Method of three-dimensional measurement with few projected patterns

• US 4,634,278 A
• Filed: 02/06/1984
• Issued: 01/06/1987
• Est. Priority Date: 02/06/1984
• Status: Expired due to Term

• Current Assignee: Robotic Vision Systems, Inc. (Acuity Brands, Inc.)
• Original Assignee: Robotic Vision Systems, Inc. (Acuity Brands, Inc.)
• Inventors: Schmidt, Richard, Ross, Joseph
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US06/577,331
• Time in Patent Office: 1,065 Days
• Field of Search: 356/2, 356/375, 356/376, 250/558
• US Class Current: 356/610
• CPC Class Codes: G01B 11/2536 using several gratings with variable grating pitch, projected on the object with the same angle of incidence

Abstract

Methods are provided for reducing the number of projected patterns required to make two- or three-dimensional surface measurements on a sub-class of surfaces comprising relatively smooth surfaces. By including apriori knowledge about the surface to be measured, pattern ambiguities can be resolved by processing rather than by additional projected patterns.

Claims

1. A method for unambiguously identifying the location of a point within the view of a two- or three-dimensional measurement sensor with a single projected pattern comprising the steps of:

projecting a binary pattern having unique codes over any span of N segments out of a total of as many as 2^N segments onto a surface to be measured, so that said segments form uniquely identifiable local patterns;

recording reflected radiation with a detector and generating a recorded signal;

analyzing the recorded signal and providing, a digital representation thereof; and

identifying the location of the point in the pattern by comparing the digital representation with a known reference pattern digital representation.

2. A method for unambiguously identifying the location of a point within the view of a two- or three-dimensional measurement sensor as defined in claim 1, and locating said point within a predetermined resolution with relatively few projected patterns;

projecting at least one higher resolution pattern on the surface to be measured;

recording radiation reflected from said surface to be measured; and

computing the location of said point to a higher resolution.

3. A method for unambiguously identifying the location of a point within the view of a two- or three-dimensional measurement sensors with an adaptive threshold comprising the steps of:

projecting a uniform light intensity beam on an area of measurement;

recording radiation reflected from said area;

determining relative reflected intensity for each part of the beam;

adjusting a decision threshold for each corresponding part;

said decision threshold being made more sensitive where said reflected intensity is determined to be low, and said decision threshold being made less sensitive where said reflected intensity is determined to be high;

projecting a binary pattern having unique codes over any span of N segments out of a total of as many as 2^N segments onto said area of measurement;

recording reflected radiation from said area and generating a recorded signal;

analyzing the recorded signal using said adjusted decision threshold and providing a digital representation of said recorded signal; and

identifying the location of the point in the pattern by comparing the digital representation with a known reference pattern digital representation.