Focus measuring arrangement and method of ophthalmic examination, and ophthalmic examination apparatus and method

Abstract

A focus measuring arrangement for ophthalmic examination comprises an infrared light source system, which directs infrared light to a pupil of an eye of a person and forms a focusing pattern of the infrared light on a retina. A receiving arrangement apertures receives the infrared light of the focusing pattern from the retina through separate areas of the pupil. An image forming arrangement causes the infrared light passed through the apertures to form an individual image of the focusing pattern for each of the apertures in an image space of the receiving arrangement, the image forming arrangement causing an optical correspondence between the at least two apertures and the separate areas of the pupil. A detecting surface arrangement is located at a non-zero distance behind the at least two apertures and the image forming arrangement in a direction of propagation of the infrared light reflected from the retina for receiving the infrared light passed through the at least two apertures. A data processing unit forms focusing adjustment information based on locations of illuminated spots of the infrared light of the focusing pattern on the detecting surface arrangement, and outputs the focusing adjustment information for further processing.