Method and apparatus for three-dimensional imaging using laser illumination interferometry
First Claim
1. In a method of forming an image of an object utilizing multiple wavelength interferometry, a method for determining the range dimension of the object, the method comprising:
- developing a two-dimensional representation of the image of the object from an interference pattern for each of a plurality of wavelengths at each of a plurality of selected points on the object;
developing a complex value from the two-dimensional representation of the image for each of the plurality of wavelengths at each of the plurality of selected points on the object;
performing a one-dimensional Fourier transform on a series of the complex values for each of the selected points to yield a range profile for each selected point; and
determining a peak value for each of the range profiles to determine the range dimension of the object.
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Abstract
A method for determining a range dimension of an object utilizing multiple wavelength interferometry to form an image of the object includes developing a discernible two-dimensional image from an interference pattern at selected points for each of a number of wavelengths, collecting complex values from the interference pattern and developing a phase value from the complex value, and determining a phase correction vector based on a difference between measured phase values and an ideal phase value associated with one or more reference points. The phase correction vector is used to correct each of the selected points. A one-dimensional Fourier transform is performed on the corrected values to yield a range profile for each selected point. A peak value is then determined from the range profile to determine the range dimension. The peak value may be determined based on a simple maximum, oversampling in selected areas prior to performing the Fourier transform, or using curve-fitting techniques. The phase correction vector minimizes phase errors due to various causes such as insufficient knowledge of the laser frequencies, or which occur when optical path lengths of the object and reference beams are not match, to provide a computationally efficient method of improving accuracy in the range dimension.
33 Citations
12 Claims
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1. In a method of forming an image of an object utilizing multiple wavelength interferometry, a method for determining the range dimension of the object, the method comprising:
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developing a two-dimensional representation of the image of the object from an interference pattern for each of a plurality of wavelengths at each of a plurality of selected points on the object; developing a complex value from the two-dimensional representation of the image for each of the plurality of wavelengths at each of the plurality of selected points on the object; performing a one-dimensional Fourier transform on a series of the complex values for each of the selected points to yield a range profile for each selected point; and determining a peak value for each of the range profiles to determine the range dimension of the object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification