Techniques for shape measurement using high frequency patterns and related systems and methods
Techniques for scanning through structured light techniques that are robust to global illumination effects and that provide an accurate determination of position as provided. According to some aspects, described techniques may be computationally efficient compared with conventional techniques by making use of a novel approach of selecting frequencies of patterns for projection onto a target that mathematically enable efficient calculations. In particular, the selected frequencies may be chosen so that there is a known relationship between the frequencies. This relationship may be derived from Chebyshev polynomials and also relates the chosen frequencies to a low frequency pattern.
1. A computer-implemented method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
wherein the first, second and third relative phases are calculated for pixels with the first, second and third images, respectively, and wherein said pixels have a common pixel coordinate in the first, second and third images.
2. A computer-implemented method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
obtaining a fourth image of the object, the fourth image being captured whilst the object is illuminated with light having the spatially repeating pattern of the first frequency phase-shifted with respect to the light illuminating the object during capture of the first image, and wherein calculating the first relative phase is further based on the fourth image.
3. The method of claim 2 , wherein calculating the first relative phase is based on intensities of at least two pixels including a pixel of the first image and a pixel of the fourth image, wherein the at least two pixels have identical pixel coordinates within respective images.
4. A computer-implemented method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
wherein the difference between the first and second frequencies and the difference between the second and third frequencies is equal to half the base frequency.
5. A computer-implemented method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
wherein calculating the at least one absolute phase is not based on an image of the object illuminated with light having a spatially repeating pattern of the base frequency.
6. A non-transitory computer-readable medium comprising instructions that, when executed by at least one processor, perform a method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
wherein the first, second and third relative phases are calculated for pixels with the first, second and third images, respectively, and wherein said pixels have a common pixel coordinate in the first, second and third images.
7. A non-transitory computer-readable medium comprising instructions that, when executed by at least one processor, perform a method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
obtaining a fourth image of the object, the fourth image being captured whilst the object is illuminated with light having the spatially repeating pattern of the first frequency phase-shifted with respect to the light illuminating the object during capture of the first image, and wherein calculating the first relative phase is further based on the fourth image.
8. The non-transitory computer-readable medium of claim 7 , wherein calculating the first relative phase is based on intensities of at least two pixels including a pixel of the first image and a pixel of the fourth image, wherein the at least two pixels have identical pixel coordinates within respective images.
9. A non-transitory computer-readable medium comprising instructions that, when executed by at least one processor, perform a method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
wherein the difference between the first and second frequencies and the difference between the second and third frequencies is equal to half the base frequency.
10. A non-transitory computer-readable medium comprising instructions that, when executed by at least one processor, perform a method of determining the shape of an object, the method comprising:
obtaining a first image of an object, the first image being captured whilst the object is illuminated with light having a spatially repeating pattern of a first frequency;
obtaining a second image of the object, the second image being captured whilst the object is illuminated with light having a spatially repeating pattern of a second frequency;
obtaining a third image of the object, the third image being captured whilst the object is illuminated with light having a spatially repeating pattern of a third frequency,
wherein the first, second and third frequencies are different and wherein a difference between the first and second frequencies is equal to a difference between the second and third frequencies;
calculating, based at least in part on the first image, at least a first relative phase representing a relative position within the spatially repeating pattern having the first frequency;
calculating, based at least in part on the second image, at least one a second relative phase representing a relative position within the spatially repeating pattern having the second frequency;
calculating, based at least in part on the third image, at least a third relative phase representing a relative position within the spatially repeating pattern having the third frequency;
calculating, for a pattern of a base frequency, and based at least in part on the first, second and third frequencies, at least one absolute phase representing an absolute position within the pattern of the base frequency;
calculating spatial coordinates for at least one three-dimensional point on the object based at least in part on the calculated absolute phase; and
wherein calculating the at least one absolute phase is not based on an image of the object illuminated with light having a spatially repeating pattern of the base frequency.