| US 7,489,390 B2 | ||
| Pulse light receiving time measurement apparatus and distance measurement including the same | ||
| Kenichiro Yoshino, Itabashi-ku (Japan); and Isao Minegishi, Itabashi-ku (Japan) | ||
| Assigned to Kabushiki Kaisha TOPCON, Tokyo (Japan) | ||
| Filed on Sep. 19, 2007, as Appl. No. 11/901,829. | ||
| Claims priority of application No. 2006-254104 (JP), filed on Sep. 20, 2006. | ||
| Prior Publication US 2008/0068585 A1, Mar. 20, 2008 | ||
| Int. Cl. G01C 3/08 (2006.01) | ||
| U.S. Cl. 356—5.01 [356/4.01] | 15 Claims |
| 1. A pulse light receiving time measurement apparatus comprising:
a light receiving element receiving reflected pulse light from an object to be measured;
a pulse light receiving time measurement circuit measuring a time when pulse light is irradiated to the object to be measured
and a time when the reflected pulse light from the object to be measured is received at the light receiving element;
a resonance circuit converting an optical pulse signal of the reflected pulse light from the light receiving element into
a damping signal;
a multi-stage amplifier group amplifying the damping signal from the resonance circuit;
a damping signal processing circuit composed of amplitude comparators and zero-cross comparators, and processing the damping
signal from each stage of the multi-stage amplifier group which is connected with a pair of an amplitude comparator and a
zero-cross comparator, the amplitude comparators comparing amplitude of the damping signal with a predetermined value, the
zero-cross comparators detecting that the damping signal crosses a bias level; and
an integrated logic circuit combining a plurality of signal lines from the zero-cross comparator into one for output to the
pulse light receiving time measurement circuit, wherein
operations of the respective zero-cross comparators are determined according to comparison results of the respective amplitude
comparators for the amplifier group.
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