Imaging systems and methods to improve backscattering imaging using circular polarization memory
First Claim
1. A method for analyzing an object located in a turbid medium comprising the steps of:
- illuminating the object through the turbid medium with circularly polarized light such that backscattered light emerges from the illuminated turbid medium;
passing the backscattered light through a first device to select out backscattered light that has an opposite helicity relative to the incident polarization; and
detecting the backscattered light with opposite helicity that passes through the first device to permit detection of the object;
wherein particles within the turbid medium have a dimension (a) that is greater than the wavelength (λ
) of the backscattered light.
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Accused Products
Abstract
An optical technique to improve the imaging of a target inside suspensions of scattering particles includes the illumination of the scattering particles with circularly polarized light. The backscattered light from the host medium preserves the helicity of incident light, while the backscattered light reflected from the target is predominated with light of opposite helicity. Based on the observed helicity difference in the emerging light that originated at the target and that backscattered from the medium, the present optical technique improves the image contrast using circular polarization. This approach makes use of polarization memory which leads to the reflected light from the target accompanied by weak diffusive backscattered light. Using the present technique, improved imaging of the artery wall is achieved and plaque composition can be assessed through a blood field associated with the artery. The scattering from the particles, such as red blood cells, in the blood is reduced due to polarization memory. The present invention can be also applied to other biomedical application, as well as image targets through adverse environmental conditions, such as fog, clouds, smoke, murky water, etc.
24 Citations
39 Claims
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1. A method for analyzing an object located in a turbid medium comprising the steps of:
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illuminating the object through the turbid medium with circularly polarized light such that backscattered light emerges from the illuminated turbid medium;
passing the backscattered light through a first device to select out backscattered light that has an opposite helicity relative to the incident polarization; and
detecting the backscattered light with opposite helicity that passes through the first device to permit detection of the object;
wherein particles within the turbid medium have a dimension (a) that is greater than the wavelength (λ
) of the backscattered light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for analyzing coronary lesions, such as vulnerable plaques inside the walls of the arteries, comprising the steps of:
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directing near-infrared circularly polarized light onto a target blood vessel with an optical instrument;
illuminating a wall of the vessel that contains blood flow;
detecting backscattered light from the artery wall and from objects within the blood vessel, the detected backscattered light having an opposite helicity relative to incident polarization; and
analyzing the backscattered light with opposite helicity from the artery. - View Dependent Claims (15, 16, 17, 18, 19)
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20. An optical system for imaging a target located within a suspension of scattering particles that at least in part define a turbid medium comprising:
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a light source producing parallel polarized light;
a first device for converting the parallel polarized light to circularly polarized light having a first handedness;
an optical instrument that illuminates the target with the circularly polarized light resulting in backscattered light being formed that comprises circularly polarized light having the first handedness and circularly polarized light having an opposite second handedness which are collected by a probe of the instrument;
a second device for converting the circularly polarized light having the first handedness into parallel polarized light and the circularly polarized light having the second handedness into perpendicular polarized light; and
a third device that is configured to select out the perpendicular polarized light for detection by a detector that is configured to process the perpendicular polarized light and provide displayable information concerning the target;
wherein a dimension of the scattering particles is greater than a wavelength (λ
) of the circularly polarized backscattered light. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A system for imaging a target that is located within a turbid medium that is defined in part by a suspension of scattering elements that have a dimension (a) comprising:
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a light source producing polarized light;
a first device for converting the polarized light to circularly polarized light;
an instrument operatively and optically connected to the light source and configured to illuminate the element with the circularly polarized light and to collect circularly polarized backscattered light that is formed;
a second device for converting the circularly polarized backscattered light into copolarized light and cross-polarized light relative to the polarized light of the light source;
a third device for filtering out the cross-polarized light from the copolarized light; and
a fourth device for receiving and processing the filtered cross-polarized light and record graphic images of the target, wherein the filtered cross-polarized light has a wavelength (λ
) less than the dimension (a) of the scattering elements. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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Specification