Dental color imaging system

• US 20040252303A1
• Filed: 06/12/2003
• Published: 12/16/2004
• Est. Priority Date: 06/12/2003
• Status: Active Grant

• Current Assignee: Carestream Dental Technology Topco Limited
• Original Assignee: Eastman Kodak Company
• Inventors: Giorgianni, Edward J., Forsythe, Alexander G.
• Granted Patent: US 7,064,830 B2
• Time in Patent Office: Days
• US Class Current: 356/402
• CPC Class Codes: G01J 3/462 Computing operations in or between colour spaces; Colour management systems
• CPC Class Codes: G01J 3/463 Colour matching
• CPC Class Codes: G01J 3/50 using electric radiation detectors
• CPC Class Codes: G01J 3/508 measuring the colour of teeth

Abstract

A method for determining visual calorimetric values for an object having particular spectral reflectance characteristics comprises the steps of: (a) photographing an object with an electronic image capture device to form device image values; (b) selecting a transform from a plurality of transforms for converting device image values to visual colorimetric values, wherein the selection of the transform is based on the particular spectral reflectance characteristics of the object; and (c) applying the selected transform to the device image values to determine the visual colorimetric values for the object.

Claims

1. A method for determining visual calorimetric values for an object having particular spectral reflectance characteristics, said method comprising the steps of:

(a) photographing an object with an electronic image capture device to form device image values;

(b) selecting a transform from a plurality of transforms for converting the device image values to visual colorimetric values, wherein the selection of said transform is based on the particular spectral reflectance characteristics of said object; and

(c) applying the selected transform to said device image values to determine said visual calorimetric values for said object.

2. The method of claim 1 further comprising the steps of:

(d) comparing said visual colorimetric values for said object to visual colorimetric values for each of a plurality of color references; and

(e) selecting one or more color references having a preferred visual colorimetric correspondence to said object.

3. The method of claim 2 wherein at least one of steps (d) and (e) uses a mathematical algorithm that includes a set of parameters associated with individual calorimetric attributes that are used for selecting the one or more color references having a preferred visual calorimetric correspondence to said object.

4. The method of claim 3 wherein the set of parameters includes a plurality of selectable sets of parameters, each set representing different criteria for preferred visual calorimetric correspondence.

5. The method of claim 2 further comprising the steps of:

(f) determining and specifying the degree of visual colorimetric correspondence between the one or more selected color references and said object; and

(g) indicating the degree of visual calorimetric correspondence between the selected one or more color references and said object in terms of at least one of numerical values, graphical illustrations, and verbal descriptions.

6. The method of claim 2 wherein step (d) comprises a visual comparison of said visual calorimetric values for said object to visual calorimetric values for each of a plurality of color references, wherein a complete or partial image of said object is shown immediately adjacent to or in close proximity to a complete or partial image corresponding to the calorimetric values of the one or more selected color references.

7. The method of claim 5 wherein said degree of visual colorimetric correspondence between the one or more selected color references and said object is shown as a complete or partial image of said object immediately adjacent to or in close proximity to a complete or partial image corresponding to the colorimetric values of the one or more selected color references.

8. The method of claim 6 wherein said complete or partial image corresponding to the colorimetric values of the one or more selected color references can be adjusted by a human operator.

9. The methods of claim 6 wherein the object and reference images are displayed in a monochrome mode.

10. The methods of claim 6 wherein chroma of the object and reference images is displayed in a mode in which the displayed chroma is increased similarly for all colors.

11. The method of claim 6 wherein chroma of the object and reference images is displayed in a mode in which the displayed chroma of colors is increased in inverse proportion to their original chroma.

12. The methods of claim 6 wherein the object and reference images are displayed at reduced spatial resolution.

13. The method of claim 7 wherein said complete or partial image corresponding to the colorimetric values of the one or more selected color references can be adjusted by a human operator.

14. The methods of claim 7 wherein the object and reference images are displayed in a monochrome mode.

15. The methods of claim 7 wherein chroma of the object and reference images is displayed in a mode in which the displayed chroma is increased similarly for all colors.

16. The method of claim 7 wherein chroma of the object and reference images is displayed in a mode in which the displayed chroma of colors is increased in inverse proportion to their original chroma.

17. The methods of claim 7 wherein the object and reference images are displayed at reduced spatial resolution.

18. A method for determining and specifying one or more shades of a natural tooth by comparing visual colorimetric values of a measurement image of said tooth to a database of visual colorimetric values of reference shades, said method comprising the steps of:

(a) uniformly illuminating at least one natural tooth in a manner that minimizes or eliminates specular reflections for a front surface of said tooth;

(b) including an intra-oral reference within the measurement image;

(c) photographing the intra-oral reference together with said tooth with a digital camera to form camera image values;

(d) using the camera image values for the intra-oral reference to correct the camera image values for errors in exposure due to lighting or camera variations, thereby providing corrected camera image values;

(e) applying a transform based on the spectral reflectance characteristics of natural teeth to convert the corrected camera image values to visual colorimetric values;

(f) specifying pixel locations corresponding to one or more areas of said tooth for which the one or more shades are to be determined;

(g) comparing the visual calorimetric values for said pixel locations to the visual calorimetric values of the database of visual colorimetric values of reference shades; and

(h) determining one or more reference shades based on their correspondence to the visual colorimetric values for said pixel locations corresponding to said one or more areas of said tooth.

19. The method as claimed in claim 18 wherein the intra-oral reference used in step (b) includes optical properties that correlate with those of natural teeth.

20. A method for determining and specifying one or more shades of a dental prosthesis by comparing visual colorimetric values of a measurement image of said dental prosthesis to a database of visual colorimetric values of reference shades, wherein said dental prosthesis is fabricated of particular types of dental materials having particular spectral reflectance characteristics, said method comprising the steps of:

(a) uniformly illuminating a dental prosthesis in a manner that minimizes or eliminates specular reflections from a front surface of the dental prosthesis;

(b) including a known reference within the measurement image;

(c) including a background within the measurement image, wherein said background simulates the geometric and color characteristics of a human mouth;

(d) including a cap on said dental prosthesis, wherein said cap simulates the geometric and color characteristics of human gums;

(e) photographing said known reference with said dental prosthesis, background, and cap with a digital camera to form camera image values;

(f) using said camera image values of said known reference to correct for errors in exposure due to lighting and/or camera variations, thereby providing corrected camera image values;

(g) applying a transform based on the particular spectral reflectance characteristics of the particular types of dental materials from which said dental prosthesis was fabricated to convert the corrected camera image values to visual colorimetric values;

(h) specifying pixel locations corresponding to one or more areas of said dental prosthesis for which the one or more shades are to be determined;

(i) comparing the visual calorimetric values for said pixel locations to the visual calorimetric values of the database of visual calorimetric values of reference shades; and

(j) determining one or more reference shades based on their correspondence to the visual colorimetric values for said pixel locations corresponding to said one or more areas of said dental prosthesis.

21. A method for determining visual colorimetric values of a reference shade sample from a measurement image, wherein said reference shade sample is fabricated of particular types of materials having particular spectral reflectance characteristics, said method comprising the steps of:

(a) uniformly illuminating a reference shade sample in a manner that minimizes or eliminates specular reflections from a front surface of the reference shade sample;

(b) including a known reference within the measurement image;

(c) including a background within the measurement image, wherein said background simulates the geometric and color characteristics of a human mouth;

(d) including a cap on said reference shade sample, wherein said cap simulates the geometric and color characteristics of human gums;

(e) photographing said known reference together with said reference shade sample, background, and cap with a digital camera to form camera image values;

(f) using said camera image values for said known reference to correct image values for errors in exposure due to lighting and/or camera variations, thereby providing corrected camera image values;

(g) applying a transform based on the particular spectral reflectance characteristics of the particular types of materials from which said reference shade sample is fabricated to convert the corrected camera image values to visual colorimetric values;

(h) specifying pixel locations corresponding to one or more areas of said reference shade sample for which visual colorimetric values are to be determined; and

(i) determining the visual calorimetric values for said areas of said reference shade sample.

22. The method of claim 21 wherein the reference shade sample is a dental shade tab.

23. The method of claim 21 further comprising the steps of:

(j) repeating steps (a) through (g) for a plurality of reference shade samples of a same basic type, thereby producing corresponding visual colorimetric values for each reference shade sample of a same basic type; and

(k) averaging the corresponding visual calorimetric values determined for all samples of the same basic type to obtain visual colorimetric values for a reference shade of that type.

24. A method for generating an image of a simulated dental prosthesis for display on a display device, said method comprising the steps of:

(a) specifying desired visual calorimetric values for one or more areas of a prosthesis that is to be simulated;

(b) adjusting the visual colorimetric values of an image of a similar natural tooth, prosthesis or shade tab to correspond to said desired visual calorimetric values; and

,

(c) transforming the adjusted visual colorimetric values of the image to display device signal values; and

(d) using said display device signal values to display an image corresponding to said simulated dental prosthesis.

25. The method of claim 24 further comprising the steps of:

(e) adjusting a size and shape of the displayed image of said simulated dental prosthesis; and

(f) placing the displayed image of said simulated dental prosthesis appropriately within a displayed image of a mouth to create a visualization of the appearance of the dental prosthesis within the mouth, thereby generating a placed display image having particular visual colorimetric values.

26. The method of claim 25 further comprising the steps of:

(g) adjusting the particular visual colorimetric values of the placed displayed image of said simulated dental prosthesis displayed within the displayed image of a patient'"'"'s mouth, thereby generating adjusted visual calorimetric values; and

(h) indicating the adjusted visual calorimetric values in terms of at least one of numerical values, shade tab specifications, graphical illustrations and verbal descriptions.

27. A dental imaging system, said system including:

(a) a first stage for illuminating teeth for producing shade-measurement images, wherein said first stage provides illumination that is substantially uniform in intensity and chromaticity within an illuminating region to be measured, and wherein said first stage also provides illumination that minimizes unwanted reflections within said illuminating region to be measured; and

(b) a second stage for illuminating teeth and other areas of the mouth, wherein said second stage provides illumination for producing images that convey additional information regarding tooth detail including at least one of gloss, texture, transparency, translucency, cracks, streaks, spots, and stains.

28. A system for determining visual calorimetric values for an object having particular spectral reflectance characteristics, said system comprising:

an electronic capture device for photographing an object and obtaining device image values corresponding to the object;

a transform selector for selecting a transform from a plurality of transforms for converting the device image values to visual colorimetric values, wherein the selection of said transform is based on the particular spectral reflectance characteristics of said object; and

a transform processing stage for applying the selected transform to said device image values to determine said visual calorimetric values for said object.