Method for measuring 3d coordinates of a surface with a portable articulated arm coordinate measuring machine having a camera

A method for measuring three-dimensional (3D) coordinates of a surface comprising:

• providing a base;
• providing a manually positionable articulated arm portion having opposed first and second ends, the arm portion being rotationally coupled to the base at the second end, the arm portion including a plurality of connected arm segments, each of the arm segments including at least one angle transducer for producing an angle signal;
• providing a measurement device coupled to the first end, the measurement device including a camera having a lens having a known focal length and a photosensitive array;
• providing an electronic circuit configured to receive the angle signal from the at least one angle transducer for the plurality of connected arm segments and to provide data corresponding to a position and an orientation of the measurement device;
• providing a processor;
• sending to the processor from the electronic circuit first data corresponding to a first position and a first orientation of the perspective center of the camera lens, forming with the lens a first image of the surface on the photosensitive array, and sending a first digital signal to the processor in response;
• sending to the processor from the electronic circuit second data corresponding to a second position and a second orientation of the perspective center of the camera lens, forming with the lens a second image of the surface on the photosensitive array, and sending a second digital signal to the processor in response;
• finding with the processor a first set of cardinal points common to the first image and the second image based at least in part on the first digital signal, the second digital signal;
• finding with the processor a first set of locations on the photosensitive array and a second set of locations on the photosensitive array, the first set of locations corresponding to the first set of cardinal points in the first image and the second set of locations corresponding to the first set of cardinal points in the second image;
• determining a first set of 3D coordinates for the first set of cardinal points, the first set of 3D coordinates including 3D coordinates for each cardinal point of the first set of cardinal points, wherein the 3D coordinates for each cardinal point of the first set of cardinal points is based at least in part on the first position and the first orientation of the perspective center of the camera lens, the first set of locations, the second position and the second orientation of the perspective center of the camera lens, and the second set of locations;
• and
• saving the first 3D coordinates.