Gaussian optics(redirected from Cardinal point (optics))
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Gaussian optics[¦gau̇·sē·ən ′äp·tiks]
An approximation which describes rays which are very close to the axis of an optical system and are nearly parallel to this axis, so that only the linear terms of Taylor series for the distance of a point from the axis or the angle which a ray makes with the axis need be considered. Also known as first-order theory.