Classifying and sorting crystalline objects

• US 5,544,254 A
• Filed: 03/08/1995
• Issued: 08/06/1996
• Est. Priority Date: 02/12/1993
• Status: Expired due to Term

• Current Assignee: Diamond Innovations Incorporated (Sandvik AB)
• Original Assignee: General Electric Company
• Inventors: Liu, Jane S., Hartley, Richard I., Grande, James C. M., Noble, Julia A., Jackson, William E., Welles, Kenneth B. II
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Shalwala, Bipin
• Application Number:
  US08/400,556
• Time in Patent Office: 517 Days
• Field of Search: 382/209, 382/215-219, 382/141, 382/152, 382/224, 382/227, 382/201, 382/203, 382/204, 382/206, 382/100, 382/108, 209/576, 209/577, 209/579, 209/588, 209/594, 356/30
• US Class Current: 382/108
• CPC Class Codes: B07C 5/10 measured by light-responsive means sorting according to colour B07C5/342
• CPC Class Codes: B07C 5/3425 of granular material, e.g. ore particles, grain investigation moving fluids or granular solids using optical means G01N21/85
• CPC Class Codes: B07C 5/365 using a single separation means

Abstract

An apparatus and method of classifying and sorting by shape crystalline objects such as synthetic diamonds in which an image of the object taken from an angle defined in relation to the object is compared to one or more templates in order to characterize the object.

Claims

1. Apparatus for sorting crystalline objects, said apparatus comprising:

image means for creating an image of a crystalline object viewed from a defined angle, said image comprising a set of polygonal outlines including a first polygonal outline corresponding to the representation of the silhouette of said crystalline object in said image and a second polygonal outline corresponding to the representation of the shape of a crystalline face of said crystalline object in said image;

comparison means for comparing said set of polygonal outlines of said image to (a) at least one template derived from a set of reference polygons including a first reference polygon corresponding to a silhouette of a reference crystal and a second reference polygon corresponding to the shape of a crystalline face of said reference crystal within said silhouette, wherein said template can be varied in position, size, and shape by changing the values of at least one parameter, and (b) at least one set of parameter values for said at least one template, for varying the position, size, and shape of said at least one template by changing the values of said at least one parameter, and for selecting at least one combination of a template and a set of parameter values corresponding to said image;

output means for indicating at least one parameter value selected by said comparison means; and

sorting means for sorting the crystalline object to one of a plurality of destinations dependent upon at least one parameter value selected by said comparison means.

2. The apparatus of claim 1 wherein the crystalline object is a cubic-system crystal.

3. The apparatus of claim 1 wherein the crystalline object is a diamond.

13. The apparatus of claim 1 wherein the image means comprises:

a clear plate for supporting said crystalline objects;

a reflective surface positioned below said plate;

a light source for illuminating said reflective surface;

a video camera positioned with its viewing axis normal to said plate.

14. The apparatus of claim 13 wherein said comparison means is a computer.

15. The apparatus of claim 14 wherein said crystalline object is a cubic-system crystal, said parameters comprise a shape parameter τ

, and said templates each comprise an inner outline and an outer outline which are defined by specifying a set of vertices for each outline as follows;

the vertices of the inner outline of a first template are defined as;

(0, 2τ

), (2τ

,

     0), (0, -2τ

), (-2τ

,

     0);

the vertices of the outer outline of said first template are defined as;

(-2τ

,

     1), (2τ

,

     1), (1, 2τ

), (1, -2τ

), (2τ

, -1), (-2τ

, -1), (-1, -2τ

), (-1, 2τ

);

the vertices of the inner outline of a second template are defined as;

(1-2τ

,

     1), (2τ

-1,

     1), (1, 2τ

-1), (1, 1-2τ

), (2τ

-1, -1), (1-2τ

, -1), (-1, 1-2τ

), (-1, 2τ

-1);

the vertices of the outer outline of said second template are defined as;

(-1,

     1), (1,

     1), (1, -1), (-1, -1);

the vertices of the outer outline of a third template are defined in polar coordinates as;

(R, g±

θ

), where g takes the values 0°

, 60°

, 120°

, 180°

, 240°

, and 300°

, and R and Θ

are defined;

R=√

(2τ

² +(2/3)(1+τ

)²), Θ

=tan^-1 (√

3τ

/(1+τ

));

the vertices of the inner outline of said third template are defined in polar coordinates as;

(r, h±

φ

), where h takes the values 0°

, 120°

, and 240°

, and r and φ

are defined;

r=√

(((1+2τ

)² /6)+((1-2τ

)² /3)), φ

=tan^-1 ((√

3(1-2τ

))/(1+2τ

)).

16. The apparatus of claim 15 wherein said cubic-system crystal is a diamond.

4. Apparatus for sorting crystalline objects, said apparatus comprising:

image means for creating an image of a crystalline object viewed from a defined angle, said image comprising a set of polygonal outlines including a first polygonal outline corresponding to the representation of the silhouette of said crystalline object in said image and a second polygonal outline corresponding to the representation of the shape of a crystalline face of said crystalline object in said image;

comparison means for comparing said set of polygonal outlines of said image to (a) at least one template derived from a set of reference polygons including a first reference polygon corresponding to a silhouette of a reference crystal and a second reference polygon corresponding to the shape of a crystalline face of said reference crystal within said silhouette, wherein said template can be varied in position, size, and shape by changing the values of at least one parameter, and (b) at least one set of parameter values for said at least one template;

varying the position, size, and shape of said at least one template by changing the values of said at least one parameter; and

selecting at least one combination of a template and a set of parameter values corresponding to said image;

sorting means for sorting the crystalline object to one of a plurality of destinations dependent upon at least one parameter value selected by said comparison means.

5. The apparatus of claim 4 wherein the crystalline object is a cubic-system crystal.

6. The apparatus of claim 4 wherein the crystalline object is a diamond.

17. The apparatus of claim 4 wherein the image means comprises:

a clear plate for supporting said crystalline objects;

a reflective surface positioned below said plate;

a light source for illuminating said reflective surface;

a video camera positioned with its viewing axis normal to said plate.

18. The apparatus of claim 17 wherein said comparison means is a computer.

19. The apparatus of claim 18 wherein said crystalline object is a cubic-system crystal, said parameters comprise a shape parameter τ

, and said templates each comprise an inner outline and an outer outline which are defined by specifying a set of vertices for each outline as follows;

the vertices of the inner outline of a first template are defined as;

(0, 2τ

), (2τ

,

     0), (0, -2τ

), (-2τ

,

     0);

the vertices of the outer outline of said first template are defined as;

(-2τ

,

     1), (2τ

,

     1), (1, 2τ

), (1, -2τ

), (2τ

, -1), (-2τ

, -1), (-1, -2τ

), (-1, 2τ

);

the vertices of the inner outline of a second template are defined as;

(1-2τ

,

     1), (2τ

-1,

     1), (1, 2τ

-1), (1, 1-2τ

), (2τ

-1, -1), (1-2τ

, -1), (-1, 1-2τ

), (-1, 2τ

-1);

the vertices of the outer outline of said second template are defined as;

(-1,

     1), (1,

     1), (1, -1), (-1, -1);

the vertices of the outer outline of a third template are defined in polar coordinates as;

(R, g±

θ

), where g takes the values 0°

, 60°

, 120°

, 180°

, 240°

, and 300°

, and R and Θ

are defined;

R=√

(2τ

² +(2/3)(1+τ

)²), Θ

=tan^-1 (√

3τ

/(1+τ

));

the vertices of the inner outline of said third template are defined in polar coordinates as;

(r, h±

φ

), where h takes the values 0°

, 120°

, and 240°

, and r and φ

are defined;

r=√

(((1+2τ

)² /6)+((1-2τ

)² /3)), φ

=tan^-1 ((√

3(1-2τ

))/(1+2τ

)).

20. The apparatus of claim 19 wherein said cubic-system crystal is a diamond.

7. Method of sorting crystalline objects, said method comprising:

creating an image of a crystalline object viewed from a defined angle, said image comprising a set of polygonal outlines including a first polygonal outline corresponding to the representation of the silhouette of said crystalline object in said image and a second polygonal outline corresponding to the representation of the shape of a crystalline face of said crystalline object in said image;

comparing said set of polygonal outlines of said image to (a) at least one template derived from a set of reference polygons including a first reference polygon corresponding to a silhouette of a reference crystal and a second reference polygon corresponding to the shape of a crystalline face of said reference crystal within said silhouette, wherein said at least one template can be varied in position, size, and shape by changing the values of at least one parameter, and (b) at least one set of parameter values for said at least one template;

varying the position, size, and shape of said at least one template by changing the values of said at least one parameter;

selecting at least one combination of a template and a set of parameter values corresponding to said image;

indicating at least one selected parameter value; and

sorting the crystalline object to one of a plurality of destinations dependent upon at least one parameter value selected by said comparison means.

8. The method of claim 7 wherein the crystalline object is a cubic-system crystal.

9. The method of claim 7 wherein the crystalline object is a diamond.

21. The method of claim 7 wherein the step of creating an image comprises:

disposing said crystalline objects on a clear plate positioned above a reflective surface, said reflective surface being illuminated by a light source;

imaging said crystalline objects by means of a video camera positioned with its viewing axis normal to said plate.

22. The method of claim 21 wherein said comparing step and said selecting step are performed by means of a computer.

23. The method of claim 22 wherein said crystalline object is a cubic-system crystal, said parameters comprise a shape parameter τ

, and said templates each comprise an inner outline and an outer outline which are defined by specifying a set of vertices for each outline as follows;

the vertices of the inner outline of a first template are defined as;

(0, 2τ

), (2τ

,

     0), (0, -2τ

), (-2τ

,

     0);

the vertices of the outer outline of said first template are defined as;

(-2τ

,

     1), (2τ

,

     1), (1, 2τ

), (1, -2τ

), (2τ

, -1), (-2τ

, -1), (-1, -2τ

), (-1, 2τ

);

the vertices of the inner outline of a second template are defined as;

(1-2τ

,

     1), (2τ

-1,

     1), (1, 2τ

-1), (1, 1-2τ

), (2τ

-1, -1), (1-2τ

, -1), (-1, 1-2τ

), (-1, 2τ

-1);

the vertices of the outer outline of said second template are defined as;

(-1,

     1), (1,

     1), (1, -1), (-1, -1);

the vertices of the outer outline of a third template are defined in polar coordinates as;

(R, g±

θ

), where g takes the values 0°

, 60°

, 120°

, 180°

, 240°

, and 300°

, and R and Θ

are defined;

R=√

(2τ

² +(2/3)(1+τ

)²), Θ

=tan^-1 (√

3τ

/(1+τ

));

the vertices of the inner outline of said third template are defined in polar coordinates as;

(r, h±

φ

), where h takes the values 0°

, 120°

, and 240°

, and r and φ

are defined;

r=√

(((1+2τ

)² /6)+((1-2τ

)² /3)), φ

=tan^-1 ((√

3(1-2τ

))/(1+2τ

)).

24. The apparatus of claim 23 wherein said cubic-system crystal is a diamond.

10. Method of sorting crystalline objects, said method comprising:

creating an image of a crystalline object viewed from a defined angle, said image comprising a set of polygonal outlines including a first polygonal outline corresponding to the representation of the silhouette of said crystalline object in said image and a second polygonal outline corresponding to the representation of the shape of a crystalline face of said crystalline object in said image;

comparing said set of polygonal outlines of said image to (a) at least one template derived from a set of reference polygons including a first reference polygon corresponding to a silhouette of a reference crystal and a second reference polygon corresponding to the shape of a crystalline face of said reference crystal within said silhouette, wherein said at least one template can be varied in position, size, and shape by changing the values of at least one parameter, and (b) at least one set of parameter values for said at least one template;

varying the position, size, and shape of said at least one template by changing the values of said at least one parameter;

selecting at least one combination of a template and a set of parameter values corresponding to said image; and

sorting the crystalline object to one of a plurality of destinations dependent upon at least one selected parameter value.

11. The method of claim 10 wherein the crystalline object is a cubic-system crystal.

12. The method of claim 10 wherein the crystalline object is a diamond.

25. The method of claim 10 wherein the step of creating an image comprises:

disposing said crystalline objects on a clear plate positioned above a reflective surface, said reflective surface being illuminated by a light source;

imaging said crystalline objects by means of a video camera positioned with its viewing axis normal to said plate.

26. The method of claim 25 wherein said comparing step and said selecting step are performed by means of a computer.

27. The method of claim 26 wherein said crystalline object is a cubic-system crystal, said parameters comprise a shape parameter τ

, and said templates each comprise an inner outline and an outer outline which are defined by specifying a set of vertices for each outline as follows;

the vertices of the inner outline of a first template are defined as;

(0, 2τ

), (2τ

,

     0), (0, -2τ

), (-2τ

,

     0);

the vertices of the outer outline of said first template are defined as;

(-2τ

,

     1), (2τ

,

     1), (1, 2τ

), (1, -2τ

), (2τ

, -1), (-2τ

, -1), (-1, -2τ

), (-1, 2τ

);

the vertices of the inner outline of a second template are defined as;

(1-2τ

,

     1), (2τ

-1,

     1), (1, 2τ

-1), (1, 1-2τ

), (2τ

-1, -1), (1-2τ

, -1), (-1, 1-2τ

), (-1, 2τ

-1);

the vertices of the outer outline of said second template are defined as;

(-1,

     1), (1,

     1), (1, -1), (-1, -1);

the vertices of the outer outline of a third template are defined in polar coordinates as;

(R, g±

θ

), where g takes the values 0°

, 60°

, 120°

, 180°

, 240°

, and 300°

, and R and Θ

are defined;

R=√

(2τ

² +(2/3)(1+τ

)²), Θ

=tan^-1 (√

3τ

/(1+τ

));

the vertices of the inner outline of said third template are defined in polar coordinates as;

(r, h±

φ

), where h takes the values 0°

, 120°

, and 240°

, and r and φ

are defined;

r=√

(((1+2τ

)² /6)+((1-2τ

)² /3)), φ

=tan^-1 ((√

3(1-2τ

))/(1+2τ

)).

28. The apparatus of claim 27 wherein said cubic-system crystal is a diamond.

29. Apparatus for sorting crystalline objects, said apparatus comprising:

image means for creating an image of a crystalline object viewed from a defined angle, said image comprising a set of polygonal outlines including a first polygonal outline corresponding to the representation of the silhouette of said crystalline object in said image and a second polygonal outline corresponding to the representation of the shape of a crystalline face of said crystalline object in said image;

a plurality of sets of reference polygons, each set corresponding to one of a plurality of possible degrees of asphericity for said crystalline object, and each set including a first reference polygon and a second reference polygon;

means for varying the positions, sizes, and shapes of the reference polygons of each of said sets, such that the degree of asphericity of said crystalline object may be determined by comparing said set of polygonal outlines of said image to said sets of reference polygons until a close match to both of said first and second polygonal outlines is found in a single set;

means for sorting said crystalline object to one of a plurality of destinations dependent upon the degree of asphericity of said single set of reference polygons.

30. A method for sorting crystalline objects, said method comprising:

creating an image of a crystalline object viewed from a defined angle, said image comprising a set of polygonal outlines including a first polygonal outline corresponding to the representation of the silhouette of said crystalline object in said image and a second polygonal outline corresponding to the representation of the shape of a crystalline face of said crystalline object in said image;

determining the degree of asphericity of said crystalline object by comparing said set of polygonal outlines of said image to a plurality of sets of reference polygons, each set corresponding to one of a plurality of possible degrees of asphericity for said crystalline object and each set including a first reference polygon and a second reference polygon, and varying the position, size, and shape of each of said sets of reference polygons until a close match to both of said first and second polygonal outlines is found in a single set; and

sorting said crystalline object to one of a plurality of destinations dependent upon the degree of asphericity of said single set of reference polygons.