United States Patent   Patent Number: 5,270,548
Steinkamp  Date of Patent: Dec. 14, 1993
 PHASE-SENSITIVE FLOW CYTOMETER
 Inventor: John A. Steinkamp, Los Alamos, N. Mex.
 Assignee: The United States of America as represented by the United States Department of Energy, Washington, DC.
 Appl. No.: 922,841
 Filed: Jul. 31,1992
 Int. CI.* G01N 21/64
 U.S. CI 250/461.2; 250/458.1;
 Field of Search 250/459.1, 461.2, 458.1,
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Primary Examiner—Constantine Hannaher
Assistant Examiner—Edward J. Glick
Attorney, Agent, or Firm—Ray G. Wilson; Paul D.
Gaetjens; William R. Moser
A phase-sensitive flow cytometer (FCM) provides additional FCM capability to use the fluorescence lifetime of one or more fluorochromes bound to single cells to provide additional information regarding the cells. The resulting fluorescence emission can be resolved into individual fluorescence signals if two fluorochromes are present or can be converted directly to a decay lifetime from a single fluorochrome. The excitation light for the fluorochromes is modulated to produce an amplitude modulated fluorescence pulse as the fluorochrome is excited in the FCM. The modulation signal also forms a reference signal that is phase-shifted a selected amount for subsequent mixing with the output modulated fluorescence intensity signal in phase-sensitive detection circuitry. The output from the phase-sensitive circuitry is then an individual resolved fluorochrome signal or a single fluorochrome decay lifetime, depending on the applied phase shifts.
4 Claims, 6 Drawing Sheets