Distance measuring apparatus

A distance measuring apparatus for measuring a time an emitted light pulse requires to travel to and return from a target before being received by using an emission time and a reception time of the optical pulse, and for obtaining a distance to the target from the measured time, said apparatus comprising:

• a light-emitting unit for emitting an optical pulse;
• a first photodetector for detecting an output from said light-emitting unit;
• a first comparator for comparing an output from said first photodetector with a predetermined threshold value;
• a second photodetector for receiving scattered light from the target;
• a delay element for delaying an output from said second photodetector so as to generate a delayed electrical signal;
• a threshold generator for holding, as a threshold value, a value of signal intensity at an intersection of the output from said second photodetector and the delayed electrical signal from said delay element;
• a second comparator for comparing the delayed electrical signal from said delay element with the threshold value held by said threshold generator, and for generating a signal whose width corresponds to a length of time during which the delayed electrical signal from said delay element exceeds the threshold value held by said threshold generator;
• a signal generator for generating an output corresponding to the emission time and the reception time based on an output from said first comparator and an output from said second comparator;
• and
• an integrator for integrating the output from said signal generator.

A distance measuring apparatus for measuring a time an emitted optical pulse requires to travel to and return from a target before being received by using an emission time and a reception time of the optical pulse, and for obtaining a distance to the target from the measured time, said apparatus comprising:

• converting means for converting a received optical pulse into an electrical signal as a received electrical signal pulse;
• a delay element for delaying the received electrical pulse signal so as to generate a delayed electrical signal pulse;
• a threshold generator for holding, as a threshold value, a half value of a peak value of a sum of the received electrical signal pulse and the delayed electrical signal pulse;
• and
• a comparator for comparing the delayed electrical signal and the threshold held by the threshold generator, and for generating a signal whose width corresponds to a length of time during which the delayed electrical signal exceeds the threshold value held by said threshold generator.

A distance measuring apparatus for measuring a time an emitted optical pulse requires to travel to and return from a target before being received by using an emission time and a reception time of the optical pulse, and for obtaining a distance to the target from the measured time, said apparatus comprising:

• a light-emitting unit for emitting an optical pulse;
• a first photodetector for detecting an output from said light-emitting unit;
• a first comparator for comparing an output from said first photodetector with a predetermined threshold value;
• a second photodetector for receiving scattered light from the target;
• a delay element for delaying an output from said second photodetector so as to generate a delayed electrical signal;
• a threshold generator for holding, as a threshold value, a value of signal intensity at an intersection of the output from said second photodetector and the delayed electrical signal from said delay element;
• a second comparator for comparing the delayed electrical signal from the delay element and the threshold value held by the threshold generator, and for generating a signal whose width corresponds to a length of time during which the delayed electrical signal from the delay element exceeds the threshold held by the threshold generator;
• an exclusive OR circuit for calculating an exclusive OR of an output of the first comparator and an output of the second comparator;
• a signal generator for generating an output corresponding to the emission time and the reception time based on the output from said first comparator and an output from the exclusive OR circuit;
• and
• an integrator for integrating the output from said signal generator.