Meade Instruments Corporation

John LaBelle

Kenneth W Baun

Steven Szczuka

A rangefinder and method are provided for measuring a distance between the rangefinder and a target by measuring the flight time of a beam reflected from the target. In an embodiment, a receiver having reduced noise detects weak reflections from the targets or targets with poor reflectivity. The receiver generates a voltage signal proportional to a reflected beam, clamps the voltage signal to remove a portion of the noise therefrom, and compares the voltage signal to a threshold. In some embodiments, the receiver also filters the voltage signal to remove a portion of the noise therefrom. In an embodiment, the sensitivity of the receiver is increased as a function of time to reduce the likelihood of detecting stray reflections from objects other than the intended target. In some embodiments, the rangefinder collects calibration data with each range measurement or group of range measurements. The calibration data comprise a plurality of simulated range measurements.

Rangefinder with reduced noise receiver

An apparatus and method for calibrating range measurements are provided wherein calibration data is collected with each range measurement or group of range measurements. The calibration data comprise a plurality of simulated range measurements. In one embodiment, the simulated range measurements are used to analyze errors that vary with time and environmental conditions. Range measurements are calibrated by correlating a measured flight time of a transmitted and reflected laser beam with the simulated range measurements and a relationship between laser beam flight times and target ranges based on the speed of the laser beam.

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Long Beach, CA, United States of America

John LaBelle