| 摘要 |
A beam of laser light is impinged on a vessel or vessels in which blood is flowing, such as vessels in the retina of the eye. The reflected light is detected with a photodetector to product a signal representative of the Doppler shift frequencies of the light scattered from the moving blood cells. If the light is impinged on a capillary bed the photodetector produces a homodyne type signal, from light reflected from blood in the various capillaries; if the light is impinged on a single vessel the photodetector produces a heterodyne type signal from the light reflected from the vessel wall and the light reflected from the blood cells flowing in the vessel. The signal from the photodetector is amplified and used to drive an audio output to produce a sound representative of the velocity of the blood. Preferably the spot at which the blood flow is measured is observed by means of an ophthalmoscope to correlate the sound with a particular vessel or area of a capillary bed, and thereby to detect or arrive at a diagnosis of disease in the eye.
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