Ophthalmic examination apparatus and alignment method
An ophthalmic examination apparatus, characterized in that the ophthalmic examination apparatus comprises at least one visual radiation source and a light manipulation arrangement, which is configured to receive light from the visible radiation source, and form light patterns from the light and direct at least one light pattern of the light patterns in a converging manner toward an pupil aperture in a pupil plane of the ophthalmic examination apparatus and locate the at least one light pattern at a non-zero radial distance from a pupil center of the pupil aperture such that a waist of the light patterns is located at the pupil plane in order to provide a person with guidance for enabling an aperture of an iris of his/her eye to approach and/or locate at the pupil aperture in the pupil plane.
1 . An ophthalmic examination apparatus of fundus of an eye, wherein the ophthalmic examination apparatus comprises:
at least one visual radiation source and a light manipulation arrangement, which is configured to receive light from the visible radiation source, and form light patterns from the light and direct at least four light patterns of the light patterns within an envelope, the light patterns having subareas on the pupil plane and the field plane, wherein:
each of the at least four light patterns is generated by a plurality of distinct beams directed toward and through the pupil aperture, the plurality of beams having a beam waist located substantially at the pupil plane such that the envelope of the beams forms a minimum cross-section at the pupil plane corresponding to the pupil aperture and avoids substantial illumination of the iris when the eye is correctly aligned, the envelope being defined as a convex hull, in planes parallel to the pupil plane, that encloses cross-sections of the plurality of beams forming the light patterns,
the light manipulation arrangement is configured to form a first pair of the at least four light patterns and a second pair of the at least four light patterns, the first light patterns and the second light patterns having opposite signs of an angle between lines that are configured to go between centroids of beams of the light patterns in the pupil plane and the field plane,
said opposite signs of convergence angle correspond to beams that intersect the pupil plane from geometrically different sides along the z-axis, producing z-axis alignment cues based on sector-specific iris occlusion rather than focus sharpness, and
the light manipulation arrangement is configured to locate the at least four light patterns at separate sectors of the pupil aperture and at a non-zero radial distance from a pupil center of the pupil aperture, wherein each sector contains a light pattern confined to a distinct radial sub-region such that misalignment in x, y, or z directions causes sector-specific iris blocking of corresponding beams, resulting in disappearance of one or more light patterns irrespective of focus based on the angles such that the beam waist of the light patterns is located at the pupil plane, and configured such that the visibility of all sector-specific light patterns is maximized only when the aperture of the iris geometrically overlaps the pupil aperture, wherein iris occlusion of any beam results in partial or full loss of the corresponding sector-specific light pattern on the retina, thereby providingx-, y-, and z-axis alignment guidance without relying on visual acuity or image sharpness.
2 . The ophthalmic examination apparatus of claim 1 , wherein the light manipulation arrangement comprises at least one image forming optical component, which is configured to form an image of an aperture plane of the at least one visual radiation source in the pupil plane, the aperture plane comprising the light patterns.
3 . The ophthalmic examination apparatus of claim 2 , wherein the at least one image forming optical component is configured to form an image of an illumination field stop to a field plane.
4 . The ophthalmic examination apparatus of claim 1 , wherein the light manipulation arrangement comprises at least one beam forming optical component, which is configured to form separate beams of light directed to the pupil plane, the beams forming the light patterns.
5 . The ophthalmic examination apparatus of claim 1 , wherein the light manipulation arrangement comprises a block of material that is opaque to visual radiation, and the block has holes which are configured to form beams of light that are configured to form the at least one light pattern that is configured to pass through the pupil aperture in a pupil plane.
6 . The ophthalmic examination apparatus of claim 1 , wherein the light manipulation arrangement is configured to limit light from the visual radiation source from entering the at least one light pattern that is configured to converge to the pupil aperture in a pupil plane, and allow light propagation beside the at least one light pattern that is configured to converge to the pupil aperture in a pupil plane, and cause the person to see a maximum of the at least one light pattern that is configured to pass through the pupil aperture in a pupil plane based on a minimum of light from the visual radiation source.
7 . The ophthalmic examination apparatus of claim 1 , wherein the light manipulation arrangement is configured to pass light from the visual radiation source optically therethrough in order to form the at least one light pattern that is configured to converge to the pupil aperture in a pupil plane and limit light propagation beside the at least one light pattern that is configured to pass through the pupil aperture in a pupil plane in order to cause the person to see a maximum of the light patterns based on a maximum of light from the visual radiation source.
8 . The ophthalmic examination apparatus of claim 1 , wherein the light manipulation arrangement is configured to direct a plurality of beams of light to the pupil plane, the plurality of beams of light being configured to form the at least one light pattern that is configured to pass through the pupil aperture in a pupil plane, and the plurality of beams of light being distributed around the pupil center of the pupil aperture at the non-zero radial distances from the pupil center.
9 . The ophthalmic examination apparatus of claim 1 , wherein one or more of the light patterns are represented in a non-blurred manner in the pupil plane of the ophthalmic examination apparatus.
10 . The ophthalmic examination apparatus of claim 1 , wherein one or more of the light patterns are blurred in the pupil plane of the ophthalmic examination apparatus.
11 . The ophthalmic examination apparatus of claim 1 , wherein an optical power distribution in a plane of a cross section of one or more of the light patterns in the pupil plane is non-flat.
12 . The ophthalmic examination apparatus of claim 1 , wherein the light manipulation arrangement is configured to form two groups of light patterns from the light and direct at least one light pattern of each of the two light patterns in a converging manner to the pupil aperture, an angle of the convergence of the at least one light pattern of a first group of the two groups of light patterns being different from an angle of the convergence of the at least one light pattern of a second group of the two groups of light patterns.