Method of determining an illuminated surface
AssigneeStfi
InventorsPer-Ake Johansson, Peter Hansson
Life of this patent
Estimating the term…
Abstract
Method of determining a surface illuminated by incident light. First the intensity (I1(x,y)) of light reflected from the surface is recorded in a first image of the surface. After this, the intensity (I2(x,y)) of light reflected from the surface is recorded in a second image of the surface, taken at a different angle of illumination. Only the diffusely reflected light is recorded. The difference between the recorded intensities of the first and the second images is determined to obtain a representation that emphasizes variations in gradient of the surface. This representation is further processed by signal-adapted integration to a topographic description, that is, a height function of the surface.
Claims22
A method for determining a surface illuminated by incident light by recording the intensity (I1(x,y)) in light reflected from the surface in a first image thereof and by recording the intensity (I1(x,y)) in light reflected from the surface in a second image thereof, taken with another angle of illumination and complementary to the first image, comprising:
- recording the intensity of only diffusely reflected light over the surface in the first and second images;
- determining the difference between the recorded intensities of diffusely reflected light over the surface in the first and second images in order to obtain a representation that emphasizes variations in gradient of the surface;
- calculating the derivative of the area by f x ′ ( x , y ) ≈ 1 tan Y I 1 ( x , y ) - I 2 ( x , y ) I 1 ( x , y ) - I 2 ( x , y )
- where Y is the angle of incidence of the light;
- and
- Fourier transformation of the derivative and multiplication thereof by a Wiener filter in order to suppress noise in the recorded intensities.
A method for determining a surface illuminated by incident light by recording the intensity (I1(x,y)) in light reflected from the surface in a first image thereof and by recording the intensity (I1(x,y)) in light reflected from the surface in a second image thereof, taken with another angle of illumination and complementary to the first image, comprising:
- recording the intensity of only diffusely reflected light over the surface in the first and second images;
- determining the difference between the recorded intensities of diffusely reflected light over the surface in the first and second images in order to obtain a representation that emphasizes variations in gradient of the surface;
- and
- polarizing the incident light and thereto crosswise polarization of the reflected light in order to eliminate reflections in the surface and obtain the diffusely reflected light.
A method for determining a surface illuminated by incident light by recording the intensity (I1(x,y)) in light reflected from the surface in a first image thereof and by recording the intensity (I1(x,y)) in light reflected from the surface in a second image thereof, taken with another angle of illumination and complementary to the first image, comprising:
- recording the intensity of only diffusely reflected light over the surface in the first and second images, wherein the first image is recorded with light in a first wavelength region and that the second image is recorded with light in a second wavelength region, distinct from the first wavelength region;
- and
- determining the difference between the recorded intensities of diffusely reflected light over the surface in the first and second images in order to obtain a representation that emphasizes variations in gradient of the surface.
Dependencies are inferred from the claim text.