Method and apparatus for determining the color of an object that is transparent, diffusing, and absorbent, such as a tooth, in particular
First Claim
1. A method of determining the color of an object that is transparent, diffusing, and absorbent, the method comprising illuminating an area of the object with a diffuse polychromatic light flux that is substantially uniform and isotropic, picking up light backscattered by the object from an aiming zone within the illuminated area, said zone being of dimensions that are considerably smaller than those of the illuminated area and being approximately centered therein, forming an image of said zone on a spectrum analysis device and determining by spectral analysis with said device the intensity of the light backscattered by the object at a relatively small number of wavelengths of predetermined values, and corresponding to hue and saturation sensitivity maxima of the human eye.
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Abstract
A method and apparatus for determining the color of an object which is transparent, diffusing, and absorbent, by illuminating an area of the object by means of a diffuse light flux that is substantially uniform and isotropic, by picking up the light backscattered by a small fraction of the illuminated area of the object by means of an optical system that comprises achromatic doublets and both infrared and ultraviolet filters, together with a diaphragm, and spectrally analyzing said light by means of interference filters and photodetectors. The invention is particularly suitable for determining the color of teeth in the mouth.
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Citations
18 Claims
- 1. A method of determining the color of an object that is transparent, diffusing, and absorbent, the method comprising illuminating an area of the object with a diffuse polychromatic light flux that is substantially uniform and isotropic, picking up light backscattered by the object from an aiming zone within the illuminated area, said zone being of dimensions that are considerably smaller than those of the illuminated area and being approximately centered therein, forming an image of said zone on a spectrum analysis device and determining by spectral analysis with said device the intensity of the light backscattered by the object at a relatively small number of wavelengths of predetermined values, and corresponding to hue and saturation sensitivity maxima of the human eye.
- 9. Apparatus for determining the color of an object that is transparent, diffusing, and absorbent, the apparatus comprising a tube having a diffusing inside surface and an open end for pointing at the object, a light source received inside the tube for illuminating an area of the object by means of a diffuse polychromatic light flux that is substantially uniform and isotropic, an optical system disposed inside the tube close to its open end for picking up the light that penetrates into the tube through said end and for forming an image of a small zone of the illuminated area of the object on spectrum analysis means themselves received with the optical system inside a box disposed inside the tube and forming an opaque screen interposed between the light source and the open end of the tube, the tube also being provided with a handle containing power supply and control means for the light source.
Specification