An apparatus comprising: an optical filter array comprising an array of optical filter elements (12a-12j) which includes an array of interior optical filter elements (12b-12i) which are not outermost optical filter elements of the optical filter array; wherein the optical filter elements of the optical filter array are in the form of strips with each optical filter element including at least one pair of opposing trapezoidal end sidewalls (46 trap) that are mutually parallel and at least one pair of opposing long sidewalls (46 par) that are not mutually parallel and are shaped as parallelograms; wherein each interior optical filter element has opposing mutually parallel principal faces (22, 24) connected by sidewalls including the at least one pair of opposing trapezoidal end sidewalls and the at least one pair of opposing long sidewalls that are not mutually parallel, the opposing mutually parallel principal faces of each interior optical filter element include larger and smaller opposing mutually parallel principal faces; wherein each long sidewall of the optical filter elements has a sidewall angle aligned with a local angle of the converging or diverging light incident on the principal faces; wherein the light incident on the principal faces converge or diverge at a focal plane at a finite position along an optical axis; wherein the sidewall angles increase as the distance from the optical axis increases; and wherein the larger principal faces of the interior optical filter elements comprise a diverging aperture of the optical filter array and the smaller principal faces of the interior optical filter elements comprise a converging aperture of the optical filter array. an optical filter array comprising an array of optical filter elements (12a-12j) which includes an array of interior optical filter elements (12b-12i) which are not outermost optical filter elements of the optical filter array; wherein the optical filter elements of the optical filter array are in the form of strips with each optical filter element including at least one pair of opposing trapezoidal end sidewalls (46 trap) that are mutually parallel and at least one pair of opposing long sidewalls (46 par) that are not mutually parallel and are shaped as parallelograms; wherein each interior optical filter element has opposing mutually parallel principal faces (22, 24) connected by sidewalls including the at least one pair of opposing trapezoidal end sidewalls and the at least one pair of opposing long sidewalls that are not mutually parallel, the opposing mutually parallel principal faces of each interior optical filter element include larger and smaller opposing mutually parallel principal faces; wherein each long sidewall of the optical filter elements has a sidewall angle aligned with a local angle of the converging or diverging light incident on the principal faces; wherein the light incident on the principal faces converge or diverge at a focal plane at a finite position along an optical axis; wherein the sidewall angles increase as the distance from the optical axis increases; and wherein the larger principal faces of the interior optical filter elements comprise a diverging aperture of the optical filter array and the smaller principal faces of the interior optical filter elements comprise a converging aperture of the optical filter array.