Time lag measuring device, distance measuring apparatus and distance measuring method

A time lag measuring device for measuring an unknown time lag between generations of two pulse signals, comprising:

• a reference signal generating section generating at least two reference signals having a phase difference of approximately π/2 [rad], and a known cycle;
• an amplitude detecting section obtaining respective amplitudes of the two reference signals at a timing at which the pulse signals are generated;
• a phase difference detecting section obtaining a phase of the reference signals at a timing at which each of the pulse signals is generated and a phase difference thereof between respective generation timings according to two amplitudes of each of the reference signals obtained by the amplitude detecting section;
• a correcting section correcting the phase difference detected by the phase difference detecting section relative to an error attributed to one of an error between the two reference signals and an error in at least one of the reference signals;
• and
• a time lag calculating section obtaining the time lag between the generations of the two pulse signals according to the phase difference corrected by the correcting section.

A time lag measuring device for measuring an unknown time lag between generations of two pulse signals, comprising:

• a reference signal section generating a single reference signal having a known cycle;
• a pulse delaying section delaying each of the two pulse signals by a time corresponding to a phase difference of approximately π/2 [rad] of the reference signal;
• an amplitude detecting section obtaining respective amplitudes of the reference signal at a timing at which each of the pulse signals is generated and at a delay timing delayed by the pulse delaying section;
• a phase difference detecting section obtaining a phase of the reference signal for each of the pulse signals and a phase difference of the pulse signals between the generation timings according to two amplitudes detected for each of the pulse signals by the amplitude detecting section;
• a correcting section correcting the phase difference detected by the phase difference detecting section relative to one of an error in the reference signal and an error in the phase difference of approximately π/2 [rad];
• and
• a time lag calculating section obtaining the generation time lag between the two measurement pulse signals according to the phase difference corrected by the correcting section.

A distance measuring method comprising the steps of:

• generating at least two reference signals having a phase difference of approximately π/2 [rad] and a known cycle;
• emitting a measurement pulse wave to an object of distance measurement;
• obtaining an amplitude of each of the two reference signals at a timing at which the emission of the measurement pulse wave is detected;
• obtaining an amplitude of each of the two reference signals at a timing at which a reflected pulse wave is detected, the reflected pulse wave being obtained from the measurement pulse wave reflected by the object of distance measurement;
• obtaining a phase of the reference signals at each detection timing for the pulse waves and a phase difference thereof between the detection timings according to two amplitudes detected for each of the reference signals;
• correcting the detected phase difference relative to an error attributed to one of an error between the two reference signals and an error in at least one of the reference signals;
• obtaining a time lag between the detection timing for the measurement pulse wave and the detection timing for the reflected pulse wave according to the corrected phase difference;
• and
• finding a distance to the object of distance measurement according to the time lag.

A distance measuring method comprising the steps of:

• generating a reference signal having a known cycle;
• emitting a measurement pulse wave to an object of distance measurement;
• detecting an emission of the measuring pulse wave;
• detecting a reflected pulse wave obtained by reflecting the measurement pulse wave by the object of distance measurement;
• obtaining an amplitude of the reference signal at a timing at which the emission of the measurement pulse is detected and at a delay timing that delays from the detection timing for the measurement pulse by a time corresponding to a phase difference of approximately π/2 [rad] in the reference signal;
• obtaining the amplitude of the reference signal at a timing at which the reflected pulse wave is detected and at a delay timing that delays from the detection timing for the reflected pulse wave by a time corresponding to the phase difference of approximately π/2 [rad] in the reference signal;
• obtaining a phase of the reference signal at each of the detection timings for the pulse waves and a phase difference thereof between the detection timings according to the two detected amplitudes of the measurement pulse wave and the two detected amplitudes of the reflected pulse wave;
• and
• correcting the obtained phase difference relative to one of an error in the reference signal and an error in the phase difference of approximately π/2 [rad];
• obtaining a time lag between the detection timing for the measurement pulse wave and the detection timing for the reflected pulse wave according to the corrected phase difference;
• and
• finding a distance to the object of distance measurement according to the time lag.