelength along a first optical path and a second optical path, the first optical path extending onto a medium to be measured and the second path undergoing a change in path length; and
detecting light from the medium and light from the second optical path to measure a change in phase of light passing through two separate points on the medium.
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Abstract
Preferred embodiments of the present invention are directed to systems for phase measurement which address the problem of phase noise using combinations of a number of strategies including, but not limited to, common-path interferometry, phase referencing, active stabilization and differential measurement. Embodiment are directed to optical devices for imaging small biological objects with light. These embodiments can be applied to the fields of, for example, cellular physiology and neuroscience. These preferred embodiments are based on principles of phase measurements and imaging technologies. The scientific motivation for using phase measurements and imaging technologies is derived from, for example, cellular biology at the sub-micron level which can include, without limitation, imaging origins of dysplasia, cellular communication, neuronal transmission and implementation of the genetic code. The structure and dynamics of sub-cellular constituents cannot be currently studied in their native state using the existing methods and technologies including, for example, x-ray and neutron scattering. In contrast, light based techniques 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 low 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 alternative the principles of LCI and LSS can be combined to result in systems of the present invention.
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Citations
85 Claims
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1. A method for measuring phase of light passing through a portion of a medium comprising the steps of:
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providing a first wavelength of light;
directing light of the first wavelength along a first optical path and a second optical path, the first optical path extending onto a medium to be measured and the second path undergoing a change in path length; and
detecting light from the medium and light from the second optical path to measure a change in phase of light passing through two separate points on the medium. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 18, 19, 20, 21, 39, 48, 49)
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12. A dual-beam measurement system comprising:
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a light source;
a splitter that splits light from the source into a first component on a first optical path and a second component on a second optical path;
a first movable reflecting surface that alters a length of the first optical path;
a second movable reflecting surface that alters a length of the second optical path;
a combiner that directs light from the first optical path and the second optical path onto a medium to be measured. - View Dependent Claims (13, 14, 15, 16, 17, 22, 23, 24)
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25. A method for measuring a phase characteristic of light passing through a portion of a sample, comprising the steps of;
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providing a first signal and a second signal generated by a first light source and a second light source, respectively, the second light source being a low coherence source;
directing the first signal and the second signal along a first optical path and a second optical path;
varying a path length difference between the first optical path and the second optical path;
generating an output signal indicative of the sum of the first and the second signal with an optical path delay between them;
modulating the output signal at an interferometer lock modulation frequency; and
determining a phase of light interacting with the sample by the time evolution of a interferometer lock phase. - View Dependent Claims (26, 27, 28)
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29. A system for measuring phase of light passing through a portion of a sample, comprising:
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a first light source that generates a first signal;
an interferometer that generates a second signal with two pulses separated by a time delay from the first signal;
a first optical path from the interferometer in communication with the sample and a second optical path from the interferometer in communication with a reference; and
a detector system that measures a first heterodyne signal from the first and the second signal from the sample and the reference, respectively, and the interference between the light reflected from the sample and the reference; and
detecting a phase of the heterodyne signal indicative of the phase of the sample reflection relative to the reference reflection. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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38. A method for imaging a sample comprising the steps of:
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illuminating a sample, the light originating from a point on the sample having a low frequency spatial component and high frequency spatial components;
interfering along a common optical path the high frequency spatial components with the low frequency spatial component to produce a first intensity signal;
shifting the phase of the low frequency spatial component to produce a first phase shifted low frequency spatial component;
interfering along a common optical path the high frequency spatial components with the first phase shifted low frequency spatial component to produce a second intensity signal;
shifting the phase of the low frequency spatial component to produce a second phase shifted low frequency spatial component;
interfering along a common optical path the high frequency spatial components with the second phase shifted low frequency spatial component to produce a third intensity signal;
shifting the phase of the low frequency spatial component to produce a third phase shifted low frequency spatial component;
interfering along a common optical path the high frequency spatial components with the third phase shifted low frequency spatial component to produce a fourth intensity signal;
generating a phase image of the point on the sample based at least in part on the first intensity signal, the second intensity signal, the third intensity signal and the fourth intensity signal. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 50)
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51. A method for non-contact optical measurement of a sample having reflecting surfaces, comprising the steps of:
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providing a first light source that generates a first signal;
generating a second signal with two pulses separated by a time delay from the first signal using a dual-beam interferometer;
providing a first optical path from the interferometer in communication with the sample and a second optical path from the interferometer in communication with a reference; and
measuring a first heterodyne signal from the first and the second signal from the sample and the reference, respectively, and the interference between the light reflected from the sample and the reference; and
detecting a phase of the heterodyne signal indicative of the phase of the sample reflection relative to the reference reflection. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63)
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64. A fiber optic probe for optically imaging a sample, comprising:
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a housing having a proximal end and a distal end and a reference optical surface;
a fiber in the proximal end of the housing coupled to a light source; and
a graded index lens in the distal end of the housing such that a numerical aperture of the probe provides efficient light gathering from scattering surfaces of a sample. - View Dependent Claims (65, 66, 67, 68, 69, 70)
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71. A method for non-contact optical measurement of an eye, comprising the steps of:
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providing a light source that generates a first signal and a second signal;
providing a first optical path from the interferometer in communication with the eye and a second optical path from the interferometer in communication with a reference; and
measuring a first heterodyne signal with light returning from the eye and the reference, respectively, in response to the first signal and the second signal; and
determining a phase of the first heterodyne signal indicative of the phase of the light returning from the eye relative to the light returning from the reference. - View Dependent Claims (72, 73, 74, 75)
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76. A light modulation system for imaging a material comprising:
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a light source;
a lens system;
a spatial light modulator;
a detector that detects a phase variation of light interacting with the material. - View Dependent Claims (77, 78, 79, 80, 81)
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82. A system for measuring neuron activity comprising:
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a light source;
an optical system that couples light from the light source onto tissue having a nerve fiber; and
a detector that collects light from the nerve fiber. - View Dependent Claims (83, 84, 85)
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Specification