skew ray

optics

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July 13, 2026

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In optics, a skew ray is a light ray that does not lie within the meridian plane of a symmetrical optical system. The meridian plane is defined as the plane containing both the optical axis and the object point. Unlike rays that are parallel to or intersect the optical axis, skew rays travel at an angle to this plane.12

This deviation can cause aberrations, which are deviations of light rays that lead to blurred images. When a skew ray passes through a lens, it is focused at a different point than rays lying in the meridian plane. This phenomenon contributes to astigmatism, where rays do not meet at a single focal point but rather form perpendicular lines.3

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aberration
…in the meridian plane, called skew rays, are focused farther away from the lens than those lying in the plane. In either case the rays do not meet in a point focus but as lines perpendicular to each other. Intermediate between these two positions the images are elliptical in shape.
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…in the meridian plane, called skew rays, are focused farther away from the lens than those lying in the plane. In either case the rays do not meet in a point focus but as lines perpendicular to each other. Intermediate between these two positions the images are elliptical in shape.
Read More