Method and apparatus for locating center of reference pulse in a measurement system

• US 4,628,469 A
• Filed: 10/17/1984
• Issued: 12/09/1986
• Est. Priority Date: 09/29/1982
• Status: Expired due to Term

• Current Assignee: Banner Engineering Corporation
• Original Assignee: Technical Arts Corporation
• Inventors: White, Steven J.
• Primary Examiner(s): Gruber, Felix D.
• Application Number:
  US06/661,780
• Time in Patent Office: 783 Days
• Field of Search: 356/1, 356/371, 356/375-376, 356/381, 356/387, 356/394, 358/103, 358/139, 358/903, 364/560, 364/561, 364/570, 364/829, 364/830, 364/839, 364/486, 364/733, 364/559, 364/715
• US Class Current: 702/152
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50

Abstract

A method and apparatus are disclosed for determining the spatial coordinates of a workpiece including: a planar light source for illuminating the workpiece; an electronic imaging device adapted to view the intersection of the planar light and the workpiece; pulse signals including pulses representative of said intersections; and a device for determining the centroid of the pulse by integrating the pulse signal over a selected interval including the pulse, integrating the result of the first integration in like manner and dividing the result of the second integration by the result of the first integration.

Claims

1. In a method for determining spatial coordinates of a workpiece, the steps comprising:

(a) illuminating said workpiece with a planar source of light;

(b) electronically viewing the intersections of the planar source of light and said workpiece from a known location spaced apart from said workpiece;

(c) scanning electronic images formed by said electronic viewing along a plurality of scan lines, in which the scanning of each line produces a reference pulse corresponding to the location at which the planar light intersects said workpiece;

(d) determining the centroid of the reference pulse on at least one of said scan lines by the substeps of;

(i) sampling a pulse signal representing said reference pulse;

(ii) digitizing said samples to generate digital values representative of the magnitude of said pulse samples;

(iii) performing a first integration by sequentially adding said digital values to produce a first sum signal;

(iv) performing a second integration by adding intermediate sums associated with said substep of sequentially adding said digital values to produce a second sum signal; and

(v) dividing said second sum signal by said first sum signal to produce an offset distance representing an offset distance by which the centroid of said pulse signal precedes the location at which the last sample of said pulse signal was taken; and

(e) calculating the spatial coordinates of said point on the workpiece using the centroid of said reference pulse and said known location of said step of electronic viewing.

2. The method of claim 1, wherein said substeps of performing said first and second integrations are carried out by digital adders.

3. In a method for determining spatial coordinates of a workpiece, the steps comprising:

(a) illuminating said workpiece with a planar source of light;

(b) electronically viewing the intersections of the planar source of light and said workpiece from a known location spaced apart from said workpiece;

(c) scanning electronic images formed by said electronic viewing along a plurality of scan lines, in which the scanning of each line produces a reference pulse corresponding to the location at which the planar light intersects said workpiece;

(d) determining the centroid of the reference pulse on at least one of said scan lines by the substeps of;

(i) electronically sensing said reference pulse to produce a signal representative of said reference pulse;

(ii) integrating the reference pulse signal by means of an analog integrator over a preselected signal interval including the reference pulse to produce an analog first sum signal;

(iii) integrating said first sum signal by means of an analog integrator to produce an analog second sum signal; and

(iv) dividing said second sum signal by said first sum signal to produce a centroid location signal linearly proportional to the distance in time from the end of said preselected signal interval to the centroid of said reference pulse.

4. In an apparatus for determining spatial coordinates of a workpiece, the combination comprising:

(a) means for illuminating said workpiece with a planar source of light;

(b) means for electronically viewing the intersections of the planar source of light and said workpiece from a known location spaced apart from said workpiece;

(c) means for scanning electronic images formed by said electronic viewing along a plurality of scan lines, in which the scanning of each line produces a reference pulse corresponding to the location at which the planar light intersects said workpiece;

(d) means for determining the centroid of the reference pulse on at least one of said scan lines comprising the subcombination of;

(i) means for sampling a pulse signal representing said reference pulse;

(ii) means for digitizing said samples to generate digital values representative of the magnitude of said pulse samples;

(iii) means for performing a first integration by sequentially adding said digital values to produce a first sum signal;

(iv) means for performing a second integration by adding intermediate sums associated with said means for performing said first integration to produce a second sum signal; and

(v) means for dividing said second sum signal by said first sum signal to produce an offset distance signal representing an offset distance by which the centroid of said pulse signal precedes the location at which the last sample of said pulse signal was taken; and

(e) means for calculating the spatial coordinates of said point on the workpiece using the centroid of said reference pulse and said known location of said means for electronic viewing.

5. In the apparatus of claim 4, said means for performing said first and second integrations comprising digital adders.