Tilt-compensated laser rangefinder
First Claim
1. A tilt compensated laser ranging device comprising:
- a housing disposed in a reference horizontal plane;
a laser transmitter disposed within the housing and adapted to fire a series of laser pulses of short duration at a selected target, said series of laser pulses having a pulse repetition rate frequency, said selected target having a target surface, said target surface reflecting at least a portion of said series laser pulses as at least one return pulse, each said return pulse having an amplitude;
a laser pulse return detection system disposed within the housing and comprising;
a laser pulse return detector adapted to emit an electronic signal upon detection of each said return pulse, each said electronic signal having an amplitude corresponding to the amplitude of the detected return pulse;
a signal-to-noise discriminator adapted to receive each said electronic signal from said laser pulse return detector;
an automatic gain control system for adjusting the gain of the laser pulse return detector such that the variance in the amplitudes of said electronic signals from said laser pulse return detector is less than the variance in amplitudes of said detected return pulses;
a vertical tilt sensor system disposed in the housing for determining a vertical angle between the target and the housing'"'"'s reference horizontal plane, said vertical tilt sensor system comprising;
a vertical tilt sensor; and
vertical angle signal circuitry adapted to produce a vertical angle data signal corresponding to said vertical angle;
a digital signal processing circuit disposed in the housing, said digital signal processing circuit comprising circuitry configured to;
store vertical tilt sensor system calibration data, said vertical tilt sensor system calibration data comprising vertical tilt sensor system calibration look-up tables;
calculate a time-of-flight range;
calculate a vertical angle from data comprising vertical angle data and vertical tilt sensor system calibration data; and
calculate a horizontal range from the time-of-flight range and the vertical angle;
wherein vertical tilt sensor system calibration data is determined by stepping the vertical tilt sensor system through a series of discrete predetermined vertical angles, measuring the vertical angle data signals corresponding to said vertical angles and storing the measurement values of said vertical angle data signals corresponding to each predetermined vertical angle; and
an output signal system disposed within the housing and adapted to selectable produce a horizontal range output data signal corresponding to the horizontal range to the target.
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Accused Products
Abstract
The present invention is a laser ranging device that incorporates an internal tilt sensor, an internal temperature sensor, and an internal pressure sensor. The tilt sensor is used to measure the target'"'"'s vertical angle relative to the horizontal reference plane. Digital signal processing circuitry controls the firing of the laser pulse, calculation of time-of-flight range, measurement of the vertical angle of the tilt sensor, measurement of ambient temperature and storage of tilt sensor and temperature sensor calibration data. The digital signal processing circuitry then provides the user temperature corrected ballistic ranging information, including horizontal range. Additionally, an automatic gain control system minimizes the effects of target to target variance in reflectivity and its associated errors. It is also an object of this invention to electronically minimize errors in the measurement of a vertical angle caused by housing vibration and by temperature variance errors.
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Citations
31 Claims
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1. A tilt compensated laser ranging device comprising:
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a housing disposed in a reference horizontal plane;
a laser transmitter disposed within the housing and adapted to fire a series of laser pulses of short duration at a selected target, said series of laser pulses having a pulse repetition rate frequency, said selected target having a target surface, said target surface reflecting at least a portion of said series laser pulses as at least one return pulse, each said return pulse having an amplitude;
a laser pulse return detection system disposed within the housing and comprising;
a laser pulse return detector adapted to emit an electronic signal upon detection of each said return pulse, each said electronic signal having an amplitude corresponding to the amplitude of the detected return pulse;
a signal-to-noise discriminator adapted to receive each said electronic signal from said laser pulse return detector;
an automatic gain control system for adjusting the gain of the laser pulse return detector such that the variance in the amplitudes of said electronic signals from said laser pulse return detector is less than the variance in amplitudes of said detected return pulses;
a vertical tilt sensor system disposed in the housing for determining a vertical angle between the target and the housing'"'"'s reference horizontal plane, said vertical tilt sensor system comprising;
a vertical tilt sensor; and
vertical angle signal circuitry adapted to produce a vertical angle data signal corresponding to said vertical angle;
a digital signal processing circuit disposed in the housing, said digital signal processing circuit comprising circuitry configured to;
store vertical tilt sensor system calibration data, said vertical tilt sensor system calibration data comprising vertical tilt sensor system calibration look-up tables;
calculate a time-of-flight range;
calculate a vertical angle from data comprising vertical angle data and vertical tilt sensor system calibration data; and
calculate a horizontal range from the time-of-flight range and the vertical angle;
wherein vertical tilt sensor system calibration data is determined by stepping the vertical tilt sensor system through a series of discrete predetermined vertical angles, measuring the vertical angle data signals corresponding to said vertical angles and storing the measurement values of said vertical angle data signals corresponding to each predetermined vertical angle; and
an output signal system disposed within the housing and adapted to selectable produce a horizontal range output data signal corresponding to the horizontal range to the target. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A tilt compensated laser ranging device for firing a series of laser pulses at a selected target and measuring target reflections of said laser pulses, said device comprising:
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a laser pulse return detector for detecting reflected laser pulses and providing an electronic signal output corresponding to each detected reflected laser pulse, said laser pulse return detector further having an automatic gain control system that adjusts the gain of the laser pulse return detector, said adjustment based on the amplitude of the previously received laser pulse return detector signal, such that a majority of said laser pulse return detector signals have amplitudes within a predetermined range;
a vertical tilt sensor for determining the vertical angle to the target and having a vertical angle signal circuitry adapted to produce a vertical angle data signal corresponding to said vertical angle;
a temperature sensor adapted to produce a temperature data signal corresponding to ambient environmental temperature; and
a microprocessor configured to;
store vertical tilt sensor system calibration look-up tables;
store temperature sensor system calibration data look-up tables;
calculate a time-of-flight range;
calculate a vertical angle from data comprising vertical angle data, vertical tilt sensor system calibration look-up tables, temperature data and temperature sensor system calibration data; and
calculate a horizontal range from the time-of-flight range and the vertical angle;
wherein measurement of vertical angle data signals are taken at each of a series of discrete predetermined vertical angles and each measurement value of said vertical angle data signals and each corresponding predetermined vertical angle are stored in lookup tables; and
wherein determination of the vertical angle to the target sequentially making multiple measurements of the data signal corresponding to the vertical angle.
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31. A tilt compensated laser ranging device comprising:
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a vertical tilt sensor system for determining a vertical angle between a reflected laser pulse and a reference horizontal plane, said vertical tilt sensor system comprising;
a vertical tilt sensor; and
vertical angle signal circuitry adapted to produce a vertical angle data signal corresponding to said vertical angle;
a digital signal processing circuit comprising circuitry configured to;
calculate a time-of-flight range;
calculate a vertical angle; and
calculate a horizontal range from the time-of-flight range and the vertical angle; and
an output signal system adapted to produce a horizontal range output data signal corresponding to the horizontal range to the target.
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Specification