Self-calibrating precision timing circuit and method for a laser range finder
AssigneeLaser Technology, Inc.
InventorJeremy G. Dunne
Life of this patent
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Abstract
A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instrument's internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a "zero" value and a "cal" value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.
Claims35
A method for determining a range to a target based upon a flight time of a pulse toward said target, said method comprising the steps of:
- initially establishing first and second reference signal levels;
- firstly unclamping said second reference signal level to allow said second reference signal level to approach, at a first rate, said first reference signal level;
- measuring a first reference time T1.sub.ref from said step of firstly unclamping until said first and second reference signal levels are equal;
- re-establishing said first and second reference signal levels;
- secondly unclamping said second reference signal level and ramping said second reference signal level, at a second rate, for a predetermined period of time to establish a third reference signal level;
- allowing said third reference signal level to approach, at said first rate, to said first reference signal level;
- secondly measuring a second reference time T2.sub.ref from said step of secondly unclamping until said first and third reference signal levels are equal;
- again re-establishing said first and second reference signal levels;
- thirdly unclamping said second reference signal level;
- again ramping said second reference signal level, at said second rate, for a period of time related to said flight time of said pulse to said target, to establish a fourth reference signal level;
- again allowing said fourth reference signal level to approach, at said first rate, said first reference signal level;
- thirdly measuring a third reference time T3.sub.ref from said step of thirdly unclamping until said first and fourth reference signal levels are equal;
- and
- computing said range to said target as proportional to (T3.sub.ref -T1.sub.ref)/(T2.sub.ref -T1.sub.ref).
A system for determining a range to a target based upon a flight time of a pulse toward said target, said system comprising:
- means for initially establishing first and second reference signal levels;
- means for firstly unclamping said second reference signal level;
- means for firstly allowing said second reference signal level to approach, at a first rate, to said first reference signal level;
- means for firstly storing a first reference time T1.sub.ref referenced from said unclamping means until said first and second reference signal levels are equal;
- means for re-establishing said first and second reference signal levels;
- means for secondly unclamping said second reference signal level;
- means for ramping said second reference signal level, at a second rate, for a predetermined period of time to establish a third reference signal level;
- means for secondly allowing said third reference signal level to approach, at said first rate, to said first reference signal level;
- means for secondly storing a second reference time T2.sub.ref referenced from said secondly unclamping means until said first and third reference signal levels are equal;
- means for again re-establishing said first and second reference signal levels;
- means for thirdly unclamping said second reference signal level;
- means for again ramping said second reference signal level, at said second rate, for a period of time related to said flight time of said pulse to said target, to establish a fourth reference signal level;
- means for thirdly allowing said fourth reference signal level to approach, at said first rate, said first reference signal level;
- means for thirdly storing a third reference time T3.sub.ref referenced from said thirdly unclamping means until said first and fourth reference signal levels are equal;
- and
- means for computing said range to said target as proportional to (T3.sub.ref -T1.sub.ref)/(T2.sub.ref -T1.sub.ref).
In a range finding device, a method for determining a range to a target based upon a flight time of a pulse toward said target, said method comprising the steps of:
- first measuring a first reference time T1.sub.ref for calibration of a zero flight time indicating an internal timing delay condition of the range finding device;
- second measuring a second reference time T2.sub.ref from a known pulse width applied to said range finding device to determine an origin and scale of the range finding device;
- third measuring a third reference time T3.sub.ref proportional to said flight time of said pulse;
- and
- computing said range to said target as proportional to (T3.sub.ref -T1.sub.ref)/(T2.sub.ref -T1.sub.ref).
Dependencies are inferred from the claim text.