System and methods for analyzing tooth shades

• US 6,206,691 B1
• Filed: 10/04/1999
• Issued: 03/27/2001
• Est. Priority Date: 05/20/1998
• Status: Expired due to Term

• Current Assignee: Maryann Lehmann, System Analyzing Technologies, Inc.
• Original Assignee: Shade Analyzing Technologies
• Inventors: Vock, Curtis A., Youngs, Perry, Lehmann, Maryann
• Primary Examiner(s): Philogene, Pedro
• Application Number:
  US09/411,919
• Time in Patent Office: 540 Days
• Field of Search: 433/29, 433/26, 433/203.1, 433/215, 364/413.28, 356/402, 356/405, 356/406, 356/408, 356/407
• US Class Current: 433/26
• CPC Class Codes: A61C 19/00 Dental auxiliary appliances dental chairs or accessories therefor, working stands whether or not combined with chairs A61G15/00
• CPC Class Codes: A61C 19/10 Supports for artificial teeth for transport or for comparison of the colour
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• 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 3/508 measuring the colour of teeth
• CPC Class Codes: G01N 21/25 Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands

Abstract

A digital camera connects to a tooth shade analyzer subsystem, e.g., a digital video processor, and a color display monitor for the electronic determination of the color of patient'"'"'s teeth. Preliminarily, the camera captures series of digital color images of tooth shades corresponding to reference shade guides, and electronically compares the reference shades to an image of the patient'"'"'s tooth. In a preferred embodiment the comparison is done over a set of pseudo-pixels, each corresponding to a group of pixels in an high-resolution camera. Once a match is found, it is communicated to a user of the system. In a specific embodiment the camera is equipped with a sleeve and illumination subsystems that help reduce the variations in the color of digital images due to external factors.

Claims

1. A method for associating a tooth shade relative to a tooth, comprising:

providing a digital image of the tooth, the digital image having pixels;

processing the digital image to generate a REAL IMAGE formed of pseudo-pixels, at least one of said pseudo-pixels comprising two or more pixels of the digital image; and

correlating the generated REAL IMAGE with two or more REFERENCE IMAGES representing tooth shades to determine which tooth shade most closely matches visual characteristics of the tooth.

2. The method of claim 1 further comprising the steps of capturing digital images of two or more tooth shades, and processing the captured digital images to form said two or more REFERENCE IMAGES.

3. The method of claim 1 wherein the REAL IMAGE and said REFERENCE IMAGES are color images.

4. The method of claim 3, further comprising the step of storing RGB values for pseudo-pixels in the REAL and said REFERENCE IMAGES.

5. The method of claim 1 wherein the step of processing the digital image of the tooth comprises dividing the digital image into segments forming said pseudo-pixels.

6. The method of claim 5 wherein the formed pseudo-pixels are not contiguous.

7. The method of claim 6, wherein the formed pseudo-pixels are based on the shape of the tooth.

8. The method of claim 5 wherein the pseudo-pixels are formed of equal-size segments.

9. The method of claim 5 wherein values associated with said pseudo-pixels are determined by averaging similar values for the pixels in the corresponding segment of the digital image.

10. The method of claim 9 wherein said values are RGB values.

11. The method of claim 1 wherein the step of processing the digital image of the tooth further comprises scaling the image to a pre-defined size.

12. The method of claim 1 further comprising displaying REAL and REFERENCE IMAGES in a humanly-readable form.

13. The method of claim 12 wherein said IMAGES are displayed on a monitor.

14. The method of claim 1 further comprising the step of communicating the determined tooth shade to a user.

15. The method of claim 1 wherein the step of processing the digital image comprises determining pixels, the values for which are outside a pre-determined range compared with values of adjacent pixels.

16. The method of claim 2 further comprising the step of capturing two or more images for each tooth shade, and combining said captured images to obtain an image representative of each tooth shade.

17. The method of claim 16 wherein the step of averaging further comprises determining pixels in each captured image, the values for which are outside a pre-determined range compared with values of adjacent pixels, and excluding said determined pixels in the step of combining.

18. The method of claim 16 wherein the step of combining comprises averaging corresponding pixel values over said two or more images.

19. The method of claim 1 wherein the step of correlating comprises computing a closeness measure.

20. The method of claim 19 wherein the step of computing a closeness measure comprises determining a composite match number (CMN) from the RGB values utilizing the following expression:

${\mathrm{CMN}}_x=\underset{q=1}{\overset{n}{\sum <br><br>}}<br><br>\sqrt{{\left(\frac{R_{x,q}-R_{i,q}}{{\mathrm{Pcount}}_x}\right)}^2+{\left(\frac{G_{x,q}-G_{i,q}}{{\mathrm{Pcount}}_x}\right)}^2+{\left(\frac{B_{x,q}-B_{i,q}}{{\mathrm{Pcount}}_x}\right)}^2}$

where R_x,q, G_x,q and B_x,q denote the R,G and B components for the q-th pseudo-pixel of the x-th tooth shade, and R_i,q G_i,q and B_i,q are the corresponding components of the REAL image, and Pcount_x, corresponds to the number of common pseudo-pixels between the REAL IMAGE and the REFERENCE IMAGE for the x-th tooth shade.

21. The method of claim 20 wherein Pcount_x=1.

22. The method of claim 20 wherein the Pcount_x number is different for at least two separate tooth shades.

23. The method of claim 1 wherein the step of providing a digital image of the tooth comprises capturing the image using a digital camera.

24. A method for determining color characteristics a patient'"'"'s tooth, comprising:

providing a digital image of the tooth, the digital image having pixels;

dividing the digital image into segments, each segment forming a pseudo-pixel comprising one or more pixels of the digital image;

computing color characteristics of each pseudo-pixel based on the corresponding one or more pixels of the original image; and

storing the computed color characteristics in a computer memory.

25. The method of claim 24 further comprising the step of communicating said computed color characteristics associated with each pseudo-pixel to a user.

26. The method of claim 24 wherein the formed pseudo-pixels are not contiguous.

27. The method of claim 24, wherein the formed pseudo-pixels are based on the shape of the tooth.

28. The method of claim 24 wherein the pseudo-pixels are formed of equal-size segments.

29. The method of claim 28 wherein values associated with said pseudo-pixels are determined by averaging similar values for the pixels in the corresponding segment of the digital image.

30. The method of claim 24 wherein said computed color characteristics are RGB values.

31. A system for associating a tooth shade relative to a tooth, comprising:

a digital camera for capturing digital images of human teeth, the digital images having pixels;

a processor for converting digital images captured by the camera to REAL IMAGES formed of pseudo-pixels, at least one of said pseudo-pixels comprising two or more pixels of the digital image; and

means for correlating the generated REAL IMAGE with two or more REFERENCE IMAGES representing tooth shades to determine which tooth shade most closely matches visual characteristics of the tooth.

32. The system of claim 31 further comprising means for illuminating the tooth when capturing a digital image.