Apparatus and method for fluorescence grading of gemstones

• US 10,488,341 B2
• Filed: 09/17/2018
• Issued: 11/26/2019
• Est. Priority Date: 03/30/2015
• Status: Active Grant

• Current Assignee: Gemological Institute of America Incorporated
• Original Assignee: Gemological Institute of America Incorporated
• Inventors: Takahashi, Hiroshi
• Primary Examiner(s): Porta, David P
• Assistant Examiner(s): Faye, Mamadou
• Application Number:
  US16/133,454
• Publication Number:
  US 20190137399A1
• Time in Patent Office: 435 Days
• CPC Class Codes: G01N 2021/6471 Special filters, filter wheel
• CPC Class Codes: G01N 21/6456 Spatial resolved fluorescence measurements; Imaging
• CPC Class Codes: G01N 21/87 Investigating jewels G01N21/88 takes precedence
• CPC Class Codes: G01N 2201/062 LED's
• CPC Class Codes: G01N 2201/0634 Diffuse illumination
• CPC Class Codes: G01N 2201/068 Optics, miscellaneous
• CPC Class Codes: G01N 2201/12 Circuits of general importance; Signal processing
• CPC Class Codes: G01N 33/381 precious stones; pearls

Abstract

Provided herein is an apparatus for assessing a fluorescence characteristic of a gemstone. The apparatus comprises an optically opaque platform for supporting a gemstone to be assessed, one or more light source to provide uniform UV and non-UV illumination, an image capturing component, and a telecentric lens positioned to provide fluorescent images of the illuminated gemstone to the image capturing component. Also provided are methods of fluorescence analysis based on images collected using such an apparatus.

Claims

1. A method of assessing a fluorescence characteristic of a sample gemstone, comprising:

by a computer with a processor and memory,

receiving image data of a sample gemstone under both UV illumination and non-UV illumination;

extracting an outline mask from the non-UV image data;

extracting an apparent fluorescent area from the UV image data;

comparing the outline mask and the apparent fluorescent area to determine if any part of the apparent fluorescent area falls outside of the outline mask;

excluding any apparent fluorescent area that is determined to be outside the outline mask;

obtaining a fluorescent mask based on the comparison of the apparent fluorescent area and the outline mask;

receiving color image data of the sample gemstone under non-UV illumination at a plurality of image rotation angles;

receiving fluorescent image data of the same gemstone under UV illumination at a plurality of image rotation angles, corresponding to the rotation angles of the non-UV illumination color images;

constructing a fluorescence mask for each of the color image pairs based on outline mask analysis of each of the color image pairs;

quantifying color components in each pixel within the constructed fluorescence mask in each fluorescence image thereby converting values of individual color components to corresponding parameters representing a color characteristic of each pixel within the constructed fluorescence mask;

determining an average value for each of the color parameters for all pixels in all color image pairs;

calculating a first fluorescence score of the sample gemstone based on the average values of the parameters of all pixels in all color image pairs.

2. The method of claim 1, further comprising:

calculating a second fluorescence score of a sample gemstone based on pixels in the outline masks for all images of the plurality of fluorescent images.

3. The method of claim 2, further comprising:

assessing the fluorescence characteristic of the sample gemstone by comparing the first or second fluorescence score to values of corresponding fluorescence scores of one or more control fluorescence gemstones which are previously determined.

4. The method of claim 2, wherein the first fluorescence score reflects the color of the fluorescence and wherein the second fluorescence score reflects the strength.

5. The method of claim 1, further comprising:

collecting the plurality of images of the sample gemstone using an image capturing component at uniquely different image rotational angles while maintaining a constant image view angle.

6. The method of claim 1, further comprising:

collecting the plurality of fluorescent images of the sample gemstone using an image capturing component at uniquely different image rotational angles while maintaining a constant image view angle, wherein each fluorescent image in the plurality of fluorescent images corresponds to an image in the plurality of image and both are captured under identical image rotational angle and image view angle.

7. The method of claim 1, further comprising:

determining a fluorescence mask for each fluorescent image in the plurality of fluorescent images.

8. The method of claim 7, further comprising:

quantifying individual color components in each pixel in the fluorescence mask in each fluorescent image of the plurality of fluorescent images.

9. The method of claim 6, further comprising:

collecting a new plurality of fluorescent images of the sample gemstone using the image capturing component at the uniquely different image rotational angles while maintaining the constant image view angle, wherein there is a time gap between the time when the plurality of fluorescent images is collected and the time when the new plurality of fluorescent images is collected;

assigning a new fluorescent grade based on the new plurality of fluorescent images; and

comparing the fluorescent grade and the new fluorescent grade based on the time gap.

10. The method of claim 9, wherein the time gap is between 2 minutes and 5 hours.

11. A non-transitory computer-readable medium having computer-executable instructions thereon for a method of assessing a fluorescence characteristic of a sample gemstone, the method comprising:

by a computer with a processor and memory,

receiving image data of a sample gemstone under both UV illumination and non-UV illumination;

extracting an outline mask from the non-UV image data;

extracting an apparent fluorescent area from the UV image data;

comparing the outline mask and the apparent fluorescent area to determine if any part of the apparent fluorescent area falls outside of the outline mask;

excluding any apparent fluorescent area that is determined to be outside the outline mask;

obtaining a fluorescent mask based on the comparison of the apparent fluorescent area and the outline mask;

receiving color image data of the sample gemstone under non-UV illumination at a plurality of image rotation angles;

receiving fluorescent image data of the same gemstone under UV illumination at a plurality of image rotation angles, corresponding to the rotation angles of the non-UV illumination color images;

constructing a fluorescence mask for each of the color image pairs based on outline mask analysis of each of the color image pairs;

quantifying color components in each pixel within the constructed fluorescence mask in each fluorescence image thereby converting values of individual color components to corresponding parameters representing a color characteristic of each pixel within the constructed fluorescence mask;

determining an average value for each of the color parameters for all pixels in all color image pairs;

calculating a first fluorescence score of the sample gemstone based on the average values of the parameters of all pixels in all color image pairs.

12. The non-transitory computer-readable medium of claim 11, further comprising:

calculating a second fluorescence score of a sample gemstone based on pixels in the outline masks for all images of the plurality of fluorescent images.

13. The non-transitory computer-readable medium of claim 12, further comprising:

assessing the fluorescence characteristic of the sample gemstone by comparing the first or second fluorescence score to values of corresponding fluorescence scores of one or more control fluorescence gemstones which are previously determined.

14. The non-transitory computer-readable medium of claim 12, wherein the first fluorescence score reflects the color of the fluorescence and wherein the second fluorescence score reflects the strength.

15. The non-transitory computer-readable medium of claim 11, further comprising:

collecting the plurality of images of the sample gemstone using an image capturing component at uniquely different image rotational angles while maintaining a constant image view angle.

16. The non-transitory computer-readable medium of claim 11, further comprising:

collecting the plurality of fluorescent images of the sample gemstone using an image capturing component at uniquely different image rotational angles while maintaining a constant image view angle, wherein each fluorescent image in the plurality of fluorescent images corresponds to an image in the plurality of image and both are captured under identical image rotational angle and image view angle.

17. The non-transitory computer-readable medium of claim 11, further comprising:

determining a fluorescence mask for each fluorescent image in the plurality of fluorescent images.

18. The non-transitory computer-readable medium of claim 17, further comprising:

quantifying individual color components in each pixel in the fluorescence mask in each fluorescent image of the plurality of fluorescent images.

19. The non-transitory computer-readable medium of claim 16, further comprising:

collecting a new plurality of fluorescent images of the sample gemstone using the image capturing component at the uniquely different image rotational angles while maintaining the constant image view angle, wherein there is a time gap between the time when the plurality of fluorescent images is collected and the time when the new plurality of fluorescent images is collected;

assigning a new fluorescent grade based on the new plurality of fluorescent images; and

comparing the fluorescent grade and the new fluorescent grade based on the time gap.

20. The non-transitory computer-readable medium of claim 19, wherein the time gap is between 2 minutes and 5 hours.