Mie scattering theory was shown in this paper to be suitable for analyzing the forward scattered light intensity distribution of micro-sized air bubble defects in glass, shining by a monochrome laser with a wavelength of 532um. The scattered light was measured by a high definition CCD camera. The scattering process can be classified as uncorrelated single scattering according to the properties of optical media. After calculating and smoothing the gray value of split rings of picture, Chahine algorithm was applied to reverse the size of defects. This technique was accurate to within 5% for defects with radii of <50um.
In this paper, a method to detect internal pocks and bubbles of optical elements based on laser line
source scanning is proposed. In dark field environment, a laser line source is used to illuminate from
one side of the glass under test, a high-resolution CCD camera is used to take pictures in front of the
glass sample. Images which contain information of defects are acquired through rough scanning and
accurate scanning. Accurate three-dimensional coordinates of the internal defects are acquired after
image processing, which descript the characteristic information of internal defects quantificationally.
Compared with the microscope imaging measurement, this proposed detection of defects in optics
based on laser line source scanning has a relative aberration smaller than 2%. In addition, the detection
time is approximately reduced to 20 minutes from 1 hour dramatically. The analysis indicates that the
error of the position of defects is much smaller than the size of them, which means the position of the
defects can be acquired accurately by this approach.