Apparatus and method for minimizing the influence of corneal birefringence on the analysis of eye fixation and focus using retinal birefringence scanning

摘要

The present invention provides apparatus and methods for detecting fixation of an eye of a subject on a target. The methods provide for optimization of parameters of the spinning half wave plate and the fixed wave plate in the retinal birefringence scanning (RBS) design to enable uses of the “spinning artifact” frequency component. Frequency of the “spinning artifact” component is determined by half wave plate rotation speed and direction. Amplitude is determined by interaction of the spinning half wave plate with any retardance encountered in the double-pass optics such as the fixed wave plate, corneal birefringence, and small amount of retinal birefringence. With optimum selection of fractional spinning frequency of the half wave plate, and the orientation/retardance of the fixed wave plate, the “spinning artifact” frequency component is essentially independent of fixation direction and is also essentially independent of the normal range of corneal birefringence.