Distance measuring device and method for calibrating the same

A method for calibrating a distance measuring device comprising:

• detecting reference pulsed light that has propagated through a predetermined optical path to obtain a first detection signal;
• making the first detection signal pass through a first band pass filter that has a first center frequency to obtain a first signal;
• detecting distance measuring pulsed light that has been emitted to an object and that has been reflected by the object to obtain a second detection signal;
• making the second detection signal pass through a second band pass filter that has a second center frequency, which is different from the first center frequency, to obtain a second signal;
• mixing the first signal and the second signal to obtain a mixed signal;
• inputting the mixed signal to an A/D converter;
• processing output of the A/D converter by FFT analysis after the A/D converter receives the mixed signal, thereby generating a first separated signal corresponding to the first signal and a second separated signal corresponding to the second signal;
• converting a phase of at least one of the first separated signal and the second separated signal into a phase of a predetermined frequency so that the first separated signal and the second separated signal have the same frequency;
• and
• calculating a distance to the object by using a phase difference between the first separated signal and the second separated signal that have the same frequency and by also using a correction parameter,
• wherein the correction parameter is obtained by
• making the detection signal of the reference pulsed light pass through the first band pass filter and the second band pass filter, thereby obtaining a first calibration signal and a second calibration signal therefrom, respectively,
• mixing the first calibration signal and the second calibration signal, thereby obtaining a calibration mixed signal,
• inputting the calibration mixed signal to the A/D converter,
• processing output from the A/D converter by FFT analysis, thereby obtaining a first calibration separated signal corresponding to the first calibration signal and a second calibration separated signal corresponding to the second calibration signal,
• converting a phase of at least one of the first calibration separated signal and the second calibration separated signal into a phase of the predetermined frequency or another frequency so that the first calibration separated signal and the second calibration separated signal have the same frequency, and
• calculating a phase difference between the first calibration separated signal and the second calibration separated signal that have the same frequency.

A distance measuring device comprising:

• a first band pass filter that has a first center frequency and that receives a detection signal of reference pulsed light, which has propagated through a predetermined optical path, thereby generating a first signal;
• a second band pass filter that has a second center frequency different from the first center frequency and that receives a detection signal of distance measuring pulsed light, which has been emitted to an object and has been reflected by the object, thereby generating a second signal;
• a mixing circuit that mixes the first signal and the second signal and generates a mixed signal;
• and
• a distance calculating unit that calculates a distance to the object based on the mixed signal and a correction parameter,
• wherein the correction parameter is obtained by
• making the detection signal of the reference pulsed light pass through the first band pass filter and the second band pass filter, thereby obtaining a first calibration signal and a second calibration signal therefrom, respectively,
• mixing the first calibration signal and the second calibration signal, thereby obtaining a calibration mixed signal,
• inputting the calibration mixed signal to the A/D converter,
• processing output from the A/D converter by FFT analysis, thereby obtaining a first calibration separated signal corresponding to the first calibration signal and a second calibration separated signal corresponding to the second calibration signal,
• converting a phase of at least one of the first calibration separated signal and the second calibration separated signal into a phase of the predetermined frequency or another frequency so that the first calibration separated signal and the second calibration separated signal have the same frequency, and
• calculating a phase difference between the first calibration separated signal and the second calibration separated signal that have the same frequency.