Contact detecting apparatus, optical measurement apparatus, and contact detecting method

A contact detecting apparatus for detecting contact between a body tissue and a measurement probe configured to emit illumination light onto the body tissue which is in contact with a distal end of the measurement probe, and to receive return light of the illumination light scattered from the body tissue, the contact detecting apparatus comprising:

• a laser light source configured to emit the illumination light onto the body tissue via the measurement probe;
• a photoelectric conversion unit configured to convert the received return light of the illumination light scattered from the body tissue via the measurement probe into an electric signal;
• and
• a signal processing unit configured to determine whether or not there is contact between the distal end of the measurement probe and the body tissue based on whether the electric signal converted by the photoelectric conversion unit includes a component of a beat signal, the contact being determined based on the beat signal not being included in the electric signal and non-contact being determined based on the beat signal existing in the electrical signal, the beat signal being caused by interference of the return light scattered from each of a surface of the body tissue and a surface of the distal end of the measurement probe, a frequency of the return light scattered from the surface of the body tissue being modulated due to Doppler Effect in accordance with relative movement of the distal end surface of the measurement probe and the surface of the body tissue.