Multi-dimensional position sensor using range detectors

• US 6,115,128 A
• Filed: 05/15/1998
• Issued: 09/05/2000
• Est. Priority Date: 09/17/1997
• Status: Expired due to Fees

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Vann, Charles S.
• Primary Examiner(s): Evans, F. L.
• Assistant Examiner(s): Smith, Zandra V.
• Application Number:
  US09/079,580
• Time in Patent Office: 844 Days
• Field of Search: 340/619, 250/577, 250/559.38, 356/375, 356/139.09, 356/182.2, 356/139.1
• US Class Current: 356/623
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates

Abstract

A small, non-contact optical sensor uses ranges and images to detect its relative position to an object in up to six degrees of freedom. The sensor has three light emitting range detectors which illuminate a target and can be used to determine distance and two tilt angles. A camera located between the three range detectors senses the three remaining degrees of freedom, two translations and one rotation. Various range detectors, with different light sources, e.g. lasers and LEDs, different collection options, and different detection schemes, e.g. diminishing return and time of flight can be used. This sensor increases the capability and flexibility of computer controlled machines, e.g. it can instruct a robot how to adjust automatically to different positions and orientations of a part.

Claims

1. A sensor which measures its position in multi-dimensions relative to an object, comprising:

a plurality of light-emitting range detectors which measure the range from the sensor to at least three different points on the object such that tilt and range of the sensor relative to the object can be determined;

a camera which images a feature on the object such that translation and rotation of the sensor relative to that feature can be determined;

a digitizer which converts analog signals from the range detectors and image information from the camera to digitized data;

a computer which uses the digitized data to calculate multiple axes of position of the sensor relative to the object.

2. The sensor of claim 1 wherein each range detector comprises:

a light source which produces an output beam;

a photodetector which produces an output signal proportional to the amount of light incident thereon;

a first lens which collects light reflected from the object when illuminated by the light source;

a second lens, which in combination with the first lens, images the collected light onto the photodetector such that the light entering the first lens illuminates the photodetector even if the incoming light is at an angle different from the optical axis of the first lens;

a display device connected to the photodetector which can directly display or record changes in the output signal or digitize the output signal and feed it into a computer.

3. The sensor of claim 1 wherein each range detector comprises:

a light source which produces an output beam;

a photodetector which produces an output signal proportional to the amount of light incident thereon;

a lens which collects light reflected from the object when illuminated by the light source, and directs collected light onto the photodetector;

a display device connected to the photodetector which can directly display or record changes in the output signal or digitize the output signal and feed it into a computer.

4. The sensor of claim 1 wherein each range detector comprises:

a pulsed light source which produces an output beam comprising a sequence of pulses;

a photodetector which produces an output signal proportional to the amount of light incident thereon;

a first lens which collects light reflected from the object when illuminated by the light source;

a second lens, which in combination with the first lens, images the collected light onto the photodetector such that the light entering the first lens illuminates the photodetector even if the incoming light is at an angle different from the optical axes of the first lens;

a micropower impulse electronic circuit which compares the time a pulse is transmitted toward the object to the time its reflected pulse is received to obtain time of flight and range.

5. The sensor of claim 2 wherein each range detector further comprises:

a second photodetector which produces an output signal proportional to the amount of light incident thereon;

a mirror positioned between the first and second lens to deflect a portion of the collected beam onto the second photodetector;

a second display device connected to the second photodetector which can directly display or record changes in the output signal or digitize the output signal and feed it into a computer;

where in the ratio of the output from the first photodetector to the output of the second photodetector is dependent only on range.

6. The sensor of claim 1 wherein each range detector, comprises:

a light source which produces an output beam;

a photodetector which produces an output signal proportional to the amount of light incident thereon;

a linear polarizer tilted at an angle with respect to the laser beam which passes a beam having a first linear polarization;

a quarter wave plate positioned after the polarizer which passes the beam and converts the beam to a circular polarization;

a reflector mounted to an object in the absorbing medium which reflects light from the source back to the quarter wave plate which converts the beam to a beam having a second linear polarization orthogonal to the first linear polarization, and then to the linear polarizer which reflects the beam to the photodetector;

a display device connected to the photodetector which can directly display or record changes in the output signal or digitize the output signal and feed it into a computer.

7. A range detector for measuring the range to an object, comprising:

a light source which produces an output beam;

a photodetector which produces an output signal proportional to the amount of light incident thereon;

a first lens which collects light reflected from the object when illuminated by the light source;

a second lens, which in combination with the first lens, images the collected light onto the photodetector such that the light entering the first lens illuminates the photodetector even if the incoming light is at an angle different from the optical axis of the first lens;

a display device connected to the photodetector which can directly display or record changes in the output signal or digitize the output signal and feed it into a computer.

8. The range detector of claim 7, further comprising:

a second photodetector which produces an output signal proportional to the amount of light incident thereon;

a mirror positioned between the first and second lens to deflect a portion of the collected beam onto the second photodetector;

a second display device connected to the second photodetector which can directly display or record changes in the output signal or digitize the output signal and feed it into a computer;

where in the ratio of the output from the first photodetector to the output of the second photodetector is dependent only on range.

9. A range detector for measuring the range to an object, comprising:

a pulsed light source which produces an output beam comprising a sequence of pulses;

a photodetector which produces an output signal proportional to the amount of light incident thereon;

a first lens which collects light reflected from the object when illuminated by the light source;

a second lens, which in combination with the first lens, images the collected light onto the photodetector such that the light entering the first lens illuminates the photodetector even if the incoming light is at an angle different from the optical axes of the first lens;

a micropower impulse electronic circuit which compares the time a pulse is transmitted toward the object to the time its reflected pulse is received to obtain time of flight and range.

10. A range detector for measuring the range to an object located in an absorbing medium, comprising:

a light source which produces an output beam;

a photodetector which produces an output signal proportional to the amount of light incident thereon;

a linear polarizer tilted at an angle with respect to the laser beam which passes a beam having a first linear polarization;

a quarter wave plate positioned after the polarizer which passes the beam and converts the beam to a circular polarization;

a reflector mounted to an object in the absorbing medium which reflects light from the source back to the quarter wave plate which converts the beam to a beam having a second linear polarization orthogonal to the first linear polarization, and then to the linear polarizer which reflects the beam to the photodetector;

a display device connected to the photodetector which can directly display or record changes in the output signal or digitize the output signal and feed it into a computer.