# US 9,518,923 B1 · System and methods for fluorescence detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,518,923 B1 - Document ID: US9518923B1 - Status: Granted - Kind: B1 - Application number: 14/960,667 - Filed: 2015-12-07 - Granted: 2016-12-13 - Earliest claimed: 2015-12-07 - Assignees: International Business Machines Corporation - Applicants: International Business Machines Corporation - Inventors: Ning Li; Devendra K. Sadana; William T. Spratt - Web page: https://patentgrep.com/patent/US9518923B1 ## CPC - G01N 21/645: {Specially adapted constructive features of fluorimeters} - G01N 21/6428: {Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" (in vivo A61B5/00; immunoassay G01N33/53)} - G01N 2021/6463: {Optics} - G01N 2021/6484: {Optical fibres} - G01N 2201/08: Optical fibres; light guides - 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 fluorescence detection system is provided. The fluorescence detection system includes a light source adapted to emit excitation light; a sample unit in which a sample is disposed; a first optical fiber adapted to connect the light source to the sample unit; an avalanche photodiode array detector adapted to receive fluorescent light generated by the sample when the sample is irradiated with the excitation light; and a second optical fiber adapted to connect the sample unit to the avalanche photodiode array detector, wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.15 and the second optical fiber is positioned such that a longitudinal axis of the second optical fiber is orthogonal to a longitudinal axis of the first optical fiber. A method for detecting fluorescence and a computer-implemented method for detecting fluorescence are also provided. ## Claims ### Claim 1 A fluorescence detection system comprising: a light source adapted to emit excitation light; a sample unit having a sample disposed therein; a first optical fiber adapted to connect the light source to the sample unit; an avalanche photodiode array detector adapted to receive fluorescent light generated by the sample when the sample is irradiated with the excitation light; and a second optical fiber adapted to connect the sample unit to the avalanche photodiode array detector, wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.15 and the second optical fiber is positioned such that a longitudinal axis of the second optical fiber is orthogonal to a longitudinal axis of the first optical fiber; and wherein the fluorescence detection system has a fluorescence detection limit of equal to or greater than about one fluorescent particle per microliter for fluorescent particles having an average diameter of about two micrometers. ### Claim 2 (depends on 1) The fluorescence detection system of claim 1, further comprising: a memory; a processor of a computer system communicatively coupled to the memory, the light source and the avalanche photodiode array detector, where the processor is configured to: activate the light source to emit excitation light; receive sample information from the avalanche photodiode array detector; and store the sample information in the memory. ### Claim 3 (depends on 2) The fluorescence detection system of claim 2, wherein the processor is further configured to select a mode of operation for the avalanche photodiode array detector. ### Claim 4 (depends on 3) The fluorescence detection system of claim 3, wherein the processor is configured to select a photon-counting mode of photon detection for the avalanche photodiode array detector. ### Claim 5 (depends on 3) The fluorescence detection system of claim 3, wherein the processor is configured to select a linear photomultiplier mode of photon detection for the avalanche photodiode array detector. ### Claim 6 (depends on 1) The fluorescence detection system of claim 1, wherein a volume of a sample in the sample unit is equal to or less than about 100 nanoliters. ### Claim 7 (depends on 1) The fluorescence detection system of claim 1, wherein a volume of a sample in the sample unit is equal to or less than about 50 nanoliters. ### Claim 8 (depends on 1) The fluorescence detection system of claim 1, wherein the fluorescence detection system has a fluorescence detection limit of equal to or greater than about 100 fluorescent particles per microliter for fluorescent particles having an average diameter of about 50 nanometers. ### Claim 9 (depends on 1) The fluorescence detection system of claim 1, wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.20. ### Claim 10 (depends on 1) The fluorescence detection system of claim 1, wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.25. ### Claim 11 (depends on 1) The fluorescence detection system of claim 1, wherein a volume capacity of the sample unit is less than or equal to about one cubic centimeter. ### Claim 12 (depends on 1) The fluorescence detection system of claim 1, wherein the sample unit is a static sample unit or a dynamic sample unit. ### Claim 13 (depends on 1) The fluorescence detection system of claim 1, wherein the fluorescence detection system further comprises a filter disposed between the light source and the first optical fiber. ### Claim 14 (depends on 1) The fluorescence detection system of claim 1, wherein the fluorescence detection system further comprises a filter disposed between the second optical fiber and the avalanche photodiode array detector. ### Claim 15 (depends on 1) The fluorescence detection system of claim 1, wherein the fluorescence detection system is lens-free. ### Claim 16 A method for detecting fluorescence comprising: emitting excitation light from a light source through a first optical fiber to a sample in a sample unit; and receiving, by a avalanche photodiode array detector, through a second optical fiber, fluorescent light generated by the sample when the sample is irradiated with the excitation light; wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.15 and is positioned such that a longitudinal axis of the second optical fiber is orthogonal to a longitudinal axis of the first optical fiber; and wherein the fluorescence detection system has a fluorescence detection limit of equal to or greater than about one fluorescent particle per microliter for fluorescent particles having an average diameter of about two micrometers. ### Claim 17 (depends on 16) The method of claim 16, further comprising selecting a mode of photo detection for the avalanche photodiode array detector. ### Claim 18 A computer-implemented method for detecting fluorescence comprising: emitting, by a processor of a computer system, excitation light from a light source to a sample in a sample unit through a first optical fiber; receiving, by an avalanche photodiode array detector, through a second optical fiber, fluorescent light generated by the sample when the sample is irradiated with the excitation light, wherein the second optical fiber has a numerical aperture of equal to or greater than about 0.15 and is positioned such that a longitudinal axis of the second optical fiber is orthogonal to a longitudinal axis of the first optical fiber, and wherein the avalanche photodiode array detector has a fluorescence detection limit of equal to or greater than about one fluorescent particle per microliter for fluorescent particles having an average diameter of about two micrometers; receiving, by the processor of the computer system, sample information from the avalanche photodiode array detector; and storing, by the processor of the computer system, the sample information in a memory. ### Claim 19 (depends on 18) The method of claim 18, further comprising selecting a mode of photo detection for the avalanche photodiode array detector.