Lens System Producing Unequal Magnification in Two Mutually Perpendicular Directions

A camera lens system, applicable to a schlieren optical system, is described, that yields an image in which the magnification perpendicular to the airflow is much greater than the magnification parallel to the airflow. Examination of boundary layer development along an airfoil surface is thereby facilitated. Optical design formulas are given and illustrated by an example in which a 24-to-1 ratio of magnifications is obtained without loss of schlieren sensitivity and without noticeable aberrations.