Patent ID: 7583383

Claim:
A detection apparatus for optically determining a biological material property, comprising: a probe base; a probe supported on the probe base and including a light emitting element for applying light to a living body and a light receiving element for receiving light from the living body; an amplifier having an input terminal connected to a signal output terminal of the light receiving element; a phase compensation circuit provided between an output terminal of the amplifier and a signal input terminal of the light emitting element for changing a signal frequency so as to cause any phase difference between an input waveform into the light emitting element and an output waveform from the light receiving element to become zero; a frequency difference detector which measures a frequency of a self-induced oscillation generated when the phase difference is made to become zero by means of a feedback loop formed by the probe, the amplifier, and the phase compensation circuit, and detects a difference between a frequency obtained when receiving light from the living body by applying light from the probe to the living body and a frequency obtained when such light is not applied to the living body; and an output unit for outputting the detected frequency difference as a material property of the living body.