Shear representations of beam transfer matrices

Phys Rev E Stat Nonlin Soft Matter Phys. 2001 May;63(5 Pt 2):056606. doi: 10.1103/PhysRevE.63.056606. Epub 2001 Apr 13.


The beam transfer matrix, often called the ABCD matrix, is one of the essential mathematical instruments in optics. It is a unimodular matrix whose determinant is 1. If all the elements are real with three independent parameters, this matrix is a 2 x 2 representation of the group Sp(2). It is shown that a real ABCD matrix can be generated by two shear transformations. It is then noted that, in para-axial lens optics, the lens and translation matrices constitute two shear transformations. It is shown that a system with an arbitrary number of lenses can be reduced to a system consisting of three lenses.