Patent ID: 9091529
Filing Date: 2015-07-28
Classification: G01B

Abstract:
1. A method for determining three-dimensional coordinates of a first object point on a surface of an object, the method comprising steps of: providing a first source, a projector, and a camera, the projector including a first diffraction grating, an objective lens, and a first plate, the camera including a camera lens and a photosensitive array, the first source producing a first source beam of light, the first plate containing a first transmissive region, a second transmissive region, and at least one opaque region, the at least one opaque region formed with a coating placed on a surface of the first plate, the projector having a projector perspective center, the camera having a camera perspective center, a line segment between the projector perspective center and the camera perspective center being a baseline, the baseline having a baseline length; sending the first source beam of light to the first diffraction grating; forming with the first diffraction grating at least a first diffracted beam of light, a second diffracted beam of light, and a residual light, the residual light being light from the first source beam of light that passes through the first diffraction grating and that is other than the first diffracted beam of light or the second diffracted beam of light; sending the first diffracted beam of light, the second diffracted beam of light, and the residual light to the objective lens; forming with the objective lens at least a first spot of light and a second spot of light, the first spot of light arising from the first diffracted beam of light and the second spot of light arising from the second diffracted beam of light; placing the first plate in a first position near the first spot of light and the second spot of light; passing first light from the first spot of light through a first thickness of glass in the first transmissive region and passing second light from the second spot of light through a second thickness of glass in the second transmissive region while blocking, with the at least one opaque region, the residual light from passing the first plate, wherein a difference in the first thickness and the second thickness is equal to a first thickness difference; combining the first light and the second light to produce a first fringe pattern on the surface of the object; imaging the first object point illuminated by the first fringe pattern onto an array point on a photosensitive array to obtain a first electrical data value from the photosensitive array; moving the first plate to a second position; passing third light from the first spot of light through a third thickness of glass in the first transmissive region and passing fourth light from the second spot of light through a fourth thickness of glass in the second transmissive region while blocking, with the at least one opaque region, the residual light from passing the first plate, wherein a difference in the third thickness and the fourth thickness is equal to a second thickness difference, the second thickness difference not equal to the first thickness difference; combining the third light and the fourth light on the surface of the object to produce a second fringe pattern on the surface of the object, the first fringe pattern and the second fringe pattern having a first fringe pitch at the first object point; imaging the first object point illuminated by the second fringe pattern onto the array point to obtain a second electrical data value from the photosensitive array; calculating the three-dimensional coordinates of the first object point based at least in part on the first electrical data value, the second electrical data value, and the baseline length; and storing the three-dimensional coordinates of the first object point.