Roughness Study of Solar Wafer by Angular Speckle and Binary Imaging Techniques
K. Rathina and R. Balamurugan
Roughness inspection of a solar wafer has been evaluated by laser speckle technique. The laser speckle is the image of the intensity distribution. It is obtained by interference effect when the laser beam illuminates on an optically rough surface of the sample. With the help of abrasive paper with the mechanical arrangement, scratches and irregularities are created on the surface. These efforts generate roughness on the wafer to trap much sunlight as possible. The speckle images are recorded as input parameters to the angle of incidence of the laser by 16, 18 and 20 degrees. The processed speckle images offer the outcome results as roughness values. The bright or white to the black or dark pixel ratio is computed from the binary imaging pattern of the speckle. The B/D pixel ratio increases with increasing roughness in the range between 90 nm and 104 nm. From this work we are able to state that laser speckle contrast indicates the solar cell roughness precisely.
Keywords: He-Ne laser, charge-coupled device (CCD) camera, solar wafer, roughness, ultrasonic, angular speckle, binary pixel imaging