Hidden change distribution grating and use in 3D moire measurement sensors and CMM applications

Method for determining the surface of an object using a mini-moire sensor and a moire process, comprising the steps of:

• providing an optical grating means consisting of a nominal pattern having a pattern frequency and small statistical variations in the pattern frequency such that phase calculations associated with the variations are unique and hidden in noise of the moire process;
• projecting the pattern onto a surface area of an object;
• recording an image intensity of the pattern projected on the surface area;
• passing the image intensity through a first pass filter to generate a residual phase plus hidden pattern phase;
• processing the generated residual phase plus hidden pattern phase in a matched filter that uses a known hidden change phase as a reference to produce a unique autocorrelation function;
• providing an N modulus map for substantially every pixel in at least a portion of a field-of-view of the moire sensor;
• and
• determining a surface phase of the surface area of the object phase from the residual phase plus hidden pattern phase, the autocorrelation function and the N modulus map, the surface phase being representative of the surface area of the object.

A high-speed three-dimensional surface measurement system for determining the surface of an object using a moire process, comprising:

• a mini-moire sensor having a hidden change Ronchi grating consisting of a nominal Ronchi pattern having a pattern frequency and small statistical variations in the pattern frequency such that phase calculations associated with the variations are unique and hidden in noise of the moire process;
• said mini-moire sensor having means for projecting the pattern onto a surface area of an object;
• said mini-moire sensor having means for recording an image intensity of the pattern projected on the surface area;
• means for passing the image intensity through a first pass filter to generate a residual phase plus hidden pattern phase;
• means for processing the generated residual phase plus hidden pattern phase in a matched filter that uses a known hidden change phase as a reference to produce a unique autocorrelation function;
• means for providing an N modulus map for substantially every pixel in at least a portion of a field-of-view of the moire sensor;
• and
• means for determining a surface phase of the surface area of the object phase from the residual phase plus hidden pattern phase, the autocorrelation function and the N modulus map, the surface phase being representative of the surface area of the object.

An upgrade for a coordinate measuring machine for high-speed surface measurement of the surface of an object using a moire process, the coordinate measuring machine having at least a pan/tilt head, comprising:

• a mini-moire sensor attached to the pan/tilt head of the coordinate measuring machine;
• said moire sensor having at least first means for illuminating at least a surface area of the object with at least one fringe pattern, said at least first means for illuminating having optical grating means for producing said at least one fringe pattern, said optical grating means consisting of a nominal pattern having a pattern frequency and small statistical variations in the pattern frequency such that phase calculations associated with the variations are unique and hidden in noise of the moire process, and said moire sensor also having a single means for receiving reflected illumination from said surface area, said at least one means for receiving reflected illumination providing an electronic signal representative of reflected illumination received thereby;
• and
• means for determining the three-dimensioned surface configuration of said surface area of the object from said electronic signal by utilizing the phase calculations associated with the variations in the pattern frequency;
• wherein said coordinate measuring machine has at least one mode wherein said mini-moire sensor continuously scans the object.

A high-speed three-dimensional surface measurement system for use in determining the surface of an object from at least one electronic signal using a moire process, comprising:

• mini-moire sensor having at least first means for illuminating at least a surface area of the object with at least one fringe pattern, said at least first means for illuminating having optical grating means for producing said at least one fringe pattern, said optical grating means consisting of a nominal pattern having a pattern frequency and small statistical variations in the pattern frequency such that phase calculations associated with the variations are unique and hidden in noise of the moire process, and also having a single means for receiving reflected illumination from said surface area, said at least one means for receiving reflected illumination providing an electronic signal representative of reflected illumination received thereby;
• means for processing said electronic signal by utilizing the phase calculations associated with the variations in the pattern frequency to provide at least a storable X-Y-Z image of the surface area of the object;
• and
• means for moving said mini-moire sensor in order to scan the object.