Optical distance measuring apparatus

An optical distance measuring apparatus operable in accordance with a phase difference detecting process, comprising:

• a light emitting portion including a light source from which a distance measuring light beam is emitted toward an object to be measured, and including means for allowing said distance measuring light beam to be oriented relative to said object to be measured, said distance measuring light beam being reflected from said object in the form of a reflected light beam;
• a light receiving portion for receiving a reflected light beam reflected from said object to be measured;
• a processing system including a central processing unit coupled to at least two local oscillating circuits for detecting and calculating a phase difference between an electrical phase of a modulated signal outputted from a reference oscillator electrically connected to said light emitting portion via a modulating circuit and an electrical phase of a demodulated signal outputted from a demodulating circuit electrically connected to said light receiving portion so as to determine a distance between said distance measuring apparatus and said object to be measured based on the detected phase difference with reference to the electrical phase of a reference signal outputted from said reference oscillator;
• said at least two local oscillating circuits comprising a first local oscillating circuit from which a first local oscillating signal is outputted and a second local oscillating circuit from which a second local oscillating signal is outputted;
• a first mixer and a second mixer electrically coupled to an output of said first local oscillating circuit;
• and
• a third mixer and a fourth mixer electrically coupled to an output of said second local oscillating circuit.