Jian Qing Weng

US Patent:

51876728, Feb 16, 1993

Filed:

Jan 22, 1991

Appl. No.:

7/644090

Inventors:

Britton Chance - Philadelphia PA
Jian Weng - Philadelphia PA

Assignee:

NIM Incorporated - Philadelphia PA

International Classification:

G06F 1500
A61B 500

US Classification:

364550

Abstract:

A phase modulated spectroscopy (PMS) system for detecting a pathophysiological condition in a subject includes two laser diodes emitting radiation at wavelengths of about 754-760 nm and 816-840 nm. These two laser diodes are modulated sinusoidally at about 220 MHz. The signals from each laser diode are brought to the subject by a bifurcated plastic optical fiber of 1 mm diameter. After transmission through the subject, the signals are detected by a Hamamatsu R928 photomultiplier (PMT), which generates two experimental signals. The experimental signals are compared to a reference signal in a phase detector. The respective phase shifts experienced by the signals are combined to form sum and difference signals, which are correlated to a pathophysiological condition.