HOLOGRAPHIC MICROREFRACTOMETER
First Claim
1. A method for determining refractive index at a plurality of points in a medium, comprising the steps of:
- providing a source of light for generating a collimated beam of coherent light;
providing an optical microscope having a focal plane;
providing a fluid medium whose refractive index is to be determined;
providing a refractive index probe comprised of at least one probe particle disposed in the medium;
inputting the coherent light to the optical microscope and illuminating the at least one probe particle disposed in the medium;
forming an interference pattern in the focal plane from light scattered by the at least one probe particle and an unscattered portion of the collimated beam;
recording the interference pattern; and
analyzing the interference pattern and fitting the pattern to obtain the refractive index of the medium in the focal plane of the refractive index probe in the medium.
2 Assignments
0 Petitions
Accused Products
Abstract
An in-line holographic microscope is used for measurements of micrometer-scale particles and associated suspending fluid medium containing the particles. The system yields heterodyne scattering patterns that may be interpreted with Lorenz-Mie theory to obtain precise time-resolved information on the refractive index of the suspending medium for determining chemical composition, concentrations and makeup thereof. This approach can perform spatially resolved refractometry with measurements on calibrated refractive index standards and monitor chemical concentration in a microfluidic channel. Using commercially available colloidal spheres as probe particles and a standard video camera for detection yields volumetric refractive index measurements with a resolution of 2×10−3 RIU for each probe particle in each holographic snapshot.
18 Citations
17 Claims
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1. A method for determining refractive index at a plurality of points in a medium, comprising the steps of:
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providing a source of light for generating a collimated beam of coherent light; providing an optical microscope having a focal plane; providing a fluid medium whose refractive index is to be determined; providing a refractive index probe comprised of at least one probe particle disposed in the medium; inputting the coherent light to the optical microscope and illuminating the at least one probe particle disposed in the medium; forming an interference pattern in the focal plane from light scattered by the at least one probe particle and an unscattered portion of the collimated beam; recording the interference pattern; and analyzing the interference pattern and fitting the pattern to obtain the refractive index of the medium in the focal plane of the refractive index probe in the medium. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for determining refractive index at a plurality of points in a medium, comprising:
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a source of light for generating a collimated beam of coherent light; an optical microscope having a focal plane; a fluid medium whose refractive index is to be determined; a refractive index probe comprised of at least one particle disposed in the medium wherein the coherent light is input and interacts with the at least one particle to provide an interference pattern in the focal plane; a video camera in communication with the optical microscope and configured to record the interference pattern; and a computer in communication with the video camera configured to receive the interference pattern and analyze the interference pattern and fitting the pattern to predict particle position, particle radius and relative refractive index to obtain refractive index of the medium in the focal plane of the refractive index probe in the medium. - View Dependent Claims (11, 12, 13, 14)
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15. A non-transitory computer-readable medium having instructions stored thereon, the instructions comprising the steps of,
receiving data pertaining to an optical interference pattern of at least one refractive index probe disposed in a medium; - and
fitting the interference pattern to obtain the refractive index of the medium in the focal plane of the refractive index probe in the medium wherein the interference pattern is formed in the focal plane from light scattered by the refractive index and an unscattered portion of a collimated beam, thereby providing data for obtaining the refractive index of the medium. - View Dependent Claims (16)
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17. (canceled)
Specification