Elimination of stray light reflected from anterior surface of cornea

The stray light reflected from the anterior surface of a cornea is about 10~100 times of the effective reflectivity of a retina, which can greatly reduce the precision of eye aberration detection and retinal imaging quality. Therefore, it is necessary to avoid the stray light. In this paper, some methods to eliminate the stray light reflected from the anterior surface of cornea are introduced and compared, such as the Polarization Beam Splitting(PBS), confocal hole, annular illumination, and the illumination with decentered thin beam. Analyzed results show that although the methods can remove the stray light reflected from the anterior surface of cornea in some degrees, they are not ideal. After analyzing, it is pointed out that the combination of annular illumination and confocal hole is the best, and the method not only has the high light-efficiency, but also is much more effective and handy than other methods.