System and method for laser range finder

• US 6,310,682 B1
• Filed: 07/06/1999
• Issued: 10/30/2001
• Est. Priority Date: 07/06/1999
• Status: Expired due to Fees

• Current Assignee: Quatron Incorporated (Quatron)
• Original Assignee: Quatron Incorporated (Quatron), Segnetron Israel Limited
• Inventors: Gavish, Moshe, Chen, Kuo-Tso
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/347,976
• Time in Patent Office: 847 Days
• Field of Search: 356/5-1-, 342/134
• US Class Current: 356/5.01
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 7/4865 Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak peak detection in noise, signal conditioning G01S7/487
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

The actual value of a parameter from a laser range finder to a target is determined by adjusting the measured parameter by a measurement error. The error adjustment is based on the relationship between the intensity of the detected pulse and the expected parameter error. The laser range finder has a laser diode for emitting a laser pulse to a target to produce a reflected pulse, and a detector for receiving the reflected pulse. A measurement circuit is coupled to the detector for determining a measured parameter based on the reflected pulse. An integrator is coupled to the detector for determining the pulse area, and therefore, the intensity of the reflected pulse. A processor is coupled to the measurement circuit and the integrator for adjusting the measured parameter based on the pulse area of the reflected pulse, to provide the actual value of the parameter.

Claims

1. A laser range finder, comprising:

a laser diode for emitting a laser pulse to a target to produce a reflected pulse;

a detector for receiving the reflected pulse;

a measurement circuit coupled to the detector for determining a measured parameter based on the reflected pulse;

an integrator coupled to the detector for determining the pulse area of the reflected pulse; and

a processor coupled to the measurement circuit and the integrator for adjusting the measured parameter based on the pulse area of the reflected pulse.

2. The apparatus of claim 1, further including a high voltage generation circuit coupled to the detector and the processor, the high voltage generation circuit including the laser diode.

3. The apparatus of claim 2, wherein the high voltage generation circuit includes a switch that is actuated to generate current that is stored as voltage in a first capacitor, with the first capacitor coupled to the laser diode for providing voltage to the laser diode.

4. The apparatus of claim 3, wherein the high voltage generation circuit includes an oscillator circuit that charges a second capacitor, with the second capacitor storing the highest voltage value in the high voltage generation circuit and coupled to the processor to provide the highest voltage value to the processor.

5. The apparatus of claim 4, wherein the processor is coupled to the switch to vary the voltage level at the second capacitor.

6. The apparatus of claim 1, wherein the parameter is distance, and the measurement circuit is a distance measurement circuit.

7. The apparatus of claim 6, wherein the distance measurement circuit includes:

a comparator coupled to the detector for distinguishing the reflected pulse from environmental noise;

a time to voltage converter coupled to the comparator for determining an approximate range of the target; and

an analog to digital converter having an input coupled to the time to voltage converter, and an output coupled to the processor.

8. The apparatus of claim 1, further including an amplification system coupled between the detector and the measurement circuit.

9. The apparatus of claim 8, wherein the amplification system includes a pre-amplifier and an amplifier.

10. The apparatus of claim 1, further including a display coupled to the processor for displaying the actual value of the measured parameter.

11. The apparatus of claim 1, wherein the determined pulse area is used to determine the intensity of the reflected pulse, the apparatus further including a memory for storing adjusted parameter errors corresponding to different intensities.

12. The apparatus of claim 11, wherein the parameter is distance, and wherein the processor adjusts the measured distance with a distance error corresponding to the intensity of the reflected pulse, to provide the actual distance.

13. The apparatus of claim 1, wherein the integrator includes a capacitor whose voltage represents the intensity of the reflected pulse.

14. A method of determining the distance from an apparatus to a target, comprising:

emitting a laser pulse to a target to produce a reflected pulse;

detecting the reflected pulse;

determining a measured distance based on the detected pulse;

determining the pulse area of the detected pulse; and

adjusting the measured distance based on the pulse area of the detected pulse.

15. The method of claim 14, further including the step of:

determining the intensity of the detected pulse based on the determined pulse area of the detected pulse.

16. The method of claim 15, further including:

storing adjusted distance errors corresponding to different intensities; and

adjusting the measured distance with a distance error corresponding to the intensity of the reflected pulse.

17. The method of claim 15, wherein the intensity of the detected pulse is determined by calculating the integral of the pulse area of the detected pulse.