High resolution measuring device for time difference
First Claim
1. A high resolution measuring device, for measuring time difference between continuous pulses, comprising:
- measurement signal means for supplying a measurement signal M having a period and comprising a continuous series of spaced pulses, including a series of reference pulses and a series of delayed pulses;
reference signal means for supplying a periodic waveform reference signal S which is asynchronous with measurement signal M over a plurality of said periods of signal M;
approximate measuring means, responsive to said signal M, for deriving a first approximate time difference between separated pulses of said signal M;
precision measuring means including sampling means, responsive to said signal M and said signal S, for sampling said signal S in correlation with said reference pulses of said signal M for deriving a first sampled waveform signal having a period which is at least twice said period of said signal M and for sampling said signal S in correlation with said delayed pulses of said signal M for deriving a second sampled waveform signal having a period which is at least twice said period of said signal M, and phase detecting means, coupled to said sampling means, for detecting phase differences between said first and second sampled waveform signals; and
processing means, coupled to said phase detecting means and said approximate measuring means, for deriving a second time difference based on said phase differences between said first and second sampled waveform signals and for utilizing said second time difference and said first approximate time difference for determining the time difference between pulses with increased resolution.
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Abstract
High resolution measuring systems use a continuous series of laser pulses in measuring distance to an object. An approximate time difference between transmitted and reflected pulses is derived. A second, more accurate, time difference is derived through use of a reference signal sampled in correlation to the pulse signal in order to derive a sampled waveform signal having a period which is long relative to the period of the pulse signal. Phase difference measurements of this sampled waveform provide delay time measurements of high accuracy. The high accuracy and approximate time difference signals are combined to determine time difference between measurement pulses with increased resolution. Time difference is converted to precision distance measurments, with greater accuracy available by averaging several measurements. Several embodiments are described.
42 Citations
8 Claims
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1. A high resolution measuring device, for measuring time difference between continuous pulses, comprising:
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measurement signal means for supplying a measurement signal M having a period and comprising a continuous series of spaced pulses, including a series of reference pulses and a series of delayed pulses; reference signal means for supplying a periodic waveform reference signal S which is asynchronous with measurement signal M over a plurality of said periods of signal M; approximate measuring means, responsive to said signal M, for deriving a first approximate time difference between separated pulses of said signal M; precision measuring means including sampling means, responsive to said signal M and said signal S, for sampling said signal S in correlation with said reference pulses of said signal M for deriving a first sampled waveform signal having a period which is at least twice said period of said signal M and for sampling said signal S in correlation with said delayed pulses of said signal M for deriving a second sampled waveform signal having a period which is at least twice said period of said signal M, and phase detecting means, coupled to said sampling means, for detecting phase differences between said first and second sampled waveform signals; and processing means, coupled to said phase detecting means and said approximate measuring means, for deriving a second time difference based on said phase differences between said first and second sampled waveform signals and for utilizing said second time difference and said first approximate time difference for determining the time difference between pulses with increased resolution. - View Dependent Claims (2, 3, 4, 5)
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6. A high resolution measuring device, for measuring the distance to an external object, comprising:
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measurement signal means for supplying a measurement signal M having a period and comprising a continuous series of spaced pulses; means for transmitting, in the form of pulses of light, said measurement signal M over a distance to an external object and for receiving such signal M pulses after reflection from said object; reference signal means for supplying a periodic waveform reference signal S which is asynchronous with measurement signal M over a plurality of said periods of signal M; approximate measuring means, responsive to said transmitted and received signals M, for deriving a first approximate time difference between separated pulses of said signals M; precision measuring means including sampling means, responsive to said signal M and said signal S, for sampling said signal S in correlation with pulses of said transmitted signal M for deriving a first sampled waveform signal having a period which is at least twice said period of said signal M and for sampling said signal S in correlation with pulses of said received signal M for deriving a second sampled waveform signal, having a period which is at least twice said period of said signal M, and phase detecting means, coupled to said sampling means, for detecting phase differences between said first and second sampled waveform signals; and processing means, coupled to said phase detecting means and said approximate measuring means, for deriving a second time difference based on said phase differences between said first and second sampled waveform signals, for utilizing said second time difference and said first approximate time difference for determining the time difference between pulses with increased resolution, and for converting said time difference determinations to precision distance measurements; whereby the distance to an external object can be measured with a high degree of accuracy. - View Dependent Claims (7, 8)
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Specification