Phase estimation distortion analysis

An apparatus for determining displacements between pixels in a captured image of a reference pattern and corresponding pixels in the reference pattern, said apparatus comprising:

• a scanner for capturing the image of the reference pattern comprising a source pattern modulated by a plurality of carrier frequencies increasing in a corresponding plurality of directions in the source pattern;
• a demodulator for demodulating at least three of the carriers in the captured image to form an amplitude image and a wrapped phase image for each of the carrier frequencies;
• and
• a combiner for combining the wrapped phase images weighted by the amplitude images to determine said displacements between pixels in the captured image and corresponding pixels in the reference pattern.

A computer readable storage medium having recorded thereon a computer program for directing a processor to execute a method for determining displacements between pixels in a captured image of a reference pattern and corresponding pixels in the reference pattern, said program comprising:

• code for capturing the image of the reference pattern comprising a source pattern modulated by a plurality of carrier frequencies increasing in a corresponding plurality of directions in the source pattern;
• code for demodulating at least three of the carriers in the captured image to form an amplitude image and a wrapped phase image for each of the carrier frequencies;
• and
• code for combining the wrapped phase images weighted by the amplitude images is to determine said displacements between pixels in the captured image and corresponding pixels in the reference pattern.

An apparatus for determining displacements between pixels in a captured image of a reference pattern and corresponding pixels in the reference pattern, said apparatus comprising:

• a memory storing a program;
• and
• a processor for executing said program which comprises:
• code for capturing the image of the reference pattern comprising a source pattern modulated by a plurality of carrier frequencies increasing in a corresponding plurality of directions in the source pattern;
• code for demodulating at least three of the carriers in the captured image to form an amplitude image and a wrapped phase image for each of the carrier frequencies;
• and
• code for combining the wrapped phase images weighted by the amplitude images to determine said displacements between pixels in the captured image and corresponding pixels in the reference pattern.

A method for determining spatial distortion introduced by an imaging system by determining displacements between pixels in an image of a reference pattern captured by the imaging system and corresponding pixels in the reference pattern, said method comprising the steps of:

• capturing using said imaging system the image of the reference pattern comprising a source pattern modulated by a plurality of carrier frequencies in a corresponding plurality of directions in the source pattern;
• demodulating at least three of the carriers in the captured image to form an amplitude image and a wrapped phase image for each of the carrier frequencies;
• and
• combining the wrapped phase images weighted by the amplitude images to determine said displacements between pixels in the captured image and corresponding pixels in the reference pattern, thereby determining the spatial distortion introduced by the imaging system.

A method of determining performance of an imaging device, the method comprising the steps of:

• capturing using the imaging device an image of a reference pattern comprising a source pattern modulated by a plurality of carrier frequencies in a corresponding plurality of directions in the source pattern;
• demodulating at least three of the carriers in the captured image to form an amplitude image and a wrapped phase image for each of the carrier frequencies;
• and
• combining the wrapped phase images weighted by the amplitude images to determine displacements between pixels in the captured image and corresponding pixels in the reference pattern, wherein said displacements between pixels in the captured image of the reference pattern and corresponding pixels in the reference pattern characterize the performance of the imaging device.