# US 7,612,880 B2 · Advanced polarization imaging method, apparatus, and computer program product for retinal imaging, liquid crystal testing, active remote sensing, and other applications > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,880 B2 - Document ID: US7612880B2 - Status: Granted - Kind: B2 - Application number: 10/567,104 - Filed: 2004-08-03 - Published: 2007-06-28 - Granted: 2009-11-03 - Earliest claimed: 2003-08-06 - Assignees: Arizona Board of Regents on Behalf of the University of Arizona - Inventors: Russell Chipman - Web page: https://patentgrep.com/patent/US7612880B2 ## CPC - G01J 4/04: Polarimeters using electric detection means (G01J4/02 takes precedence) - A61B 3/12: for looking at the eye fundus, e.g. ophthalmoscopes (A61B3/13 takes precedence) - A61B 3/1225: {using coherent radiation} - A61B 3/14: Arrangements specially adapted for eye photography - G01N 21/21: Polarisation-affecting properties (G01N21/19 takes precedence) - G01N 2021/217: {Measuring depolarisation or comparing polarised and depolarised parts of light} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A method, apparatus, and computer program product for identifying features in a sample by analyzing Mueller matrices to calculate an average degree of polarization, a weighted average degree of polarization, a degree of polarization map, a degree of polarization surface. Also, a method, apparatus, and computer program product for identifying features in a sample by analyzing Mueller matrices to calculate depolarization relative to a retardance axis and/or a diattentuation axis, and to calculate a ratio of diattenuation to polarizance or ratios of row and column magnitudes. Also, a method for retinal polarimetry, including a non-depolarizing light tube configured for insertion into the eye. ## Claims ### Claim 1 A method for identifying features in an object, comprising: positioning and focusing a polarimeter onto the object; illuminating the object with a series of at least 16 polarization states; analyzing a plurality of reflected images corresponding to said at least 16 polarization states; obtaining a Mueller matrix from the plurality of reflected images; and calculating a plurality of depolarization parameters, except for the depolarization index, from the Mueller matrix as a contrast mechanism for identifying features of the illuminated object. ### Claim 2 (depends on 1) The method of claim 1, wherein said depolarization parameters comprise: at least one of an average degree of polarization or a weighted average degree of polarization of the illuminated object. ### Claim 3 (depends on 1) The method of claim 1, wherein said depolarization parameters comprise: at least one of a degree of polarization surface or a degree of polarization map of the reflected images. ### Claim 4 (depends on 1) The method of claim 1, further comprising: calculating at least one of a minimum and a maximum degrees of polarization of the reflected images. ### Claim 5 (depends on 4) The method of claim 4, wherein said step of calculating at least one of a minimum and a maximum degrees of polarization comprises: calculating both a minimum and a maximum degrees of polarization; and calculating a difference between said minimum and a maximum degrees of polarization. ### Claim 6 (depends on 1) The method of claim 1, further comprising: decomposing said Mueller matrix into a depolarization matrix and at least one of a diattentuation matrix and a retardance matrix. ### Claim 7 (depends on 6) The method of claim 6, further comprising: calculating a depolarization relative to a corresponding diattentuation or retardance axis. ### Claim 8 (depends on 6) The method of claim 6, further comprising: calculating a depolarization relative to a corresponding diattentuation or retardance off-axis. ### Claim 9 (depends on 1) The method of claim 1, further comprising: calculating a ratio of diattenuation to polarizance. ### Claim 10 (depends on 1) The method of claim 1, further comprising: calculating a ratio of an average magnitude of Mueller matrix rows to an average magnitude of Mueller matrix columns. ### Claim 11 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9, 10) The method according to any one of claims 1-8 or 9-10, wherein said polarimeter comprises at least one of an optical polarimeter, an X-ray polarimeter, an IR polarimeter, or a UV polarimeter. ### Claim 12 A method of retinal polarimetry, comprising: emitting laser light to a retina via (a) a polarizer, (b) a first liquid crystal polarization controller, (c) a non-polarizing beam splitter, (d) a rotating half-wave retarder, and (e) an objective lens, the laser light passing through (a), (b) and (c) in this order; reflecting light from the retina to a co-polarized photodetector via the objective lens to generate reflected images, the rotating half-wave retarder, the non-polarizing beam splitter, a second liquid crystal polarization controller, and a polarizing beam splitter; obtaining a Mueller matrix from the plurality of reflected images; and calculating a plurality of depolarization parameters, except for the depolarization index, from the Mueller matrix as a contrast mechanism for identifying features of the illuminated retina. ### Claim 13 (depends on 12) The method of claim 12, further comprising: passing light from said polarizing beam splitter to a cross-polarized photodetector. ### Claim 14 (depends on 13) The method of claim 13, further comprising: adjusting a light parameter by controlling the retardance of said first and second liquid crystal polarization controllers by changing a respective retardance over more than one wave of retardation. ### Claim 15 (depends on 14) The method of claim 14, further comprising: acquiring four sets of images, wherein a first set of images corresponds to the two liquid crystal polarization controllers being adjusted to +7/8 and +7/8 waves retardance, a second set of images corresponds to the two liquid crystal polarization controllers being adjusted to +7/8 and +9/8 waves retardance, a third set of images corresponds to the two liquid crystal polarization controllers being adjusted to +9/8 and +9/8 waves, and a fourth set of images corresponds to the two liquid crystal polarization controllers being adjusted to +9/8 and +7/8 waves. ### Claim 16 A method of retinal polarimetry, comprising: illuminating a retina with polarized light via a probe inserted into the eye; producing a depolarization parameter and one of a retardance and a diattenuation parameter; collecting light reflected off the retina with a receiver located outside of the eye or inside of the eye; analyzing the reflected light with a polarization state analyzer; obtaining a Mueller matrix image from the reflected light; and analyzing said Mueller matrix by calculating a plurality of depolarization parameters, except for the depolarization index, from the Mueller matrix as a contrast mechanism for use in identifying features of the retina. ### Claim 17 (depends on 2) The method of claim 2, further comprising: generating a polarization image with at least one of the average degree of polarization or the weighted average degree of polarization of the reflected images to detect a structure in the illuminated object. ### Claim 18 (depends on 16) The method of claim 16, further comprising: generating a polarization image with at least one of an average degree of polarization or a weighted average degree of polarization of the reflected light to detect a structure in the retina. ### Claim 19 (depends on 11) The method of claim 11, wherein the polarimeter is a retinal polarimeter.