Distance measurement device using two light modulation frequencies and operating method thereof

A distance measurement device, configured to measure a distance of an object, the distance measurement device comprising:

• a light source, configured to emit light to illuminate the object;
• a light detector, configured to detect reflected light from the object to generate a detection signal;
• a time control circuit, configured to control the light source to illuminate at a first modulation frequency in first measurement and to illuminate at a second modulation frequency, higher than the first modulation frequency, in second measurement, the time control circuit comprising:
• a first delay circuit, configured to delay a phase of a light driving signal of the light source;
• and
• a second delay circuit, configured to delay a phase of a detecting control signal of the light detector;
• and
• a processor, configured to
• calculate a rough phase according to the detection signal generated by the light detector in the first measurement,
• calculate a fine phase according to the detection signal generated by the light detector in the second measurement, and
• determine a delay phase between the light driving signal and the detecting control signal in the second measurement according to the rough phase,
• wherein the processor is configured to output an object distance corresponding to the fine phase but not to output an object distance corresponding to the rough phase.

An operating method of a distance measurement device, the distance measurement device comprising a light source, a light detector and a processor, the operating method comprising:

• controlling, using a light driving signal, the light source to illuminate at a first modulation frequency, and controlling, using a detecting control signal, the light detector to detect reflected light from an object to generate a first detection signal;
• calculating, using the processor, an operating phase zone of a first phase according to the first detection signal to accordingly determine a delay time;
• controlling, using the light driving signal, the light source to illuminate at a second modulation frequency, higher than the first modulation frequency, and controlling, using the detecting control signal, the light detector to detect reflected light from the object to generate a second detection signal, wherein the light driving signal and the detecting control signal have a difference equal to the delay time;
• and
• calculating, using the processor, a second phase according to the second detection signal.