The invention relates to an optical phase
retarder for measuring the length of the ocular axis. The optical phase
retarder comprises a fixed first right-angle
prism and two movable right-angle prisms. The second right-angle
prism and the third right-angle
prism are stacked vertically and located on a transverse movement platform. The transverse movement platform is driven by a motor to move, and therefore the second right-angle prism and the third right-angle prism move synchronously. The hypotenuses of the three right-angle prisms have the same angle, thereby being in fit on a straight line. Light
ray of a
light source achieves incidence and penetrating through the right-angle edge of the second right-angle prism or the third right-angle prism, reaches the right-angle edge of the first right-angle prism in a vertical incidence mode through the
hypotenuse of the first right-angle prism, is reflected through a high-reflection film plated on the
hypotenuse of the first right-angle prism and returns back in the same way, the
light source is not moved, the transverse movement platform moves, and the light
ray reaches the two right-angle prisms in an incidence mode to produce the distance difference so as to achieve phase
delay. Linear scanning is achieved, no aberration is introduced, the structure is simple, the cost is low, and whole-eye scanning of the anterior segment and the posterior segment of the eye is achieved.