Methods and systems for grain size evaluation of multi-cystalline solar wafers

1. A system for evaluating a multi-crystalline wafer comprising:

an imaging apparatus; and

a computing device coupled to the imaging apparatus, the computing device comprising a processor and a non-transitory computer readable medium coupled in communication with the processor and containing instructions that, when executed by the processor, cause the processor to:

capture a plurality of images of the multi-crystalline wafer in the imaging apparatus, at least three images of the plurality of images illuminated in the imaging apparatus in accordance with different lighting parameters;

stack and project the plurality of images to generate a composite image to display at least one enhanced boundary of one or more grains of the multi-crystalline wafer;

analyze the composite image to identify the one or more grains of the multi-crystalline wafer based at least in part on the at least one enhanced boundary; and

generate a report based on the analysis of the composite image.

2. A system according to claim 1 , wherein the imaging apparatus comprises an imaging device and a plurality of lights positioned to illuminate the multi-crystalline wafer in the imaging apparatus.

3. A system according to claim 2 , wherein the plurality of lights comprise at least a first light oriented to illuminate the multi-crystalline wafer in the imaging apparatus from a first angle and a second light oriented to illuminate the multi-crystalline wafer from a second angle different than the first angle.

4. A system according to claim 3 , wherein the plurality of lights consists of four lights oriented to illuminate the multi-crystalline wafer from the first angle and four lights oriented to illuminate the multi-crystalline wafer from the second angle.

5. A system according to claim 3 , further comprising a third light, wherein the first light is positioned to illuminate the multi-crystalline wafer from a first direction and the third light is positioned to illuminate the multi-crystalline wafer from a second direction different than the first direction.

6. A system according to claim 2 , wherein the plurality of lights comprises at least a first light positioned to illuminate the multi-crystalline wafer in the imaging apparatus from a first height above the multi-crystalline wafer and a second light positioned to illuminate the multi-crystalline wafer from a second height above the multi-crystalline wafer different than the first height.

7. A system according to claim 6 , wherein the first light is oriented to illuminate the multi-crystalline wafer in the imaging apparatus from a first angle and the second light is oriented to illuminate the multi-crystalline wafer from a second angle different than the first angle.

8. A system according to claim 6 , wherein the plurality of lights consists of four lights positioned at the first height and four lights positioned at the second height.

9. A system according to claim 6 , further comprising a third light, wherein the first light is positioned to illuminate the multi-crystalline wafer from a first direction and the third light is positioned to illuminate the multi-crystalline wafer from a second direction different than the first direction.

10. A system according to claim 2 wherein the plurality of lights comprises at least a first light positioned to illuminate the multi-crystalline wafer in the imaging apparatus from a first direction and a second light positioned to illuminate the multi-crystalline wafer from a second direction different than the first direction.

11. A system according to claim 2 , wherein the plurality of lights comprise light emitting diodes.

12. A system according to claim 1 , wherein the instructions further cause the processor to analyze and process each image of the plurality of images to determine one or more boundaries of one or more grains of the multi-crystalline wafer.

13. A system according to claim 2 , further comprising a controller coupled in communication with the computing device and the plurality of lights, the controller configured to control a sequence of illumination of the multi-crystalline wafer in the imaging apparatus.

14. A system according to claim 2 , wherein the non-transitory computer readable medium contains instructions that, when executed by the processor, cause the processor to convert the plurality of images to binary images.

15. A system according to claim 2 , wherein the non-transitory computer readable medium contains instructions that, when executed by the processor, cause the processor to determine a size of each of the one or more grains of the multi-crystalline wafer identified in the composite image.

16. A method for use in evaluating a multi-crystalline wafer comprising:

illuminating the multi-crystalline wafer according to a plurality of lighting parameters;

capturing a plurality of images of the multi-crystalline wafer, wherein the multi-crystalline wafer is illuminated according to a different one of the plurality of lighting parameters in at least three images of the plurality of images;

stacking and projecting the plurality of images to generate a composite image to display at least one enhanced boundary of one or more grains of the multi-crystalline wafer;

analyzing the composite image to identify the one or more grains of the multi-crystalline wafer based at least in part on the at least one enhanced boundary; and

generating a report based on the analysis of the composite image.

17. A method according to claim 16 , wherein illuminating the multi-crystalline wafer according to a plurality of lighting parameters comprises illuminating the plurality of lighting parameters from at least two different angles of illumination.

18. A method according to claim 16 , wherein illuminating the multi-crystalline wafer according to a plurality of lighting parameters comprises illuminating the plurality of lighting parameters from at least two different heights of illumination.

19. A method according to claim 16 , wherein illuminating the multi-crystalline wafer according to a plurality of lighting parameters comprises illuminating the plurality of lighting parameters from at least two different directions of illumination.

20. A method according to claim 16 , wherein analyzing the composite image further comprises determining a size of each of the one or more grains of the multi-crystalline wafer identified in the composite image.