Noise free defect detection in ceramic tableware using a portable digital holographic camera.

This paper describes detection of cracks in ceramic tableware using a portable digital holographic camera working on the principle of double-exposure digital holographic interferometry. Digital image processing techniques are applied on amplitude and phase information obtained from the numerically reconstructed wavefronts of the test object to locate position of the defect. Speckles generated due to illumination of the rough surface of the ceramic cup with the coherent light source deteriorate quality of the interferometric phase. Several iterations of the averaging filter with optimized kernel size are applied on sine and cosine components of the interferometric phase to minimize the speckle noise. The effect of kernel size of the matrix used in the averaging filter on quality of the interferometric phase is analyzed by evaluating the signal-to-noise ratio. The experimentally obtained size of crack on a ceramic cup (0.08 mm) is validated by a mechanical profiler with an error of 6.6%. This study may help in improving the quality criteria of tableware items.