Method and apparatus for performing three-dimensional measurement

• US 8,648,895 B2
• Filed: 08/28/2008
• Issued: 02/11/2014
• Est. Priority Date: 08/29/2007
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Ikeda, Yasuyuki, Fujieda, Shiro, Yano, Hiroshi
• Primary Examiner(s): LIN, WEN TAI
• Application Number:
  US12/230,441
• Publication Number:
  US 20090066968A1
• Time in Patent Office: 1,993 Days
• Field of Search: None
• US Class Current: 348/42
• CPC Class Codes: G01B 11/03 by measuring coordinates of points
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence

Abstract

A control processing unit simultaneously drives cameras to produce images of a measuring object, the control processing unit searches corresponding point on a comparative image produced by one of the cameras for a representative point in a reference image produced by the other camera, and the control processing unit computes a three-dimensional coordinate corresponding to a coordinate using the coordinate of each point correlated by the search. The control processing unit also obtains a shift amount at the corresponding point specified by the search to an epipolar line specified based on a coordinate of a representative point on the reference image side or a parameter indicating a relationship between the cameras, and the control processing unit supplies the shift amount as an evaluation value indicating accuracy of three-dimensional measurement along with three-dimensional measurement result.

Claims

1. A three-dimensional measurement method in which a plurality of cameras are disposed while a positional relationship and optical axis directions are fixed such that visual fields of the cameras overlap within a predetermined range, one camera of the plurality of cameras is set as a reference camera, and three-dimensional measurement is performed to a measuring object by performing a first step, a second step, a third step, and a fourth step for predetermined times, the measuring object entering a range where visual fields of the plurality of cameras overlap being taken by the cameras in the first step, a plurality of representative points of the measuring object being extracted from a reference image produced by the reference camera in the second step, a plurality of points corresponding to the plurality of representative points on the reference image side being searched in an image produced by a camera except for the reference camera in the third step, a three-dimensional coordinate corresponding to a coordinate being obtained using the coordinate of each point correlated by the search of the third step in the fourth step,

wherein, when three-dimensional measurement processing is performed to one measuring object, a plurality of shift amounts at the corresponding points obtained by the search of the third step to an epipolar line based on a predetermined relationship between the camera and the coordinate of the plurality of representative points in the reference image is computed for each of the plurality of representative points, evaluation information indicating accuracy of three-dimensional measurement result is set based on the computed shift amount, and the evaluation information is supplied along with the three-dimensional measurement result of the measuring object,

wherein a first camera and a second camera of the plurality of cameras are individually driven in combination with the reference camera to obtain the three-dimensional coordinate and the computed shift amount corresponding to each combination,

wherein a maximum value of the computed shift amount obtained from the combinations is set as an evaluation value and the three-dimensional coordinate having the smallest shift amount of the computed plurality of shift amounts corresponding to a same representative point is fixed as the three-dimensional measurement result, wherein a notification unit is configured to make a notification for warning when the evaluation value is greater than a predetermined reference value.

2. The three-dimensional measurement method according to claim 1, wherein the evaluation information includes data as to a measurement accuracy of the plurality of cameras from amongst a plurality of measurement accuracy levels.

3. A three-dimensional measurement apparatus comprising:

an image input unit into which an image of a measuring object entering a range where visual fields of a plurality of cameras overlap is individually fed from the plurality of cameras, the plurality of cameras being disposed while a positional relationship and optical axis directions are fixed such that the visual fields of the cameras overlap within a predetermined range;

a representative point extraction unit configured to extract a plurality of representative points of the measuring object from a reference image produced by a reference camera while one camera of the plurality of cameras is set as the reference camera;

a corresponding point search unit configured to search a plurality of points corresponding to the plurality of representative points on the reference image side in an image produced by a camera except for the reference camera;

a three-dimensional coordinate computation unit configured to obtain a three-dimensional coordinate corresponding to a coordinate using the coordinate of each point correlated by the search processing of the corresponding point search unit; and

an output unit configured to supply three-dimensional measurement result information based on the three-dimensional coordinates computed for predetermined representative points extracted by the representative point extraction unit,

wherein the three-dimensional measurement apparatus further comprises a shift amount computation unit configured to compute a plurality of shift amounts at the corresponding points obtained by the search of the corresponding point search unit to an epipolar line based on a predetermined relationship between the camera and the coordinate of each of the representative points in the reference image is computed for each of the representative points when three-dimensional measurement processing is performed to one measuring object, and

the output unit is configured to set evaluation information indicating accuracy of three-dimensional measurement result based on the shift amounts computed by the shift amount computation unit and supplies the evaluation information along with the three-dimensional measurement result of the measuring object,

wherein a first camera and a second camera of the plurality of cameras are individually driven in combination with the reference camera to obtain the three-dimensional coordinate and the computed shift amount corresponding to each combination,

wherein a maximum value of the computed shift amount obtained from the combinations is set as an evaluation value and the three-dimensional coordinate having the smallest shift amount of the computed plurality of shift amounts corresponding to a same representative point is fixed as the three-dimensional measurement result, wherein a notification unit is configured to make a notification for warning when the evaluation value is greater than a predetermined reference value.

4. The three-dimensional measurement apparatus according to claim 3, wherein the evaluation information includes data as to a measurement accuracy of the plurality of cameras from amongst a plurality of measurement accuracy levels.