Light beam range finder
First Claim
1. An apparatus for measuring distance, comprising:
- a transmitter which transmits a sequence of visible electromagnetic pulses in response to a transmit timing signal;
a receiver which samples reflections from objects of the sequence of visible electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples, the sample signal indicating distance to an object, wherein the receiver includes an avalanche photodiode or a PIN photodiode, a sampling gate having an output and an input coupled to the avalanche photodiode or PIN photodiode, and an amplifier coupled to the output of the sampling gate;
a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the reflections such that time between transmission of pulses in the sequence and sampling by the receiver sweeps over a range of delays.
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Accused Products
Abstract
A "laser tape measure" for measuring distance which includes a transmitter such as a laser diode which transmits a sequence of electromagnetic pulses in response to a transmit timing signal. A receiver samples reflections from objects within the field of the sequence of visible electromagnetic pulses with controlled timing, in response to a receive timing signal. The receiver generates a sample signal in response to the samples which indicates distance to the object causing the reflections. The timing circuit supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver. The receive timing signal causes the receiver to sample the reflection such that the time between transmission of pulses in the sequence in sampling by the receiver sweeps over a range of delays. The transmit timing signal causes the transmitter to transmit the sequence of electromagnetic pulses at a pulse repetition rate, and the received timing signal sweeps over the range of delays in a sweep cycle such that reflections are sampled at the pulse repetition rate and with different delays in the range of delays, such that the sample signal represents received reflections in equivalent time. The receiver according to one aspect of the invention includes an avalanche photodiode and a sampling gate coupled to the photodiode which is responsive to the received timing signal. The transmitter includes a laser diode which supplies a sequence of visible electromagnetic pulses. A bright spot projected on to the target clearly indicates the point that is being measured, and the user can read the range to that point with precision of better than 0.1%.
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Citations
37 Claims
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1. An apparatus for measuring distance, comprising:
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a transmitter which transmits a sequence of visible electromagnetic pulses in response to a transmit timing signal; a receiver which samples reflections from objects of the sequence of visible electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples, the sample signal indicating distance to an object, wherein the receiver includes an avalanche photodiode or a PIN photodiode, a sampling gate having an output and an input coupled to the avalanche photodiode or PIN photodiode, and an amplifier coupled to the output of the sampling gate; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the reflections such that time between transmission of pulses in the sequence and sampling by the receiver sweeps over a range of delays. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A swept range gate sensor for detecting distance to objects within a field, comprising:
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a transmitter, including a light source, which transmits a beam comprising a sequence of pulses from the light source into the field in response to a transmit timing signal; a receiver, including a light detector, which samples reflections from objects in the field of the beam with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples, wherein the light detector comprises an avalanche photodiode or a PIN photodiode; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the reflections such that the time between transmission of pulses in the sequence by the transmitter and sampling by the receiver sweeps over a range of delays; and a signal processor, coupled with the receiver, to indicate a distance to the object in response to the sample signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A swept range gate sensor for detecting distance to objects within a field, comprising:
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a transmitter, including a laser diode, which transmits a light beam comprising a sequence of pulses in response to a transmit timing signal, the pulses in the beam characterized by an interval at a leading edge during which the beam is not highly pure; a receiver, including an avalanche photodiode coupled with a sample gate, which samples reflections from objects illuminated by the beam with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the reflections such that time between transmission of pulses in the sequence by the transmitter and sampling by the receiver sweeps over a range of delays; and a signal processor, coupled with the receiver, which generates an output indicating a round trip time-of-flight of leading edges of the reflections within said interval. - View Dependent Claims (29, 30, 31)
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32. A method for measuring distance from a first location to a second location, comprising:
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transmitting from the first location to the second location a visible light beam of pulses with controlled timing; sampling at the first location reflections of the visible light beam using an avalanche photodiode or a PIN photodiode such that the time between transmission of pulses in the beam in the transmitting step and sampling periodically sweeps over a range of delays; and processing the resulting samples to determine a round trip time-off-flight of pulses in the beam. - View Dependent Claims (33, 34, 35, 36, 37)
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Specification