Optical probe with overlapping detection fields

A method for measuring position of the centerline of a tube comprising the steps of:

• providing a working head having first and second mutually spaced emitting sections and first and second mutually spaced receiving sections defining a sensitive region between the receiving sections and the emitting sections,
• projecting broad beams of light from first and second point sources on said first and second emitting sections toward said first and second receiving sections respectively and through said region,
• positioning a tube within said region, thereby occluding portions of said receiving sections relative to light projected from said emitting sections, and
• generating a set of signals representing positions relative to said working head of a point on the centerline of the tube.

A method of measuring position of the centerline of a tube comprising the steps of:

• providing a working head having a sensitive region in which a measurement is to be made,
• providing first and second point light sources on said working head to illuminate said sensitive region,
• mounting first and second light sensors to said working head positioned to have overlapping fields of view for reception of light projected from said first and second light sources respectively and passing through said sensitive region,
• causing said first and second light sources to project first and second light beams through said sensitive region and toward said first and second light sensors respectively,
• positioning a tube of which position is to be measured at least partly within said sensitive region, thereby partially occluding the fields of view of respective light sensors in accordance with position of the tube within said sensitive region to provide occluded areas, said occluded areas having edges lying on first and second tangents to the tube from said first and second light sources respectively,
• measuring slopes of said tangents, and
• employing said slopes to generate a set of electrical signals defining coordinates of a point on the centerline of the tube.

A measuring instrument comprising:

• a support,
• a probe, including means for sensing position of a tube relative to said probe,
• an articulated arm mounting the probe to the support for movement with components of rotation about a plurality of mutually angulated axes,
• said probe being adapted to move in a scanning path relative to a tube to be measured,
• means responsive to said articulated arm and probe for generating sets of signals that collectively define three dimensional coordinates of points on a tube positioned to be sensed by said probe, said means for generating sets of signals comprising:
• means responsive to said probe for generating tangent data defining first and second tangents to said tube from said probe,
• means responsive to articulation of said arm for generating probe location data defining location and orientation of the probe,
• means for repetitively sampling said data at successive scan points along said scanning path,
• means responsive to said sampled data for computing coordinate data sets representing approximate coordinates of a plurality of points on the centerline of a tube to be measured,
• means responsive to said sets of signals for computing skew angles between said probe and said tube at each of a plurality of said points along said scanning path, and
• means responsive to said coordinate data sets and said skew angles for computing corrected coordinate data sets representing corrected coordinates of points on the tube to be measured.

A method of defining the centerline of a tube comprising the steps of:

• moving a probe to a plurality of positions along the tube,
• generating sets of orientation signals at said positions, each set of signals defining orientation of said probe in a fixed coordinate system at each of said positions, respectively,
• measuring, at each of said positions, tangent data defining slopes of pairs of tangents to said tube from first and second mutually spaced locations on said probe,
• generating sets of coordinate signals at said positions based upon said tangent data, tube diameter, and an assumed perpendicular relation between the probe and the tube centerline, each said set of coordinate signals defining approximate coordinates of a point on the centerline of the tube,
• employing said sets of orientation and coordinate signals to define an approximate centerline of the tube,
• generating sets of corrected coordinate signals defining corrected coordinates of points on the centerline of the tube corrected for the angular relation of the tube centerline and probe orientations, and
• employing said sets of corrected coordinate signals to define a corrected tube centerline.

A method of determining the centerline of a tube by using a probe that projects light toward light sensors through a probe sensitive area at which a tube to be measured is positioned, said method comprising the steps of:

• moving the probe to at least two positions mutually spaced along and in proximity to a length of tube to be measured,
• positioning at least a part of said tube in said probe sensitive area at each of said positions;
• employing the probe at each of said positions to measure slopes of first and second tangents to the tube from points on the probe, and
• calculating from said measured slopes, and for each of said positions, sets of offsets of first and second points on the tube centerline relative to said probe.

For use with an optical probe comprising a probe body having a sensitive region lying in a sensing plane and optical means for generating signals in response to presence of an object to be measured in the sensitive region, said probe being configured to move in a selected path toward an object to be measured, and having means for generating data defining position and orientation of the probe, a method for determining the end point of a tube comprising the steps of:

• generating data defining a centerline of a tube of which the end point it to be determined,
• moving the probe from a point displaced from the tube and beyond the tube end point toward the tube in a direction along the tube centerline until the tube end penetrates the probe sensing plane and sensitive region,
• generating a first set of probe signals at the time of initial penetration of an end of the tube into the probe sensitive area,
• employing said first set of signals to produce data defining a first point on the centerline of said tube in said probe sensing plane,
• calculating the skew angle between the tube centerline and the probe plane, and
• employing said skew angle to generate data that defines the distance between said first point and the tube end point.

A method of measuring the centerline of a straight section of a tube employing an optical probe that is movable in a scan path along the tube, said probe having a sensitive region lying in a probe sensing plane, said method comprising the steps of:

• (a) moving the probe in a scan path along the tube, with the tube positioned so that at least a part of its periphery extends into said sensitive region of the probe,
• (b) generating sets of probe location data at each of a plurality of positions along said scan path, said probe location data defining location of the probe in a fixed coordinate system,
• (c) causing the probe to generate camera data at each of said plurality of positions, said camera data comprising data defining first and second tangents to the tube from points on the probe,
• (d) converting the camera data to sets of offsets in said sensing plane of the centerline of the tube relative to a probe coordinate system,
• (e) converting the probe location data to probe coordinates defining location of the probe in the fixed coordinate system,
• (f) combining the probe coordinates with the offsets to define sets of approximate centerline coordinates of points on the centerline of the tube in the fixed coordinate system, for a group of said positions along said scan path,
• (g) storing the approximate centerline coordinates,
• (h) storing the probe location data,
• (i) employing the approximate centerline coordinates to determine an approximate best fit line through points on tube centerline,
• (j) computing skew angles between the probe sensing plane and said approximate best fit line for each position of said group,
• (k) calculating corrected sets of approximate centerline coordinates for each position of said group based upon said skew angles,
• (l) determining a corrected best fit line through points defined by the corrected sets of approximate centerline coordinates, and
• (m) repeating steps (j) through (l), employing in step (j) the corrected best fit line calculated in step (l).